Good evening from Southern Connecticut Weather! 

Winter looks poised to start off quickly, with our first winter storm of the season coming in the next 48 hours. As is usually the case with early season storms, there is high uncertainty over what looks to be a mixed bag event. Our first winter storm watch of the season is up for northern Litchfield County, and while there are no other winter weather headlines up for the state at the time of this forecast, they're likely coming (winter weather advisories most likely) as confidence increases. What can we expect? Let's dive in. 

Above: Our first call snow map for the coming winter storm. In the southern CT zone, we expect a coating to 2" with the least at the immediate shoreline. There we expect a snow to mix to rain event. For much of central and eastern CT we expect 2-5" of snow, with the higher amounts focused the further north and west you are. Here we think the storm stays mostly snow, but it's an extremely close call along the gradient between C-2 and 2-5. Finally, we have a 3-6" zone for NW CT. This is the area most likely to stay below freezing and snow the entire time. 

Overall Setup
There isn't much change from what we described yesterday. As expected, our pre-frontal rain is moving through the state and will clear later tonight. A cold front will bring our antecedent air mass, and our Monday--the first day of December and Meteorological Winter, will be colder than normal. Get used to hearing that for the first half of December.

As our storm approaches early Tuesday, the high pressure holding the cold air in the region will begin retreating, which will open the door for our mixed bag system. Again, that's a totally normal evolution for a winter storm, especially this early in the season. 

The differences between the 500mb evolution of our storm are subtle between the GFS and Euro, but they're significant enough to mean very different things for our weather on Tuesday. 

Above: the 18z GFS showing the 500mb evolution of our system from late Monday through early Wednesday. Below is the 18z Euro depiction for the same time frame. In the images, you can see how the shortwave in the GFS continues to be a bit more robust and north, while the Euro is a bit flatter and further south. 

The result of these differences plays itself out in critical ways. With the GFS more amplified and north, it introduces more southerly flow in advance of our system, warming the surface and the column of air all the way up to 850mb. That is a recipe for mixing and rain for a substantial portion of the state, especially southern CT where Long Island Sound temperatures are still approximately 50 degrees. This is much less pronounced on the Euro, as a flatter system doesn't have nearly as much inland push of warmth. 

The best way to see this is by looking at temperatures aloft. This is 850mb at about 7pm on the GFS (top) and Euro (bottom). The Euro is much colder even down to the coast. That would increase the odds of staying snow for longer even down to the coast. The GFS would probably bring rain well inland. 

Remember though, models are guidance not gospel. And those 10:1 ratio snow maps are the devil. A forecaster needs to sift through the noise to understand the trend and environment. Of the three scenarios presented yesterday, it now looks like the most common forecast method of blending guidance is the best way to go. With that overview out of the way, let's get to the forecast. 

Timing
Regardless of what happens with the rain/snow line, the guidance is already in good agreement on the timing for this storm. Snow will begin across the state Tuesday morning from SW to NE as the storm moves into the region. Exact timing TBD. The worst of the storm is likely mid-afternoon into mid-evening, and the precipitation likely starts shutting off late Tuesday night into early Wednesday morning. 

Snow & Ice Accumulation
As you saw at the beginning of the discussion, a blend of the guidance gives us our first call snow map. In the southern CT zone, we expect a coating to 2" with the least at the immediate shoreline. This is because we expect a snow to brief mix to rain event.

For much of central and eastern CT we expect 2-5" of snow, with the higher amounts focused the further north and west you are. Those are the areas least likely to have the surface and mid levels warm above freezing. Here we think the storm stays mostly snow, but it's an extremely close call. 

Then the easiest part of the forecast. In NW CT we expect 3-6". This may be a touch conservative, but the speed of the storm and potential for this to shuffle further south or less amped means we don't feel the need to go with bigger totals. This is the area most likely to stay below freezing and remain snow the entire time. 

Finally, it's important to note that even though we may have periods of mixing in the state on Tuesday, we expect any mixing to be sleet rather than freezing rain, and for any icing from mixed precipitation to be minor at best. 

Wind & Power Outages
Although this is a modestly strong coastal low as coastal lows go, the lack of a significant pressure gradient and the lack of a closed off and well organized low means that we do not expect significant wind or power issues. 

Overall Impact
Now, some will say that this is a nothing burger and that's fine, but we do this every year: that perspective is not entirely true.

Timing often makes a big difference in impact, and the fact that we will likely have accumulating snow starting Tuesday morning and the worst of the storm happening in the afternoon/evening means that this is probably a higher impact event than it'd otherwise be if you just looked at the snow map. While yes it is New England and we certainly get bigger snowfalls, everybody knows that there are big impacts on many if there are widespread school delays and cancellations, and if the roads are a mess when you're commuting to or from work. 

In southern CT we expect a minor impact event, but even there we could see widespread school delays. For inland areas that are in the 2-5" or 3-6" zone, widespread school cancellations and road delays are possible, triggering a moderate impact event. 

Expect our final call forecast tomorrow. 

​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
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Thank you for reading SCW. 

-DB

Good evening from Southern Connecticut Weather! 

Well, the **SCW 2025-26 Winter Forecast** was released yesterday, and we quickly turn the page to actual tracking and forecasting for the start of Meteorological Winter, which officially begins December 1.

​We have increasing confidence that winter gets off to a fast start with a quick moving storm system expected to move into the region Tuesday. This is a quick look at what we're seeing so far, and where the current forecasting uncertainty is. 

Expect our first call forecast and snow map to be issued tomorrow with a final call on Monday.  

Above: our new forecasting timeline graphic. This storm is currently at the edge of the medium range, which means that while there is increasing confidence that a storm is possible, there's still a lot of uncertainty. 

Overall Setup
A coming cold front on Sunday is a big factor in what happens in Connecticut on Tuesday. Tomorrow we will start off with rain showers and perhaps some snow showers in colder spots in northern CT as a system that is moving well to our north drags in a reinforcing shot of cold. Tomorrow will be wet, particularly in the afternoon and evening, so expect some minor travel issues given how many are traveling tomorrow. 

Above: the 18z high resolution NAM depicting the rain showers that are likely to be around tomorrow. Although morning showers (and snow showers/mixed precipitation) is possible, the heaviest rain is likely in the afternoon before clearing tomorrow evening. 

In the wake of the storm, a high pressure system will hold colder air in place on Monday, and the storm approaches Tuesday. 

Above: the 18z Euro depicting the high pressure in New England. This will hold the cold in place, at least temporarily. 

As you can see from the image above, by late Monday (00z Tuesday is 7pm Monday Eastern Time) our storm is starting to take shape, with two distinct pieces over the south and Great Lakes region respectively. 

Here's where it gets complicated. Our high pressure will start retreating, which makes our hold to slip on the kind of cold necessary at the surface and aloft for an all snow event. This retreating high also helps open the door for the storm to more north, which could introduce more warmth depending on how strong it is.  

Above: the 18z Euro 500mb depiction of the system moving through the region late Monday through Wednesday morning. Below is the 18z GFS depiction in the same time period. The subtle differences in how they manage the development of the storm have a big impact on what the overall weather will be. 

The Current Scenarios
Earlier I wrote about three scenarios, but I've refined them a little since then.

1. "North Track": 40% Chance
In this scenario, a strong low pressure amplifies further north, which would bring a snow to mix to rain event to most of the state. This would keep snow totals down for most of the state, with more rain for the coast and areas east of I-84. The GFS and long range NAM (which we do not find to be in its useful range yet) lead the way with this scenario. 

Below is the 18z GFS depiction for Tuesday. The storm quickly moves through the region, and while we start off as snow, the surface low crosses SE Mass, bringing warmth to much of the state--enough for a flip to rain for many. Note the second graphic with temperatures at approximately 7pm Tuesday. 

2. "Thread the Needle": 50% Chance
In this scenario, our high pressure still retreats, but because the low pressure amplifies less and further south, the cold is locked in for longer, and most of the state stays snow or snow/sleet. This scenario provides the most frozen precipitation, though even at the coast there's likely going to be some rain. In early December it is simply climatologically favored (read: normal) for the shoreline to rain, especially in a retreating high scenario. 

After leaning toward the third scenario for a while, the Euro has shifted toward this scenario, and is followed by some (but not all) of the second tier guidance. Note how temperatures are much colder for interior CT. 

3. Well South and Shredded: 10% Chance
This scenario has fallen out of favor a lot in the last day because of the guidance ticking more amplified, but if this were to occur, essentially our wave would end up much weaker and further off the coast. This would probably be the coldest solution, but it would also be the least impactful for the state. 

At this time, only a few members of the ensembles show this potential. I do not think it is terribly viable at this time.

Ok, so how much snow?
Given how closely scenarios one and two are in likelihood, and how different our weather will be depending on which wins out, it's not the time for a snow map. That's coming tomorrow. What we can say however is that we currently expect a low to moderate impact event in CT on Tuesday with accumulating snow possible as early as Tuesday morning statewide. For inland CT, this looks like a plowable snowfall. Along the shoreline, there is much more uncertainty.

​If I were making a map right now (and I am definitely not!) I would probably go with a coating to 2" along the coast and for much of New London County, with 2-5" elsewhere. But let's see how I feel tomorrow. 

Stay tuned. 
​
A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
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Thank you for reading SCW.
​
​-DB

Introduction
Connecticut is a state filled with winter lovers and winter haters, and both have been spoiled. In the 2010s, winter lovers had a run for the ages, with BIG snow events in 2011 (all time event), 2013 (all time event), 2015, 2017, and 2018. There were several huge snow seasons as well all the way to the coast during that decade. 

But now, winter haters are on a heater, literally and figuratively, with some of our warmest winters on record in the 2020s. In fact, despite the big snow events of the 2010s, last winter was the first time since 2015 that we had a below normal temperature winter season. That's an incredible period of warmth, which has also resulted in winter 2020-21 being the only season this decade anywhere close to normal in the snow department. 

You have heard me repeat this a lot, but what we really need is a return to normal. Our environment is resilient to be sure, but it's also delicate. Too much of anything in either direction has an impact. Normal temperatures help slow the expansion of invasive species. Invasive insects like some of the recent tick populations we've seen can bring disease, while invasive plants can harm the population of native species. Normal precipitation and yes, even snowfall, helps our farming community in spring planting, and helps us avoid some of the droughts we've seen in recent years by adding reserves to our water table that get our wells through drier periods. 

It's easy to be inconvenienced or even harmed by the weather in any season, but it's important to remember that our atmosphere is always trying to restore balance. 

Will we see balance this winter? This winter forecast aims to give you the basics of what we're looking for this winter in a readable and educational format. Expect a lot of explanatory graphics!

​Our big caveat is that there are others that spend a ton of time going into more detail. If you are looking for a deep dive on how sun cycles and Siberian snow cover may or may not impact our winter, this forecast won't do that. We try to focus on the biggest factors in our view. 

We begin with what you're looking for most. In past forecasts, we showed snowfall as a percentage of normal. This year, it just makes more sense in our visual world to show you what that means in a map as well. Our final grade is NOT just based on snow, though it will be graded with extra weight, just as we do during our winter storm forecasts. For us, the snowfall forecast covers all snow that falls. If we're still frigid in April and winter is holding on, snow that falls then counts too. 

Above: The Official SCW Seasonal Snowfall Forecast. We expect near normal snowfall across the state with 25-35" in southern CT (lowest in SE CT), 35-45" for most of interior CT, 45-60" in the eastern CT hill towns and far north central CT (including BDL), and 50-65" in the NW hill towns. The snow ranges are weighed toward approximately 80-100% of normal snowfall and the wider ranges in far northern CT accounts for the changes in snowfall climatology based on elevation. 
​
Winter Forecasting
Before we get too deep the seasonal forecast, let's talk about winter forecasting generally. For winter systems, you can't forecast the way you can in the summer. The general pattern aloft is different, and the temperature contrasts between the warmer air in the south and cold to frigid air in the north can lead to explosive storms, blowtorches that feel like early spring, and Arctic blasts that plunge our temperatures below zero. Aside from our standard updates that may cover daily conditions, as we forecast there will be two general types of conversations we're having:

1. Pattern Discussion--This is a 7-14+ day look at the mid/upper level features that influence our general weather. For example, a discussion of teleconnections that could lead to colder/warmer temperatures or more/less stormy weather.

This is easier to view and forecast with accuracy in the longer range because we are looking at fundamental mid/upper level features such as ridges and troughs. 

This is where you would see many of our 500mb height images. 

Above: An EPS (European Ensemble) forecast at 500mb for December 8. 

2. Storm Discussion--This is a short to medium range look at a specific "threat", regardless of whether it is rain/mixed precipitation/snow. For example, a discussion of a possible low pressure inside 5 days. 

What's important here is that we're looking at medium to short range here, when things are in better view. This is where you may see us use graphics showing surface or mid level cold, or surface depictions. 

Above: Examples of the operational GFS being used to depict surface cold and surface conditions, with perhaps an easter egg for those tracking next week's storm ;).

Now, we know that often times it's easy to get caught up in long range computer models, but when we are forecasting, we're generally using a tried and true timeline for forecasting and discussion. I figured it was time to put it in graphical form! 

Expect to see this a few times this winter. 

The bottom line is that at certain ranges, the snow maps and discussion you see elsewhere isn't always based in reality. If you see snow maps outside of the short range (with some exceptions) DO NOT BITE. 

Even if something turns out to be real (think Great Blizzard of 2013 which was predicted on some models more than a week out) it's not worth taking seriously unless there's a serious ensemble signal. Even then...grain of salt to say the least. 

Forecast Factors
As we've noted before, seasonal forecasting is extremely difficult. Folks have been trying to predict seasons in America since the Farmer's Almanac. The methods today may be more technologically advanced, but there will always be parts that will be right, close to right, and painfully wrong. Here are the major factors we're using this time around. Not much different than what we've done before. 

• ENSO (30%): ENSO stands for the El Nino Southern Oscillation, and it represents sea surface temperature anomalies that determine whether an El Nino or La Nina is present. ENSO influences global atmospheric conditions, hemispheric weather patterns, and downstream that means our sensible weather. This is often the biggest factor in what our season will look like. Our changing climate has changed how we use ENSO to forecast seasons, as we see tropical forcing and other factors we're not discussing here muddy the waters, but the fundamentals are still the same.
  
  
• Teleconnections (30%): ENSO in its own way influences teleconnections, which are always there. There are many indices measuring current conditions in different parts of the world, from upper level features to regional ocean temperatures. While ENSO is global, teleconnections are regional. These are the conditions that drive the overall hemispheric pattern and are critical to how frequently we get cold or warm and how stormy it is.
  
  
• Seasonal Guidance (15%): These models are longer range versions of some models, monthly or even seasonal looks. This area also includes climate models. We look at the overall averages when reviewing these, such as the average 500mb pattern, rather than specific output such as total snowfall. They have some skill, but not enough to hug tightly. 
  
  
• Current Conditions (15%): This takes into account the general trend in the seasonal transition that happens every year. Some parts of the upper level pattern in the fall have a strong correlation to what the baseline weather pattern is during the winter months. 
  
  
• Analogs (10%): We look at past years that have similarities to this year, whether it's conditions observed through the year, ENSO state, or teleconnections. Again, this brings some skill, but no two years are alike. 

Above: The latest sea surface temperature anomalies across the globe. The area to the west of South America is our ENSO region, and with cooler temperatures extending westward, we still have a La Nina, though its hold is becoming more tenuous. 

ENSO
As the image and text above shows, we're still in a La Nina. Generally speaking, anything within .50 degrees of normal for what is effectively a three month period is a neutral ENSO, with colder temperatures being a Nina and warmer temperatures being a Nino. One of the most important regions we look to is the 3.4 region, and as you can see we are squarely in Nina territory. 

A La Nina usually brings a relatively fast start to winter in the east, followed by a winter thaw, oscillations between warmer and colder, and sometimes, an early spring. However, that's only if you have Nina conditions throughout the winter. 

Above: A typical La Nina winter, image courtesy of NOAA. The variable jet stream usually means that can have periods of significant cold early followed by significant warmth in the middle to latter part of the season. It also often means that our region is the battle zone for storms, with several mixed precipitation and rain events depending on where the baroclinic zone (area where warmth and cold contrast) sets up. If that zone is further offshore, it usually means that storms take a track offshore, increasing the odds of snowier weather. If the zone is over us, that means expect mixed bag events and rain events. 

​This season La Nina is expected to persist through part of the winter, but we may revert to neutral conditions sometime in early 2026. 

Above: The computer model forecast for the 3.4 region SST anomalies. Note how the models move toward a cool neutral state by January.

Below: The result is we see that possibility reflected by the official Climate Prediction Center (CPC) forecast for ENSO. By January, odds are greater than 50% that we are in a neutral regime. 

So what does all this mean? I agree that at some point in the winter we go from a La Nina to a neutral position. Given the atmospheric lag time in translating the change in the ocean to change in the atmosphere, I think it means that we do have some sort of winter thaw--a multi-week period of above normal warmth, but that it does not lead to an early spring, meaning snow chances continue later into the season. 

Teleconnections
There's been a lot of recent talk about Sudden Stratospheric Warming (SSW) leading to big cold in the east in December. That was not quite accurate in reality for reasons we don't need to discuss here. A SSW event would have an impact on teleconnections, and we think folks jumped the gun in forecasting the influence of a SSW event. Given the reflection event that is likely underway, we think the impact on teleconnections is more muted early in the season, with more impact later in December and January that may be reinforced with an actual SSW--furthering the odds that we do not have an early spring. If you like more reading, this is a great technical paper on reflection events.

Above: An image from the cited paper showing how a reflection event in the stratosphere generally occurs. 

Given the image above, we are entering "Phase B" which is showing up in the 500mb depictions as cold from the pole starts moving into the central U.S. and will propagate east into our region in early December. 

Below is a discussion on the major teleconnections we look at. If you are a longtime follower, much of this you've seen before. 

Atlantic Teleconnections 
​
Arctic Oscillation (AO)
​The Arctic Oscillation, or AO, measures pressure anomalies in the Arctic, and is strongly correlated with temperatures in our area for the winter months. A positive phase of the AO consists of below average geopotential heights. A negative phase consists of the opposite. In a negative phase of the AO, the polar vortex over the Arctic is more prone to being stretched and displaced, allowing Arctic air to penetrate further south. With a positive AO, the opposite is true. Stronger upper level winds keep the polar vortex in check, making it less likely for deep cold air intrusions and ideal storm tracks.

We start this winter with the AO in a negative regime, but by mid-month, the expectation is that the AO rebounds to neutral or positive. That said, I think this winter we see a fair amount of fluctuations of the AO, with a possible return to negative on balance in February.  

Below is an image showing what a strong AO looks like. The image is merely illustrative, but note how the heights are well below average in the polar region. That’s a warm period.

North Atlantic Oscillation (NAO)
The North Atlantic Oscillation, or NAO, is a close relative of the AO. Here, forecasters look at two pressure centers in the Atlantic--an area of low pressure near Greenland, and a high pressure system near the Azores. Generally, during the winter we’re paying close attention to heights around Greenland. The strength and exact placement of these features tend to have a significant impact on the placement of the jet stream--absolutely critical for cold air placement and storm track in tandem. During a negative phase, we see higher heights over the Greenland area, and below average heights over the western Atlantic and (usually) the eastern US. The opposite generally occurs with a +NAO, which means more progressive tracks and more warm storm tracks. 
 
While a persistently negative NAO is not necessary for a cold and snowy winter, having a -NAO, even if transient, can be a major factor in producing some of our biggest winter weather events, as a -NAO usually implies more blocking is available, while a +NAO represents a faster pattern with less room for storms to amplify. Further complicating matters is the position of the heights. A west based -NAO is more likely to produce a cold and stormy period than an east based -NAO. Too much -NAO can also lead to suppressed storms, leaving us cold and dry. Last year is a good example of that for some of our missed events. 

Much like the AO, I expect a mostly neutral regime during the season, with transient periods of -NAO in tandem with the AO. This is in line with a EPS forecast below that takes us into January. NAO blocking in December correlates significantly with Atlantic blocking the rest of the season and the signal here is more neutral than strongly leaning one way or another. 

Pacific Teleconnections

Pacific/North American Pattern (PNA)
If we've learned anything in recent years, it's that the Pacific is king. The Pacific is vital to determining the whether we are flooded with warmer air or Arctic cold, and whether storms cut to our west or will be able to amplify off the coast. The PNA is one of the most important teleconnections, with a massive influence over North America. A positive PNA phase occurs when there are higher heights over the Pacific and western US. This correlates to ridging over the western US and a trough (transporting colder air) over the eastern US. In a negative phase, the opposite occurs. 

To hammer home the point, here's what that would look like on the models. This is the EPS depiction of 500mb heights nearing mid December. Note the ridge in the west, and trough in the east. That pattern below is good for cold delivery but not necessarily ideal for storm track. The ridge being centered further east over the Rockies would be more favorable, though this as it stands is favorable. 

Last winter, we had frequent periods of a PNA favoring normal temperatures, but not storminess, with frequent events burying a trough in the west, forcing storms to either cut to our west or get suppressed/shredded as they approached in a fast and compressed flow. That's really important to repeat: the position of the western ridge matters a lot. Too far west and storms can cut to our west, bringing rainy systems or nothing at all. Too far east and storm tracks could develop too far offshore to bring significant precipitation events.

This winter I think the PNA is less hostile, and while blockbuster events don't look particularly favorable, I do think there will be one or two windows as a favorable Pacific links with blocking from the Atlantic (likely in transition) from a -NAO to +NAO. 

East Pacific Oscillation (EPO)
The East Pacific Oscillation, or EPO is a major driver in allowing Canada to develop cold air that feeds into the U.S., or shutting off any mechanism to deliver cold to much of Canada or the United States. Here, we’re looking at heights over the northeast Pacific and Alaska. Higher heights over this region brings warmer than normal weather over that region, but it serves up an almost ideal mechanism for cold air delivery in the continental U.S., as a resulting Arctic high in northwest Canada and trough over the US work in tandem to funnel cold into the region. At times, we can see a sprawling enough -EPO to develop what is called “cross-polar flow”. This is the extreme cold that comes straight from the polar region without much moderation. That's part of how we got the brief Arctic plunge in early February 2023, a historic cold shot in the second warmest winter on record. 

With a positive EPO phase, we potentially see extended fall. In a +EPO, we get a persistent low (vortex) in the northeast Pacific and Alaska, which creates favorable conditions for the Pacific jet to inundate Canada and much of the continental U.S. with warm Pacific air. If you have this kind of pattern persist, you can almost guarantee little cold and snow. In recent years, we've had a raging Pacific jet minimize the cold that could build in Canada. That has reversed so far this fall, with a strong jet remaining but focusing more equatorward, avoiding the disruption of cold loading in Canada. 

Here's a look at the positive and negative phases of the EPO and their effects on our sensible weather.

Much like the other teleconnections, I expect this to remain near neutral for the balance of the season, increasing confidence in a more normal season than what we've seen in recent years. That may sound blah, but having near neutral indexes means that there's enough ridging to blunt the warm weighted extremes that we've seen when left unchecked. 

Western Pacific Oscillation (WPO) 
The Western Pacific Oscillation, or WPO, is a teleconnection we haven't talked about much, but we're recognizing its importance after recent years of Pacific domination on our weather pattern. This analyzes the heights in the Bering Sea (west of Alaska) and northwest of Hawaii. The atmosphere is a fluid, and the ridges/troughs we see in the central and western Pacific influence the amplitude and orientation of ridges and troughs over North America. ​

Once again, we're expecting less pronounced extremes either way with this teleconnection. I do think that this one looks a little more favorable for warmth in the longer term, given the historic warmth in the western Pacific that may lead to more ridging in that index region, and that's reflected in the final temperature forecast to blunt a bias toward colder conditions than we would otherwise expect.  

Seasonal Guidance
With ENSO and Teleconnections covering 60% of what defines our winter forecast, there's not much to be said about the rest before getting to the final numbers. The seasonal guidance is kind of all over the place, with some showing a very quick flip to spring, and others leaning more toward a normal-ish year. The guidance giving us an early spring are cause for some pause and give confidence in some sort of winter thaw at some point, but not enough to significantly impact the forecast. ​

Above: The November CFS showing monthly heights December, January, February, and March. That quick animation shows a more favorable orientation of heights for wintry weather in December, some return of warmth in January, and a rebound to more troughing in the east leading to cooler weather in February and March.

​Below: The late October CanSIPS, showing a likely wintry December followed by gradual southeast ridging and warming which would possibly "end" winter sometime in February. 

Current Conditions
We've had a trend this fall that has made me pause when looking at some of the warmer guidance later in the winter. We've had a normal transition through fall so far, with temperatures either near normal or below during the fall months. Now, that by itself doesn't mean much, but we've seen a persistent pattern of guidance reversing course with eastern ridging and warmer temperatures throughout the fall. One of the benefits of such a late winter forecast is that we can also see into the early part of December, which shows a similar pattern showing up. A fast start to winter is on tap, and while that doesn't mean much in the whole scheme of things, what we're seeing in the upper level pattern, especially with the Pacific jet and Pacific pattern, is more favorable for winter weather than we've seen in a few years, even with last year being our first colder winter in a decade. 

Above: An example of the model trend of reducing ridging in the long range. This has been a consistent trend for months, and it shows no sign of slowing down. It's not everything, but it is something. 

Analogs
Finally, let's talk analogs. I almost didn't add them. They matter least in the whole forecast, and with good reason in my opinion. No two years are alike, and in our warming climate looking at past climatological periods (which run 30 decades at a time) gets real risky real fast. Analog years of near normal/below normal temperature 2024-25, 2021-22, snowy 2017-18, and 2007-08 (even though this year was a strong Nina) lead the way. 

The Forecast (Finally!)

Above: The seasonal snowfall map reposted. 

Snowfall
Once again, we expect near normal snowfall across the state with 25-35" in southern CT (lowest in SE CT), 35-45" for most of interior CT, 45-60" in the eastern CT hill towns and far north central CT (including BDL), and 50-65" in the NW hill towns. Given everything above, you can see that we lean toward slightly below normal to normal snowfall, mostly because excessive warmth/cold/precipitation looks to be checked in either direction. However, with a Pacific that has been hostile the balance of this decade, there's no reason to hedge snowier, especially with uncertainty on how ENSO transitions.

Our primary storm type will be southwest flow events (SWFEs), which usually start as snow before mixing and either turning to rain or precipitation shutting off. That's a result of the predominant trough being just west enough to run warmth into the region at least aloft, but our source region for cold in southeast Canada being legitimately cold for the first time in quite some time.

The second predominant storm type is likely to be redeveloping Miller B storms, which can be prolific snow producers...if timed right. The fast flow of the Pacific jet has me doubting we see many windows of opportunity for that this winter. 

Remember, each month has its own snowfall average. You are least likely on average to see significant snow in December, with more in January, a peak in February, and some snow during the first 20 days of March. 

Snowfall Forecast
December: 100% to 120% of normal
January: 70% to 90% of normal
February: 90% to 110% of normal
March: 80% to 100% of normal

Winter Snowfall: 80%-100% of normal across Connecticut

Temperatures
In recent years, it has been a given that we're warmer than normal DJFM (December, January, February, March). Not so this season. I think December looks near normal, with a cold start, mid-month thaw, and perhaps more cold in the last third of the month. January is when I think we're most likely to see a thaw, especially in the first 2/3 of the month. By mid-month we may be seeing a SSW event take place, but remember that there's usually a lag in what happens in the upper atmosphere and the surface, and there's no guarantee that the Polar Vortex gets displaced on our half of the globe. That said, with ENSO in transition, I expect that by the time we're moving into February we are looking at a wintry pattern returning. That puts January in near to slightly above normal territory. February and March look near normal, with a possible lean later in February and into March on the colder side. 

Temperature Forecast
December: -1 to +1 (note that we consider anything inside a degree of normal as near normal) 
January: 1 to 2 degrees above normal
February: -1 to +1 
March: -1 to +1
Winter Composite: -1 to +1 

Above: Using our analogs, this is about what we'd expect in DJFM temperature. Right near normal, with a degree of wiggle room between below and above normal and dead center normal. 

Precipitation
Much like our temperature forecast, I think we are near normal in overall precipitation, with each month likely being near normal in precipitation. We do not foresee a high end high precipitation winter, but some months may be above given the more neutral Pacific pattern. We doubt the spigot will go dry given the predominant variable northern stream jet, but during periods of more southeast ridging (like January) we may be dry.  

Precipitation Forecast
December: 100% to 120% of normal
January: 80% to 100% of normal
February: 90% to 110% of normal
March: 90% to 100% of normal
Winter Composite: 90% to 110% of normal

Above: Using our analogs, this is about what we'd expect in DJFM precipitation. Unlike the temperature forecast, I think there's more precipitation in the north Central U.S. and western U.S. than this map shows, giving respect to the variable jet stream we're likely to see. 

Overall, to us it looks like we are on the path toward a season that balances out as normal. Will we see a continuation of normalcy after a pretty normal fall? Will we see two winters in a row with cooler temperatures? Will we get normal snowfall for the first time in half a decade?

We shall see.
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​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
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​-DB

Good morning from Southern Connecticut Weather! 

Hype season is already going strong as Thanksgiving week comes into view. If you were following some of the stuff on social media, this week was supposed to feature a huge storm followed by a massive attack of the dreaded Polar Vortex. 

Of course, none of that was ever truly real. The reality is a lot more boring. The final week of November looks to feature seesawing temperatures and mostly quiet weather, but we will have a little precipitation to navigate along with some uncertainty on timing. Let's take a look at the facts and talk about one of the biggest travel holidays of the year! 

Above: the 18z European ensemble showing the likely 500mb pattern on Thanksgiving Day. This eventual outcome on the models--a more seasonable temperature regime after (wrongly) predicting warmth at long range, has been a frequent feature across guidance in recent months. 

Monday-Wednesday
​The start of the week is quiet. We will have a clipper system remain well to our north on Monday, and other than the chance of an isolated rain/snow shower, the day is seasonable and dry. There should be no travel issues in the state. 

Tuesday we get a little unsettled. The guidance are in general agreement that another weak system will cross into the region on Tuesday, most likely bringing rain showers starting in the afternoon. Now, there is a bit of a discrepancy among that guidance on how meaningful this rainfall is, with the GFS, which was originally more robust (and accurate) on our Saturday system before losing the signal having heavier rain late Tuesday into early Wednesday, with the Euro and NAM weaker overall. I'm inclined to think that this is more meaningful rain, so expect rain showers that may be moderate to heavy at times late Tuesday afternoon and evening into at least early Wednesday.

Tuesday is a touch bit warmer than Monday, but there's not a heck of a lot of difference between temperatures in the upper 40s to low 50s, and although our average high is dropping into the 40s now, that's still pretty seasonable. 

Below are the 00z GFS, 00z NAM, and 18z Euro models for Tuesday morning into Wednesday morning. Note the subtle differences, even though the timing is generally the same. The GFS is most organized, which would lend itself to slightly more precipitation, with the Euro bringing more showery rainfall and the NAM least robust. 

While there may be some lingering showers early on Wednesday, it looks like most of the day is dry. In fact, in advance of a front we should warm sector and may very well see temperatures that are meaningfully above normal--60 degrees is on the table! It won't last long. 

Thanksgiving Day
Turkey day is where we have a bit of uncertainty on the models, but it isn't major. A strong front will be moving through the region, heralding the first stage of a pattern change. More on that later. On Thanksgiving, models like the GFS want to bring some rain showers in during the predawn hours before clearing things out before sunrise. The Euro was more dry, but the 00z run seemed to come around to the GFS idea. 

Above: the 00z GFS showing rain showers in the very early morning Thursday. 

With regard to temperatures, once the front moves through in the morning hours we will get a seasonably chilly Thanksgiving. We'll see the temperatures drop before daybreak as is usually the case, but temperatures will not rise much during the day, and will quickly fall after sunset. Highs look to be colder than normal and with colder air advecting in it could be a little breezy during the day. Overall however, I am not expecting any significant issues. 

Friday-Sunday
Fortunately, the post-Thanksgiving period looks quiet for travelers in Connecticut. With colder air in place we may see some snow showers in the state on Friday. I'm not expecting anything significant from that. It may be more festive than anything, if there is even any residual moisture for snow. Otherwise, we're sunny and quiet. 

The models split once again for the weekend, with the GFS trying to bring rain/snow showers into the region in advance of another storm system, while the Euro is dry. For now I think we're dry, but we'll keep an eye on it. 

The Coming Pattern Change
We've seen about as traditional a step down from fall to winter as we've seen in years. At Hartford (BDL), September finished +0.9, October finished +1.0, and November is currently -1.8 and is poised to finish near normal if not slightly below.

Last September, October, and November finished +2.1, +4.3, and +6.0, respectively. There's been a lot of chatter about storminess and the Polar Vortex, but as I said recently, we have ample examples in the recent of past of pattern changes meaning absolutely nothing in snowfall production.

This coming pattern seems like the next step in our gradual transition to winter. A change in the Pacific pattern will allow for ridging in the west to develop, which will likely force cold from the Arctic down into the Midwest before moving east into our region after a final push of brief warmth. Importantly, the pattern looks to allow cold to build in our source region for cold in southeast Canada.

Now, will that mean a fast start to winter? It's way too soon to tell. It's also too soon to tell whether this is a durable pattern, or just more of the same that we've seen in recent winters when things looked good in the long range only to be middling for snow and cold in the short range. Expect much more discussion in the winter forecast, which will come out Thanksgiving week! 

Above: Various Climate Prediction Center (CPC) outlooks on December. 

The Dailies
Monday: Partly sunny. Highs in the upper 40s to low 50s. 

Tuesday: Mostly cloudy with rain showers. Highs in the low 50s. Chance of rain 70%. 

Wednesday: Mostly cloudy and warmer. Highs in the upper 50s to low 60s. Chance of rain 30%. 

Thanksgiving Day: Mostly sunny, colder, and breezy. Daytime highs in the upper 30s to low 40s. 

Friday: Mostly sunny and breezy. Highs in the upper 30s to low 40s. Chance of snow showers 20%. 

Saturday: Partly sunny. Highs in the upper 30s to low 40s. 

Sunday: Partly sunny. Highs in the upper 30s to low 40s. 

​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
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Thank you for reading SCW. 

​-DB

Good evening from Southern Connecticut Weather! 

After an early start to fall in August, our fall so far has seen a pretty standard step down toward winter. Unlike recent years with blowtorches in October and 80s in November, we have been seasonable. In both September and October the respective months finished within one degree of normal. So far this November, we have been right within that same range. 

We will get our first taste of winter in the week ahead, in the wake of the latest storm to bring rain to the region tonight and tomorrow. A big trough will dive into the eastern U.S., bringing with it our coldest temperatures of the season so far and for some...the first chance of snowflakes. Let's dive in. 

Above: the 18z GFS surface temperature anomaly for the week ahead, this is the result of a direct intrusion of the Polar Vortex, bringing Arctic air (for early November) into much of the eastern U.S. with record temperatures possible in the south this week. 

Monday
Tomorrow is probably our most unsettled day of the week as a broad area of low pressure continues to develop and move across the region to our west. This storm while bringing us rain showers will be dragging enough cold to bring the first lake effect snows to the snow belt in western New York and even out toward Chicago, where 6-12" of snow is possible! 

This storm system will move through fairly quickly, and it is on the front end of the coming trough that will drop our temperatures. Tomorrow doesn't look like an all day rainer or washout, but there will be chances of showers throughout the day with a chance of heavier rain in the afternoon, much like today. By tomorrow evening we should be starting to dry out. 

Below is an 18z high resolution NAM depiction of the rainfall chances tomorrow. 

Tuesday-Thursday
The coldest air of the season likely arrives Tuesday, and that's when we will see our first real winter like temperatures. Highs on Tuesday will struggle out of the 30s for much of inland CT, though I think most will end up in the upper 30s to low 40s. It's possible temperatures may be even a touch colder as the models have been pretty aggressive with this cold shot, but I think we moderate a little bit. Most of us have had freezes by now so the growing season is over, but Tuesday morning has the best shot yet of a freeze even to the coast. 

As the low departs Tuesday and a strong northwest flow keeps us cold, an upper level low and its flow will potentially allow snow flurries and snow showers to move further east than usual, and that will give CT its first shot at first flakes. In the NW hills, you have the best shot of flakes, and that may even lead to a coating, but for the rest of the state flurries/snow showers will be hit or miss with the best chances in northern CT. No accumulation is expected outside of the hills. 

Wednesday is another cold day but temperatures moderate some. I think there will be another chance of snow showers, but I also believe the odds are lower on Wednesday. We remain quiet and colder than normal on Thursday as well. 

Above: the 18z high resolution NAM again depicting the lake effect streamers that may bring some snow flurries or snow showers into the state Tuesday. Wednesday also has a chance of producing first flakes. 

Friday-Sunday
The weekend is currently looking quiet and colder than normal, with potentially another blast of cold from Canada. The GFS does want to send a weak clipper through the region Saturday which would bring another chance of snow, but I'm discounting that for now given the lack of a signal from other guidance. The 18z Euro maybe tries something similar for Friday, but I think the signal is too disjointed to read much into it right now. For now, I will just introduce low odds for something Friday and Saturday, but not that it's likely one day or the other that would see precipitation.  

Although it is out of the forecast range, this may set the stage for another storm system early in the following week, which is forever away but may be interesting if the signal remains (which...at this range is not all that likely haha). 

Above: the 18z Euro model depicting a reinforcing shot of cold in the coming weekend, especially on Saturday. 

The Dailies
Monday: Mostly cloudy with a chance of rain. Highs in the mid to upper 50s. Chance of rain 80%. 

Tuesday: Partly sunny and breezy with a chance of snow flurries and snow showers. Seasonably cold. Highs in the upper 30s to low 40s. Chance of snow 30%. 

Wednesday: Partly sunny and seasonably cold with a chance of snow flurries and snow showers. Chance of snow 20%. 

Thursday: Mostly sunny. Highs in the mid to upper 40s. 

Friday: Partly sunny with a chance of rain or snow showers. Highs in the mid to upper 40s. Chance of precipitation 10%. 

Saturday: Partly sunny with a chance of rain or snow showers. Highs in the low to mid 40s. Chance of precipitation 10%. 

Sunday: Mostly sunny, breezy, and seasonably cold. Highs in the upper 30s to low 40s. 

​A​s always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
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Thank you for reading SCW. 

​-DB