Good morning from SCW!

I couldn't get to this until early morning, but here's the forecast for your week ahead! The cold of last week recedes temporarily as a pattern shift allows for warmth to start the week and a significant storm by midweek. The midweek storm is likely to bring significant rainfall, but what I'm really watching is the wind potential. 

Above: the 18z EPS depicting the 500mb pattern progression from last week through the week ahead. Note how the ridging in the west at the start of the animation creates the ability for cold to flow into the east, but the pattern becomes less stable as we shift to ridging over the east leading to warmth, a storm, and then more cold back in the east. How this pattern cycles will be important as we get closer to the holidays. 

Monday-Tuesday
This is an active week, with multiple chances of rain. A weak system will approach the region, with rain overspreading the state during the afternoon. Expect a wet evening commute, but the temperature will be too warm for any frozen precipitation. This is a quick mover, so while showers may be around during the evening we should be clear Monday night. 

Tuesday looks quiet and warmer than normal as our next system approaches. 

Above: the 00z GFS depicting the weak system impacting CT later today. 

Wednesday-Thursday
I'm declaring Wednesday a SCW Period of Interest. In recent years, we've had powerful winter storms, but most of those storms were "screamers", i.e. storms that cut to our west, putting us in the warm and windy sector. It looks like the pattern continues with another storm this week. 

Rain is likely to start in the predawn hours of Wednesday, as low pressure rides up a slow moving boundary that will divide the warmth from the cold. As you will see below, we will be on the warm sector, and there's a strong signal for significant rain, on the order of 2-4 inches. As the storm moves up the boundary and rapidly deepens we will watch for a strong low level jet that could bring significant wind. The further west the storm trends, the more likely a significant wind event will be possible in CT.

As it stands, the biggest risk is in eastern CT and further east. Some guidance shows strong mixing of the wind aloft, and with winds possibly 60-70 knots above the surface, this is something to watch. For now, it's worth caution, and we will continue to follow trends. 

Above: the 00z GFS depicting the progression of the storm, which brings heavy rain over the state and cold air in the wake of the storm. 

Below: the 18z Euro depicting the progression of the storm, which very heavy rain and significant wind as the storm passes over the region. 

Thursday-Sunday
​We quiet down in the wake of this big storm, and the colder than normal temperatures return. As I mentioned at the start of this discussion, the pattern looks to cycle frequently, so this could be a fairly brief intrusion. By Sunday, we may be watching another coastal storm. 

The Dailies
Monday: Mostly cloudy with rain. Highs in the mid to upper 40s. Chance of rain 100%. 

Tuesday: Mostly cloudy. Highs in the upper 40s to low 50s. 

Wednesday: SCW Period of Interest. Rain and wind. Highs in the upper 50s to low 60s. Chance of rain 100%. 

Thursday: Decreasing clouds, breezy and cold. Highs in the mid to upper 30s. 

Friday: Mostly sunny. Highs in the upper 30s to low 40s. 

Saturday: Mostly sunny. Highs in the low to mid 40s.

Sunday: Partly cloudy. Highs in the low to mid 40s. Chance of precipitation 30%. 

Grading Last Week's Clipper
The first forecast for our first measurable snow event was ok, but left something to be desired. We had 1-3" with isolated 4" amounts in hill towns, and that was too conservative. While our C-2" zone worked for most of the state, there were some places that ended up higher.

I regret the Trace zone, as there were places in SE CT that saw snow accumulations and places in south central and SW CT that saw northing, which was odd. I'm thinking the radar returns weren't strong enough to deliver a cold enough column for measurable snow. The hill town accumulations hurt the grade significantly, Timing worked well with the storm starting and ending on time. Impact was higher than I thought, particularly because many ended up at the higher end of the forecast range, and for the hill towns, well over. Meh. 

Timing: A-
Accumulation: C (double weighed)
Impact: D

Overall Grade: C

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​-DB

Good morning from Southern Connecticut Weather. 

We have our first map of the season for a minor snow event that's coming to the state. While some precipitation may start late Wednesday, the bulk of the event will occur on Thursday, possibly impacting the morning commute. The storm will be followed with a breezy and frigid (by early December standards) Friday. 

Above: Our SCW forecast map. This is a minor event. For most, a coating to an inch or two is likely. For our hill towns in NW and NE CT, 1-3" looks more likely, with some isolated areas getting 4" if everything breaks right for them. Along part of SE CT, it looks as if temperatures will be too warm for much if any accumulation, though snowflakes are still likely. 

Timing 
The timing looks pretty straightforward for this one. Our clipper is currently over central Canada and is moving east. Today looks like another colder than normal but quiet day, with increasing clouds later in the day as the clipper approaches the region. Precipitation may start as early as 8-10pm across the state and because of the track of the storm, it may start out as rain, particularly in coastal and eastern CT. The expectation is that overnight we see a gradual change over to snow for most, especially inland. Some of that snow could be moderate at times, especially in hill towns, leading to our accumulations. 

The Thursday morning commute does look to be impacted as bouts of precipitation continue into the morning hours on Thursday. By the afternoon, the storm will be mostly over, with some scattered rain or snow showers gradually ending. This will be a windy storm, with wind advisories up for each of the southern four counties. The wind should die down by Thursday night, with breezy conditions possible Friday. 

Above: the latest 12km NAM depicting the evolution of the storm. There are a number of factors that influence our snow forecast below. 

Snow Accumulation
As you see in the map above, this is a minor event. For winter weather lovers, that's probably frustrating, as usually we do not have precipitation type issues for a clipper. There are a few things that have me leaning more conservative. First and foremost, the track of the clipper puts us in a southerly and southwest flow. If this were the kind of clipper that tracked under the region, we'd be in much better shape for all snow statewide. However, the clipper will track to our north, giving us that relatively warm wind direction. As a result, temperatures at the surface look marginal. 

For places like the coastline and CT River Valley, you know what that means. Snow may fall because it's cold enough aloft, but it may struggle to accumulate because the surface is too warm. The timing with snow falling overnight helps, which is why I think a measurable coating is likely for most. The further inland you are, the more likely you end up with a higher total. 

The other significant factor is the nature of the system itself. It's not terribly dynamic, but may have enough "juice" to allow for minor but more meaningful accumulation in our hill towns, especially in eastern CT where the precipitation shield may be more likely to blossom and a southwest flow could enhance lift in the NE hills. If there's a place that could overperform some and top out with an isolated 4 or even 5" total, it's in this zone. That said, if this comes in weaker, accumulations will be lower in the forecast range. 

I would say that there's a 60% chance that we fall within our range on balance, with a 25% chance of a widespread bust (less snow than forecast), and 15% chance of a widespread boom (more snow than forecast).

It's important to remember that although we can get significant storms around this time of the month, climatology overall is still pretty hostile, especially at the coast. It's not until mid to late month that conditions for snow become much more prevalent historically. 

Above: the latest GFS depiction of the storm. The temperatures just look too marginal for most for a significant event, though even here much of the state does get measurable snow verbatim. Note that the GFS does keep some precipitation around Thursday afternoon, which is why I think rain/snow showers will still be around though less impactful. 

Impact
This looks like a minor event overall. For interior CT, especially the hill towns, the impact may be a touch higher given the timing of the snow. We also have to watch for isolated to scattered power outages due to wind. That said, because the leaves are down, widespread outages and tree damage looks unlikely, especially since we're not expecting major accumulation.

It's important to note that the majority of car collisions happen under these very conditions--with minor snowfalls. People overestimate their ability to drive in the snow. Give yourself plenty of time to travel on your Thursday morning commute, and during the evening commute as any water on the roads could refreeze. I do not expect major airline issues with delays or cancellations. 

In the wake of the storm, Friday looks very cold. Both the Euro and GFS has most of the state below freezing through the day. The Euro even toys with temperatures struggling to escape the low 20s for many inland. With breezy conditions possible, expect even colder wind chills. 

Above: GFS temperatures Friday afternoon. 

Below: Euro temperatures Friday afternoon. 

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​-DB

Good evening and happy meteorological winter from Southern Connecticut Weather! 

December is here and for once it actually feels wintry outside. Many of us saw first flakes this week, and some of our highest elevations saw some minor measurable snow. The incredibly stable pattern that brought us the warmest November on record and driest fall (September-November) on record has radically changed, driven by a major flip in the Pacific that has dislodged cold into the continental US.

This pattern--featuring colder than normal temperatures (on balance) and continued precipitation chances--is likely to hold on until the middle of the month. For the first time in quite some time, the Climate Prediction Center believes a winter month has greater odds to finish below normal in our neck of the woods. It's important to remember that cold does not automatically mean snow, but this week it looks like the pattern is trying to bring back a seemingly near extinct weather system--a clipper. 

Above: the CPC temperature outlook for December. Note that these are probabilities, but even a few weeks ago the CPC had December warmer than normal.

Just as a reminder, for Hartford at the start of December the average high is 45, while the normal low is 29. At Bridgeport, the December 1st average high is 48, with a normal low of 34. We will be well below normal at times in the first half of this month. 

Monday-Tuesday
The start of the work week is cold and quiet. For inland areas, we will see highs in the mid to upper 30s, while the shoreline could be a little warmer, but not by much with highs in the upper 30s to around 40. With a fairly persistent northwest flow and the lake effect machine gradually slowing down, there could be some random flurries in NW CT. Nothing meaningful. 

Wednesday-Thursday
Wednesday should be a fine day for the most part, and I do not expect any travel issues. By the overnight period we should see our clipper move into the region. We have to watch to see if this becomes a little more amplified over the next few days on the guidance, but for now it looks like a weak system that will bring our first measurable snow to many in CT overnight Wednesday into Thursday. Despite the colder than normal pattern, a weak system and southerly flow ahead of the precipitation make temperatures look marginal, especially in southern CT. That would cut back on snow totals. 

For now, I expect a general coating to 2" of snow, with light coatings in southern CT and more measurable the further north and NW you are. If this requires a map, we'll issue one. The system clears Thursday, and we get a reinforcing shot of cold air in its wake. It's too soon to know if there will be widespread delays, but they could be possible in northern CT. 

Above: the latest GFS depicting the marginal nature of temperatures and precipitation on Thursday. 

Below: the latest NAM with a little more robust depiction of the clipper system. Note the more coherent precipitation shield, at least early on. This helps cool the column and bring snow further south. 

Friday-Sunday
The end of the week looks cold and quiet again, though there is a faint signal that another system could try to pop near the very end of the forecast period. IF it did, the airmass looks more favorable for snow, but a system is far from guaranteed or even likely at this time. Highs statewide look to be in the 30s, well below normal once again. 

Below are the 12z EPS temperature anomalies at the surface. For winter lovers, you need these kind of patterns to produce if you want to have a shot at a normal snowfall winter. 

The Dailies
Monday: Mostly sunny and cold. Highs in the upper 30s to low 40s. 

Tuesday: Mostly sunny and cold. Highs in the upper 30s to low 40s. 

Wednesday: Increasing clouds with snow likely late. Highs in the upper 30s to low 40s. Chance of snow 50%. 

Thursday: Mostly cloudy with rain and snow. Highs in the mid to upper 30s. Chance of precipitation 50%. 

Friday: Mostly sunny and cold with snow showers possible. Highs in the mid to upper 30s. Chance of snow 10%. 

Saturday: Mostly sunny and cold. Highs in the low to mid 30s. 

Sunday: Partly sunny with snow possible. Highs in the low to mid 30s. Chance of snow 20%. 

​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 evening from Southern Connecticut Weather! 

What a difference a pattern change makes. The last three months we struggled to get any rain. Now, we are looking at two additional chances for precipitation in the next week after our most recent storm finally broke through our remarkably persistent dry pattern. 

The week ahead is an important one as it's one of the most travel-heavy weeks of the year, and it will feature a modest rain chance Tuesday, a potential storm Thanksgiving and/or the day after, and then the second phase of this major pattern change--a strong shot of cold driven by the ongoing upper level shift in the hemisphere.

Monday
Tomorrow is seasonable, sunny, and dry. Our storm continuing to move away from the region means that it should be another breezy day, but not as bad as today. 

Clouds will increase tomorrow night as our first system advances toward the region. 

Tuesday-Wednesday
A modest system will move to our north on Tuesday, and it should bring a period of rain. It's currently timed to make most of Tuesday a damp and overcast day, even though we're not expecting a lot of rain. Less than a half inch of rain is expected, but we will take whatever we can get. 

Above: a GFS depiction of the fast moving system. We are likely drying out by late afternoon Tuesday. 

Tuesday's storm passage brings a boundary through the region, which means Tuesday night should be chilly and Wednesday will be a little colder. The day looks sunny and dry however, with increasing clouds again late in advance of the next storm system. 

Thanksgiving Day & Friday
This is our first SCW Period of Interest of the fall season. We declare these periods because there is a greater than usual chance of impactful weather. It's basically a "pay closer attention" notice during the fall and winter months. 

There was a lot of social media chatter about a big snowstorm for Thanksgiving, but for CT, even late November is not a climatologically favorable period for big snowstorms. There is high uncertainty about this period, because the pattern is still evolving. There are questions about how much antecedent cold will be available in the wake of Tuesday's system, and how the mid/upper levels amplify and steer a storm. There is guidance that keeps the entire storm to our south, guidance that brings snow (hill towns) changing to rain, and guidance that brings all rain. That's why we were quiet on the storm generally. There was no sense in saying much when was nothing meaningful to say. 

Here's what I think right now:

1) I do think that there will be a storm, and I am discounting the total whiff scenario. I think this storm will not be so weak and strung out that it misses to the south.

2) In terms of timing, it does look like this is an actual Thanksgiving Day system, so plan accordingly. This means Friday is more likely to be dry and much colder, but how long the storm lasts will also depend on how it evolves. 

3) For now, this looks like a mostly rain event. Before, which may have tricked the models, it looked like the antecedent airmass was plenty cold for snow for most inland spots. However, we see this from time to time--particularly in the last few years--where the extent of cold is overestimated in the absence of a high to the north locking cold in. That said, there is still time for this to trend warmer or colder. It probably wouldn't take much for the hill towns, particularly in NW CT, to end up with a cold enough solution for some snowfall or mixed precipitation.

For the rest of us, we would need substantial changes in how upper level temperatures evolve to have a chance at accumulating snow. Whether it snows or not aside, it does look like this could be another storm with meaningful rainfall, which would impact travel on Thanksgiving Day. Stay tuned. 

Above: 18z GFS. It has bounced around a lot between a whiff and rain event. 

Above: the 12z Canadian. This has a significant and longer duration rain event.

Above: the 12z European depicting a snow to rain event in the NW hills and rain elsewhere. 

The one key thing consistent across guidance--the cold afterward. 

Saturday-Sunday
The weekend looks cold. In the wake of the storm we will see the winter-like cold arrive and it will feel like a switch has been flipped, even though the week isn't likely to be particularly warm. If the Lake Effect machine gets going, there will be a chance of snow showers, especially in NW CT. 

Afterward, the start of meteorological winter looks cold. Whether that translates into snow or just another way to fail at delivering a more normal December remains to be seen.

The Dailies
Monday: Mostly sunny and slightly warmer. Highs in the upper 40s to low 50s. 

Tuesday: Mostly cloudy with rain showers. Highs in the low to mid 50s. Chance of rain 80%. 

Wednesday: Mostly sunny and seasonably cool. Highs in the mid to upper 40s. 

Thursday: Mostly cloudy with rain, possibly heavy at times. Possibility of snow or mixed precipitation changing to rain in the NW hills. Highs in the upper 30s to low 40s. Chance of rain 70%. Chance of snow in the hills 30%. 

Friday: Decreasing clouds, colder, and breezy. Highs in the upper 30s to low 40s. Chance of precipitation 20%. 

Saturday: Mostly sunny and seasonably cold. Highs in the upper 30s to low 40s. Chance of snow showers 10%. 

Sunday: Mostly sunny and seasonably cold. Highs in the mid to upper 30s. Chance of snow showers 10%.

​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 evening from Southern Connecticut Weather! 

You know it's bad when I'm excited to talk about rain. Since August 20, my own backyard here in central CT has received a paltry .90" of rain! After months without meaningful rainfall overall, the pattern change that I previewed about a week ago is finally on the way, and it will bring an upper level bowling ball that will arrive with rain, colder temperatures, and for some--the real possibility of first flakes. 

The Pattern Change
Above is the 12z European Ensemble (EPS) with a northern hemisphere view of 500mb. To date, our exceptionally persistent pattern in simplest terms has featured strong ridging over the eastern U.S., which has kept storm systems from developing or getting close to the region in the last few months and kept us much warmer than normal.

This stagnant pattern is finally breaking down because of a wholesale hemispheric change, starting in Pacific which is a huge driver of our pattern especially as we head into winter. Normally we see coastal storms try to develop this time of year. These are early season nor'easters that bring us the bulk of our rainfall in the fall, as opposed to frontal passages and thunderstorms bringing us the bulk of our rain in the summer. The changes in the Pacific will dislodge more cold from the north and bring us more seasonable conditions, and with it push out the persistent ridging at least for now. 

The result should be the end to well above normal temperatures and that start of a much more active (read: stormy) pattern as we finish out the last half of November. There are indications that this kind of pattern could continue into early December, but we're not looking that far ahead yet. 

Above: the 18z EPS with a zoomed in look at 500mb. Note how ridging dominated our weekend and even into early next week, but a big storm system moves through to reshuffle everything in a big way by late week. This is the first stage that we will see in the pattern change, even though things are subtly changing before this storm arrives. 

Monday-Wednesday
The start of the week continues with more of the same in terms of our sensible weather. Tomorrow did look like it had a chance of bring rain showers at one point, but much like the failed retrograding storm offshore, the rain chances dried up. Tomorrow starts out cloudy, but should remain dry and warmer than normal with highs in the low 60s. If we're able to get some clearing, we could see temps top out in spots in the mid 60s. 

Tuesday should be slightly cooler in the wake of the weak Monday system with highs in the upper 50s, but we should have more sunny conditions. This continues into Wednesday, but our storm system will be approaching by then with increasing clouds. Right now I think the rain holds off into Thursday, but we can't rule out some showers starting very late Wednesday. 

Thursday-Friday
Beneficial rain should arrive on Thursday, when our storm arrives. The models have been consistent in showing a surface low developing, potentially a strong one, just to our south and bring moderate to heavy rain at times, particularly Thursday morning. It could be breezy as well, but I am not expecting power issues. 

From there, precipitation should become more showery in nature, and our upper low will then drive in colder temperatures aloft and at the surface. By Friday, it could be quite a cold day for this time of year (where normal highs are still in the low 50s), and higher elevations could very well see their first flakes of the season. For now, I do not expect accumulation.

Here are the latest depictions from the Euro and GFS operational models. The main takeaways here are:

1) There's a good chance for meaningful rain and

2) Some much colder air is likely to be here late Thursday and possibly into the weekend depending on how where exactly the upper level low tracks.

This rain won't come close to ending our drought, but if we can maximize our potential and see widespread totals of .75-2" of rain, that will be a good start. For now, I think most end up with between .5-1.5" of rain. 
​
​GFS 

Euro

Saturday-Sunday
As you can see above, after the main rain storm departs late Thursday we will be dealing with the showers of the upper level low and colder air filtering into the region. Saturday is this period where there could be more widespread flurries and snow showers in lower elevations, especially if there is left over moisture. This is non-accumulating stuff as we are going to be above freezing, but it would be a reminder that the seasons are changing. 

By Sunday, we should be clearing out and warming back up to more seasonable temperatures, even if slightly below normal overall in terms of daytime highs.  

The Dailies
Monday: Mostly cloudy to start with gradual clearing. Highs in the low 60s. 

Tuesday: Mostly sunny and slightly cooler. Highs in the mid to upper 50s. 

Wednesday: Partly sunny early with increasing clouds. Highs in the upper 50s. Chance of showers late 20%. 

Thursday: Mostly cloudy with rain, heavy at times especially early. Highs in the mid to upper 40s. Chance of rain 90%. 

Friday: Mostly cloudy with rain and snow showers. Highs in the upper 30s to low 40s. Chance of precipitation 50%. 

Saturday: Partly cloudy with a chance of rain and snow showers. Highs in the low to mid 40s. Chance of precipitation 30%. 

Sunday: Mostly sunny and slightly warmer. Highs in the upper 40s to low 50s.

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.
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​-DB