Disc: We're going to probably ride the proverbial temperature roller coaster the next few weeks, which is pretty typical for the time of year.  There are no serious winter storm threats on the horizon, and obviously, w/every passing day, the chance becomes lower and lower.

Currently: Low pressure was over the U.P. of Michigan, w/a trailing cold front down into OH.  A warm front, associated w/that same sys was bisecting the state as of this writing.

Tonight: Cold front goes thru, w/a band of showers possible around midnight.  Moisture is very limited, so not expecting anything widespread.  Slight chc to chc pops should suffice.  Temps fall rapidly after fropa, and I think guidance is underdoing this, so I went quite a bit under guidance for that period.  Look for lows around the freezing mark, a few deg either side.

Tomorrow: Guidance is in very good agreement.  Sunshine, temps a deg or two above norm.  Temps reach around 50 most of the state.   There will be a noticeable breeze, but gusts look to stay near 30 MPH tops, so no need to mention them in the zones.

Tomorrow Night/Sun: Split the guidance up a bit.  For most zones, went a bit above guidance, w/downsloping winds expected.  However, up North, you'll be closer to a cold high and fresh CAA, so there I went a deg or two under guidance.  So highs range generally in the low 40s, but mid to upper 30s NW hills and NE corner.  Wind gusts will be mentioned in the zones, as they will gust up to 35 MPH, and some isolated 40 MPH gusts on the ridgetops.

Long Term: Next week: Most of the week is quiet, unsettled wx should begin later Thu and continue at least 24 hrs.  Because it's so far out, details remain unclear, so this disc will be fairly short and focus on the relatively pleasant wx expected before that.

Monday: Generally went close to guidance on temps, maybe a bit higher in the I91 corridor, with still something of a downsloping component to the wind and the usual compressional heating in the valley.  Highs generally around 50, but 50-55 in that valley.

Tuesday: Did not stray too far from guidance at all.  Sunny and nice, w/highs generally in the mid to upper 50s, warmest away from the Sound.  Gradient could be bigger than I am portraying here, but I don't want to get too fancy on Day 4/5.

Weds: Here I went just a shade under guidance.  Air mass is actually warmer, but clouds increase and there appears to be deep-layer southerly flow setting up, which would allow for onshore flow to penetrate more inland.  Kept a dry fcst for now, as precip should stay well of to the west.  High temps for now generally mid 50s, coolest near the shoreline.

Thursday: Again went just a shade under guidance, for the same reasons as Wed.  IF this system follows the usual progression, we'd get a good shot of rain Thu morning and then clear out, which could result in temps being higher than fcst.  But not much as followed "usual progression" this year.  For now, high temps mentioned 50-55, coolest near the shoreline.

Friday: Very complex day.  A lot will depend on the positioning of the front.  Showers and t-storms in the warm sector, w/a few rounds of strong storms possible. Cool and drizzly in the cold sector.  Where that sets up at this point is anyone's guess.  Guidance pushes the front pretty far north- into Southern CT.  In another yr, I'd say no way, but this yr, given how the SE Ridge has always been stronger than modeled, I'll accept guidance pretty closely for now.  High temps in the mid 50s- coolest along the shores.  Strong winds and much cooler temps are possible behind that sys into the subsequent weekend.

No graphics today, since the only sig pcpn is at day 6 & 7.

See ya next week!

-GP!

Good afternoon from Southern Connecticut Weather. 

In over a decade of forecasting, this is the toughest challenge I've seen. This is probably the latest SCW has made a final call forecast as well. 

​With more time, we're finally seeing things come into better focus. Somewhat.

​Let's dive in. 

Above: our final call snow map. We are holding firm with most of our original map, with the only substantive change being moving our 2-4" zone down to 1-3", and expanding that zone into more of southern CT. We expect the least along the immediate shore. 

The Overall Setup
It's the same as yesterday's forecast. 

The powerful storm from the upper Midwest is rolling through the Great Lakes region, and is expected to phase (combine) with the southern stream of the jet. It's a high-end setup. 

At the same time, our coastal low has formed off the Carolina coast, and is moving northeast, gradually intensifying. When the storm from the upper Midwest (northern stream of the jet) begins to phase, the intensification of the coastal low will become explosive. This, combined with blocking well to our north, will cause the storm to effectively stall and loop near Cape Cod before pulling away on Wednesday. 

Above: the GOES-E satellite loop. As you can see, a low is off the coast to our south, and the massive northern stream disturbance is moving toward the coast. How efficiently this phases is critical to the overall outcome. 

The Forecast

Timing 
Not many changes here. We still think this is a long duration event, even though today is mostly rain. With cooling, snow is expected to break out in the elevated parts of Litchfield County this evening between 6-9pm. The rain/snow line will collapse south and east overnight, particularly between 12am and 7am. 

The guidance has tried to coalesce around a cooler scenario for Tuesday. We lean toward a less than perfect phase that allows for snow in the northern four counties, but keeps the surface a little too warm for southern CT in the morning. However, everyone is likely to change to snow by Tuesday afternoon. Tuesday evening should still have all of CT as snow, and snow departs very early Wednesday morning, before 5am. I should note that the guidance has produced dry slotting in the state for part of Tuesday, and we will need to watch that closely. 

Below is the 12z high resolution NAM, which highlights the general evolution of the storm (even though the details are still TBD).

Snow Accumulation
When I woke up this morning, I thought our map might be in trouble and that we'd need to slash across the board outside of Litchfield County. Fortunately, patience prevailed.

The guidance, while still dramatically split over the overall outcome, have come back to Earth a bit with the extreme solutions in opposite directions. At the end of the day, our last call will mostly reflect our first, a testament (I think) to the experience and effort put into the first call. 

There is high confidence in our 12+ zone. If you are located in this area, you will see over a foot of snow. In fact, someone may end up over 20". Now, most probably won't see the higher end of that range, but it's possible in isolated spots. Some guidance really goes crazy up there. 

There is moderate confidence in our 6-12 zone. We still think elevation helps significantly in flipping you to snow earlier on Tuesday, and staying snow even if the low pressure lobe or some variation of it makes an appearance. 

There is still low confidence in our 3-6" zone, and as I told SA this morning, I am worried about this zone. If the globals are to be believed, we see minimal snow here. If you take the high resolution guidance, a major snowstorm is on the way.  Our 3-6 zone is the middle ground, and we're keeping it. As you will see below, in this case there is a big difference between 3" and 6" of snow.  

There is moderate confidence in the 1-3" zone. Simply put, the temperatures are warmest here and this zone is last to flip to snow. Along the immediate shoreline, and I mean within a few miles of the beach, you may very well never accumulate if the low pressure lobe appears. However, we think it's more likely that you see at least a minor accumulation...and a lot of heavy rain. The northern part of the zone should see accumulating snow, and western CT could see snow outside of this zone if the low is more consolidated.  

Below is the 12z GFS. It's a little more bullish in western and northern CT with heavy snow Tuesday, but with the low pressure lobe, it's mostly rain Tuesday morning in southern CT before a flip to snow. 

Wind 
As I mentioned yesterday, the combination of wind and heavy wet snow is a big issue, especially inland. 

We anticipate maximum wind gusts between 35-45mph inland, and between 40-50mph along the shoreline. Highest gusts would be in eastern and SE CT. The winds are strongest in CT on Tuesday as the storm rapidly intensifies to our east. These aren't actually too bad in the whole scheme of things, but with dense snow, it becomes a problem if there's enough accumulation. 

Power Outages
The combination of strong winds and heavy wet snow means that scattered power outages are possible in much of the interior. In our 12+ zone and 6-12 zone, we have particular concern that we see widespread outages. 

Our concern has also increased in the 3-6" zone. If we see less snow than currently anticipated, or end up around 3", there are little power concerns. However, if we see a widespread area at or over 4-6", the risk of scattered to widespread power outages increases substantially.

Again, 12-18 inches of powder is far less impactful than 4-8+ inches of paste. The load on trees and power lines is a legitimate concern, even in areas expected to see less snow. 

​Overall Impact
Overall, we still see a moderate to high impact event, with moderate impact in the 2-4 and 3-6 zones and high impact in 6-12 and 12+ zones. Based on the current forecast, we would see widespread cancellations statewide on Tuesday. There is minor coastal flooding expected, but we don't see a major impact with that. 

Now is the time to follow radar trends and see what happens.

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.

Thank you for reading SCW. 

​-DB

Good evening from Southern Connecticut Weather. 

It's time to make a call, but I really don't want to. 

It seems as if we have been following this one for a long time, with a long way to go. Unfortunately, we continue to see a complex and highly sensitive forecast as we get close to the start of the storm. 

With winter storm watches now covering most of the state, here is our first call snow map.

Above: Our first call snow map. We expect that the bulk of snow falls on Tuesday after rain begins later on Monday. Our shoreline zone is at 2-4" because of the high uncertainty over how the system consolidates. Our middle zone has 3-6", and we expect more snow the further north and elevated you are. We have a 6-12" zone for part of eastern CT, Litchfield County, and far northern Fairfield County. The "jackpot" zone is the elevated portion of northern Litchfield County, where snow totals over 1 foot are possible. 

I already know how this goes. Some will look at this accumulation map and say

"what major storm!"

"hype"! 

If you watched my video discussion you know how explosive a setup this is. Read a little further to understand why we still think this is a major storm with changes possible. 

Above: the latest GFS 500mb depiction of the storm. It's a beautiful depiction for a major storm...but...there's a slight imperfection that throws the entire surface and thus sensible weather into chaos. Can you spot the imperfection?

The Overall Setup
The synoptic evolution is actually pretty straightforward, and it hasn't changed much since yesterday. The powerful storm from the upper Midwest is moving toward the east, and is expected to phase (combine) with the southern stream of the jet. 

A coastal low will form from the southern jet off the southeast coast tomorrow, and as it moves northeast it will begin to intensify. When the storm from the upper Midwest (northern stream of the jet) begins to phase, the intensification of the low will become explosive. This, combined with blocking well to our north, will cause the storm to effectively stall and loop near Cape Cod before pulling away on Wednesday. 

Here's where it gets complicated, however. How quickly do we see the phasing happen and the coastal low consolidate? The models have waffled all over the place with this, and continue to be split on the eventual outcome. The imperfection is evident in the GFS loop above through the Tuesday time frame, where we see two areas of vorticity. This results in the low pressure lobe I've described previously, which dramatically reduces snowfall potential as it brings warmer air to the state on Tuesday. 

On the other side of this is the NAM from earlier today. As you will see below, the phasing happens sooner, which keeps the cold in the state and brings a widespread major snowstorm to the state. A small change with a big difference at the surface. 

The Forecast

Timing--High Confidence 
We think this is a long duration event, even though Monday is mostly rain. We will see the coastal storm begin to develop tomorrow. It'll be well to the south and normally we wouldn't see precipitation, but we will see what resembles an inverted trough appear as the northern stream energy works toward the region. Temperatures will be too warm for snow anywhere early on. Expect rain showers to develop over the state late tomorrow afternoon. We do not expect any travel issues. 

With cooling, snow is expected to break out in the elevated parts of Litchfield County between 6-9pm. The rain/snow line will collapse south and east overnight, particularly between 12am Tuesday and 7am. 

This is where it gets tricky. What happens next? If there is no low pressure lobe over CT, the entire state likely stays snow during the day. If there is a lobe over the state, it's going to be a struggle. For now, I take the middle ground. While I don't expect an all out torch in CT on Tuesday, I lean toward a less than perfect phase that keeps the surface a little too warm for some. By Tuesday afternoon we are likely snow statewide with the exception of the coastline where rain is more likely. Tuesday evening should have all of CT as snow, and snow departs very early Wednesday morning, before 5am. 

Snow Accumulation--Low Confidence 
After moving toward a higher snowfall event yesterday, the midday and later guidance has slid backward in large part because of the low pressure lobe. I don't fully believe it, otherwise we'd go with a Coating to two inches along the shoreline, but it is enough to have us lean more conservative overall. 

There is high confidence in our 12+ zone. If you are located in this area, expect a high end snow event. This is a big dog for you.

There is moderate confidence in our 6-12 zone. We think elevation helps significantly in flipping you to snow earlier on Tuesday, and staying snow even if the low pressure lobe or some variation of it makes an appearance. Honestly, there's room to take this zone up, but because there's significant uncertainty on how much low level warmth moves into the state Tuesday, we keep a 6" floor and 12" ceiling, for now. 

There is low confidence in our 3-6" zone. This zone really feels the impact of the potential low pressure lobe. If we keep that away, the zone would stay colder and I believe easily accumulate more snow. However, given marginal temperatures and the latest trend of the guidance, we are holding tight on going with bigger numbers. We choose to set a low floor and reevaluate for our final call. 

There is moderate confidence in the 2-4" zone. Why is there higher confidence here than the 3-6" zone? It's the shoreline. Regardless of the low pressure lobe potential, the temperatures are warmest here and this zone is last to flip to snow. To be sure, there could be less if the lobe appears, but because we aren't fully endorsing that idea, yet, we keep a higher floor than what could easily be a Coating-2" zone. 

You can easily see the split in guidance. Below is the 18z GFS, which looks good at 500mb but is a strung out mess at the surface.

Below the GFS is the 18z high resolution NAM, which is more effectively phased at 500mb and results in a major statewide snowstorm. ​

Wind--Moderate Confidence 
How does a snowfall map like the one above end up being a high impact event? Wind and snow type. While there will be times where snow is likely to be lighter and fluffier, most of the snow is expected to be heavy and wet.

This kind of paste is always an issue, and is a hallmark of March snowstorms. However, even in the absence of a big high pressure to the north (which could have easily made this an historic blizzard) the rapid intensification of the low is likely to bring strong winds. 

We anticipate maximum wind gusts between 35-45mph inland, and between 40-50mph along the shoreline. Highest gusts would be in eastern and SE CT. The winds are strongest in CT on Tuesday as the storm rapidly intensifies to our east.  

Power Outages--Moderate Confidence 
The wind forecast leads us to the power outage forecast. Many of you already received a text from Eversource about the storm, so you know this is one to pay attention to. The combination of strong winds and heavy wet snow means that scattered power outages are possible for most of the state. In our 12+ zone and 6-12 zone, we have particular concern that we see scattered to widespread outages. 

Folks need to keep in mind that 12-18 inches of powder is far less impactful than 4-8+ inches of paste. The load on trees and power lines is a legitimate concern, even in areas expected to see less snow. The impact only goes up as the snow forecast increases, if it increases. 

Above: the 18z Euro, which has quickly become more bearish on snowfall in our 2-4 and 3-6 zones due to the low pressure lobe. This is just a single frame, the rain/snow line collapses after this passes, if it even materializes. 

Overall Impact--Moderate Confidence
Overall, we envision a moderate to high impact event, with moderate impact in the 2-4 and 3-6 zones and high impact in 6-12 and 12+ zones. Based on the current forecast, we would see widespread cancellations statewide on Tuesday. 

I cannot emphasize enough how big a red flag there is with this low pressure lobe that I've talked about ad nauseam this evening. It will have a dramatic impact on the overall outcome of this one. This is one of the most difficult forecasts I've written in over a decade of forecasting. I expect changes in the final forecast, but I honestly can't tell you if they will result in a higher or lower impact. 

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.

Thank you for reading SCW. 

​-DB

Good morning from Southern Connecticut Weather. 

We have double trouble on the horizon between the coming system and a potentially major event early next week, but this brief forecast will focus on Wave #1, which will bring a mix of rain and snow to the state late tonight and into Saturday morning. 

Above: the GFS depiction of the storm early Saturday morning. Note how close the rain/snow line is to the state. 

The Forecast
This one trended more aggressive in the last 48 hours, but overnight it has looked a lot more marginal to this forecaster. The overall setup is a weak low that begins to quickly intensify once it gets offshore. Because the low is so far to the south, normally, we wouldn't see much of anything.

However, in this case it looks like we will see a brief period of strong lift, which will bring rain changing to snow over the state. The main issue with this system is that it's warm. We don't have a good antecedent airmass now that we are approaching mid-March. It's a wintry pattern, but there is no widespread deep cold to be found. It gets harder, but certainly not impossible, to get significant snow.

Despite the pattern, we are marching toward spring. 

Snowfall accumulation

UPDATED 9:56 AM: Our forecast snowmap is below. We're generally expecting a coating to a couple inches for most of the state, with elevated areas having the highest chance at picking up accumulating snow. In the western and northern portions of the state, where we're closer to the center of the system and have the strongest lift, we're looking at a widespread 3-6", with the highest totals likely coming in the elevated portions of Fairfield/New Haven/southern Litchfield county. -SA 

​
East of the CT River & CT Shoreline: I am not expecting much east of the CT River and near the shoreline. A coating to 3" seems to be the right amount for this region. The valley will likely struggle to produce much accumulation, while elevated areas may be able to grab an inch or two of snow. Along the shoreline, even in SW CT, temperatures look too warm for significant snow. 

Litchfield & Northern New Haven, Northern Fairfield County: This is the zone to watch. I am very concerned that temperatures will limit potential, but if it doesn't this is a significant snow event. Even here, things are likely to start out as rain, but the best lift looks to be a bullseye right over this region and into Upstate New York, with the heaviest snow falling during the early morning pre-dawn hours. A widespread 3-6" seems like the right amount for this region. 

Above: The latest depiction of the storm from the GFS. We go from rain late Friday night to snow early Saturday morning. Most of the precipitation is done Saturday morning and most of the day should be fine. 

Timing
The timing on this one looks straightforward, though the guidance is a little split. Today is fine weather wise. While some showers are possible a little earlier, we don't see precipitation really start moving into the state until between 9-11pm. Virtually all the guidance has this starting out as rain statewide. As the evening progresses, the rain/snow line will begin to drop down from the NW hills into the rest of the state as heavier precipitation moves in and temperatures cool. The best chance of accumulating snow will be roughly between 11pm and 7am. As precipitation lightens up and the sun rises tomorrow morning, whatever precipitation remains likely flips back to a mix or rain except in the highest elevations. With the March sun angle accumulation on roads and sidewalks will be over. 

Even if there is lingering precipitation, most of Saturday looks fine. By fine I mean unpleasant, but good enough for travel. 

The 06z European model (courtesy of weathermodels.com) showing a messy and later depiction of the storm tomorrow. 

Impact
This one is pretty tricky, because if it gets a little colder it's a more widespread snowfall. That said, as it stands we expect a minor impact along the shoreline and in central/eastern CT, and a more moderate impact in western CT away from the shoreline. This is likely to be a more wet snow, and with the timing overnight, a plowable one in our 3-6" zone. Some spot may put up a 7" or 8" report but I don't feel confident enough to create a 4-8" zone.

That said, clearing snow should not be too difficult on the roads and sidewalks tomorrow as temperatures warm above freezing statewide. 

This one moves out fairly quickly, and we turn all of our attention on next week...

​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.

Thank you for reading SCW. 

​-DB

Good afternoon from Southern Connecticut Weather. 

Our latest storm has passed and it's time to grade the forecast. 

Above: our final call map for the storm. 

​Below: the NWS final map of accumulation, which includes sleet. 

Timing
We predicted that precipitation would begin between 7-10pm on Friday, and that turned out to be accurate. It was a little interesting to see far southern CT end up one of the latest places to see precipitation start, but on balance this part of the timing forecast was good.

In our central zone, we thought a change to rain would eventually happen, and it looks like the GFS was more right than the NAM in the end as sleet really held on into early Saturday morning. As expected, roads were much better by late morning and early afternoon for most in the accumulation zones. 

Grade: A-

Accumulation
As you can see from the NWS map, we did pretty well. It was too warm for much in far southern CT. In the central zone, with a few exceptions most saw a coating to two inches of snow/sleet. In nor northern zone, we didn't bust, but there were a few outliers that had over the 3" ceiling we predicted. That takes the grade down a bit but not too much. A 2-4" zone may have been a little better. We would not have predicted 3-5" up there. 

Grade: B+

Overall Impact
At the end of the event this seemed pretty spot on. In the southernmost zone, it was a minor to nonevent. We didn't see as much wind as expected, but we were right that we were not going to have major power issues.

We were right that the central zone would be minor to moderate, and I think if you were out on the roads early Saturday, it was more moderate than minor. That fell within our range. The same is true for the northern zone, even though a few areas went higher than our accumulation forecast. By afternoon, roads were mostly clear and we already saw significant melting in most spots. 

Grade: A

Overall Grade
Despite the very tricky forecast, it essentially played out as expected. It's good to see us on a hot streak with another great forecast overall. Because we weigh accumulation 2x, it takes our grade down a little. 

Final Grade: B+

​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.

Thank you for reading SCW. 

​-DB