Good afternoon from Southern Connecticut Weather. 

For the second time this winter season, a blockbuster storm is poised to impact our state. In this discussion, I encourage you to think beyond just snowfall accumulation. As I mentioned this morning in our update, the trend in the last 24-48 hours has been toward a more impactful storm for the state, and that has continued through this afternoon. We now have high confidence in a high impact event across Connecticut. Let's dive in. 

Here is our final call snow map. We are expecting 5-10" of snow for far SE CT due to mixing potential, and a general 8-14" across the rest of CT. Higher end potential remains in both zones, but these are the numbers we have the greatest confidence in. 

Overall Evolution
Things have not changed too much in terms of the overall evolution. Perhaps the low is showing up a little stronger on the models, with a tighter upper level (non-surface) depiction, but overall we still expect the current low over the Mid Atlantic region to redevelop offshore late tonight/early tomorrow and begin the journey northeast. Things do seem to be moving a little faster, so don't be surprised especially in SW CT if you see some flurries or snow showers tonight. That's no big deal, as we now expect the accumulating snow to begin after 11pm in far SW CT and the rest of the state during the pre-dawn hours. 

Below is the latest high resolution NAM model, which has done a decent job depicting the storm so far. I am posting for the purposes of showing the overall evolution, with snow starting late tonight and blossoming into bands of heavy snow tomorrow. 

Storm Details
Once again, here are the details on the storm and our grading criteria. 

Snow Accumulation
We are taking the numbers up modestly from our first call forecast. As mentioned at the start of the forecast, this is where we have the highest confidence. We have 5-10" for the SE CT area. We think that mixing could cut down on snowfall in far SE CT, and we could see a situation where the immediate shoreline is lower while just a few miles inland we see totals closer to the high end of this range.  

For inland areas, we think a general 8-14" is the best forecast, though we do note that there is higher potential in this zone, especially in SW and NE CT due to banding signals. The lower amounts relative to others may be in the CT River Valley between Hartford and the CT/MA border. That hasn't changed. This is due to potential dryslotting that is caused by downsloping into the valley from a strong easterly flow. 

With regard to precipitation type, we think the storm is mostly snow for most of the state, even down into parts of SE CT. However, as the snow begins to taper to lighter returns late tomorrow and early Tuesday morning, we do think sleet is possible. It is most likely to be prevalent along the shoreline, but even some inland areas deeper into the southern four counties of CT, especially New London and Middlesex counties, could see some mixing. Be sure to measure before the mixing takes place to prevent undercounting!

Below are the depictions of the total precipitation that falls from the GFS (left) and Euro (right). Even if they're off (they will be) this gives us high confidence in a significant snowfall and a minima in the CT River Valley. Images courtesy of weathermodels.com.

Timing
We're now looking at snowflakes beginning to fly by later tonight in SW CT, though we are not expecting any accumulating snow to take place until after 11pm tonight. Snow will break out from SW to NE with most of the state dealing with light to moderate snow by daybreak. Things will quickly become moderate to heavy between 11am and 2pm, and the worst of the conditions are likely to be late tomorrow afternoon through the evening hours. We will then see the mixing begin in SE CT and perhaps other parts of the immediate shoreline as lighter snow occurs overnight and into Tuesday morning. 

It's important to note that some guidance tries to string out the snow longer, with snow showers continuing through Tuesday and perhaps into early Wednesday. That's something to watch, and is still uncertain, but the storm as we see it will be occurring in earnest all of Monday through at least Tuesday morning. 

Wind/Power Outages
As I mentioned this morning, the thing that may have stood out most in the last 12 hours has been the increase in wind potential. This is important, because wind has a significant impact on power outage potential and overall impact. We now see an increased likelihood of blizzard conditions in much of Connecticut, with the best chance of a blizzard verifying along coastal Connecticut. As a refresher, blizzard conditions are defined as:

• Three consecutive hours of 35+ mph wind gusts
• Visibility of 1/4 mile or less for 3 consecutive hours

That's easier said than done, so I am unsure if we see Blizzard Warnings without more confidence in strong wind.

​For inland CT, we expect maximum wind gusts between 35-45mph, centered Monday afternoon into early Tuesday morning as the low passes to our south. As always, remember that gusts are gusts. Most of the time wind speeds will be lower here and at the shore. 

For coastal CT, we expect maximum wind gusts between 45-55mph, also centered Monday afternoon into early Tuesday morning. If there's a place that could go higher with an isolated 60mph gust, it would be the Groton/New London area. 

Which leads me to power outages. Last night, it looked like a heavier and wetter snow was likely, but looking at the data today, I think many inland areas have more of the lighter/fluffy type snow, especially during the height of the storm. This is because better mid-level dynamics should allow for higher ratio snow. Along the coast however, and especially in SE CT where the mix line could be lurking, a heavier wetter snow is still likely.

Combined with strong wind gusts, I think scattered outages are likely in southern CT with more isolated outages possible in inland CT. If you're in a place that loses power during wind events, be prepared. I am a little worried about far SE CT, but I'm not confident in calling for widespread outages. 

Road Conditions
With blizzard conditions possible during the afternoon and evening commute, expect road conditions to be awful across the state. If you don't have to be on the roads, I strongly recommend avoiding them tomorrow afternoon through early Tuesday during the worst of the storm. It won't be pretty Monday morning or Tuesday morning either. Expect widespread cancellations on Monday and Tuesday. 

Overall Impact
The combination of heavy snow, strong wind, coastal flooding and timing during most of the day Monday and at least part of Tuesday makes this a high impact event statewide. The worst impacts should occur tomorrow afternoon through early Tuesday morning. Coastal flood warnings are up for all of the CT shoreline, so if you are in a flood prone zone during noreasters take note. 

As always, there are going to be "winners" and "losers" with regard to snow totals due to banding, but this has unusually high upper end snow potential, beyond what we are forecasting. We'll see if that potential is maximized, but as it stands we are looking at our most significant winter weather event since 2018. We will have updates as necessary during the storm. 

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. 
​
-DB​   

Good evening from SCW. 

Winter Storm Watches are up for all of Connecticut in anticipation of a winter storm that will impact the state Monday and Tuesday. In this first call, I am forecasting a moderate to high impact event, with highest impacts occurring Monday afternoon into Tuesday morning. 

There's still a good amount of uncertainty so let's dive right in. 

Above: the SCW First Call Snow Map. For now, we want to hedge more broad and conservative with snowfall given the continued uncertainty and changes we've seen today on the guidance.

Overall Evolution
Things remain consistent with what I mentioned in prior updates. Our storm that came in on the California coast earlier in the week has reached the Midwest, with snow falling at this hour in Chicago. Tomorrow the storm will move into the Mid-Atlantic and begin redeveloping offshore, making it a Miller B type storm.

As it develops, it will be a strong low, but a bit more broad than usual. That means two things. First, there will be a very strong easterly flow that should throw heavy precipitation back into southern New England for a period. It also means that there's more of a chance of at least some dryslotting in the CT River Valley (Hartford and points north) as downsloping takes shape. Even so, right now I think whatever dryslotting that takes place is relatively minor, allowing for significant snow totals across the state. 

As the low moves northeastward, there is a greater likelihood that mixing takes place along coastal CT, especially in SE CT. This is fairly typical in our noreasters, and has become a more prominent feature on the guidance today. That said, the antecedent cold looks pretty good, and most of what falls is likely to be snow even at the shore as the front end of the system comes in. Sleet would be the predominant mixing type.

The 18z GFS depiction of the storm. Although it tries to bring rain into parts of the state, I think we keep things all snow inland with mixing possible at the shore, especially in SE CT. I am also posting the precipitation map from weathermodels.com. This is the 18z European forecast. That's a lot of precipitation. That leaves me thinking that there's more upside to this forecast for someone if banding breaks right. 

Here are more details, and our grading criteria. 

Snow Accumulation
As you can see above, we are going with a general 6-12" for most of CT with a 4-8" zone for SE CT based on the increased likelihood of mixing. We wanted to go broad because there is significant uncertainty over where the best banding will line up--more than usual. This is also a more conservative call I believe, given the uncertainty regarding the placement of the banding and mixing potential at the shore. It's better to be prudent at this point in time.

There are two possible zones where higher totals have an elevated chance of happening.

The first is in NE CT--think the hill towns like Tolland and points east, where there's been a consistent signal of getting into the deformation banding zone. The second is SW CT--a place with a lot of downtrodden snow lovers, due to the proximity of another very strong banding signal that is just to the south of the region. No one in the SW zone should be doing cartwheels because I'm not saying there's a coming snow jackpot, but it's a place that's right on the cusp of higher totals should the precipitation distribution pan out. 

For the rest of the state, 6-12" seems reasonable right now, with lower totals expected in the CT River Valley and higher totals possible in the (almost) always favorable snow spot of the NW hills. In this instance, I think a heavier and wetter snow is more likely in much of the state outside of the NW hills. 

Timing
The overall timing has not shifted too much. We expect snow to break out from SW to NE on Monday morning, starting out fairly light. By afternoon, likely 1-4pm, we start to see some of the heavier snow work its way into the state. This is the beginning of the time period with the most impact, as I expect a very difficult Monday afternoon and evening commute.

Moderate to heavy snow is likely, with increasing wind especially in coastal areas. The transition to mixing would happen during the evening hours in coastal areas with moderate to heavy snow in the other parts of the state. Monday night does not look good for travel. This should continue into Tuesday morning, where things likely begin tapering before daybreak. That said, snow is still possible through the day on Tuesday, so expect a lot of delays and cancellations. 

Road Conditions
Roads will be a mess, especially during that period between the afternoon and early morning when snow is likely to be heaviest. Expect a lot of early dismissals and afternoon/evening cancellations on Monday. The commute is likely to be a mess statewide during the late afternoon and evening so plan accordingly. Roads are likely to be slick into Tuesday, even as snow diminishes. The exception may be the coast, especially SE, where temperatures may rise above 32 during the mixing period or moments where there are lighter returns on radar. 

Wind/Power Outages
I am a bit split on wind and outages in this first call. On one hand, I am not as impressed with the wind signal as I would be if this were a tighter low with more of a pressure gradient to work with. That said, it will be windy, with near blizzard conditions possible, especially at the shoreline. Right now, I think we're looking at maximum wind gusts between 35-50mph along the shore (highest in SE CT) with maximum wind gusts of 30-40mph inland. Essentially, the wind signal is fairly strong, but nothing particularly alarming to me at this time. However, the combination of strong wind and heavy wet snow is a concern, and I think we may see scattered outages, with the problems concentrated near the shore. 

Overall Impact
This is likely to be our second high impact storm of the season. The combination of timing, heavy snowfall rates during the afternoon and evening, and wind should cause hazardous road conditions and a meaningful snowfall across the state. There are still significant points of uncertainty, such as the extent of mixing at the coast and wind potential, but overall, we have moderate confidence in a moderate to high impact event, with high impacts focused from Monday afternoon through early Tuesday morning. We will be refining this forecast tomorrow as we make our final call. 

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. 
​
-DB​  ​

Disc: The header sums it up thru Tuesday.  Got a later start today, due to data ingest.  A bitterly cold weekend will be followed/ended by the beginnings of what looks to be a classic major East Coast snowstorm.  Of course, details are not perfect yet, but I will explain that further down.

Currently: Strong storm offshore and Arctic high pressure over the MS Valley will create gusty winds that will only add to the chill today into tomorrow.

Tonight: Took a couple deg off guidance, due to fresh CAA and a little radiational cooling, though winds will be up, so we won't radiate all that much.  Lows generally near 10, except 0 to 5 above NW hills.

Tomorrow: Sunny, bitterly cold, and windy.  Wind gusts increase to 45-50 at least for a time.  NBM guidance generally accepted for temps.  Highs only near 20 degrees, and it will feel much colder with strong winds!

Tomorrow Night/Sat: Tomorrow night's temps should be similar to those of tonight- another bitter night in store.  Sat will recover a little, as advection becomes neutral, but still cold. Highs Sat 20-25, except upper 20s along the I 91 corridor.

Long Term: Long Term concerns revolve around the major winter storm potential, beginning Sunday night and lasting thru Tue night.  It's too early for any maps or anything, but I'll go thru some details regarding the storm as of now.  

First, all models are basically in agreement, except the UKMET, that this track will evolve like a classic East coast snowstorm.  I will not give much weight to the UKMET at this time, since nothing really agrees with it.  It also has flipped and flopped a lot with this storm and a lot this winter in general.  Heaviest weight for this package is being given to the ENS and OP models minus the UKMET, since they're all in reasonable agreement.  I am also discounting the UKMET because it is very, very rare for all of the "big three" (EURO/GFS/GGEM) operational models AND their ensembles to be pretty much in lock step and ALL be wrong.  That said, models will likely bounce around some more until they arrive at a final solution.  I did give a tiny bit of weight to the UKMET, in that I'll paint the entire state pretty much in likely POPS, but hold them at chance N of I 84.  At any rate, it is going to start later N of 84, because it is a slow-moving system, so we have more time to refine the fcst up there.

As far as storm timing, as I mentioned, this is a VERY slow moving system.  In SW CT, a flurry is possible any time on Sunday, with light snow/snow showers becoming more likely by dawn Monday.  Steadier snow then arrives Monday afternoon and ends around midnight Monday night.  However, light, accumulating snow, with a few moderate bursts, continues all day Tuesday, and even until late Tuesday night.

For NE CT, light snow arrives Mon afternoon, and quickly becomes heavier.  The steadiest snow ends by dawn Tuesday, with light snow and snow showers continuing another 24 hours.

This storm has the potential to produce major (double digit) accumulations for the entire state, esp S of I 84.  

Things to Watch: As with many large East Coast lows, there will likely be areas of deformation snow, where it snows very heavily, and keeps snowing over the same spot repeatedly, as well as a large dry slot.  Unfortunately, these are absolutely the last things we know with these storms.  We often do not know where these zones will be until the storm has already started and has a presentation on radar.  We also do not know what kind of dry slot will set up.  What I mean by that is, there are two types of dry slots: a "clean" dry slot, and a "dirty" dry slot.  A "clean" dry slot has very little or no precipitation at all inside of it, while a "dirty" dry slot has showers inside of it, some of which could be locally heavy.  In addition, this storm will likely stall, or come very close to doing so, and could even perform a bit of a loop, before heading out to sea.  Where it stalls and performs this loop is critical to our sensible wx here.  A stall too far S would keep the bands of snow down over SNJ and SE PA.  A stall too far N would lash Boston, RI, and far NE CT.  A stall further NW could bring p-type issues to the SE Coast.  Right now, I am calling for all snow to keep it simple, but this is just something to watch.  

Finally, some of the guidance, not all, namely the ECMWF/UKMET and EURO ENS showed a subtle shift to the south today.  It could be the start of a trend.  It could be a hiccup.  Or it could just be a "tightening up" of the guidance, where it comes into better agreement.  There won't be any way to really know about that until tonight's 00Z cycle is complete, to see where the modeling goes.  But for this reason, I kept POPs north of I 84 to chance.

Winds could also be very strong, with wind gusts to at least 50 MPH and blizzard conditions possible, esp along the S coast.  All of this will come into better focus as the event draws closer.  Stay tuned!

As for temperatures, expect highs in the 20-25 Sunday, near 30 Monday, and around freezing on Tuesday.  There will likely not be much diurnal variation on Monday and Tuesday, and depending on when/where heavier snow falls, they may follow a non-diurnal trend.

We clear out Wed behind the storm. I shaved a deg or two off guidance assuming snowcover, but I did not really spend much time fussing over temps.  Highs should be somewhere near the mid 30s.

Thu clouds increase ahead of the next sys.  That storm is probably a mostly rain event, but with cold air around, could certainly start as snow or a mix, esp N of 84.   I cut several deg off temps on Thu due to snowcover and increasing clouds.  Expect highs around freezing.

Long Range: Obviously, with all that's going on in the short and medium term, I did not really have time to dig deeply into the long range.  However, the aforementioned rain storm next Fri sets the wheels in motion for what appears to be an extended period of intense winter, w/many chances for coastal storms and Arctic blasts.  Let's just leave it at that for now...

Since the fcst is really focused around one event this time, I'll post the GFS and GGEM models valid at the same time (7 PM Monday)... that seems like a good time where much of the state will be in on the action.  I'll just post the maps, no commentary.   GFS will be on top, GGEM on bottom.  EDIT: Scratch the GGEM.  It never ran on most sites today, and the Environment Canada site is a strain on the eyes.  So here is the GFS:

​

Anyway, that's all for now.  I'll see you next week, or possibly earlier if conditions warrant!

-GP!

Good evening from Southern Connecticut Weather. 

As I mentioned in my Facebook post earlier this afternoon, yesterday's trend of a stronger system has continued into today and even this evening. Our team made a map revision as I began writing this post! We don't see that too often here at SCW. Winter Weather Advisories are up for most of Connecticut, but we are all looking at a low to moderate impact event beginning late Tuesday morning/early afternoon into Wednesday morning. 

Overall Setup
Here's our map for the event. Originally, we were going to go with 1-3" at the immediate shoreline but the trend today has been more moisture and colder temperatures even at the shoreline, which would mean more snowfall. As a result, our current forecast is for a widespread 2-5" for the state. There are some indications that the potential may be a bit higher in the snowfall category, but we're not biting on that for now. 

The overall setup is pretty straightforward. A system will develop to our west and spawn secondary development of a low pressure system to our south. This will allow for precipitation to enter our region and with colder air in place most of it should fall as snow. In fact, most of the state is now likely to stay below freezing during the duration of the event in my opinion. That will help with accumulation.

​There may be a chance of some mixing in the lighter returns at the end of the storm, especially along the coastline, but we're not expecting meaningful icing in this situation. 

Above, the 12z Canadian depiction (no, I do not show the Canadian a lot but I think the overall evolution makes sense) of the storm. Mostly snow for the state. 

Timing
Snow should begin from SW to NE from late tomorrow morning in far SW CT through early-mid afternoon in central and NE CT. ​Although the snow will start light, we're seeing more indications that there will be a pretty decent front end burst of moderate snow. This may make tomorrow afternoon's commute more tricky than originally expected. For this reason, we think this could briefly be a moderate impact event where heavier returns set up during the commute. 

In addition, this is looking like a longer duration event. The latest European model run has continued to signal light to potentially moderate snow falling through Wednesday morning, making that commute tricky as well. 

Above: the 18z European model depiction of the snow event. Note that even along the shore there is snow, and moderate snow looks possible through tomorrow afternoon's commute. Image courtesy of weathermodels.com.

Overall Impact
We think this is a low to moderate impact event. It's moderate because the timing of the heavier snow is likely to impact the Tuesday afternoon commute and to a lesser extent, the Wednesday morning commute. We do not expect significant wind or power outage issues, and the overall accumulation falls within our general low to moderate impact range.

There's still some upside to this event, so it's possible there's another map revision upward early tomorrow, but for now we think a broad 2-5" zone with heaviest snow falling in places that receive the better "banding" or dynamics is the strongest forecast.

I am inclined to say that more snow is likely to fall the further inland you go, but should better dynamics setup along the shoreline, that area can do well in the snowfall department too.

​I guess winter is back. 

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. 
​
-DB​ 

Good evening from Southern Connecticut Weather. 

I have a confession to make. I'm down on this winter. After a great start for snow lovers in December, we've gone quite a bit into January without a significant snow event, defying our winter forecast. Even worse, it's been hot! Hartford (BDL) is 6 degrees above normal for January! Despite a upper level pattern that most winter lovers dream of, we're stuck in the suck. 

This week brings a few potential snow chances, but it doesn't look like another significant event is on the way. Either way, this week is poised to be more wintry, with cold diving in by the end of the work week. Let's dive in. 

Departure from normal temperature in January so far. Yes, it's been quite warm overall.

Monday
Tomorrow looks like a fine day. We should see seasonably cold (a few degrees warmer than today) conditions and mostly sunny conditions early, followed by increasing clouds as the first storm system we're watching moves in.  

Tuesday-Wednesday
A fairly weak storm system will take shape to our south. Originally, it looked like this system would be shunted too far to our south for any real impact here, but recent global guidance from both the Euro and GFS shows a system that is close enough to bring a period of snow to the state. At this time, it looks like there are some lingering questions over how warm temperatures will be in southern CT, and how much precipitation falls, i.e. dynamics. This doesn't look like a significant event, but there may be a stripe of lift that brings more precipitation to some location in southern New England. 

Right now, I expect light snow to begin breaking out late Tuesday morning, with potentially moderate snow for a period Tuesday afternoon or evening, especially in northern CT. There may be mixing in southern CT. Both models want to keep light precipitation going into Wednesday, but we'll see about that. 

At this time, I think we're looking at a broad Coating-2" with more the further inland you go. I'm not biting on higher snow totals at this time given the lingering questions on "band" placement and temperatures. Stay tuned as this forecast will need to be refined tomorrow. 

Thursday-Friday
The system should depart on Wednesday, and then, as you can see in the GFS depiction above, we're watching another system. There's not much to say with this one honestly as it looks highly likely that the actual storm will pass well to our south. That said, it's worth noting because there are some indications that we could see an inverted trough set up with this one, which could bring some snow showers on Thursday. In addition, the passage of the storm will draw down the polar vortex for our region on Friday, bringing very cold conditions for Friday and Saturday. If we do end up with snow accumulation that could put us in play for morning temperatures near to possibly below zero on Friday (especially) and Saturday morning for inland areas. 

​Friday is looking cold and windy with clearing conditions as cold air advects in. 

Above image from Tropical Tidbits shows the GFS depiction of the Thursday storm. It is well out to sea, but there's a signal for snow showers over CT Thursday afternoon. The signal is there on the Euro as well. This looks very light, but it's something to watch. The big story will be the cold Friday and Saturday. 

Saturday-Sunday
​The storm clears and it looks like Saturday is a cold, but nice, day. Highs are likely to be below freezing statewide. By Sunday, we're possibly looking at another wintry system approaching. The signal for this one has been fairly consistent in recent days on the guidance, but it's a long way out. Not worth really thinking about at this time. 

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

Tuesday: Mostly cloudy with snow, mixing possible in southern CT. Highs in the low to mid 30s. Chance of snow 60%. 

Wednesday: Mostly cloudy with snow or mixed precipitation early, followed by mostly cloudy conditions. Highs in the mid to upper 30s. Chance of precipitation 30%. 

Thursday: Mostly cloudy with a chance of snow showers. Highs in the low to mid 30s. Chance of snow 20%. 

Friday: Mostly sunny, cold, and breezy. Highs in the mid to upper 10s. Morning lows may be near zero inland. 

Saturday: Mostly sunny and cold. Highs in the mid to upper 20s. Morning lows may be near zero inland. 

Sunday: Increasing clouds with a chance of snow late. Highs in the mid to upper 20s. 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.

Thank you for reading. 
​
-DB​  ​