Merry Christmas from Southern Connecticut Weather! 

Unfortunately, for virtually all of the continental US, 2023 will not bring a White Christmas. In fact, the lack of snow cover so far this season is notable. For whatever reason, December has been a difficult month to produce consistent wintry conditions. The final week of December so far looks no different, with most of the week much warmer than normal.

However, change is on the way.

​Let's dive in.

Above: the European Ensemble showing the 500mb pattern from today through the start of January. Note how the ridging over the east that's bringing us the warm Christmas fades as ridging begins to develop in the west and importantly, near Alaska toward the end of the run. This is a medium range change that is increasingly likely, giving confidence in a major pattern change to start January. 

Christmas Day
Today is going to be warmer than normal but quiet. It's a foggy start out there with drizzle in spots, and that will give way to a cloudy day. Not much to discuss here as highs will near 50. At least there are no travel issues. It's a small section of the country waking up to a White Christmas, as shown by the snow depth map below. Most see nothing and even those with some snow are seeing very little. ​

Tuesday
Boxing Day looks fine on the guidance, but the predominant state this week will be cloudy. Again, we're warmer than normal with highs in the upper 40s to low 50s! 

Wednesday-Thursday
It's the middle of the week where I have the highest confidence we get unsettled. This is an increasingly high confidence forecast. A meandering system over the Midwest will finally make its way to the east coast Wednesday. The day looks mostly quiet, but showers will be possible through the day. Once again, we will be warmer than normal with highs in the 50s. By evening, we will see a secondary low develop off the coast bringing more widespread rain into Thursday. 

This is nothing like the big storm we had last week. In this case, we're just looking at a steady rain late Wednesday into early Thursday afternoon. The rainfall doesn't look heavy but it will add to our very wet December. Highs Thursday look to be in the upper 40s to low 50s again. That may be our last 50 degree day for a bit. 

Above: the 06z GFS depiction of the midweek system. It's weak, fast moving, and keeps most of the rain centered Wednesday evening into early Thursday. 

Below: the 00z Euro depiction of the midweek system is quite similar, but a touch stronger with the surface low. Overall, it's a nuisance event more than anything. No significant flooding or wind issues are expected. 

Friday-Sunday
The very end of the forecast period is a little tricky. While our main storm departs, there's a signal that some upper level energy will linger. What does that mean? Colder air will begin filtering in on Friday and as the upper level energy cycles through the region it may produce some more unsettled weather. This could come in the form of rain showers Friday and Saturday, or, it could bring a little snow if we get some offshore development. The Euro last night tried to show this scenario but it seems unlikely for now. The GFS has played around with it too, and the ensemble signal has been a touch stronger than operational models. It's worth watching, but not worrying about. 

New Year's Eve looks quiet and seasonable. ​

The Dailies
Christmas: Foggy start with patchy drizzle, giving way to mostly cloudy skies. Highs in the upper 40s to low 50s. 

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

Wednesday: Mostly cloudy with scattered showers early, becoming steadier rain Wednesday night. Highs in the low 50s. Chance of rain 80%. 

Thursday: Mostly cloudy with rain. Highs in the low 50s. Chance of rain 90%. 

Friday: Partly cloudy and colder. Highs in the low to mid 40s. 

Saturday: Mostly cloudy with a chance of rain and/or snow showers. Highs in the low 40s. Chance of precipitation 30%. 

New Year's Eve: Partly cloudy and seasonable. Highs in the upper 30s to low 40s. 

The Coming Pattern Change
With apologies to the winter haters out there, it wouldn't be Christmas without providing some hope--focused on the winter lovers among us. 

I don't need the next seven days to play out to know that much of the winter forecast for December will be wrong. We predicted December being 1-2 degrees above normal and we are poised to have another blowtorch December. We predicted below normal snow but at least half of normal, and it's quite possible we get shutout in the snow department. We'll probably be close to right about rainfall.

The most important thing in that December forecast, however, had nothing to do with December at all. 

From our Winter Forecast:

"It's important to remember El Nino climatology. A Nino in itself isn't bad for a normal winter. Normally you have a warmer and less wintry December, followed by a transition to colder and more wintry conditions in the second half of January and through February and sometimes even early March. This is what we call a "backloaded winter" and that's the expectation here.

This year, we think the El Nino is balanced out by a favorable December teleconnection pattern. Even if December ends up less snowy than normal, the expectation is that after January 15, we see a return of favorable conditions for colder and snowy periods. There is a huge difference between this pattern on December 10 and January 10.

The thing to watch is not snow in December, but rather 1) whether the mild period materializes in mid-December/how strong it is, and 2) what the end of December upper level pattern becomes. If it is a transition earlier to more wintry conditions, that is a likely signal of an active and wintry 2024." 

The last days of 2023 will have a lot of folks thinking that a repeat of the horrific 2022-23 season is upon us, but I am here to say this season does not look anything like last year. 

The mild period arrived in a big way, but it does not look persistent
Yes, December will be a blowtorch. It will bring another snowless Christmas. But the overall pattern, where an anomalously strong Pacific jet filled the continental US and importantly, Canada, with warm air does not look to persist. In fact, that pattern is going to start to break down this week. 

Above is the European Ensemble, showing a 5 day average or 500mb heights over our part of the hemisphere. The key to follow here is the ridging (upward moving lines) and heights (red shading). Look at how it transitions from the east to the west over into January. That's a strong signal for breaking the continuous Pacific jet and allowing for some cold loading into Canada. That's our source region for cold. 

This will take time but it's likely to happen. Let's look at the same view a little lower in the atmosphere, with an average of 850mb temperatures. It's an absolute furnace relative to normal in Canada, but watch how the warmth is cutoff and erodes over Canada and the US in January. We don't need (and probably don't want) massive cold departures if you're looking for snow. This signal tells me that the window for wintry events will open soon. 

Finally, how does that translate to the surface? Note Canada again. While 850mb temperatures return to near normal, that translates (roughly) to temperatures near 0 degrees F in our cold source location. With an El Nino supplying an active storm track, we should have chances. Will every storm be an all snow bomb? No, that's unlikely even in the best of winters, but it tells us that the window, which was closed most of December, is opening up. 

Good evening from Southern Connecticut Weather!

Another storm is on the way. An unusually strong low pressure system is developing in the Gulf and will develop explosively as it treks north over the next 48 hours. With the current overall upper level pattern, this is going to be one that cuts near or just to our west, bringing more wind and coastal flooding than last weekend, in addition to another high rainfall event. Let's dive in. 

Above: a listing of the current hazards for the region. Unlike last storm, we have more widespread wind headlines and coastal flood warnings for the shoreline, in addition to flood watches for the entire state (not pictured). 

The Overall Setup
As mentioned at the start, a powerful low is developing in the Gulf of Mexico. As it travels north, northern stream energy will get injected into the system, causing rapid deepening of the low. Why aren't we seeing snow with this? There is no high pressure to "block" the storm from cutting to our west and flooding us with warm air. With a further west track likely with this storm, we increase the coastal flooding and wind potential, particularly in southern Connecticut. 

Above: Euro depiction of the storm progression from the Gulf all the way to Canada. With no block, the low center cuts to our west, bringing multiple hazards and an overall stronger storm than last weekend from Sunday through Monday. 

Timing & Impacts

Timing
We expect rain showers to move in as early as tomorrow morning, but kind of like last Sunday we are likely to stay mostly dry through the morning hours. We probably start off as light showers and drizzle after noon that makes the afternoon and evening unpleasant followed by increasing intensity in rain and wind as the storm approaches overnight. Overall, tomorrow morning through noon is a yellow flag for activities (watch the radar) with outdoor activities becoming more messy after gradually. 

The worst of the rain and wind will happen overnight Sunday into Monday morning. Coastal flooding should peak with the Sunday night and Monday high tides, so shoreline folks should watch out for that. 

Rain Impacts
We have flood watches for the state up again, and with the significant rain last Sunday-Monday the flood risk is a little higher. Expect a general rainfall of 2-4" again, with localized flooding alongside river/stream flooding. 

Coastal Flooding
Unlike last storm this one should cut to the west. This brings an onshore flow that will allow for minor to moderate coastal flooding. If you are near the coastline in a vulnerable area, this is something to watch closely tomorrow night through Monday. 

Wind Impacts
Unlike last storm as well, with this one cutting to the west we have a higher chance of strong winds. More mixing of the atmosphere is expected, meaning that we should see higher gusts generally than last week. With high wind watches for New London County and coastal CT, the wind risk just inland of the immediate shoreline (more mixing) means peak wind gusts could be in the damaging range. 

For inland CT, peak wind gusts should top out between 40-50mph. Generally, that's not too bad given the lack of leaves on trees, but isolated to scattered power outages late Sunday into Monday is possible. 

For coastal CT and New London County, peak wind gusts are likely to top out between 50-60mph. This is the high wind watch area. Highest wind gusts would be in eastern and SE CT especially. Here more scattered power outages is possible, especially if we see gusts over 55mph. 

This is not something to panic over, but just be prepared if you're a place that loses power in seasonal wind events. 

Again, peak winds are late Sunday into Monday, most likely 11pm Sunday through 11am Monday followed by a gradual decrease in winds. 

Above: the 3km NAM (high resolution) depicting wind speeds late Sunday through Monday. This is not to be taken verbatim because sometimes we see overmixing with the high res models, but this would probably be a worst case scenario, with high winds well into CT. Some other high resolution guidance is aggressive as well. 

This is something we'll watch, but for now max gusts of 40-50 inland and 50-60 at the coast/New London County works. 

The storm departs Monday afternoon, and then we go into a quiet period. Potentially through Christmas. We'll talk about Christmas after this storm but even though a white Christmas looks unlikely temperatures look seasonable. 

The Dailies
Sunday: Mostly cloudy early with increasing rainfall. Breezy. Rain may be heavy at times late. Highs in the mid to upper 50s. Chance of rain 100%. 

Monday: Rain and wind. Rain will be heavy at times. Highs dropping from the upper 50s. Chance of rain 100%. 

Tuesday: Mostly cloudy early with rain and snow showers possible. Highs in the low to mid 40s. Chance of precipitation 30%.

Wednesday: Partly cloudy with snow showers possible. Highs in the upper 30s to low 40s. Chance of snow 20%. 

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

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

Saturday: Mostly 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.
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-DB​ 

Good evening from Southern Connecticut Weather. 

December is shaping up to be a battle between warmth and cold, with seesawing temperatures so far though broadly warmer than normal. We've been tracking this system for at least a week, and with it poised to impact Connecticut Flood Watches have been issued for the entire state. Let's take a look at this storm system, which now puts snow in the forecast for part of the state. 

Above: the latest National Weather Service (NWS) watches and advisories for the state. For now, we only have a flood watch up for the entire state as heavy rain is expected Sunday into Monday. ​

The Overall Setup
This is worth a separate discussion during an insanely busy work week because we have multiple things we're tracking with this. While the signal for a storm has existed for a while, the details have waffled significantly, from originally showing a weekend washout, to shifting to a late Sunday/Monday system, to what we expect now, a wet Saturday afternoon into Monday with possible snow on the backside in the hills of CT, especially NW CT. 

Essentially, a strong cold front will pass through the eastern US. The extent of the front is quite impressive and will bring colder air, but it isn't an Arctic front by any means. As the front reaches our region, we will see a storm develop along it, enhancing precipitation and wind while bringing heavy rain. As the front and storm pass to our east, we will see decreasing temperatures and possible snow on the backside for elevated areas of the state. 

This is likely to be a significant winter weather event to our north and west, where climatology tends to be a little better for significant enough cold to allow for significant snow this time of year. Ski country rejoice. The timing of the low could even allow for snow all the way down to the DC region, illustrating the potential from this system. 

Above: the latest GFS model run through Sunday and Monday. Saturday continues to look fine, but Sunday now looks wet on balance with rain showers working into the state Sunday afternoon followed by heavy rain during the evening and overnight period. 

Below: the afternoon Euro model depiction. Note that just like the GFS there's a low riding along the front, with snow or mixed precipitation on the backside. Image courtesy of Pivotal Weather. 

Timing & Impacts
As mentioned above, the timing has shifted back and forth.

Timing
Saturday is fine, but we now expect rain to move into the state by Sunday afternoon. It will be light at first, but the wind will pick up and heavy rain will move into the state over the course of the evening. The heaviest rain is likely overnight Sunday into Monday. Rain will taper off Monday morning into afternoon. 

For higher elevation areas, any change to snow would happen on the tail end of the system on Monday. 

Rain Impacts
The impact that we have most confidence in at this time is rainfall. This will likely be a heavy precipitation event,  with the low enhancing the lift along the front. This means expect rainfall on the order of 2-3" on average with some spots possibly seeing higher amounts. This is why we have the flood watches. 

Wind Impacts
Wind is likely to have an impact, but it's a little more uncertain how much wind we get to mix down. A stronger system would likely bring stronger wind. With leaves off most trees, this limits damaging wind potential. There will be a strong jet aloft with high winds, but a temperature inversion will likely keep much of that wind from maximizing wind potential over CT. It'll generally be windy Sunday and Monday, but we're really watching gusts. Currently, we think maximum gusts between 35-45mph occur inland and 40-50mph at the shoreline.

I wouldn't be surprised to see wind advisories hoisted at some point, and scattered power outages. The strongest wind zone currently looks like eastern and SE CT. Stronger winds are expected to be east of Connecticut. 

Snow Impacts
This is where we see the least impact, but it's worth discussing. It'll be warm on Sunday in advance of the front with highs near 60! In the wake of the front however, temperatures will drop and that's where the chance of snow gets introduced for the elevated locations of CT, particularly the NW hills. Accumulating snow looks increasingly likely in NW CT, but should remain a light accumulation on Monday of an inch or two. Other parts of the state (again elevated spots) could see snowflakes Monday with little to no accumulation. 

This remains an uncertain part of the forecast, as a lot depends on what kind of low develops--does it quickly intensify or slowly? Does it track further to our east as moisture is still available allowing for a change to snow as things cool off for more?

For now, the focus is really just the highest elevations of NW CT for a light accumulation. Normally snowfall after a front passing isn't even worth considering as the atmosphere dries out. Here, it's worth a closer eye. The higher resolution guidance, NAM in particular, has been more aggressive getting cold in before the moisture departs in western CT. That is discounted for now.

Above: the 12km NAM with its more aggressive depiction of moisture remaining after the front passes Monday morning. For now that's discounted but we do think snow does fall in NW CT leading to a minor accumulation. 

Overall
Saturday looks fine and much of Sunday will be ok as well despite showers and rain moving into the state in earnest by afternoon. Be prepared for showers late morning given the shift we've seen to earlier rainfall, but the heaviest rain and wind is overnight Sunday into Monday morning. Rain will be heavy at times. 

Winds will be strong, but not terribly out of the ordinary for a strong wintertime system. Scattered power outages are possible. 

The storm will depart Monday afternoon leaving breezy conditions and the seesaw back to colder conditions. 

Finally, we've gotten a lot of questions about snow prospects for the time around Christmas. It's still too early to have a real sense of the pattern around the holiday, but note that on average we do not see a White Christmas. Give it a week before we're in medium range to look at the Christmas pattern. 

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! 

Dry weekends have been hard to come by, and it was no different this weekend with a washout today. The week ahead looks mostly quiet, but there are a couple of systems I'm watching as the week progresses. 

Above: the EPS averaged temperature anomaly for much of our forecast period. After a warm few days to start December, we seesaw this week with dropping temperatures and another potential mild up this coming weekend.

Monday-Tuesday
The storm system that brought us rain and brought snow to much of northern New England will be slow to depart, meaning that we are likely to see additional cloudy conditions tomorrow, though not to the extent of what we saw today obviously with the rain. There may be a spot shower, but tomorrow looks dry. Tuesday looks dry and colder with temperatures closer to normal. Expect a mix of sun and clouds. 

Wednesday-Thursday
The middle of the week is tricky, as colder air filters in and a low develops well to our south. The storm system itself is a miss on Wednesday, but some of the models are signaling an inverted trough--essentially a narrow area where conditions converge for precipitation to fall--somewhere in eastern New England.

For CT, especially eastern CT, that mean that some snow showers are possible. Further east into eastern Mass, some minor accumulations are possible. These are notoriously difficult to predict, but the signal is there. Stay tuned for additional updates if necessary. Temperatures look below normal during this period with highs in the 30s for most. 

Thursday is tricky too, though less so than Thursday. The models try to dive a clipper down from the north, but most guidance says the upper pattern is such that the system is shredded and brings no precipitation. The Euro however tries to keep it together a touch. This is discounted for now, but something for us to just keep an eye on for more rain or snow showers. Thursday is seasonably cold as well. 

Friday-Sunday
The weekend looks unsettled again. While Friday looks fine with temperatures rebounding near normal, all guidance has a big storm developing at some point over the weekend--most likely Sunday at this time--that would bring more rain. For now, I'll keep rain centered on Sunday, but just keep an eye out for potential shifting in guidance to bring in rain earlier or later. 

Above: the 18z GFS depiction of the possible weekend storm. A (rain) storm is coming, but timing remains up in the air. Most likely Sunday at this time. 

The Dailies
Monday: Mostly cloudy with a slight chance of showers. Highs in the upper 40s to low 50s. Chance of rain 10%. 

Tuesday: Partly cloudy and colder. Highs in the low to mid 40s. 

Wednesday: Partly cloudy with a chance of snow showers. Colder. Highs in the upper 30s to low 40s at the shoreline. Chance of snow 20%. 

Thursday: Partly cloudy. Highs in the upper 30s. 

Friday: Mostly sunny and seasonable. Highs in the low to mid 40s. 

Saturday: Mostly cloudy with a chance of showers late. Highs in the low to mid 40s. Chance of rain 30%. 

Sunday: Mostly cloudy with rain. Highs in the mid 40s. Chance of rain 50%. 

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.
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-DB​