Good evening from Southern Connecticut Weather. 

After a cloudy start, today ended up being pretty nice with seasonable conditions. The next few days look fairly quiet but our stormy pattern looks to continue on New Year's Eve and New Year's Day. 

Above: the latest snow totals for the season so far. Note that for both Hartford (BDL) and Bridgeport we are well above normal. 

Tuesday-Wednesday
As I mentioned at the start, the next few days look quiet. Temperatures are looking to be a bit cooler than today. I expect a mostly sunny day on Tuesday, followed by increasing clouds on Wednesday in advance of two waves, the first of which will take aim at the state and give us one final kick as we end 2020. 

Above: GFS depiction of Wave 1. 

Thursday
There's actually not a whole lot to say about Wave 1, which is expected to impact the state on Thursday. This is associated with a quick moving clipper. We're not expecting temperatures to be cold enough for snow on New Year's Eve, so that is good for those that will be on the roads. We're expecting rain, and while showers will be on and off during the day, especially early, we're expecting a minor event at best. 

Friday
New Year's Day however, may be another story. First of all, we're not expecting this storm to be as windy as our Christmas Grinch storm (King Grinch according to this forecaster haha). Second, there's an increasing chance for wintry precipitation on the front end. The image below is of the GFS surface depiction through New Year's Day and early on January 2nd. Note that the timing on the GFS is pretty early, and probably wrong. The preponderance of the other guidance brings the storm in later. 

The first and probably easiest thing to notice is that the model wants to bring mixed precipitation into the state the morning of January 1. Under this verbatim depiction however is an in-situ setup that favors cold air damming (CAD). This is when a cold high to the north allows for colder air to funnel down to the surface even as areas aloft warm. This signal is fairly consistent across guidance. What is also consistent is that the mixed precipitation turns to rain as cold air erodes. This is the case whether the GFS timing is wrong or not.  

At this time, we're expecting a period of sleet or freezing rain Friday afternoon or evening, followed by cold air eroding and a flip to rain overnight and into Saturday. This does not look like a major or particularly significant event, but it doesn't take a lot of icing to cause problems and we are always perked up with a CAD signal as colder air could hang on longer so we will continue to sharpen this forecast. Happy 2021! 

Saturday-Monday
The weekend and start of the first full week of 2021 also looks potentially unsettled. Wave 2 on NYD looks to be a fairly slow mover, so it could take a little time to clear things on Saturday, especially if the storm arrives later than currently expected.

Sunday and Monday there is a signal, albeit weak, for another storm to make a close approach. This one could be a colder system, so it is something we will be watching. At this range however, it could easily be an errant signal from the guidance. Not giving it high odds at this time. 

The Dailies
Tuesday: Mostly sunny and seasonable. Highs in the mid to upper 30s. 

Wednesday: Increasing clouds. Highs in the upper 30s to low 40s. 

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

Friday: Mostly cloudy with mixed precipitation in the PM and evening possible. Highs in the low to mid 30s. Chance of precipitation 60%. 

Saturday: Mostly cloudy with mixed precipitation in the early AM changing to rain. Highs in the mid to upper 30s. Chance of precipitation 70%. 

Sunday: Mostly cloudy with a chance of snow. Highs in the low to mid 30s. Chance of snow 10%. 

Monday: Decreasing clouds. Highs in the low to mid 30s. Chance of snow 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.

Thank you for reading. 
​
-DB​  ​

Disc: As I write this,  a major storm was wrapping up and getting ready to affect the area just at the height of Christmas celebrations across our area.  

Currently: You can call today the calm before the storm, as high pressure was lined up along the I 95 corridor.  Our storm was over IA and MN.

Tonight: Another nice night.  With warm air advection, I'll go a couple degrees warmer than guidance.  Lows should generally be in the 30s.

Tomorrow: Generally increasing clouds.  Not much precip yet.  Although I do have a 30% or so chance of showers for the SW 1/2 of the state starting in mid afternoon, basically W of 91 and S of 84.  Steady rain should hold off everywhere until after dark.  Winds should steadily increase during the day, becoming breezy by afternoon and windy by dark.  Even  if I slice a few degs off temp guidance, highs still get to the mid 50s, so it's a very warm day across the state.

The following NWS hazards are in effect: A flood watch is in effect for Litchfield County.  A High Wind Watch is in effect for: Srn Fairfield, Srn New Haven, and all of Middlesex, New London, Tolland, and Windham Counties.  In between, generally along the I 84 corridor from Danbury to Hartford, no hazards are in effect.  However, these areas will also likely get at least wind advisories and urban flood advisories as the storm unfolds.

Let's go through the hazards.  First, there will not be any more rain in Litchfield County than anywhere else in the state.  The reason for the Flood Watch there and nowhere else is that there is more snowcover there and the ground is frozen.  The warmish weather the past few days has helped us, in that the ground has unfrozen a bit, which should minimize the flooding threat and allow for more runoff.

Winds should gust 55-65 MPH throughout the state from later tomorrow night into early Friday morning.  If we get any thunderstorms (the chance is very low for most of the state, but not zero), even higher gusts could get mixed down.  Up in Litchfield County, if they can retain snowcover, the wind risk will be quite a bit lower, because the snowcover would create a low-level temp inversion, which would significantly lower the wind risk.

Rainfall amounts should be a solid two to three inches.  I am using a small range, because there is really very good agreement amongst the models.  In fact, when comparing the GFS to the NBM, the total is nearly exactly the same.  When agreement is that good, you have to ride it.

So, to summarize, a very high-impact storm is set to impact the area.  Widespread power outages and travel difficulties are expected and unfortunately, this is going to hit at a very inpportune time.  But at least Santa will get a fast ride back to the North Pole on those southerly winds!

Temperatures tomorrow night will not move very much at all, and may even rise a bit before beginning to fall before dawn.  This all depends on the timing of first the warm front and then the cold front.   Needless to say, I went well above temp guidance for tomorrow night's temps.

For Friday, Christmas Day, cold air will pour into the area, on gusty, but lighter NW winds.  There is also the chance of a flurry or maybe even briefly heavier snow squall, as a combination of unstable air aloft, strong cold air advection, and streamers from the lakes, generate a possibility of some snow showers making it down to our area.  As usual, the most favored areas are the NW hills.  Went below guidance by as much as 10 degrees for temps, since highs will be in the morning, and temps fall, possibly rapidly, thru the day.  Look for temps to fall into the 30s during the day.

Long Term:  A fairly quiet period here.  Of course, the next major storm probably affects the state right in time for New Years celebrations, but we'll leave that out of the fcst, since it's more than 7 days out, and let later crews refine that, as we go along in time.

For the weekend after Christmas, I chopped a couple deg off temp guidance for Sat, since there will still be good cold air advection in place.  Highs should only be in the low 30s, despite a good deal of sun.

I went close to temp guidance for Sun, as advection is nearly zero.  Clouds should increase ahead of the next sys, which right now does not look to be a big deal.  It looks to be a clipper passing to our N, with either no or very late coastal development.  But we'll keep an eye on it, just in case things change.  As far as Sunday, it's a fairly nice day, albeit chilly, with highs in the mid to upper 30s.

Now for that next system, I already pretty much covered its evolution.  Right now, it looks like a quick burst of mostly light precip centered around midday Mon, maybe lingering into the aftn across far NE CT.  It also looks like it should be all rain, but soundings are close, and some sleet could mix in far N.  We'll keep an eye on it in case it trends colder.  I chopped a few deg off temp guidance with clouds and light precip, but even so, highs reach the low 40s, so most likely looking at all rain.

For Tuesday, fair and cold.  I went a few deg below temp guidance, with more cold air advection.  Despite sun, highs only 30-35.

For Wed, continued cold, with increasing clouds ahead of the next sys.  Highs in the low 30s.

Long Range: Not a lot of time to spend on this section today, but the pattern continues cold and stormy with lots of high-latitude blocking.  It's hard not to like that pattern if you like wintry wx!

Now, let's take a graphical look at some systems that will affect the area this week.  I'll focus on tomorrow's system and a brief map of our clipper for Monday. On this map, valid midnight tomorrow night, you can see the very heavy moisture headed for CT.  Underneath that moisture is where the high winds and dangerous wx will be colocated.

​

Finally, on this map, valid midday Monday, you can see a clipper low going thru Srn Canada.  Clipper lows w/no coastal redevelopment passing N of the area typically do not produce much winter wx here and this does not look to be an exception to the rule!

Anyway, that's all for now! I'll see you next week! Merry Christmas and Happy Holidays!

​-GP!

Good evening from Southern Connecticut Weather. 

Last week it was a major snowstorm, but this week we may be looking at an even higher impact event. As it stands there is significant potential in a multi-hazard weather event on Christmas Eve and Christmas Day. There is still a fair amount of uncertainty, but confidence is increasing. 

Above: GFS depiction of Christmas morning in CT. Heavy rain has been a unanimous signal across guidance so we have high confidence in a significant rain event. What you don't see here, and is less clear, is what the wind will do. 

Overall Progression
The overall progression that I discussed a few days ago hasn't changed much. A powerful storm is expected to develop to our west in a highly amplified pattern. A powerful cold front is expected to push through the state. As that occurs, a strong wave of low pressure will develop and ride the front, bringing heavy rain, strong winds, and warm temperatures to the state. The timing of the passage has slowed down, meaning that while a good portion of Christmas Eve morning and afternoon look ok, Christmas Eve night and much of Christmas Day now look awful. I use the word awful intentionally.

This period will see strong winds, heavy rain, and with high dew points a rapidly melting snow pack that will increase the chances of localized flooding. If your basement floods frequently, get ready to possibly deal with that on Christmas morning. All of that will be followed with rapidly dropping temperatures and possible icy conditions by Christmas night. 

The worst of the rain should exit by early afternoon according to current guidance, but we will be dealing with strong to damaging winds that will make outdoor activities difficult if not impossible. In addition, once the front passes temperatures will begin to drop. While we're not expecting a flash freeze, this is something that we'll be watching closely in case the ending precipitation and dropping temperatures are more closely tied. 

​Let's look at specific impacts. 

Wind Potential
High Wind Watches have been issued for SE CT, and I expect this to be expanded to the rest of Connecticut eventually. This is the most impactful part of the forecast and most uncertain item at this time. The two images above show why. 

Above and to the left you will find a GFS averaged sounding during Christmas Day in central CT. It's a small image here but what you will notice is just off the ground there are very strong winds inland. Not all of this will "mix" to the ground, but I think enough will right now to cause significant issues. One possible saving grace would be an inversion and weaker lapse rates that prevent mixing. 

Above and to the right is a Euro model depiction of 925mb winds on Christmas Day. Again, not all of this will mix to the surface but the image itself is a signal of a robust storm and low level jet that signals a damaging wind threat.  

As it stands, I think we're looking at a moderate statewide wind event that but could become high end should some of the signals we see become stronger. 

Unlike some of the other events where strongest winds are isolated at the shoreline, I think the potential exists across the state, though not every town will see high end wind gusts.

At this time I think maximum wind gusts will vary between 45 mph--strong but not terribly damaging, and 65 mph--which would be much worse. We're not at the stage where we're able to pinpoint with confidence which areas of the state could be near the higher end of that range. 

Those gusts would likely be focused on Christmas morning and early afternoon, diminishing during the latter part of the day but remaining fairly strong.

If these winds verify, we can expect scattered to widespread power outages on Christmas Day due to tree damage. 

Heavy Rain/Flooding
As I said earlier in the discussion, there is much higher confidence in a heavy rain event than a high end wind event. The image above also comes from today's European model, and it shows a very impressive swath of rainfall across the state. This is a signal that exists across guidance.

​Right now we are looking at a statewide 1.5-3" rainfall range. 

Maybe some of that precipitation is overdone, but in advance of the cold front we're also going to see higher dew points that will obliterate the snow pack from last week's storm. What this means is that moisture will be released as well in the form of water runoff. Combined with heavy rain Thursday night/Friday morning, localized flooding in the form of basement trouble, small stream flooding, and road ponding is likely.

River flooding looks less likely at this time, especially among the big rivers, but that's something to watch as well in the days after the event. 

Crashing Temperatures/Flash Freeze
This is looking like the least likely threat at this time as we see a longer lag time between the end of precipitation Friday afternoon and temperatures falling below freezing. It's something to watch I suppose, but the cold really looks to be in place Saturday.

That said, folks will need to watch out for some black ice Christmas night. If you see ponding or wet conditions on your walkway/driveway later in the day you will likely want to salt. While some of the guidance wants to bring in some snow showers Christmas Day, don't hold your breath. This may very well be the king of Grinch storms. 

Overall
We're looking at a potential high impact event. Wind is the biggest threat but the details still need to be worked out. Heavy rain is likely to cause some flooding and make outdoor activities much of Christmas Day difficult. After the storm passes, we head back to the cold. At least for the weekend. 

We will be fine tuning the forecast as we get closer. The signal for this one looks legitimate. Be prepared. 

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 afternoon from Southern Connecticut Weather. 

Connecticut has been in a deep freeze most of the past week. The week ahead brings a gradual warm up until we have what has seemingly become our annual Christmas (or thereabouts) torch. The forecast is a touch complicated so let's dive right in. 

Above: an 11:20am radar image showing precipitation beginning to edge into the state. Today should bring snow shower (and rain shower at the shoreline) chances. No significant accumulation is expected. 

Today
Just briefly about today. As you can see above, some precipitation is expected to cross Connecticut today. For inland areas, temperatures remain cold enough where snow is possible. It's expected to be light. For southern areas, some snowflakes are possible, but it's also possible that far southern sections of the state only see rain showers. We're not expecting any significant accumulation (maybe a coating in spots) but be careful on the roads. It doesn't take much to cause problems. 

Monday-Wednesday
The first part of the week is actually looking quite quiet. Tomorrow a storm system will pass well to our SE, meaning we will see clouds but nothing in terms of precipitation. The only exception may be far SE CT but even there I'm not expecting anything unless the storm tracks a bit more northwest. Tuesday looks a little better but there may be some snow flurries in the air in NW CT. Not expecting anything meaningful there. Wednesday looks quiet in advance of Christmas Eve and Christmas, where we have a strong signal for a significant storm passing through the region. 

Temperatures during this period look a bit warmer than last week, but still fairly chilly with highs in the 30s and low 40s. 

Above: 12z GFS depiction of Thursday and Friday. Note that the GFS is an outlier here, with a faster storm passage. 

Christmas Eve (Thursday)-Christmas Day (Friday)
I am going to declare this a SCW Period of Interest, but not because of snow. As you can see above, the GFS wants to push through a cold front during this period. Looking deeper, this is a strong cold front associated with a strong storm that is expected to pass to our west. What does that mean? It means the White Christmas that many look for is in jeopardy. 

Other guidance is much slower with the frontal passage, bringing heavy rain on Christmas Day. What all the models agree on though is that a period of heavy rain and warm temperatures for this time of year will move through Connecticut during the Thursday/Friday timeframe. Right now, it looks like the heaviest rain will happen Christmas Eve night but timing is critical and uncertain here. With so much snow on the ground, heavy rain and rapidly melting snow could cause flooding issues on Christmas.

In addition, this front is also likely to come with strong winds. We're seeing a damaging wind signal, but for now we think an inversion keeps the strongest winds from mixing down at the surface. We have to get closer to the event to better understand the wind potential, but it's a legitimate signal even at this range. 

Temperatures will be warm. Expect highs in advance of the front in the 50s followed by a sharp drop in temperatures after the front passes--another reason why timing is so important. For snow lovers, the only hope is that there's some moisture left over after the front passes to allow for some snow to fall late on Christmas. There's a chance of that, but at this moment in time I wouldn't hold my breath. Cold chasing precipitation isn't a recipe for success.  

Below is the latest Canadian model depiction for the period. It looks like an ugly Christmas in Connecticut. 

Saturday-Sunday
After the front passes, we get cold and quiet again. Temperatures may struggle to reach freezing again, with some snow showers possible, especially on Saturday. At this time, I am not expecting any significant travel issues in the region. 

The Dailies
Monday: Mostly cloudy with a slight chance of showers in far SE CT. Highs in the upper 30s to low 40s. Chance of showers 10%. 

Tuesday: Partly cloudy with a chance of flurries in NW CT. Highs in the upper 30s to low 40s. Chance of flurries 10%. 

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

Christmas Eve: SCW Period of Interest. Increasing clouds with a chance of rain late. Breezy. Highs in the low to mid 50s. Chance of rain 50%. 

Christmas Day: SCW Period of Interest. Heavy rain and strong winds. Highs in the low to mid 50s followed with a sharp temperature drop after the front and a chance of snow showers. Chance of rain 60%. Chance of snow showers 10%. 

Saturday: Decreasing clouds and cold. Breezy with snow showers possible. Highs in the upper 20s to low 30s. Chance of snow showers 20%. 

Sunday: Mostly sunny and cold. Highs in the upper 20s to low 30s. 

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. 

What a week! After a minor appetizer at the start, the major winter storm that we had been seemingly tracking forever impacted our state on Wednesday and Thursday. For many, it was the largest snowfall since March 2018. Now that the storm has passed and we have had time to breathe, it's time to post our grade. 

Our verification map using NWS spotter reports. Note that the locations are approximate. 

As you know, we grade ourselves to get better and hold ourselves accountable. For this storm, we are using the following criteria from our final forecast: snowfall accumulation, timing, wind, power outages, and overall impact.

​For this storm (and perhaps moving forward) I decided to weigh the snowfall accumulation twice as much as the other elements. I think this may be a bit more fair given this is what the general public cares about the most. Let's dive in. 

Snowfall Accumulation
As the map above shows, we decided to go pretty big with out snow accumulation forecast. We upped our numbers from our original forecast of 8-16" and with the benefit of hindsight, that didn't work out. That said, it wasn't a surprise that some areas inland received less snow, as we communicated that the banding nature of the storm could bring some variation in snow totals. We did particularly well with our SE zone forecast, and did ok with our inland forecast with a number of towns ending up at the 12" mark.

However, there was a bit too much variation with dry slotting and a real surprise to us with far SW CT doing poorly relative to the rest of the state due to the combination of dry slotting and mixing with sleet. I'm a little disappointed personally since it was my call to take the numbers up, but it wasn't a disaster. 

Grade: B-

​Timing
We did well here. We expected snow to break out late afternoon and early evening and that's what happened. SA noted that heavy snow would would cross the state in the evening hours and that was right with the first big band that rolled through the state shortly after our call for snow for everyone after 8-9pm. We were right on the snow banding after midnight, and the burst of moderate to heavy snow early Thursday. Great job here. 

Grade: A

Wind
Despite some of the guidance trying to bring blizzard conditions and high winds, we were confident that we would not verify blizzard conditions and wind would be relative pedestrian. We thought 35-45 mph would be the max gust along the shoreline and both Bridgeport and Groton gusted to 47 mph. To be within 2 mph is an excellent call.  

Grade: A 

Power Outages 
Not much to say here. We didn't expect widespread power outages due to the snow being lighter (it was in most places but not everywhere which I'll get to below) and there being less wind. There were no major power issues from what I saw. 

Grade: A 

Overall Impact
We did end up seeing a major winter storm. This was a high impact event despite the timing. Most places saw double digit snowfalls, as we expected, and conditions were hazardous Wednesday night and Thursday morning, as expected.

However, we need to deduct points for the under forecast of mixing. We were fine in northern CT and much of inland CT, but more areas along the shoreline mixed than expected, which caused heavier wetter snow to fall. For anyone that expected to shovel powder but ended up shoveling concrete, that's a meaningful forecast miss. 

Grade: B+

Overall Grade
Overall, we did very well. The snowfall forecast was off for too many in SW CT, but it wasn't a bad forecast. We were spot on for many of the other elements, and while we under forecast the mixing in coastal CT, it could have been a lot worse. Factoring all the elements in and weighing the snow accumulation forecast 2x, we did well. That's important, because reputations are build on the high impact forecasts. 

Final Grade: B+

Above, the final result. Snow across New England as a result of our major 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 trusting SCW. 
​
-DB​