Good evening from Southern Connecticut Weather!

Let’s get right down to business—the next few days will be ugly. From shower chances, to impressive cold for this time of year, to snow chances, the next seven days look to be…stormy. A series of cold fronts and clipper like systems will bring us continuing chances for rain and snow showers, and a clipper next week may be another period of interest. To be clear, at this time I do not anticipate a widespread and significant winter weather event for Connecticut. 

Friday
​Friday looks to be the first of what will be many unsettled days in the next week, as a low pressure system well to the north and its attendant cold front pushes through the region. Showers will be possible all day long, and some isolated thunderstorms are even possible. With the cold front approaching, it will be a relatively warm day with highs likely to reach the low to mid 60s. Although not a washout, it’s still a shame that many will be carrying umbrellas during the day. Like we’ve seen the last few days—expect a breezy day. 

Saturday
Saturday the changes really begin to take shape in Connecticut. As the cold front passes and stalls to the southeast of the region, the chance of showers will remain. Again, not a washout, but with cooler temperatures as cold air advects in, it will probably be a worse day than Friday. 

Sunday
Saturday night into Sunday is probably the most intriguing period for me, honestly. As the cold air rushes in Saturday evening there is a chance that the showers in the area turn to snow, and there looks to be enough instability and sufficient lift to open the door for a period of snow squalls. Timing is a bit uncertain right now, but I am looking at the overnight/early morning period. 
​
Sunday morning the first of two clipper systems looks to approach from the west. As I mentioned earlier this season, clippers are not known for dropping large amounts of precipitation. It will be windy with a winter like chill in the air, and the chances for snow showers during the day could add to those looking for one last look at true wintry appeal in early April. I don’t anticipate there being a widespread or significant snow event out of this, however.

Above you see the 18z GFS simulation of the surface weather and temperatures. In the second image in particular, it is easy to track the cold air filtering into the state as the weekend progresses. It will be seasonably cool at first and then impressive cold arrives by late weekend and early next week. I'm not sold on us getting as cold as this particular simulation suggests, but the overall progression of features at the surface is consistent with other guidance. 

Monday/Tuesday
​Monday and Tuesday? You guessed it—chilly with the chance of rain and snow. Here, we see another weak area of low pressure approach from the west, and with cold air in place, we could see another period of snow. Currently, the track of the low does not look ideal for a snow event, let alone the fact that temperatures may be marginal at the surface, which is a killer for significant accumulating snow in April. The period is something worth watching casually, but I currently lead to a minor to nonevent.  

Above you will see the GFS ensembles looking at the upper levels of the atmosphere. At 500mb, you see the transition to a deep trough over the weekend and lower heights, signaling a potentially unsettled and colder than normal period. By Monday and Tuesday, notice the dip in isobars over the region. This is another signal for a period of unsettled weather, and with a better orientation, you see perhaps a better track with would open the door for a wintry event. Still not great, however. 

Wednesday
Wednesday looks nice! With the prior system departing and high pressure potentially building in,  we should see a decent day with sun! Although we are still likely below normal in terms of high temperatures, seeing nicer weather will feel good to many!

Thursday
As Thursday rolls around, we see another system approaching. This far out, timing is not something worth discussing much, but the chance of rain exists—especially in the evening hours. 

The dailies:
Friday: Showers with a chance of thunderstorms. Seasonably warm as the cold front approaches. Breezy. Highs in the low to mid 60s, but dropping quickly by evening. Chance of rain 80%.

Saturday: Mostly cloudy with a lingering chance of showers early, transitioning to a chance of snow showers or squalls by evening. Snow squalls could produce a quick coating of snow. Cooler with highs in the low to mid 50s, with lows falling near freezing overnight. Chance of precipitation 40% early and 60% late. 

Sunday: Chance of snow showers and squalls early, becoming mostly cloudy with a chance of snow showers. Highs in the lower to mid 30s. Chance of snow 50%

Monday: Chance of rain and snow, otherwise, mostly cloudy. Highs in the lower to mid 40s. Chance of rain 60%. Chance of snow 30%.

Tuesday: Chance of snow early, transitioning to sunnier conditions as the day progresses. Highs in the upper 30s to lower 40s. Chance of snow 40%. 

Wednesday: Sunny with highs in the upper 40s. ​

Thursday: Sunny early with an increasing chance of rain late. Highs in the mid 50s. Chance of rain 20%. 

Thank you for reading SCW!

-DB

The upcoming weather pattern will feature rapidly changing weather and could feature some wintry surprises.  First off, it was a windy and quite cool day today, as it felt cooler than it was, due to gusty winds.

Tonight: Winds diminish.  Clear skies and calm winds should allow for good radiational cooling conditions.  Temperatures should fall below freezing everywhere in the state, with lows ranging from the low 20s in the colder spots to near 30 along the south coast.

Tomorrow: Lots of sunshine, very low relative humidity, and nearly calm winds should allow temperatures to skyrocket under the strong late March sun.  Despite the cold start, afternoon highs should make it into the low to mid 50s.  The south coast, especially east of I 91, may stay in the 40s, due to an afternoon sea breeze.

Tomorrow Night and Thursday: Clouds increase ahead of the next system, but will keep this period dry.  It appears all the precipitation associated with a storm passing to the west of the state should stay to our west during both periods.  With increasing cloudiness and some warm air advection, temperatures will not be nearly as cold tomorrow night.  There also won't be as much variation, with radiational cooling not being much of a factor.  Low temperatures should range from the upper 30s to the low 40s.  Thursday will be much warmer ahead of the storm, but there will be two possible inhibiting factors: First, the clouds.  Depending on how cloudy it gets and how fast, temperatures may not rise as much as models indicate.  The second factor will be southerly flow.  I'm hesitant to call this a sea breeze, because a sea breeze means a wind off the water because of a temperature difference between the land and the water.  This will be an onshore flow because of the flow around the storm.  At any rate, the net effect is the same- cooler temperatures near the water.  Because of these two factors, I'm hesitant to go too warm on temperatures, especially right along the south coast.  For now, high temperatures struggle to make it to 60 along the south coast, and get to the mid 60s further inland.  

Long term- the weekend and beyond: First, it looks like we're in for about a 24-hour period of rain chances, although it likely won't rain all the time.  The highest chance of rain will occur Friday afternoon.  It is not totally out of question for a rumble of thunder to accompany the rain away from the coast, but any stronger thunderstorms will remain well south and west of the state.  The winds will turn more westerly on Friday, so high temperatures will get into the mid 60s throughout the state.

On Saturday, the main issue will be the passage of an Arctic cold front.  Right now, it appears this frontal passage will be at night.  So temperatures will still have a chance to rise during the day.  High temperatures should be in the mid 50s.  At night, a very strong cold front approaches.  A big issue with this front will be the wind.  Similar to last night, winds will increase abruptly as this front approaches.  Winds could be even stronger this time around, since the upper level jet streak is actually stronger this time.  This will need to be monitored in subsequent packages.  A burst of showers and squalls will probably also accompany this frontal passage.  These showers will start as rain and could change to snow all the way to the coast, but no accumulations are expected.

On Sunday, strong winds will continue throughout the day, with a very tight pressure gradient behind the frontal passage.  Temperatures will be significantly cooler.  For now, I'll forecast high temperatures ranging from the upper 30s to the mid 40s, but these could even trend colder as we get closer! Low temperatures Sunday night will likely fall into the teens and 20s throughout the state.

The next issue is a potential coastal low, which could affect the state later Monday into Tuesday.  Believe it or not, thermal profiles will probably be cold enough for snow all the way to the coast at the start and end of the event, since there will be Arctic air before the storm and another shot of Arctic air arriving after the storm pulls out.  The main issue, as usual, will be the track of the storm.  The latest European model takes the storm so far south that the state sees no precipitation.  The GFS model takes the storm inland over New Jersey in a WSW to ENE track.  That would be a mainly rain event at least south of I 84, with some snow possible at the start and end of the storm.  North of I 84 could see mostly snow in this setup.  Keep in mind, it is very difficult to pull off a significant snow storm in April.  The Arctic air is real and that is the easier part of the forecast.  In the middle of winter, a lot of things can go wrong that can prevent a significant snowstorm.  In April, even more things can go wrong.  However, there have been significant snowstorms in April before, and there will be more in the future.  Whether or not this will be one of those times is yet to be determined.  Here are a few maps to put this forecast into a graphical perspective.

Here is the GFS' wind profile for Saturday night, valid at 7 PM.  This may not be the best frame to look at, as the core of the winds will probably pass over the state around 10 PM, but that frame is inaccessible, so this one will have to do.

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Next, here is a look at the GFS' depiction of the potential coastal low, valid Tuesday morning.
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On that frame, it is probably snowing, but rain is knocking on the door.  Keep in mind, however, that the ECMWF (European) model is so far south, no precipitation even makes it into Connecticut.  The GGEM (Canadian) model is in between and brushes South of I 84 with some snow, but that would be an all-snow scenario.
Anyway, that's all for now, have a good evening!
-GP!
​

There has been a lot of talk about the complexity of our latest winter weather event, and now that the snow has fallen (and melted) it is time to look at the maps. Before I continue, I would like to note something important: we do our best, just like many other forecasters at other outlets. We try to provide you with the best information as quickly as possible, and we try to do it without adding additional hype. That is our model, and it will not change. 

We will not always be right. This time, we missed much of Tolland County and far southeast Connecticut.

​Even when we are mostly right, we will have areas that overperform and underperform. That's the business. In a field where there is inherent unpredictability and where small scale features can literally impact one area of a town and not another, we try to hone in on the possibilities as fast as possible to give you a heads up. 

At the same time, we don't want to be guided solely by models. The data they provide is essential to forecasters, but if we flip flopped like the models did every six hours with this latest event, that wouldn't be terribly difficult either. 

Let's look at the map. White numbers mean that they were correct for our forecast zone. Black numbers indicate where we were wrong. I used member submissions and National Weather Service observations. I tried to include as much data as I could. 

SCW Final Map/Verification

In this case, I won't grade our performance. I will leave that to you. 

By our count, 50 of the 66 reports, or 75.7% fell within our zones. 

62 of the 66 reports, or 93.9% were accurate to within one inch. 
​
I want perfection every single time. When I fall short of that, I like to go back to the drawing board and learn from my mistakes. My colleagues at SCW are no different. As we head into spring, we will continue to get better, and we will continue our commitment to

1) Get the forecast right
2) Communicate that forecast effectively and quickly, and
3) Do it without unnecessary hype  

We will continue to shoot straight, give you insight into how we make our forecasts, and provide you the quality information that has allowed us to grow from a small group to over 15,000 followers. 

The week ahead
The week ahead looks less exciting than the last few days. Tomorrow should be a beautiful day, with sunny skies and highs near 50. Tuesday night and early Wednesday we deal with a few showers in the area, but Wednesday actually looks pretty nice with highs in the low 60s clearing skies. Unfortunately, that will not last long, as both Thursday and Friday look to be cool days with shower chances. We should have a full forecast out by the middle of the week.

Thank you for reading SCW!

​-DB

​A quick venting session:
 
In the close to ten years that I’ve been forecasting, I can’t remember a winter that has had as many variations in the modeling as this one. In most winters, the forecast progression goes something like this:

• 5-7 days out: Identify a storm chance
• 3-5 days out: Confirm the reality of the system; start narrowing the goalposts as to where it will form and impacts.
• 72-48 hours: Last chance for significant shifts, if models remain consistent, begin discussing preliminary accumulations
• 48-24 hours: First call maps, subtle shifts in temperature or placement, last few details are worked out.
• 24-0 hours: Final call maps, minor trends towards stronger/weaker systems, verification.

In this winter, here’s what most of our storms have looked like:

• 5-7 days out: Identify a storm chance.
• 3-5 days out: Build an excellent consensus for either a big hit or a miss, only to have it promptly swing back the other direction.
• 72-48 hours out: Models agree on a miss, and forecasters begin to downplay the event.
• 48-36 hours out: A strong northwest trend happens and the storm comes back.
• 36-24 hours out: We’re almost back to the original idea from 5 days out.
• 24-12 hours out: The storm goes southeast, then northwest again, then back southeast, and now looks like a much more insignificant event.
• 12-0 hours out: Model discontinuity continues to be all over the map, verification occurs and an unmodeled band forms somewhere and jackpots a portion of the state that no one was expecting.
• Constantly: A general sense of chaos, uncertainty, and diminished confidence, leading to this forecaster pulling his hair out.

 
The question that you’re probably asking yourself is: Why? Unfortunately, I don’t know the answer. I can take a guess or two(Which will be the subject of a later piece), but there’s no concrete explanation for it. Regardless, we have to work with the cards that we’re dealt, and as such, we go into another event with little idea of what is actually going to happen.
 
Continuing what Don showed us last night, here’s the next 3 runs of the RGEM(I can’t continue to show the GFS as it hasn’t run yet at 12z due to technical difficulties): 0z, 6z, and 12z. This sort of discontinuity is what you’d usually expect to see at 3-4 days before a storm develops, not a few hours, and that’s been the pattern all winter.

What we do know:
 

• There is still a storm system that is approaching the area, and will pass near the 40/70 benchmark later tonight or early tomorrow morning.
• Some snowfall is expected across the area, with the highest totals in the eastern portion of the state, and the lowest in the northwest corner.
• Timing has been pushed back, with steady snow not reaching the state until after midnight, and lasting into the morning rush tomorrow in eastern areas.
• Generally, the model trend over the 0z and 12z cycles has been deamplification and lessening of the impact, however, some guidance continues to push west with each run.
• The short-range guidance has continued to be bullish with each run.

What we don’t know

• Exactly how much snow will fall. 12z guidance has generally cut back on amounts, however, there still remains a wide range of totals, from the SREFS, NAM and ICON showing warning level amounts across most of the state to the GGEM and RGEM showing no more than a couple of inches in eastern areas and little to nothing elsewhere.
• Where any bands may form: With the midlevel frontogenesis that is modeled, it is likely that there will be a surprise band or two of heavier snow that will allow whoever gets under it to jackpot. Modeling can and does give us an idea of where those bands may develop, hence the favoring of the eastern portions of the state, however, one could argue for them to develop just about anywhere in the state.
• What the impact to Monday will look like: With the less intense solutions, impacts to the Monday morning commute as well as school closings and delays will be relatively minor. However, with a solution like the one on the ICON or NAM, we’ll see a significant impact to the commute and widespread school cancellations.

 
Here’s total precipitation on the ICON(Most bullish model) and on the RGEM(Least bullish model). The difference, especially in eastern areas where it would mean 3” vs. 10”, is pretty remarkable for the lead time.

What we think we know.
A look into my thought process while making the below map("Behind the scenes", so to speak):

• Trends this winter have been for events to look like they are going to miss, then come back west at the last minute and verify a little further NW than model progs.
• Guidance has been all over the map, but the general idea has been east, west, east, west, east... essentially alternating back and forth each model cycle. That suggests take the middle.
• Despite total precipitation being all over the map, midlevels haven’t really changed that much. So small large-scale shifts lead to major shifts in outcome on the ground.
• ICON has lead the way with west shifts on our other two systems like this one, but it’s a total outlier.
• UKMET is east and was other leading model on the previous two systems.
• There’s going to be a band somewhere that modeling doesn’t usually forecast well, probably over eastern areas of the state since it’s been NW of consensus all season and consensus is in the Boston to Providence corridor right now.
• The RAP is very bullish and continues to be. Maybe an initialization error with the 12z data and RAP excludes that since it initializes hourly?

Putting all these thoughts and more together on paper gets us something like this:

Essentially, we scaled down totals slightly across the state, going from slightly below the guidance consensus to slightly above it. I think that the east trend that we’re seeing now will reverse itself somewhat later today as each previous model cycle has done, and I think that we will see banding develop that will allow for most areas to reach an advisory criteria snowfall, but warning criteria amounts will be limited. The best chance for any 6”+ totals will be in the current 3-6” zone, but I think they will generally be isolated.
 
Precipitation will start after midnight from south to north, and will taper off west to east throughout the morning commute. I do expect the morning commute to be impacted in eastern areas, especially in the I395 corridor, and also expect some cancellations and/or delays in that area. Further west, some delays are possible, but I think that, as things stand now, cancellations are unlikely.
 
We’ll keep watching the midday and afternoon guidance, and will be back later tonight on Facebook with some commentary on the trends. Until then, enjoy this final day of winter and thank you for continuing to trust SCW for the very best in Connecticut weather!
-SA

Good evening from Southern Connecticut Weather!

As many of us make final preparations to watch our beloved UConn Huskies take on the #1 Kansas Jayhawks, we continue to watch a very tricky winter weather event take shape to our south. 

When I wrote our morning update today, I noted that the overnight and morning guidance had shifted east, making the potential late season winter storm far less impactful event for much of the state. If you pay attention to other weather outlets, some took it a step further, slashing snow totals after those runs. ​

Essentially, as soon as everyone hoisted the red flags on this event, all the guidance trended toward a more significant event. Fun times. Here’s the latest.

I expect watches/warnings/advisories to be expanded overnight and tomorrow morning. 

The basics remain the same—we are looking at a wave of low pressure riding up the coast tomorrow into Monday, and keeping a close eye on the strength of the low, the low track, and how the midlevel development of the system contributes to the expanse and intensity of precipitation over our region. 

The Models
If there was ever a time where you needed to blend guidance and use your own judgment to make a forecast, this is it. Relying solely on guidance in this instance, where there are almost wild swings from suite to suite, is a recipe for disaster. Here, I’m just hoping for a semblance of consistency within a given model and across all models. Looking at the latest data, I am more confident in a significant event taking place across most of Connecticut. Let’s take a look at the morning (06z), afternoon (12z) and evening (18z) GFS. This model has been the least bullish of an event so far. 

06z GFS simulation above. 

12z GFS

With each run, the 500mb progression is better, and with a sharper trough the low comes in more amplified, resulting with a further northwest extent of significant precipitation.  

So why are we keeping the map the same if data is showing a more robust system?

Given the volatility of the guidance, we made a good call keeping our map where it was this morning. Even with guidance showing a higher impact event currently, taking numbers up or down doesn’t make much sense, as our map remains the most likely outcome right now. ​

I will say however, that this map likely represents a floor of the event’s potential rather than a ceiling. We are not far from forecasting a major (6+) event for a substantial part of the state.

​Although we have seen events trend weaker and further east this winter, we have also seen events trend stronger and further northwest in the very short range. With the afternoon “trend” I think there is a reasonable chance that stronger and northwest trend happens here now. If that is the case, we have enough time to issue another map tomorrow. If things trend weaker overnight, our map likely remains valid. We’re staying the course.

Timing 
The timing looks more or less on track. Very light snow may occur tomorrow afternoon, but I currently expect snow to overspread the state from south to north between 6pm and 11pm tomorrow evening.
As the temperatures drop below freezing statewide overnight Sunday into Monday morning, I expect moderate to significant impacts on the roads, especially in hill locations (which will be colder) and eastern areas (where heavier precipitation is more likely). 

Moderate snow, with some heavier bands will continue throughout the overnight hours into Monday morning, and the storm should be pulling away by early Monday afternoon. Depending on the timing, I expect more of a travel impact on Monday than originally expected.
Bottom line

• Moderate confidence in a moderate snowfall for most of the state, with plowable amounts likely across in all but the far northwest corner of the state.
• Difficult travel late Sunday evening into Monday morning is likely as temperatures drop below freezing 
• Some flight delays Sunday evening through Monday are possible from Hartford and New Haven, as well as NYC airports and Boston.
• School closings and delays on Monday are possible, but far from certain.
  ​

We will continue to watch the trends overnight and will have another full discussion tomorrow morning or early afternoon. At this time, I think many Sunday activities can continue without interruption, but stay tuned in case there are changes with timing and our overall outlook on this late season winter weather event. 

Please like, share, ask questions and follow us on Facebook and Twitter @SouthernCTWX. Thank you and GO HUSKIES!!!

-DB