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Snowmap and Discussion for 1/31/2017 Clipper

1/30/2017

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Good evening to you from Southern Connecticut Weather!
 
As Don talked about last night, we’ve got a light snow event on our hands for tomorrow, with the core of the snow focused around the evening commute. An Alberta Clipper dives south out of Canada and across the Northeast before redeveloping as an inverted trough just offshore of eastern New England. While significant totals are not expected, there is good lift in place and snow ratios will be fairly high, and so while rates will be fairly light, we should be able to stack up a couple inches of fluff for most of the state.
 
Models and Trends
 
Guidance is in excellent agreement with the overall track of the event. The clipper system comes down through the lakes overnight tonight into tomorrow, reaching the south coast by early afternoon. As the area of best lift works its way northward, expect snow to move steadily north throughout the afternoon, with snow across most of the state in time for the evening commute.
 
The system then redevelops off the coastline and spawns a weak inverted trough, moving the area of precipitation north a bit. Snow will likely taper off in southern areas later tomorrow evening, but further north, depending on the eventual orientation of the trough, light snow could persist through the overnight and possibly into the morning commute on Wednesday before tapering off.
 
As far as QPF goes, generally, it looks like between a tenth and a quarter of an inch of QPF will fall with the initial clipper, with the higher end of that range likely reserved for areas where the best banding forms.  The American models along with the UKMET are a little more bullish than the rest of the foreign guidance, but the general consensus is strong.
 
Here’s a look at the 18z NAM, representing the stronger end of the model spectrum, and the 12z GGEM, representing the weaker end, as well as the NAM later on tomorrow night to show the inverted trough - notice the enhanced area of echoes in northeast MA there.
While we saw a fairly strong trend yesterday to strengthen the system a bit, today’s trends have been a bit murkier, with the various models bouncing around a bit but generally remaining consistent when a consensus blend is taken. As such, confidence levels are fairly high with the clipper portion of the system. With the IVT, confidence is lower, as they are notoriously fickle and difficult to model. The general rule is that they will often verify a bit north and east of where the models place them, which would take northern portions of our forecast area out of the target area, but some rules are made to be broken, and this one is no exception. As such, while I think it is relatively unlikely, a small shift south with the placement of the inverted trough could result in a couple of tenths more QPF for the northern portion of the state, which would bring total QPF into the third to half an inch range – enough for a moderate to low end significant snowfall. Low probability, but worth keeping an eye on.
 
Looking at snow ratios, algorithms such as the Kuchera method suggest ratios of around 13:1 in northern areas and 10:1 in southern areas. This passes the “sniff test”, as we’ll see temps near 32 along the coastline and a bit cooler inland. Some of the heavier banding could have higher ratios, but not confident enough in that at this time to go any higher.
 
Forecast and Timing
 
Here’s a look at our forecast snowmap for this event.
Picture
Overall, this is a fairly classic Alberta clipper, with a relatively uniform area of light snows. I do think that there will be a slight latitudinal gradient to the system, with northern areas probably coming in towards the higher end of the range due to higher snow ratios and the potential for some bonus snow from the inverted trough, but wasn’t confident enough in that to go for a 2-4” zone for the northern tier, although we will probably see a few totals in the 4” range where the best banding sets up. Generally though, this is a 1-3” event, and will allow the map to reflect that.
 
Snow will start around midday on the southwest coast and spread north and east throughout the afternoon. Snow impacts the PM commute before tapering off late evening for southern areas and by daybreak Wednesday morning in northern areas. We could see some lingering snow squalls on Wednesday, but widespread snows should wrap up by the start of the commute.
 
Impacts
 
  • A light to moderate snowfall – low end plowable in some areas.
  • Difficult travel during the Tuesday PM commute.
  • Early dismissals are possible from schools, especially along the shoreline and in western areas.
 
Overall, a fairly straightforward system and a nice return to winter after our warmth the past few weeks. We’ll keep an eye on the radar tomorrow and update you as needed throughout the day. Send us your reports and photos on Facebook and on Twitter @SouthernCTWX so we know what’s happening on the ground and we may feature your photo on our social media!
 
Thanks for reading SCW and enjoy the snow!
-SA
Follow @SouthernCTWX
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Forecaster Discussion 1/29/17--minor snow event Tuesday...the end of the torch (for now)...

1/29/2017

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​Good afternoon from Southern Connecticut Weather!
 
Happy Sunday. January is drawing to a close, and with it, the blowtorch that has settled itself over our part of the world. We have seen temperatures above normal for fourteen consecutive days, which is very impressive considering 1) many of those days have been above normal more than ten degrees and 2) this is typically the coldest time of year!
 
Well, that’s coming to an end…for now. As I alluded to in my two-week outlook, the end of January and start of February is bringing change. We’re returning to seasonable temperatures for the foreseeable future, and will be watching for a more active pattern heading into early February. I’ll have more on the pattern and outlook for February in a few days with my next two-week outlook. For now, let’s look at the week ahead. 
Picture
​The visible satellite image from this morning and afternoon.
Sunday-Monday
The next two days look quiet. Today, we’re dealing with a mixture of clouds and sun, but I expect dry conditions. Tomorrow is much of the same, but colder air begins to settle in. A clipper is expected to dive south of us later tonight into tomorrow. As it heads off the coast, it will deepen a bit as it moves northeast. I think the system is weak enough and far enough off the coast to keep us from experiencing anything but clouds, but I won’t rule out a flurry along the shoreline. 
Picture
Tuesday-Wednesday
As you can see from the RGEM image above, the overall idea, shared by all the other guidance, is that the Sunday/Monday clipper has no impact on the state. What you can see from the end of that loop however, is another system approaching. That’s our weather maker for the forecast period.
 
On Tuesday, a more potent clipper works its way through the region. With cold air in place, accumulating snow seems likely. It will be a minor event, with snowfall currently expected on the order of 1-2” with an isolated area getting more. We will continue to monitor the trends with the system, as the GFS has trended better with the amount of precip that gets into the area, which is a potential flag. Right now it looks like light snow would begin from west to east early Tuesday afternoon through the overnight hours. Evening delays are possible but unlikely if snow remains light throughout the day. Scattered snow showers will remain possible on Wednesday, with no accumulation expected. 
Picture
4KM NAM 850mb temperatures (top) as snow overspreads the state on Tuesday. NAM temperatures are well below freezing throughout the column, including the surface (bottom) so there should be no precipitation type issues here.
Picture
Thursday-Saturday
After the system departs, cold air remains and we turn our attention to the pattern ahead. The guidance has been signaling the potential for a storm just outside of this forecast period. It’s something to keep an eye on but it is an eternity away. 
Picture
GEFS showing the first few days of February being below normal overall. That's a marked difference from much of January.

The Dailies

Sunday: Partly sunny. Highs in the low to mid 40s.

Monday:
Partly sunny with a chance of a flurry along the shoreline. Highs in the mid to upper 30s. Chance of flurries 10%

Tuesday:
Snow. Highs in the upper 20s to low 30s. Chance of snow 80%.  

Wednesday:
Partly cloudy with a slight chance of snow showers. Highs in the mid to upper 30s. Chance of snow 20%.

Thursday:
Mostly sunny with highs in the mid to upper 30s.

Friday:
Mostly sunny and colder with highs in the upper 20s to low 30s.

Saturday:
Mostly sunny and seasonably cold. Highs in the upper 20s to low 30s.
 
As always, don’t forget to like us on Facebook and share our discussions, and follow us on Twitter @southernctwx and retweet our posts!
 
Thanks for reading SCW.​
 
-DB
Follow @SouthernCTWX\n\n
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..AS STORM PULLS AWAY, A PATTERN OF TRANSITION SETS IN...

1/24/2017

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Something to think about: I was pondering why the models have been so bad this winter and the conclusion I came to is that the pattern this winter seems to be in a near-constant state of transition.  Models do not perform well in transitioning patterns and do much better when there is a pattern that is locked in.  Let that be food for thought, and perhaps if we can get a pattern to establish itself, models will do better.

Current surface analysis shows a low pressure center (the storm that has been hitting us the past couple days) over Providence, Rhode Island.  A trough extended westward from the low to about Toronto.  This combination is still producing frozen precipitation across much of the state.

Tonight: The precipitation will gradually wind down.  Plan on an ending time of 9 PM to 3 AM, from southwest to northeast.  This is a slow-moving storm and will end slowly, as well.  As for temperatures, expect low temperatures within a few degrees of 30- uniform temperatures due to cloud cover.

Tomorrow: A bright ball that produces warmth may actually appear in the sky.  Those sensitive to it may need to wear glasses to cover their eyes or a hat to cover their head! A beautiful day is expected, with high temperatures in the mid 40s, and maybe even a few upper 40s in the CT Valley! Any precipitation with the approaching frontal system should hold off and will keep the entire "day portion" of the forecast dry.

Tomorrow Night/Thursday: A frontal system will approach and bring occasional light showers and perhaps even a period of steadier rain to the state.  The main timing of this will be late morning to mid afternoon, from west to east.  There may also be a brief period of precipitation ahead of the main system in the predawn hours.  This first period of precipitation will need to be watched for interior locations, as this could produce a period of light freezing rain or freezing drizzle there.  As for high temperatures on Thursday, expect readings to range 40-45 degrees.

Longer Term (The weekend and beyond):Generally fair weather expected through this time frame.  Temperatures will be much cooler, closer to normal levels.  A reinfocing shot of cold air could bring snow showers or squalls Friday later in the day.  Snow showers from lake effect streamers will be possible for the hillier terrain up north on Saturday.  

As far as temperatures for the long term: basically mid to upper 30s for highs every day except Monday, which will see highs in the low 30s.

​Long Range: Basically think of it as the pattern taking a little break right now to recharge & reload.  Temperatures should be at or below normal the vast majority of days in the long range, and the overall pattern does look to get a lot more stormy as we enter February.  Therefore, one would think the chances for individual storms to produce wintry precipitation in our area would go up.  Of course, it is all going to depend on the individual storm track of each wave.  I like the period February 4 to 8 for a very widespread snow chance for now.

There really isn't a whole lot to show graphically this time around, but let's take a look at the frontal system slated to pass through the area on Thursday.

Picture
You can see the weak low over Virginia and the 540 line is a good indicator of where the front is on that frame, so it's basically bisecting the state.  Although most of the rain remains to the south, at least a little light rain should find its way into our state.

Next, let's take a look at the long range pattern progged for the first week of February.

​
Picture
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Potentially Dangerous Storm- 1/23/17-1/25/17- Discussion

1/22/2017

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Good evening from Southern Connecticut Weather!
​
   You could classify today as the proverbial "calm before the storm". Across the state today, we had a brief period of sun before the clouds moved in. Conditions stayed dry today and will continue to do so through early this evening. Temperatures stayed steady in the mid 40s to lower 50s at the shore. Heading through this evening, temperatures will drop back into the 30s statewide, lower to mid 30s inland, with mid and upper 30s at the shore. I see chances for showers building throughout the evening as our next weather maker begins to make itself felt. Along with precip chances increasing, winds will be on the increase as well. This evening should be fine as you make your last minute storm preparations in coastal Connecticut. Then we move onto early Monday morning...
Picture
Synopsis: We have a very potent and complex weather system moving in from the southwest bringing along with it heavy rain, winds, periods of snow and sleet in northern areas, and possible coastal flooding.

Timing: Starting Monday morning through Tuesday evening, height of the storm would be Monday afternoon through early Tuesday morning, with precipitation continuing through late Tuesday night.

​Main impacts: High winds, heavy rains, coastal flooding, extended periods of snow and sleet well away from the shore and north of I84.
Technical discussion: There is a potent shortwave system moving in from the southwest which will greatly strengthen over the next few days. Usually storms that strengthen to this magnitude tend to track far to the west while the entire state is enveloped in a "warm sector" with temperatures rocketing into the 50s and 60s in some cases, with rain. In this case, we have 2 things preventing this storm from tracking in such a way. First, we have a high pressure block in central Canada prevented this storm from riding way up into the Great Lakes region and also a well placed high pressure area just north of main. So the storm will track just off Delmarva Peninsula then most likely over Cape Cod. Now you noticed in the timing how impacts will be felt from Monday morning through Wednesday morning, a rather long duration storm for this area, that's another function of the "block" in central Canada, it is preventing the storm from escaping and scooting out to sea. Which is bad news for most of us, especially on the shoreline. 
Picture
Picture
​   While the storm moves very slowly, and the storm remains very strong and still strengthens while in the Atlantic. The state, especially the shore, will be pounded with quite strong winds for a long period of time. This will not only extending the likelihood of wind damage, but cause a risk for coastal flooding as these strong east winds pile up water into Long Island Sound. Timing for this flooding to occur would be throughout the storm from Monday afternoon through Tuesday morning, when winds do look to subside a bit. Across the state, there are various wind related warnings and advisories. Along the immediate Connecticut shore, there is a high wind warning in place where sustained winds are expected to be 30-40 mph with gusts to 70 mph, in this area, extreme caution should be exercised. The northern portions of the coastal counties are under wind advisories for sustained winds 25-35 mph with gusts to 55 mph, this advisory is also in effect for Litchfield county as well. Hartford, Tolland and Windham counties do not have any wind related advisories issued, but that does not mean to let your guard down, wind gusts could mix down from the mid-levels of the atmosphere at any time, I'd still expect some wind gusts to exceed 45 mph. Still enough to cause issues with power. Timing for these wind advisories extend from 1 am Monday to 1 am Tuesday, but expect gusty winds to last well into Tuesday as well.
Picture
​   So you see that I haven't mentioned that 's' word yet. Impacts from snow look to be quite minimal from this system, and confined to far northern Connecticut. I could see a solid 1-3 inches of snow falling in portions of the Litchfield hills. You are probably saying to yourself, potent system tracking to our south, shouldn't there be more of a snow threat? Well, no. Right now we are in more of a mid-March pattern than a mid to late January pattern in terms of temps. Surface temperatures throughout the system will remain basically mid 30s to around 40, with temps in the 850 and 925 levels (or mid levels) hovering right around freezing to just below. Even with a storm of this magnitude making it's cold air, we would need some very heavy areas of precip to form, promoting dynamic cooling to get even the slightest bit of frozen precipitation to the ground. That said, I do see there being an extended period of heavy sleet or snow from Monday afternoon through Monday evening as the storm really gets going in these parts, I feel all frozen should have changed to rain by daybreak on Tuesday and continue as rain, statewide, through the day on Tuesday. As the storm pulls away and winds begin to blow out of the northwest, I do think some areas away from the shore could change briefly to snow or a mix. The bigger issue with this storm, as far as precipitation goes, will be pouring rain. I'm expecting on the order of 1-2 inches of rain statewide, at times, the rains could be quite heavy so please take caution if you need to travel over the next few days and watch for ponding on the roadways.
Picture
   I cannot stress enough how dangerous this storm can be for the state of Connecticut, especially the shoreline. Just because this isn't going to be a nor'easter with extreme snows does not mean you shouldn't be prepared. Make sure you have all of your essentials ready, flashlights, generators, non-perishables, etc in case the lights go out in your home. On the shoreline, this could essentially be 24 hours of tropical storm conditions with gusts approaching hurricane strength. The conditional coastal flooding threat is nothing to be joked about either. On the flip side, don't freak out, stay calm, most of us are seasoned vets when it comes to strong coastal storms, just doesn't hurt to be prepared, is all.

So to recap...
-Storm starts to impact area early Monday morning and goes through late Tuesday

-Winds will gradually pick up through this evening, and will peak on Monday afternoon and evening. Sustained winds of 30-40 mph for the shore, and 20-30 mph for the rest of the state with along Gusts along the coast approaching  70+ mph. The rest of the state could see gusts up to 55 mph.

-Sleet and snow threat for areas north of I84, 1-3 inches snow/sleet NW hills

-Coastal flooding looks to be an issue from Monday through Tuesday

-Heavy rain expected from Monday through Tuesday

​-We clear out for the day on Wednesday

​Have a great evening everyone! We will be with you right through the storm. Keep it locked to Southern Connecticut Weather for all of the latest updates.- TW

Follow @SouthernCTWX
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SCW Two Week Outlook--1/20/17

1/20/2017

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Good afternoon from Southern Connecticut Weather.
 
I’m a few days late, but it’s time to grade my last outlook and talk about the next two weeks. Before doing so, I wanted to take a moment to reset expectations.
 
There has been a fair amount of talk about this winter being a bust, but the data does not back that perception up. It is important to know that a winter that is cold and snowy from start to finish is very rare in Connecticut. While the larger hemispheric pattern can often remain persistent, the factors that bring cold/warm and wet/dry conditions to our region vary quite a bit. So far, this is what we’ve seen.
 
Hartford
Normal snow to date: 16.8”
Observed snow to date: 15.8”
Observed snow last year at this date: 1.8”
December temperature departure: +0.5
January temperature departure: +4.5
 
Bridgeport
Normal snow to date: 10.7”
Observed snow to date: 14.5”
Observed snow last year at this date: 1.5”
December temperature departure: +2.4
January temperature departure: +4.7
 
If you like winter, this year is a marked change from the last two, where there was barely any cold or snow. Although we are warmer and slightly below normal in Hartford, we are above normal in snow in southern Connecticut!
 
The last few days have significantly increased the monthly temperature, and the next few days will only take those temperatures up
 
Grading the last outlook
I had to cool off at some point. Overall, my outlook was meh. I busted on temperatures in both weeks, but called for a significant event at the end of the first period, which happened. Almost immediately after I posted my last outlook, I knew I’d bust on temperatures. Not cool. As a result, I give this last outlook a C+.
 
Week one—Sunday January 1 to Saturday January 7
Temperatures—near average (moderate confidence) Miss
Precipitation—above average (high confidence) Check
Wintry Precipitation—above average (low confidence) Check
 
Week two—Sunday January 8 to Saturday January 14
Temperatures—below average (high confidence) Fail
Precipitation—near average (low confidence) Check
Wintry Precipitation—near average (low confidence) Miss ​

Two Week Summary
Picture
 * Note—high confidence (70% or greater belief of event occurring), moderate confidence (36-69%), low confidence (0-35%); nothing significant (less than 1” snowfall and .25” ice)
 
Forecast period—Friday January 20 to Tuesday January 31
Temperatures—above average (high confidence)
Precipitation—above average (high confidence)
Wintry Precipitation—below average (high confidence)
 
In a slight departure from my usual format, I am covering the entire period in one section. This might be the easiest forecast of the winter. We torch to end the last third of January and turn our eyes toward a significant pattern shift by the end of the month. We also watch a significant storm that will impact the region in the next few days. It will be a rain maker for most if not all of the state. Afterward, we begin a gradual cool down and begin to watch a potentially more active pattern with the northern stream, opening the door for clippers.
 
​Technical Discussion
First, let’s talk about the pattern that’s been. It hasn’t been pretty if you love winter. 
Picture
​There has been a very strong area of troughing and lower heights over the west coast and Alaska. That’s usually a death knell for wintry conditions around here. That looks to persist for a while longer.
 
By Monday and Tuesday, we are dealing with a significant storm. The track is to our south, yet we are likely dealing with a rain and wind storm. Our team will have more detail about it, but this could be quite a storm with very heavy rain and windy conditions that could be damaging in spots. Stay tuned. 
Picture
​In the wake of this event, the guidance has honed in on a pattern change. We’ve been tracking this potential for almost a week now, and while I am skeptical of any type of forecast in the medium to long range, I think there is a growing consensus on the very end of January and start of February returning to a colder and potentially more active pattern. 
Picture
So to close, winter hasn’t been as bad as some might think. We’ve had a warm run for sure, but in terms of snow, we’ve been near to slightly above normal. The warm pattern continues for now, as the large scale pattern prepares to reshuffle for early February.
 
As always, don’t forget to like us on Facebook and share our discussions, and follow us on Twitter @southernctwx and retweet our posts!
 
Thanks for reading SCW.​
 
-DB
Follow @SouthernCTWX
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