Extremely Cold Weekend

We have some really impressive cold on the way this weekend. While we may not set records for the day the combination of cold and wind will be brutal.

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By Saturday morning the core of the cold will be over eastern Ontario. With 850mb temperatures of -40º this is an exceptionally impressive blast of cold. In fact, SUNY Albany professor and meteorologist extraordinaire Lance Bosart would refer to this as the “creme de la creme” with a -40º isotherm appearing.

Obviously, this will modify some before reaching New England. Still, it will be a shock to the system. By 7 p.m. Saturday the GFS is forecasting 850mb temepratures (about 5,000 feet up) of -30C over parts of Connecticut. If a -30C 850mb temperature is measured during the evening weather balloon launch in Albany it would be the 5th coldest on record. The all time record for Albany of -30.4C from 1/4/82 is in jeopardy.

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This kind of Arctic outbreak is exciting for meteorologists like me who love to drool at weather maps and soundings. The tropopause will be exceptionally low Saturday night across the state. This forecast sounding shows the stratosphere beginning around 800mb or about 6500 feet above our heads! You’ll almost be able to sniff the Ozone!!!!

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You can also see how low the dynamic tropopause is on this map off the GFS showing the core of the cold right over southern New England. In fact the dynamic tropopause is lower here than anywhere in our slice of the hemisphere south of 60N.

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So – enjoy the cold this weekend if you can. Stay inside and read a book or watch some movies. If you’re skiing or snowshoeing throw on an extra layer or two and you’ll be just fine!

More Snow Expected

This is a super tough forecast for tomorrow. This is the kind of setup that can produce isolated bands of heavy snow while other areas almost get completely shut out. A forecast of 0″-6″ is probably a reasonable spread across the state – though we won’t be showing that on air for obvious reasons.

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I’m going to start out with the GFS which shows the potential for 4″ or 5″ of snow on the Connecticut shoreline with an impressive looking setup. Strong lift in the snow growth zone coupled with a conditionally unstable temperature profile sends up plenty of warning flags for a big event! But, is the GFS right?

Our convection-allowing UCAR ensembles which I’ve had tremendous success with do show the potential for several inches of snow. Here is how they look in the Hartford area.

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Fairly tight clustering between 0.15″ and 0.35″ of liquid (read: 2″-4″ of snow) tomorrow – especially around 7 a.m. Given the instability modeled (total totals approaching 60!) our convection allowing and high resolution models should have a better handle on this event.

That said, other computer models remain quite unimpressive. The RPM (a WRF model run by WSI) shows less than a tenth of an inch of precipitation statewide – with most of the state getting 0.00″!

So it’s a bit of a conundrum. While there are many signals pointing to an “overperformer” in some area – there are other signals that are less impressive. I’d say the most likely scenario is 1″-3″ across the state with the potential for a pocket of up to 5″ of snow if a band of heavy snow were to develop – though this is by no means a certainty!

Impressive Weekend Chill

eps_t850a_noram_25It’s becoming more and more likely that some brutal cold will settle over New England this weekend. A blob of 850mb temperatures of more than 20C colder than average will lead to some impressively cold temperatures. This afternoon’s GFS run shows 850mb near or below -30C over a good chunk of New England Saturday night – that is some impressive with!

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So – how cold will it be? Right now we’re predicting a low of -7F at Bradley Airport Sunday morning along with wind. Wind chills below -20F are possible across parts of the weekend. Painfully cold stuff.

There is the potential for some snow prior to the cold’s arrival on Saturday morning though that is presently a low probability event. Odds are no better than about 1 in 4 for accumulating snow. We’ll have to watch it, however!

Another Storm

I’ve been out of the loop this weekend doing a bit of skiing! The best kind of trip is when you can come home to some exciting weather to talk about! A big ocean storm is going to pass pretty far east of us BUT there appears to be enough going on nearby to give us something fun.

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So what is producing that precipitation so far west of the storm? If we look about 10,000 feet above our heads we can see a fair amount of convergence over southern New England (basically air piles up and is forced to rise).

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At 700 mb you can see winds out of the due east decelerating from Cape Cod to Connecticut. This essentially creates an atmospheric traffic jam with nowhere to go but up.

There are a few negatives here too. The amount of “lift” in the atmosphere doesn’t appear particularly strong. It also appears to be a bit removed from the “snow growth zone” – which is the area in the atmosphere around -15c where ice crystals grow most efficiently.

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Our SREFs show about 0.4″ of liquid at Bradley Airport – and about 0.5″ for Willimantic. These tend to be a bit juicy. There’s not a tremendous amount of spread here so that gives us confidence that this storm won’t be a total dud (read: 1″ or 2″) and it also won’t be a prolific snow maker (read: Friday’s busted forecast with nearly 12″ in places).

SREF plume diagram for BDL
SREF plume diagram for BDL

Most of the state should expect 3″-5″ of snow. There could be a touch less along the New York border and a touch more along the Rhode Island border. The snow will be of the light to moderate variety (heavy snowfall rates are unlikely) and the peak will be during the mid to late morning though light snow and flurries should last well into the night. Happy shoveling!

Friday Storm Surprise

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Well isn’t this storm a real treat to forecast. My forecast from yesterday is going to bust in a big way. No denying that – this forecast has been a train wreck from the beginning. While we’re much better than we used to be – meteorology continues to be a humbling science!

All that said, I for one am excited about a Friday morning snowstorm! This storm has trended stronger and farther west just about every run since Tuesday. The reason why is that a powerful upper level disturbance will swing through and produce a rather expansive – and impressive – swath of snow.

There will be a few issues to contend with here. One issue is going to be timing the transition from rain to snow – and even a bit of sleet. This forecast sounding for the area around New London shows that potential around 4 a.m. tomorrow with the atmosphere hovering around 0c.

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Expect a real mess tomorrow morning across the state. Heavy, wet snow will cause issues and I expect roads to be quite messy in most areas. There are several things that make me quite bullish on this event – including our short range ensembles all showing a very significant storm.

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This plume diagram from BDL shows mean precipitation around 0.8″ with many higher members! That would be approximately 8″ of snow though some will be lost to mixing at the onset.

I expect this storm will be a fun one for us weather geeks and a real pain for commuters tomorrow.