Storm to Miss

Well this forecast was a bust. Most of our reliable modeling was showing a major storm two days ago but it’s just not going to happen. Props to the GFS for getting this right. 

Right now only minor accumulation is expected later tomorrow especially out in eastern Connecticut.

On to spring!

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Weekend Storm – Will it Snow?

As of 8 p.m. Tuesday I picked up about 0.2″ of snow here in West Hartford – Winter 2015-2016 is just full of epic excitement.

This weekend it seems fairly likely that we’ll see a storm developing off the coast. This afternoon’s GFS run has an intriguing solution with a period of rain and snow – possibly heavy.

There are several reasons why this storm likely will not be a big snow storm. One of the biggest reasons is that there’s no source of cold air to the north. You can see no high pressure over Maine or the Canadian Maritimes which is a problem. Also, before this storm forms a primary low moves over the Great Lakes which manages to bring a lot of warmth north – especially since as mentioned previously there’s no big high pressure system.

We are quite confident in a storm passing just underneath us. Today’s European Ensemble shows a strong signal for a nor’easter developing off of Montauk Point.

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Even though odds do not favor a major snowstorm we can’t rule it out. Occasionally, a storm with an unfavorable set of ingredients can “thread the needle” and intensify in the right place at the right time and result in a storm that’s just cold enough for snow. It is January after all so a storm bombing out to our southeast needs to be watched. This afternoon’s GFS run effectively does that for parts of inland Connecticut – especially the hills.

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This sounding from the height of the storm shows temperatures just a hair below 32 degrees in the lowest few thousand feet of the atmosphere. Other computer model solutions, particularly the ECMWF, are a bit milder and would mean a rain rather than snow solution.

I’m not excited about this one yet – but I reserve the right to get excited about it in the next couple days!

 

Tuesday Snow

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For winter 2015-2016 this is a big event! I’m kidding – sort of.

An “Alberta Clipper” will swing through New England and produce a blossoming area of snow (and coastal rain) tomorrow afternoon and evening. As the clipper approaches the coast we’ll see an injection of moisture with a brief burst of snow possible.

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While overall totals will be pretty unimpressive there is a chance someย areas are able to get a quick inch or two of snow in a 30-45 minute window. Our computer models are not all on the same page with this – some are more impressive than others – but some of our high resolution modeling does show a brief, impressive burst of heavy snow. The NAM is one of those models showing a surge of instability for a period of time shortly before 7 p.m.

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Additionally, snow growth should be optimized with lift maximized near -15c which supports efficient crystal production and quick to pile up dendrites. Dropping temperatures through the event could support some freeze up on untreated roadways.

Bottom line – not a big storm but enough to foul up the commute – particularly away from the shoreline.

Two More Rain Events

In winter 2016 it shouldn’t come as a surprise our next two storms will be wet and not white. On Saturday, a weak disturbance will move in with the chance for a light wintry mix around daybreak. This sounding off the GFS shows a little wedge of cold near the surface which could bring some freezing rain.

Courtesy: College of dupage

Courtesy: College of dupage

So storm 1 is sort of a bust. What about storm 2 on Sunday? It’s looking warm(er) and wet. The most likely storm track is to our west – the dreaded “cutter”. The track to the west puts us on the east side of the low pressure circulation allowing warm air to race north.

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There’s a small chance that the storm is able to take a more classic offshore/snow track. The GGEM or Canadian model shows just that. Don’t get excited about it though. Take a look at what’s missing.

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There’s no cold, dry high pressure to the north – which is almost always a necessary ingredient for a snowstorm around here.

As I’ve been mentioning the weather pattern is quite interesting going forward. During the week of 1/11 (next week) I see an average to below average temperature regime and possibly a snow threat or two. Don’t give up yet snow lovers – I think there is still hope with the nice looking pattern beginning next week!

Surprise Snow!

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Snow in Danielson / Courtesy: Scott Cormier

It wasn’t a major deal but a period of light snow managed to cover the roads and highways this morning in eastern Connecticut. While this was a relatively minor event it did catch people off guard and resulted in a few accidents. Considering my forecast at 11 p.m. prior to the event was for “partly cloudy skies” without mentioning flurries I wanted to look back at the event. What did I miss here?

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I’ll start with a real basic look at one of the computer models from Sunday night. The high resolution 4km NAM showed no precipitation over Connecticut or Rhode Island. No signal there.

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There were signals showing up on the end of the high resolution rapid refresh model or HRRR Sunday night. Here’s a look at the sounding for Willimantic (IJD) valid 8 a.m. Monday morning.

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You can see an area of moisture around 800 mb with a zone of lift in that area as well (note the white line jutting to the west). Underneath that area is a very dry lowest 7,000 feet of the atmosphere so I would expect snow flakes to sublimate on the way down.

The actual sounding (or at least a close approximation) from a Monday morning HRRR run shows a more impressive picture.

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You can see a much deeper saturated level and slightly deeper and stronger upward vertical motion. All of this is occurring around -15c which is the preferred temperature for efficient ice crystal growth (dendrites).

While actual precipitation amounts were only one or two hundreths of an inch a quick 1/4″ of snow in some towns was enough to really muck up the roads. A good rule of thumb is to always beware when the models show lift and saturation around -15c. While I probably wouldn’t have forecast accumulation snow (however minor) I think it would be reasonable to forecast flurries in retrospect.