6″-12″ Statewide

The exact track of Tuesday night’s storm is still a bit up in the air. A track over Buzzards Bay would drop 12″-18″ of snow in Connecticut. A track over Nantucket would drop less snow. At this point I’m going with a middle of the road solution with 6″-12″ statewide. By tonight I should be able to fine tune this and give more specific numbers.

The 9z SREF guidance shifted the heaviest snow potential east into Rhode Island and Massachusetts and this is certainly possible.

More later

More Snow Likely Wednesday

This is the winter that keeps on giving. A strong upper level disturbance is going to tap into a ton of Gulf and Atlantic moisture and produce an impressive moisture-laden storm near southern New England Tuesday night and Wednesday.

The storm is going to drop snow on Connecticut. I have a high level of confidence we’ll see over 4″ of snow. Whether we see a blockbuster storm with double digit accumulation numbers remains to be seen.

The 21z SREFs are about as impressive as you’ll see for a 66 hour forecast.  The ensembles show a >70% probability of 8″+ of snow by Wednesday morning.

Other models show impressive snowfall totals at this juncture. The question will be how close to the coast does the low track. If it’s too far offshore we’ll get a 4″-8″ kind of snowfall. Certainly respectable and I have a high confidence in at least that much snow.

If the storm tracks just southeast of Montauk and up over Cape Cod over a foot of snow would be probable in many areas, especially if the mid level lows (at 700mb and 850mb) can close off and strengthen fast enough. This will get sorted out in future model runs but another significant storm seems likely. My gut tells me this will be a big one and probably the biggest we’ve seen this year (on average across the state)

What an Odd Day

Doesn’t get much weirder than this in the weather world. The 12z GFS sent a shot heard around the meteorological world with an exceptionally dramatic blizzard with no other model support. The shots kept coming through today with the American models going crazy with an extreme westerly track that pummels the Mid Atlantic and southern new England with snow.

Shortly after all of this model insanity the Hydrometeorological Prediction Center sent out this statement (they run the American models) saying to basically ignore them.

INITIALIZATION ERRORS IN NUMEROUS DIAGNOSTIC QUANTITIES… INCLUDING HEIGHT/VORTICITY FIELDS/RH…ARE EVIDENT IN
BOTH THE 12Z NAM/GFS WITH SMALL BUT LIKELY SIGNIFICANT SHORTWAVE TROUGHS OVER SOUTH DAKOTA/NEBRASKA ALONG WITH SASKATCHEWAN/MANITOBA…WITH THESE AREAS ALSO NOT PARTICULARLY RESOLVED OR PREDICTED WELL BY THE 00Z ECMWF. THUS…THE SPECIFIC PREDICTIONS BY ALL DETERMINISTIC GUIDANCE ARE IN QUESTION…WITH THE RECOMMENDATION TO FOLLOW CONTINUITY…WITH THE FINAL OUTCOME MOST BELIEVED TO LIE BETWEEN THE 06Z GFS AND 00Z ECMWF…WITH ALL ENSEMBLE GUIDANCE INCLUDING THE SREF MEAN/GEFS MEAN (EXCEPT NOT
THE 12Z VERSION)/ECMWF ENSEMBLE MEAN ALSO CONSIDERED USEFUL TO ADDRESS THE CONTINUED UNCERTAINTY. THIS APPROACH DISREGARDS THE SUBSTANTIALLY DEEPER AND WESTWARD SHIFT OF THE 12Z GFS REGARDING THE POWERFUL LOW TRACKING UP THE EASTERN SEABOARD…AND TO A LESSER EXTENT THE 12Z NAM WHICH LIES NEAR THE FAST EDGE OF THE GUIDANCE WITH THE DEVELOPING LOW.

Though the 12z GFS may have been an aberration it was quite a shock to many of us to see all subsequent American models come west at 18z. In fact the ensembles (both the GEFS and SREF) are west as well. Every GEFS member comes close to bringing blizzard conditions to parts of Connecticut.

It’s important to note that if the 12z data assimilation and initialization was wrong the GFS subsequent run can be impacted. The 18z GFS and NAM use the 12z GFS 6-hour forecast as a first guess. From there additional data is assimilated (at 18z we’re talking about surface obs, remotely sensed or satellite data, and aircraft data) and the model is re-initialized. An egregious error with the 12z initialization could reappear at 18z. By 00z the additional data that’s assimilated includes 00z RAOB data which should help things significantly.

The 12z GFS (and 18z) both show 2 very strong shortwaves phasing and blowing up a monster storm. The 12z Euro (with a superior initialization scheme – no one disputes that) initialized both shortwaves weaker than the 12z GFS. I’d go with the Euro right now but I’m sweating this one out.

It’s hard to go against the foreign global models in a situation like this. If you like snow we’re rooting for a 1980-style Lake Placid miracle.

Just How Close Will it Get?

This is the storm that refuses to die. For most of Connecticut the storm is basically a non-event with no snow expected at all. In southeastern parts of the state it’s possible that the storm backs in just enough to produce a quick burst of light snow.

Areas further east like the South Shore of Boston and Cape Cod now may actually get hit by a decent thump of snow. The SREF and GEFS have lead the way showing the potential for this storm to come a bit closer than forecasted in the last day or so. Keep in mind this is after or medium range models totally backed away from this storm impacting us at all. What a long and strange trip it’s been with this storm.

Here’s the 00z NAM forecast precipitation. The light blue is >0.1″ with and the dark green is >1″ of precipitation. The NAM is likely too robust with the northwest extent of snow but it has continued to push west.

I’d say the odds of an inch or two of snow in southeastern Connecticut are about 25% but the rest of the state should get by with flurries at the worst. Never say never but right now it would take something close to a miracle to get a more significant (say 4 or 6″ snow) back into the Connecticut River Valley.

This weather pattern has been raising hell with our computer models. A fast flow coupled by an extreme block in the northern Latitudes complete with a retrograding polar vortex make this a very unusual and anomalous pattern that is difficult for the models to resolve.