9 Days After a Hurricane – Winter Strikes Back

Here comes winter. It’s hard to believe that a little over a week following Hurricane Sandy we have to deal with our first winter storm of the year.

A few days ago I wrote that in order for this storm to produce wintry weather we needed one of two things to happen. One, the storm would have to strengthen much closer to Connecticut and not mature/occlude so far south. Two, the antecedent cold and dry airmass would have to overperform in subsequent model runs. The latter happened.

15z Surface Analysis / UCAR

While the storm will begin to fill, effectively shutting down the poweful advective processes that drive these nor’easters, the atmosphere is pretty chilly and dry across New England. We don’t need to rely on a burst of strong upward vertical motion to dynamically cool the atmosphere. We have a very impressive reservoir of low dew point air across northern New England.

Here’s the 15z surface analysis and you can see dew points in the teens and twenties across most of the region. With a strong northerly ageostrophic wind component we will get a steady supply of cold, dry air during the storm.

Since the storm is no longer strengthening the models develop some funky looking disjointed bands of precipitation. It’s hard to pile up a lot of snow like this. You can see on the 12z NAM a little sucker hole over Connecticut with the 3-hour 21Z QPF forecast with heavier totals west and east.

This is going to be a challenge to forecast. A poorly timed and placed mesoscale band could dump a decent bit of snow in a short period of time. Thermal profiles look cold enough for snow and the boundary layer temperatures look cold enough for accumulating snow across a large portion of the state. If mid level temperatures tick up a bit as warm air wraps into the storm there will still be plenty of low level cold for sleet and potentially a glaze of freezing rain.

Here’s the 12z OKX sounding and you can see a sharp dry level between 700mb and 850mb. It’s going to take some time to get this precipitation shield inland but as we wet bulb that mid level warm punch near 850mb will be eaten away.

Most of us will see a thump of snow today. Especially this afternoon.  1″-2″ of snow is likely in many areas, especially away from the shoreline, with the potential for higher totals in some inland towns. A band of 2″-4″ is likely up in Litchfield County and potentially into the Valley as well though this will be hard to pin down. Even the shoreline may wind up seeing a bit of minor accumulation of wind whipped sleet and snow. This is by no means a big storm but it’s an odd weather twist following a hurricane last week.

One final note about storm surge because after Sandy a lot of people have it on their mind. We’re likely looking at a 3 or 4 foot surge in the Sound from this nor’easter. Tides, however, are astronomically low and wave action will be oriented offshore with a more northerly than easterly wind component. I’m not expecting anything out of the ordinary in terms of coastal flooding.

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