Desierto norte de Chile

Thursday, January 12, 2012

No sign of any snow whatsoever

Since returning from the Dominican Republic a week ago, I've been regularly checking the middle- and long-range forecast models for any hint at winter precipitation. We received a surprise 1/2" of snow on Monday - falling from an upper-level environment clearly supportive of snow, but into a low-level thermal profile that, at least at first glance, wasn't that supportive (sfc temps at precip onset were 36F). Turns out low-level dry air advection (dew point temps 23-25F) allowed just enough wet bulb (evaporative) cooling to bring the surface closer to 33-34F. As soon as precip ended, temperatures returned to near 36F, providing some support for the evaporative cooling scenario.


For getting anything beyond that quick 1/2", though, the long-range forecast is bleak. Both GFS and ECMWF mid- and long-range predictions (out to 240h) bring several surface low pressure systems across the eastern U.S., but always to the west of the Appalachians, placing Annapolis in the "warm sector" of the cyclones and ensuring the precipitation falls as rain.

We'll have to see how the rest of the winter shapes up, but at least for the next 7-10 days, the outlook for significant accumulating snow in the non-mountain mid-Atlantic is bleak.

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