Tuesday, January 16, 2018

Weather It Is (Winter Storm Watch Continues)

Good Evening:  After issuing my "Winter Storm Watch" for Thursday night and Friday morning, the forecasts from the GEFS trended a bit warmer.  There were still some forecasts with unusually cold temperatures, but the majority were pointing towards "just" a rain event.  This was discouraging if you're a snow-liking person.

I know where my wife stands on this matter, because she was going around telling people that I said that it wouldn't snow.  What I really said was that looking at the weather maps Tuesday morning made me less optimistic, but not completely pessimistic.  Well, "A man hears what he wants to hear and disregards the rest..." (so aptly said Simon in Garfunkel in the song "The Boxer.")

However, today's (0z (00:00 UTC)) forecasts were again pointing towards a cold event.  Looking at the GEFS mean weather forecast field maps, one notes the arrival of unusually cold air Thursday night into Friday morning.  In terms of the potential for snow accumulation, this will be helped out by very cold temperatures at 700 mb in the presence of strong vertical velocities.  The ideal temperature for "growing snowflakes" (interlocking dendrites; see:http://www.iweathernet.com/educational/winter-precipitation/general-snow-forecasting) is between -12 and -18 C, and at the moment 40% of the forecasts indicate a drier, more likely to accumulate snow after the rain transitions to snow Thursday night.

In the last blog, we spoke about the possibility of snow at even low (or lower elevations). However, the current forecast puts this probability at just 10%.  Still, the ECMWF forecast at 500 mb is colder than the GEFS, so this may not be the last word on this subject.

In the meantime, Wednesday (tomorrow) should bring more rain, and Thursday's storm should bring even heavier precipitation, strong winds, and a chill just about everywhere.

The temperatures should warm up on Shabbat and Monday, but the next storm should also bring chilly weather (with another chance for snow) mid-next week.

In terms of actual snow amounts, the reader should check back on Thursday morning for an estimate by location.

Barry Lynn

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