Monday, January 15, 2018

Weather It Is (Winter Storm Watch)

Good Evening:

There is a winter storm watch for Thursday night into Friday morning for the higher elevations of Jerusalem, Gush Etzion, and the northern mountains.

The latest  (0000 UTC) GEFS forecast mean temperatures at 850 mb are just below freezing, with temperatures at 700 mb (the level near which snow grows most quickly) comparatively even colder with more than 60% of the forecasts below -12 C.  The "fly in the ointment" are the forecast temperatures at 500 mb.  Similar to a storm last year that brought a light accumulation to Gush Etzion, most forecasts within the ensemble are not below -25 C.  However, 20% of the forecasts are, and apparently the ECMWF forecast at 500 mb is colder (in the mean) than the GEFS.  If these colder forecasts verify, there could be snow in Mitzpe Ramon as well as areas lower down (e.g., Ramat Bet Shemesh) -- but this is unlikely.

Snow accumulation amounts -- like always -- are very sensitive to elevation heights and the degree of cold aloft, and it isn't possible to speak about accumulation amounts just yet.  In addition, this storm should be arriving from the west, meaning that relatively warm sea-temperatures could cause the snow to melt as it approaches ground level.  Moreover, temperatures on Shabbat and Sunday are forecast to be well above freezing, which should melt just about any snow. So, the snow may literally be here Friday morning, and gone by Shabbat morning or afternoon.

Nevertheless, the upcoming storm is forecast to be quite strong with gale force winds, high waves, and probably thunder and lightning.  Flooding is again likely within cities and the desert areas to the south.

Until then, rain is again forecast for Wednesday and possibly next week as temperatures become chilly again as the next storm arrives.

Barry Lynn

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