WEATHER: Snow On Its Way

January 6, 2019

Illustration (Image credit: Wix)

 

After our brief warm-up on Friday and Shabbat, a stronger storm is developing just west of Cyprus. Just where this storm develops (just east of Cyprus is better) will determine the elevation at which snow falls on Sunday into Monday. The further east it develops, the colder the temperatures at the surface will be (as cold air moving over the sea absorbs heat from the Mediterranean Sea).

 

Temperatures at upper levels should be cold enough for convective precipitation, which when combined with temperatures at middle levels just cold enough for good snow growth, means that this storm will give it a good try to bring snow to Jerusalem.  

 

The problem is that any snowflake making the plunge towards earth will encounter temperatures near the surface that will probably be above freezing (with 850 mb temperatures possibly from just above freezing to a degree or so below). Basically, this is not a good situation to be in if you're a snowflake, and many of them may simply choose to stay aloft in the clouds, instead of taking the risk of melting on the way down.

 

We have a Winter Storm Warning for Har Hermon Sunday/Sunday Night into Monday for 50 to 100 cm of snow. The Winter Storm Warning for the Golan for Sunday Night is for up to 20 cm of snow.

 

There is a Winter Weather Warning for the area of Safed and Jerusalem’s north and southern hills for Sunday evening and night; mixed rain, snow, and ice is expected with a coating of ice possible during heavier precipitation periods (but the ice should melt in the above-freezing temperatures). A light snow accumulation is also possible on mountains north of Jerusalem.

 

Heavy Rain is expected along the coastal areas, with 25 to 50 mm and 50 to 75 mm in the far north (outside of the Hermon and Golan).

 

Strong and gale force winds are expected during Sunday and Sunday night in many locations. There is a possibility of snow in higher elevations of the central mountains Tuesday night into Wednesday morning.

 

Discussion: Very cold air is poised to move in at upper levels (500 mb) Sunday evening. This will trigger heavy precipitation, and would normally would bring snow to Jerusalem. However, the middle levels of the atmosphere are only marginally cold enough for snow, and temperatures near the surface should be 2 to 3 Celsius.  This mean that there can be some ice in heavier precipitation, and rain mixed with snow (most likely between late evening hours until midnight), but a snow accumulation is (currently) very unlikely in Jerusalem.

 

However, the forecasts are showing colder air at lower and middle levels arriving Tuesday night, along with heavier precipitation. There is also an indication of additional phasing at upper levels. If everything comes "together," there could be a wet snow in Jerusalem Tuesday night into early morning.

 

Check here for further updates as the storm(s) progress. 

 

Jerusalem forecast (click here for updated national forecasts):

Image credit: The Jerusalem Herald

 

Dr. Lynn is a lecturer at The Hebrew University of Jerusalem, Earth Sciences Department. He is also CEO of Weather It Is, LTD, a company that specializes in reducing weather risk.  Click here to read more of this writer’s work in The Jerusalem Herald.

 

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בס"ד

...הָרִימִי בַכֹּחַ קוֹלֵךְ מְבַשֶּׂרֶת יְרוּשָׁלִָם הָרִימִי אַל תִּירָאִי אִמְרִי לְעָרֵי יְהוּדָה הִנֵּה אֱלֹקֵיכֶם! (ישעיה  מ:ט)

...Raise your voice with strength, herald of Jerusalem; raise it, do not be afraid; say to the cities of Judah, "Here is your G-d!"

(Isaiah 40:9)

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