WEATHER: Friday Snow?
Illustration: Girl Standing in Snow (Photo credit: (c) Yael Lynn)
Last erev Shabbat, I was accosted by a Beit Knesset Member who told me not to write anything about the possibility of snow this past week. He was worried about the "evil-eye" being cast on the potential upcoming snowy weather. The evening after, my son noted that whenever I mention that it might snow, but need to check the weather maps after Shabbat, the snow in the forecast goes away.
So, you can imagine my surprise when the weather maps and global forecast ensemble (GEFS) graphs suggested that the upcoming (past) week was going to be cold, and the end of the week quite possibly even colder and quite snowy.
The weather this year has been quite different from last year. Last year, there were a number of small rain events, interspersed with a few heavier rain events. The rain started late this year (the last week in December), but since then, in contrast, we've had one heavy rain event after another.
For instance, even Sunday's storm exceeded expectations, with more than 25 mm of rain being measured here in Efrat. Moreover, it was a very quiet storm, without a crash of thunder or the hammering of hail — it just rained, and rained, and kept on raining. It shows that one can accomplish quite a lot with consistent, but quiet effort, and with great modesty.
There was a disagreement in the global forecast models. After the European and American ensemble models indicated a significant storm at the end of the week, their forecasts diverged; the American model suggested that there would be a cold mid-week storm, while the European model indicated a late week storm.
We did have a mid-week storm that brought (as forecast) some snow (but not accumulating) to Gush Etzion and some flakes in the air in Jerusalem. The problem was that temperatures were cold enough for snow, but not cold enough to "stick" on the ground (without turning to slush or just disappearing). For a while, I kept putting on my jacket to go outside and take pictures, but the snow would stop before I could step out the door. In the end, it was exciting to watch our first snow, even if the amounts were negligible.
We're now before our next winter storm, and we're going to miss this one. While early in the week the forecasts showed a very cold 500 mb trough dropping down off our coast, the forecasted storm began to drift eastward, and now the coldest air should pass over Jordan.
We mentioned this before, but we were hopeful the colder and further west forecasts in the ensemble might "win out." The problem was, as noted, was that within the developing ridge to our west was a fierce low pressure area that brought lots of snow and unusually cold weather to Spain. Rather than remaining with the ridge, it is now merging with the polar jet stream to its north. The result is that the ridge trough couplet has shifted eastward, and so has our storm.
For later today and tomorrow, expect rain in most places except the Golan, where from 5 to 50 cm of snow should accumulate, depending on elevation (5 cm, for example in Neve Ativ, and 50 cm on the Hermon). Otherwise, temperatures should become cold in the area of Safed and Jerusalem, with temperatures in the lower single digits from about mid-day Friday until mid-day Shabbat. There should be snow mixed with rain in the early morning in Safed and late morning and early afternoon in Gush Etzion. It will feel quite cold because of the wind chill, as strong winds develop from morning to afternoon.
Next week should turn milder, but the month should end on a colder and rainier note. At the moment, we do not see the possibility for an accumulating snow before February. But, even if we did, we wouldn't really know until just two or three days before at most.
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.