Weather It Is (Winter Storm Warning: Noon Update)

Good Afternoon:

The latest high resolution model forecast now extends until midnight Friday.  The following snow and rain forecasts represents the latest forecast information from the 4 km forecast model.

To understand the forecasts below, it is important to note that the latest synoptic scale pattern has changed for the colder.  Average minimum temperatures are down to -31 C in the Jerusalem area at 500 mb, -14  C at 700 mb, and -3 C at 850 mb.  Moreover, more precipitation is predicted to fall than the last update in the Jerusalem area. This means that the snow should fall a bit heavier and for a few more hours in the morning on Friday than in the previous forecast expectation.

The snow forecast has also evolved to favor the center of the country at the expense of the area of Sefad and the Golan. The reason for this is that the precipitation amounts in the center are suppose to be about twice those in the north.

Here are the latest snow forecast totals.

Hermon: 50 cm
Golan: 25 cm
Gush Etzion: 25 cm
Jerusalem: 10-20 cm, including about 15 cm in the Old City.
Bet-El/Har Bracha: 15-20 cm
Sefad: 5 to 15 cm.

If nothing significant changes in the forecast synoptic pattern, then these values are conservative snowfall projections because they are from the 4 km versus the 1.3 km gridded forecast.  However, changes in the forecast synoptic pattern can, as noted, change the forecast snow amount irrespective of any impacts of changing the grid resolution to 1.3 km within 36 hours of the event. Yet, all of the 500 mb temperatures are now below -30 C, with some as low as -33 C, so the potential for changes in the forecast snow amounts because of changes in the synoptic pattern is somewhat less than the previous forecasts. 

Regarding the forecast for Friday night, there is a 10% chance that another surge of cold air will enter the system, extending snowfall into this period.

Additional note: the area of potential flooding will extend through Gaza eastward to Beer-Sheva, where 50 to 100 mm of rain will likely fall.

Barry Lynn