Weather It Is (Storm Update)

Good Afternoon:

Winter Storm Warning.

Heavy snow possible on Tuesday/Tuesday night for Jerusalem and surrounding areas.

The first part of our storm is proceeding as forecast.

In fact, a coating of snow is possible tonight in Jerusalem and several centimeters in higher locations surrounding the city and Gush Etzion. Light snow amounts are expected in the city of Sefad.

With regard to forecasting the second part of this event, there is a major difficulty.  While temperatures are going to turn frigid, we have the unusual situation where the lower atmosphere (850 mb) will somewhat disconnect from the 700 mb and 500 mb levels.

The 850 mb level will bring intense code from Tuesday afternoon into Thursday morning (and temperatures may not rise above freezing until Thursday night or even Friday morning). The 700 mb and 500 mb levels will bring in two periods of very cold air, Tuesday and Thursday mornings.  The cold air will bring a "kink" in the isobars, indicating the potential for strong upward motion as a "vorticity" maximum moves through.

However, because of the disconnect between the 850 mb and other levels, moisture will become more confining.  Yet, our 12 km WRF shows continuing high 700 mb humidities Tuesday night from about Sefad southward to Mitzpe Ramon.  If this verifies, then the potential for heavy snow Tuesday and Tuesday night will more likely be realised in Jerusalem and surrounding areas.

The global models do not show very much precipitation occurring after Tuesday evening.  However, they don't have the grid resolution to be able to predict small scale, but potentially very high snow producing convective clouds from Tuesday night into Wednesday afternoon.

Our high resolution model is showing more precipitation than the global models, but we are hesitant to spell out accumulation amounts until we get closer to the time of interest.  The temperatures will be cold, but without the added focus of our high resolution model were just guessing.

In the meantime, heavy rain continues with gale force winds in many locations.  Late this afternoon snow accumulates several centimetres or more in high areas around Jerusalem, including Gush Etzion. Jerusalem will see a coating of snow as well after midnight.

Barry Lynn