Thursday, January 07, 2016

Quick update

I have been away this morning, so just a quick update for the current (third) event of this week. Yesterday (January 6th) all of the severe thunderstorm activity in the country occurred in California - above shows SPC plot of storm reports they received.

Currently it is snowing away up on Mt. Lemmon and sprinkling some down here in the city. Below is General Store webcam view up in Summerhaven this morning - unfortunately their webcam does superpose a time stamp, so exact time of image unknown.

The GFS QPF plumes for TUS (above, from 06 UTC last night) forecast a very substantial event for the airport between now and tomorrow morning (average of the ensembles in black indicates around 0.60 inches of rain).

While the new, 12 UTC WRF-NAM run does not forecast as much rainfall here in the City, it does forecast a number of periods with quite strong radar echoes (above shows composite echoes valid at 8:00 pm MST this evening). Mike Leuthold emailed similar forecasts to me last evening, noting that it looked like there could be thunderstorms around later today. The forecast WRF-NAM soundings forecast for late in afternoon through the night are very interesting. There are some periods with enough CAPE for thunderstorms to occur in eastern Pima County. The forecast skew-T shown below is valid at 3:00 am tomorrow morning and indicates that the model forecasts the 500 mb temperature to fall to -30 C. So as the cold air at 500 mb moves across southern Arizona this afternoon and during the night, there could be thunderstorms and graupel, with the snow level falling very low. Thicknesses could drop low enough during the night for parts of the metro area to see a few flakes before the event winds down.

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