Sunday, December 30, 2018

Stormy Start To New Year in Southeastern Arizona

First, cold and snow yesterday morning - two views of higher foothills of Catalinas with first visible snow of winter. Above is from my later-than usual morning walk, and view below from the Ferner's looking across our circle.

Temperatures were very cold with the low here dropping to 23 F (currently 24 F this morning) - there was moderate frost and ice on the puddles when I walked.

Above is this morning's  500 mb analysis from NCAR. The very cold, closed low over northwest Sonora is probably causing many temperature problems for so far south and likely snows in the mountains. Below is this morning's NAM forecast of the 500 mb level valid at 5:00 pm MST tomorrow evening. The strong short wave currently over the Northwest digs southward, into the long-wave trough that has persisted for a number of days over the west-central U.S., and is entering northwestern Arizona.

The 06 UTC QPF plumes for the airport from GEFS (above) are very similar to the last two events, forecasting amounts at airport of 0.30" to 0.40" during the night tomorrow. The GEFS actually has 20% to 30 % chances for some snow mixed with the rain by morning on New Years. The forecast below of snowfall through 5:00 am on 1st is from the 06 UTC run of the WRF-GFS at Atmo. If forecast were to verify, road conditions late New Years night would become very dicey on Highway 83 south of I-10 - same for Texas Canyon on I-10 east of Benson.

Finally, a bit about the winds. I wasn't paying close attention to WRF forecasts and Mt. Hopkins is apparently have a 50 - 60 mph high wind event event this morning, although RAWS observations are missing since midnight last night.

As the shortwave approaches tomorrow afternoon winds from the southwest become quite strong over southeastern Arizona. The forecast below is valid at 5:00 pm tomorrow afternoon. If you're going to be out and about New Year's eve, take care.

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