Some Snow On Catalinas Yesterday

It was a very chilly and windy day yesterday, as a portion of the western US trough came by at 500 mb. There were some very light spits of rain here at house and also at other low-elevations. However, snow showers were heavy enough to cause some accumulations and driving restrictions up in the Catalinas - a bit of a winter surprise. The top image shows snow showers sitting on the Catalinas about a quarter to 5 pm yesterday (Sunday, November 28th). The bottom graphic shows the accumulated precipitation forecast from the U of AZ WRF-GFS model run from modningh Friday night. That run indicated accumlations on the highest Catalinas for the period ending at midnight last night. Subsequent GFS model runs continued to keep the precipitaion focus on the Catalinas.

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Summerhaven access restricted by snowfall

Clayton R. Norman, Arizona Daily Star Arizona Daily Star

The first snowfall of the season on Mount Lemmon caused authorities to restrict access on the road to Summerhaven to vehicles with four-wheel drive or snow chains on Sunday.

The Weather Service issued a winter-weather advisory for Mount Lemmon on Sunday, warning of blowing snow, icy roads, low visibility and gusts of up to 45 mph. Shoemaker said the Weather Service had received reports of accumulation of about 3 inches of snow on the mountain around 4:30 p.m. and expected "about another inch or two."

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Another cold morning here at the house, with a low of 21 F (the sixth "hard" freeze here so far this month), and enough humidity for there to be a touch of frost on the roofs at sunrise. The NWS has out a hard freeze warning for the warmer areas of the Tucson metro region for this coming night, as per:

A HARD FREEZE WARNING MEANS WIDESPREAD TEMPERATURES AT OR BELOW 

28 DEGREES ARE EXPECTED...WITH SUB-FREEZING TEMPERATURES EXPECTED

FOR SEVERAL HOURS. TO PREVENT FREEZING AND POSSIBLE BURSTING OF

OUTDOOR WATER PIPES...THEY SHOULD BE WRAPPED...DRAINED...OR

ALLOWED TO DRIP SLOWLY. THOSE THAT HAVE IN-GROUND SPRINKLER

SYSTEMS SHOULD DRAIN THEM...AND COVER ABOVE-GROUND PIPES TO

PROTECT THEM FROM FREEZING. THESE CONDITIONS WILL ALSO KILL CROPS

AND OTHER SENSITIVE VEGETATION.