Thursday, December 21, 2017

Cold, Winds, And More Dry For Christmas

There is a large and very cold closed low at 500 mb over the Great Basin (above) this morning. Model forecasts bring this system southeast but also forecast it to weaken rapidly. The matching 850 mb analysis (below - both from SPC) shows an arctic front over the Plains and a pronounced cold front over the Southwest, which will come by here later today. The MIMIC (from the Univ. of Wisconsin) total precipitable water analysis for 6:00 am MST  (second below) shows that very dry air prevails, as this system moves toward the Southwest.

The NWS has issued a hard freeze warning (temperatures of 28 F and colder for several hours) for the early morning hours tomorrow. Here at house, in north part of the City, we have already had two hard freezes - the coldest of which (back on December 9th) took down a 7 ft tall prickly pear at lowest point of backyard.

Looking ahead to Christmas, I've shown 4 panels from the 00 UTC GEFS forecast system - 500 mb above and surface plus precipitation below. Both are valid at 12 UTC (5:00 am) on Christmas Day. Model forecasts weather for the day only over the Northeast and the Northwest. The WRF-GFS forecast from Atmo at 00 UTC (bottom valid thru 5:00 pm on Christmas) forecasts continued over part of the Southwest. 

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