Monday, October 28, 2013

Red Sky at Morning...

Salt Lakers enjoyed a spectacular sunrise this morning, but as the old saying goes, red sky in morning, sailors take warning.  The winds of change are upon us and our long run of sunny fall weather is coming to an end.

Sowing the seeds for this change is a trough that dug rapidly and deepened over the Great Basin overnight last night.  This is a classic case of what meteorologists call downstream development in which the ridge over the Gulf of Alaska amplifies followed by trough amplification over the western U.S., as shown in the 500-mb geopotential height loop below which covers the 48-hour period ending at 1200 UTC (0600 MDT) this morning.

The trough amplification has led to gusty winds over much of Utah.  Over the past 6 hours, peak gusts reported to MesoWest include 61 miles per hour at Cedar City, 54 miles per hour at Stockton Bar (Tooele Valley), and 52 miles per hour at Dugway Proving Grounds.  The deepening low has also generated a modest downslope windstorm with easterly flow observed along the Wasatch Front north of Olympus Cove.

Source: MesoWest
Some of the strongest winds thus far have been observed at the University of Utah, which experienced a peak gust of 39 miles per hour at 7:40 AM this morning.

The models the past couple of days have been all over the place with regards to the timing, distribution, and amount of precipitation that will accompany the trough as it moves across Utah between now and Wednesday afternoon.  I feel like that computer in WarGames, which concludes after playing many rounds of simulated thermonuclear war that the only winning move is not to play.

Source: WarGames
Let's just go with periods of mountain snow beginning late today through Wednesday with a total accumulation of several inches in the upper Cottonwoods.  The weather in the valley will be unsettled and much cooler than we've experienced over the past week.  The benches may even see some flakes on Tuesday and Wednesday.

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