Settled weather moves in

Posted Wednesday, December 5th, 2018 by Pete Saunders

TLDR: Low level moisture will linger through late week with mostly cloudy conditions and very light mountain snow accumulations (slightly more snow for southern Utah/Brian Head). Then, settled weather moves in over the weekend with sunny, bluebird days for the mountains and valley haze as high pressure builds in. This ridged pattern looks to dominate over our area for awhile until possibly next week Tuesday when models indicate a possible trough making its way through Utah.


TODAY

Ok so it’s been an interesting past couple of weeks, wouldn’t you say? Several systems have come through Utah, providing us with plenty of mountain snow for most of our resorts. And just this morning, we had a band of snow move through northern Utah associated with a mid level deformation axis extending from an upper level low off the coast of California. This produced an additional 1-2″ of snow across the upper Cottonwoods and Park City ski area, with little to no accumulations elsewhere.

Webcam at Park City Mountain Resort's Crescent Ridge at 3:00 PM MST
Webcam at Park City Mountain Resort’s Crescent Ridge at 3:00 PM MST. Image courtesy of parkcitymountain.com

Throughout the day, it’s been cloudy with low level moisture and very light low level winds as promised by the GFS time-height forecast chart Lucas shared yesterday. Above is an eastward facing webcam image from Park City Mountain Resort’s Crescent Ridge this afternoon showing pleasant but cloudy conditions at the mountain. Below is a southward facing webcam time lapse from the University of Utah’s William Browning Building (chpc.utah.edu) this afternoon, showing a steady stream of mid-upper level moisture flowing from out of the southwest ahead of that upper level low off the California coast. Note the valley haze and periods of low level moisture condensing into low stratus clouds over the Salt Lake Valley.


Thursday – Friday

We’ll be stuck in somewhat zonal (west to east) flow over the next couple of days in northern Utah as the low pressure system currently just off the California coast slides well to our south and east. So, expect cloudy conditions with maybe a snow shower or two in the northern Utah mountain resorts during this time, but don’t expect to see much in the way of accumulation. However, in southern Utah things should be a bit more interesting as shortwaves ahead of that low pressure system should be able to draw more moisture into that region. Brian Head should see increasing snow shower activity Thursday afternoon and evening, with the bulk of snow activity occurring Thursday night into Friday morning, winding down by Friday evening. Expect 2-3″ of snow Thursday through Friday evening.

THE WEEKEND!

As a ridge builds in from the west, expect the middle and upper level moisture to move out, and sunny skies to make their way in over Utah. While beautiful blue bird conditions should exist for the mountain resorts this weekend, valley haze associated with trapped moisture and particulate matter (…pollution) will pay us a pretty lengthy visit as a low level inversion (temperatures increasing with height) sets in. Below is a forecast sounding from weathernerds.org showing a weak inversion Saturday morning. Unfortunately, we could see some valley low stratus/fog associated with the inversion this go around, especially Sunday through Monday. Great excuse to get up to the mountains and ski under near perfect conditions!

Weathernerds 12z 5 Dec GFS forecast sounding valid Saturday morning at 12Z (5 am MST) over Salt Lake City. Note the low level inversion, where the red line indicates warming with height from the surface (850 hPa) to approximately 800 hPa (~6,500 ft above sea level). You can tell this is an inversion by the way the red line is tilted slightly to the right compared with the light brown lines (temperatures) going from bottom left to top right. Image courtesy of  weathernerds.org by Matt Onderlinde.

Early Next Week

High pressure should stick around until about Tuesday next week when a trough looks like it could make its into northern Utah. Right now the ECMWF has this as a rather strong, compact wave that would definitely break up the inversion and likely provide the mountains and valleys with precipitation. Below is the ECMWF 500 hPa relative vorticity, height and streamline forecast for 18Z 11 Dec (11 am MST next Tuesday morning) where it shows this trough entering into northern Utah with strong relative vorticity values and cyclonic flow.

ecmwf_z500_vort_west_26
12Z 5 Dec ECMWF 500 hPa relative vorticity, height and streamline forecast for 18Z 11 Dec (11 am MST next Tuesday morning). Image courtesy of models.weatherbell.com

While we wait to see what happens with the potential next system on Tuesday, stay out of the valley smog and enjoy mountain sun and snow this weekend!

-Pete

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