More Sun, More Haze, Little Snow

Posted Saturday, December 15th, 2018 by Pete Saunders

TLDR:

Expect sunny conditions to remain through Sunday evening. On Monday, there looks to be a decent chance for light mountain snow with small accumulation totals. There’s another chance of light snow in the mountains Tuesday night into Wednesday. Afterward, high pressure and an associated inversion entrench themselves over the Intermountain West during the middle-latter parts of next week.


Today – Monday

Well, it’s been another gorgeous Saturday in the mountains with plenty of sunshine and great visibility for skiers and boarders out there. In the valley,  it’s also been a sunny one, but as most of you know already, it’s also quite hazy. We currently are sitting under a subsidence inversion today while a shortwave ridge passes through the area. There will be a slight increase in cloud cover tonight with a passing weak short wave trough, but it looks like there will be very little moisture associated it, and thus no precipitation. The ridge will “amplify” (grow stronger along an approximate north/south axis) during the day tomorrow, providing another sun-filled day; beautiful in the mountains, but rather hazy in the valley. Below is a NAM forecast sounding for tomorrow morning from weathernerds.org showing a strong inversion as temperatures increase rather rapidly with height at low levels from the surface to about 800 hPa (~6500 ft).

NAM forecast sounding for SLC valid tomorrow morning at 12z (0500 MST). This profile shows a rather strong inversion (temperature increasing with height) at low levels from the surface up to ~6500 ft Courtesy: weathernerds.org

On Sunday night, an approaching long wave trough associated with a Pacific storm will allow increasing cloud cover that will continue throughout the day on Monday. That trough (shown below) will remain rather strong over the West Coast from Washington down to California until Monday afternoon or so, and provide the northern Wasatch Mountains with a chance for a little bit of snow. Expect small amounts in the rage of 0.5-1″ for most resorts.

GFS 250 hPa winds forecasts valid 12z (0500 MST) Monday morning showing a rather strong long wave trough over the West Coast of the U.S. Courtesy: tropicaltidbits.com
FV3-GFS 250 hPa winds forecasts valid 12z (0500 MST) Monday morning showing a rather strong long wave trough over the West Coast of the U.S. from Washington down to California. Courtesy: tropicaltidbits.com

Tuesday – Thursday

The aforementioned long wave trough will move in to the area, but will have weakened, and with flow splitting a bit to the north and south, Utah looks like it will lose out a bit on quite a bit of precipitation. Below is a figure of the GFS forecast for 06z Tuesday (2300 MST Monday) showing how the flow within the long wave trough is forecast split just a bit, leaving Utah in more stagnant flow region.

GFS 250 hPa forecast winds valid for 06z Tuesday (2300 MST Monday) showing flow within the long wave trough forecast split to the north and south of Utah. This places us in a more stagnant region between the jet stream. Courtesy: tropicaltidbits.com
FV3-GFS 250 hPa forecast winds valid for 06z Tuesday (2300 MST Monday) showing flow within the long wave trough forecast split to the north and south of Utah. This places us in a more stagnant region between the jet stream. Courtesy: tropicaltidbits.com

There should be enough energy to produce snowfall in the mountains, and potentially snow and/or a snow/rain mix in the valleys. However, accumulations should be rather light, and the trough may not be strong enough to completely break us free of inverted coditions. Details of actual accumulations will be posted in the next couple of days. After Wednesday, though, a ridge builds in and keeps us locked in on valley haze and potential fog as an inversion is allowed to stay settled in. Below is the SLC NWS office inversion outlook for Sunday through Monday. As you can see, conditions worsen from Sunday through next Thursday as haze, fog and stratus increase during that time period.

NWS Salt Lake City office outlook for the current and upcoming inversion setups
NWS Salt Lake City office outlook for the current and upcoming inversion setups

Long Range:

We’ll continue keeping our eye out for potential storms and inversion-breaking weather in the long range. As of now, it doesn’t look like we will see much of anything until perhaps next Saturday when a short wave trough might make its way through. And as has been mentioned by Lucas already, there is another potential for a storm on or near Christmas Day. Stay tuned for more details on that!

Have a great rest of the weekend, and enjoy those bluebird conditions!

-Pete

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