Snow is back already! Active period to last awhile

Posted Saturday, February 9th, 2019 by Pete Saunders

A weakening low pressure system currently over the Intermountain West is providing cloudy conditions over Utah’s mountains today with a bit of snowfall as well. Only up to a couple of inches of snow are forecast for today through this evening, though, as the decaying trough ejects out of our area.

View from Snowbasin Resort this afternoon. It's been mostly cloudy with snow showers for most of the day so far.
View from Snowbasin Resort this afternoon. It’s been mostly cloudy with snow showers for most of the day so far. Courtesy: snowbasin.com

In the meantime, a Winter Weather Advisory has been issued for the Wasatch Mountains from 12Pm Sunday until 4AM Monday morning. A Winter Weather advisory for snow means that periods of snow can cause difficulties traveling on roads with poor visibility. From the National Weather Service office in Salt Lake City:

WinterWxAdv_9 Feb

As a side note, there also is a Winter Weather Advisory for the valleys (and a good portion of the state of Utah).


Sunday and Monday

It should be relatively quiet Sunday morning through the early afternoon as shortwave ridging briefly moves through. There could be a few passing snow showers, but little accumulation is expected during that time. The real fun begins on Sunday afternoon/evening as a cold front associated with an upper low moves through Utah. Between 2-4PM, heavier snow showers should develop just ahead of and along the cold front as is moves into northern and central Utah. 700 mb temperatures (seen below) will be plenty cold for precipitation to be all snow, even in the valleys.

ECMWF 700 mb temperatures at 00Z 11 Feb (Sunday evening) around the time heavier snow will move into the area. Note that temperatures are at least as cold as -11 Celsius, indicating that everything that falls will be snow at all levels, including the valley floors.
ECMWF 700 mb temperatures at 00Z 11 Feb (Sunday evening) around the time heavier snow will move into the area. Note that temperatures are at least as cold as -11 Celsius, indicating that all precipitation that falls will be snow at all levels, including the valley floors. Courtesy: models.weatherbell.com

HRRR forecast analysis shows heavy snow along a convective line associated with the baroclinic zone (area in which cold/dense air is separated from warmer/less dense air) moving through Utah.

HRRR forecast snow/rain radar from 14Z 10 Feb (Sunday morning) through 06Z 11 Feb (Sunday night). Since temperatures will be cold at middle and lower levels, everything that falls should be snow, except for the far SW portion of the state.
HRRR forecast snow/rain radar from 14Z 10 Feb (Sunday morning) through 06Z 11 Feb (Sunday night). Since temperatures will be cold at middle and lower levels, everything that falls should be snow, except for the far SW portion of the state. Courtesy: weathernerds.org

Another look at the HRRR forecast radar without the rain/snow mask reveals relatively strong reflectivity values (>25 dBz) as the line of snow moves through. Contour lines of frontogenesis at 700 mb (crest level) show that these stronger reflectivities are associated with the cold front.

HRRR forecast radar reflectivity and frontogenesis at 700 mb from 14Z 10 Feb (Sunday morning) through 06Z 11 Feb (Sunday night) showing heavy precipitation moving through Utah throughout the day. Since temperatures will be cold at middle and lower levels, everything that falls should be snow, except for the far SW portion of the state. Also note that the heaviest precipitation will be along a baroclinic zone (cold front) at 700 mb noted by the purple contour lines moving along with the higher reflectivity values.
HRRR forecast radar reflectivity (shaded contours) and frontogenesis (unshaded purple contours) at 700 mb from 14Z 10 Feb (Sunday morning) through 06Z 11 Feb (Sunday night) showing heavy precipitation moving through Utah throughout the day. Since temperatures will be cold at middle and lower levels, everything that falls should be snow, except for the far SW portion of the state. Also note that the heaviest precipitation will be along a baroclinic zone (cold front) at 700 mb noted by the purple contour lines moving along with the higher reflectivity values. Courtesy: weathernerds.org

Snow showers should linger behind the low pressure system as a small warm air slowly moves through under a middle level cold pool. This instability (warm air under cold air) should allow for additional accumulations in the mountains and parts of the northern Utah valleys. So how much snow will we get? Here’s a breakdown of what we can expect as of right now through Monday evening:

  • Beaver Mountain: 15-20″
  • Powder Mountain: 20-25″
  • Snowbasin: 16-21″
  • Park City area: 10-15″
  • Cottonwoods: 17-22″
  • Sundance: 7-12″
  • Brian Head: 8-13″

Long Range

After next Monday, things look very active still. There is a lot of model agreement on another strong winter storm with a ton of moisture arriving next Wednesday into Thursday. Furthermore, the overall pattern for the second half of February looks very favorable for storms to pass through our region as models forecast us to be in a generally trough-like pattern. See the 500 mb geopotential height and anomalies animation below showing that the West and Intermountain West will generally have troughs passing through the area for the foreseeable future.

GFS forecast 500 mb geopotential height and normalized anomalies between next Tuesday and two weeks from today. This shows that as of right now the GFS is forecasting for Utah to be under generally "troughy" pattern. If this were to hold up, it could be great for winter storm activity for a long while.
GFS forecast 500 mb geopotential height and normalized anomalies between next Tuesday and two weeks from today. Blue contour shading indicates that as of right now the GFS is forecasting for Utah to be under a generally trough-like pattern. If this were to hold up, it could be great for winter storm activity for a long while. Courtesy: tropicaltidbits.com

Let’s hope we make good use of the “troughy” pattern and keep the winter storm train rolling! Check back tomorrow for an update on forecast storm totals for the storm Sunday/Monday, and we’ll keep you up to date on the potentially big storm Wednesday/Thursday.

-Pete

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