Winter Storm in Wyoming, April 17, 2018

Area Forecast Discussion
National Weather Service Billings MT
319 AM MDT Tue Apr 17 2018

.SHORT TERM...valid for Tdy and Wed...

Satellite imagery and upper air analysis show a deep trof over
the western CONUS with a 130kt jet lifting through Utah. Radar
imagery shows an area of showers west of Big Timber-Harlowton and
east of Hysham-Hardin as of 3 am. Ascent will increase over the
next several hours as the UT jet couples with a weaker speed max
lifting through central MT. As this occurs we will see an area of
showers enhance and spread slowly east through the day. Heaviest
precipitation will occur in our south central upslope areas as
N-NW winds deepen from the surface to mid levels.

Main concerns involve the potential for wet snowfall in our
southern upslope areas as surface temps fall to the lower 30s. In
fact, a web cam near Red Lodge currently shows snow falling. Will
need to watch Red Lodge but believe strongest forcing and heaviest
precip will end up east of the Beartooths. Nonetheless have given
Red Lodge a quick inch of snow early this morning. Better snow
potential will be at places like Pryor, Fort Smith, Dayton and
Sheridan. All indications are that we will see a change over to
snow in these areas this morning. Have raised QPF/snow amounts
slightly for 1-3 inches, mainly on the grass. Will hold off on any
winter highlights as we expect roads to remain wet, including
I-90, however there will be areas of poor visibility for the
morning commute. Higher hills of southeast MT will also see some
wet snow, such as Lame Deer Divide, Hysham Hills and Government
Hill. A heads up to travelers. Billings may or may not mix with a
wet snow, but surface temps should stay too warm to allow even a
minor accumulation. Do not think we will get the 0.1 inches of
snow to break the season record at the Billings airport. Lastly,
as N-NW winds deepen, snow will become moderate to heavy for a
period of time over the Pryor and Bighorn Mountains. Have issued a
Winter Weather Advisory for 4-8 inches of snow, with impacts to
travel expected on Hwy 14. This system will exit to the east by
evening.

Otherwise, today will be much cooler with gusty W-NW winds, on the
order of 25-40 mph. There should be some weak showers develop
under the cold pool aloft across our western/central cwa this
afternoon and evening. Will keep pops at isolated to cover this.
Cannot rule out a few low-topped afternoon showers near the
Dakotas border Wednesday afternoon under lingering cyclonic flow
aloft. Otherwise, dry conditions will prevail Wednesday and
Wednesday night as ridging builds in from the west.

Look for temps in the 40s to lower 50s today, then upper 40s to
mid 50s Wednesday.

JKL

.LONG TERM...valid for Thu...Fri...Sat...Sun...Mon...

The 00z guidance came in the the low across the Central Rockies
for Thursday and Friday farther south. The ECMWF did not change
much as its solution has been farther south in general, but the
GFS has trended to be more in line with the EC's solution. As such
have reduced the PoPs. Also, temperatures are trending warmer, The
MEX now has a high on Friday for Billings of 64. While the EC is a
little cooler at only 60, have trended temperatures warmer through
the weekend, with highs in the upper 50s to lower 60s.

Things will cool off some Sunday and into early next week as the
flow flattens in response to a shortwave moving through southern
Alberta and Saskatchewan Sunday. This generally brings an un-
settled pattern to the area, but the models are somewhat uncertain
on the timing of any precip event. Far now generally have some
chance PoPs. Temperatures will generally be in the 50. Reimer
&&

.AVIATION...

Expect breezy northwest winds to continue through most of the day
across the area. Gusts up to 35 mph are possible at all terminals.
Expect precip to end at KBIL and KLVM during the morning, with
KMLS and KSHR seeing rain and snow showers into the afternoon.
Some of these showers could produce MVFR to IFR conditions.
Reimer
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Wed     Thu     Fri     Sat     Sun     Mon
-------------------------------------------------------
BIL 050 031/055 033/055 034/058 035/063 039/061 036/053
    9/W 20/U    11/E    11/B    01/U    11/B    23/W
LVM 045 026/053 028/053 031/059 032/065 033/061 033/054
    4/W 20/B    12/W    21/B    01/U    22/W    24/W
HDN 050 031/055 030/057 033/056 033/062 039/060 034/053
    +/W 20/U    01/E    21/B    01/U    11/B    22/W
MLS 046 033/052 031/055 035/056 034/062 041/060 035/052
    9/W 11/B    01/B    11/B    01/U    11/B    22/W
4BQ 045 033/050 031/054 034/052 034/059 039/059 035/051
    8/W 21/B    01/B    23/W    01/U    11/B    13/W
BHK 040 031/049 028/049 033/048 034/056 039/055 035/049
    7/W 22/W    01/B    12/W    01/B    11/B    22/W
SHR 043 028/053 028/056 033/056 032/065 036/062 034/055
    +/W 20/U    01/E    32/W    11/U    11/B    12/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...Winter Weather Advisory in effect until 6 PM MDT this evening
      FOR ZONE 98.

&&

weather.gov/billings