FXUS65 KBYZ 181020

Area Forecast Discussion
National Weather Service Billings MT
320 AM MST Fri Jan 18 2019

.SHORT TERM...valid for Tdy and Sat...

Shortwave moving through the region this morning was bringing
areas of light snow. Light snow will continue over the area
today as the shortwave shifts south and east into the Dakotas.
Best snow chances are for areas generally east of a Billings to
Sheridan line. Snow chances will gradually diminish by this
evening as forcing decreases. Outside of the mountains, an inch or
less of snow accumulation is expected today. At the surface, a
trough over central Montana will induce downslope winds over
western areas, with easterly winds elsewhere. Westerly winds to
50 mph are possible along the western foothills.

Ridging then builds over the region for Saturday, with some
moisture working into the southwest mountains producing snow
showers. Lee-side troughing at the surface will once again tighten
the pressure gradients causing winds to increase along the western
foothills. May need a Wind Advisory for the Livingston and Nye
areas on Saturday as winds could gust to 60 mph. A warm front then
looks to lift north into the area Saturday night increasing snow
chances over the southwest mountains and decreasing winds. A few
inches of snow are possible on south and west facing aspects. High
temperatures will range from the 40s west to the teens east today,
warming into the 40s for most places on Saturday and Sunday. Low
temperatures will range from the 20s west to the single digits
east tonight, with lows in the 20s and 30s Saturday night. STP

.LONG TERM...valid for Sun...Mon...Tue...Wed...Thu...

Heights will fall on Sunday in response to an approaching Pacific
shortwave, and a passing wave to our north in southern Canada. The
combination will result in frontogenesis and the potential for
some light precip especially in our west and north. Surface temps
will be mild enough (highs in low-mid 40s) such that precip will
be in the form of a rain/snow mix and not significant.

Upper trof will move across the area Sunday night and Monday
bringing a chance of snow along with colder temperatures. Latest
trends of the operational models are highly suggestive of a
rather unorganized system as the wave splits moving through the
Rockies. The GFS shows a period of deepened north winds and
upslope snowfall along our southern foothills Monday and Monday
evening, but the ECMWF/GEM/NAM show a less interesting solution
with drier NW winds behind the shortwave. It should also be noted
that the GEFS plumes show a good deal of spread in QPF, but
certainly some of this is due to its poorer resolution. In
summary, there is still a lot of uncertainty but the latest trends
show less snow potential especially for non-upslope areas. Expect
snow amounts to range from an inch or less across the lower
elevations (including Billings), to 2-5 inches along the southern
foothills, and a little more than that over the mountains. If
moisture remains high on the back side of the trof when winds
shift northerly, places like Red Lodge and Story could see more
snow than this.

The remainder of next week will be characterized by a strong ridge
along the Pacific coast and northerly flow over our region. This
is a pattern of high uncertainty for us, with potential for gusty
downslope winds and periodic surges of colder Canadian air.
Currently, it looks like a period of strong foothills wind late
Tuesday into Wednesday, followed by a Canadian front on Wednesday,
another period of wind Thursday and perhaps a another clipper by
next Friday. A reasonable expectation of temperatures would be
above normal in our west and near to below normal in our east, but
again high uncertainty here.




The combination of light snow, low clouds and some fog will bring
continued poor flight conditions across much of the region today,
especially from KBIL eastward. Expect widespread MVFR to LIFR, and
mountains will be predominantly obscured. The western foothills
will improve to VFR as downslope winds increase. Gusts of 30-40
kts are expected at KLVM tonight. Flight conditions will improve
from west to east across much of the forecast area tonight as
winds shift from light easterly to westerly.

For KBIL, though early morning light snow has improved flight
conditions as of 09z, occasional reductions to IFR/LIFR are
expected through the early morning hours and may impact some




Tdy Sat Sun Mon Tue Wed Thu
BIL 030 023/045 033/045 030/036 021/037 027/040 025/039
4/S 11/E 24/O 66/S 21/B 24/W 32/J
LVM 041 028/046 034/046 028/035 018/036 027/039 023/038
3/O 13/W 35/O 76/S 21/N 35/W 32/J
HDN 028 018/045 028/046 026/037 017/037 022/041 021/039
5/S 11/E 23/O 67/S 31/B 25/W 42/J
MLS 021 013/038 026/041 024/031 014/031 021/036 018/033
6/S 11/B 11/E 46/S 11/B 13/J 22/J
4BQ 025 017/042 027/043 025/034 015/032 019/036 019/033
6/S 21/B 11/E 26/S 30/B 14/J 32/J
BHK 018 008/037 024/041 022/029 010/030 016/034 015/031
6/S 11/B 10/B 36/S 20/B 13/J 22/J
SHR 032 018/046 026/046 024/035 014/035 017/040 018/036
3/S 21/B 22/S 37/S 31/B 24/W 42/J




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