Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 192210

Area Forecast Discussion
National Weather Service Billings MT
310 PM MST Sun Feb 19 2017

.SHORT TERM...valid for Mon and Tue...

Northern branch of upper split flow will affect our region
tonight as a Pacific trof moves across the region. This will
produce rain and snow showers, most numerous in the high country
with isolated to scattered variety on the plains overnight. Things
are evolving a little faster in the pressure fields than
originally progged, so we sped up the timing of showers in the
east a bit.

Flat ridging/westerly flow in the mid levels then prevails for
Monday. However, pacific moisture will continue to stream into the
Absaroka/Beartooth mountains. So will keep PoP`s categorical in
the high country through Monday night. By late Monday into Monday
evening model proggs continue to show increasing 700 mb winds
across our west along with a tightening pressure gradient over the
foothills. We expect this to result in gap flow winds in usual
areas around Livingston, Big Timber and Nye by Monday night. The
best chance of hitting advisory level speeds is Tuesday as strong
850-700 MB winds and steep lapse rates develop by the afternoon
affecting areas from Billings westward. Models are not quite in
sync at this point timing-wise or spatially, so will let future
shifts determine the when and where details for any wind

Temperatures will continue to run well above normal with highs in
the 50s Monday, and with strong downslope winds to aid warming
Tuesday, temps into the 60s look likely. BT

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

An unsettled period is still expected for the extended, but the
chances for any significant precipitation are looking less and
less likely.

A trough will be oriented N-S along the W coast on Wed., with
vorticity moving downstream through the forecast area out of the
trough. A cold front pushes through NE MT on Wed., with the bulk
of the precipitation behind the front. Kept chances for rain/snow
showers over and near the mountains and along the northern
periphery of the forecast area. Deep mixing ahead of the front
will allow temperatures to climb through the 40s. The upper trough
rotates E through Thursday with limited energy over the area. The
GFS keep the trough an open wave as it moves into the central
plains Thu. night, while the ECMWF moves a weak cutoff into IA.
Comparing these solutions with previous model runs showed a
weakening system. Had chance PoPs over the area through Thursday,
when the low-level flow becomes easterly upslope for high chance
PoPs. Had lower PoPs Thu. night as the system shifts away from the

More energy crosses the area on Friday before a trough moves SE
through the region Sat. or Sat. night depending on the model.
There were moisture differences between the models during this
period so went with CONSALL PoPs which reflected a model blend.
Next upper low/trough starts digging into the Western U.S. on
Sunday, sending moisture into the western zones for slight chance
PoPs. Wed. will be the warmest day of the extended, before 850 mb
temperatures drop below zero degrees C, allowing for highs in the
30s. Arthur



Isolated rain and snow showers will affect the area for the
remainder of the afternoon, accompanied by MVFR/IFR conditions or
lower. Isolated to scattered rain and snow showers will move E
across the area tonight with MVFR to IFR conditions. An isolated
lightning strike is not out of the question through this evening
with the showers. There will be areas of mountain obscuration
through tonight with widespread obscuration over the Beartooths
and Absarokas. VFR will return to the region on Monday with
mountain obscurations increasing in the W in the afternoon. Expect
LLWS over KSHR on Monday. Arthur



    Mon     Tue     Wed     Thu     Fri     Sat     Sun
BIL 034/055 039/065 035/049 026/037 020/031 016/032 018/035
    20/B    02/W    11/B    35/J    33/J    22/J    21/B
LVM 029/050 039/056 029/041 017/032 015/028 010/028 013/033
    22/W    24/W    23/W    35/J    33/J    32/J    22/J
HDN 030/054 035/062 032/050 024/037 018/033 016/033 015/037
    30/B    02/W    11/B    35/J    33/J    22/J    11/B
MLS 033/053 035/062 034/048 027/036 019/032 017/034 019/038
    20/U    02/W    12/W    23/J    22/J    32/J    11/B
4BQ 033/057 037/067 034/050 025/038 018/032 016/034 016/039
    20/U    01/B    11/N    36/J    32/J    32/J    11/B
BHK 034/052 034/063 033/046 025/033 016/028 014/031 016/035
    30/U    01/B    12/W    24/J    21/E    32/J    11/B
SHR 030/055 036/063 031/048 023/035 016/030 011/030 011/036
    20/U    02/W    12/W    46/J    33/J    32/J    11/B




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