Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 200316
AFDBYZ

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

.UPDATE...

Surface low pressure over southeastern Montana continues to push
eastward at this hour. Associated with that low, scattered rain
showers extending from the southern Bighorns northeastward to
Miles City will continue to move eastward through the rest of the
night. Given the radar coverage, have bumped precipitation chances
up overnight for those areas. As temps fall behind the low some
change to a rain/snow mix along the higher terrain is possible.
Moisture will continue to plume into the Beartooth/Absarokas
tomorrow, but shower coverage will come to an end over the low
country as ridging slides in place. Walsh

&&

.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 though 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 when and where details for any wind
highlights.

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
area.

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
&&

.AVIATION...


Scattered rain and snow showers will bring the potential for local
IFR conditions this evening across the area, trending into far SE
MT overnight. Wind gusts to 30kts are also possible near this
activity. Expect shower activity to diminish from west to east
overnight, with VFR ceilings persisting into Monday morning.
Isolated pockets of fog are possible east of a Miles City to
Broadus line after midnight with local IFR conditions,
dissipating around sunrise. Chambers
&&

.PRELIMINARY POINT TEMP/POPS...

    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
    30/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
    50/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
    50/U    02/W    12/W    46/J    33/J    32/J    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings


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