Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 191031

Area Forecast Discussion
National Weather Service Billings MT
331 AM MST Sun Feb 19 2017

.SHORT TERM...valid for Tdy and Mon...

Water vapor imagery shows a low over AZ and northwestern Mexico,
with a weak/sheared northern trof extending through ID and western
MT, the latter of which is producing an area of showers from
southeast ID into our southwest mountains. Further west, a
stronger Pacific trof is moving ashore in WA/OR, with some
lightning noted along the OR coast.

Morning precipitation will be confined to the Beartooth Absarokas.
Look for shower potential to increase this afternoon as stronger
Pacific trof approaches. Cold air aloft along PV axis will allow
for destabilization, and in fact, the timing is such that we could
see a few lightning strikes in our far west in the late afternoon
with lifted indices near -1C. Chance of showers will extend east
across our cwa tonight, with downslope winds limiting precip
potential especially over our western lower elevations. It had
previously looked as if energy/moisture lifting up the high plains
would increase shower potential in our east late tonight, but it
now appears that the Pacific flow will be more dominant, so have
lowered pops back down to scattered for our eastern zones.
Drying/subsidence will work across our cwa late tonight.

Moist Pacific flow will bring more mountain snowfall to the
Beartooth Absarokas Monday and Monday night, with drier downslope
winds prevailing across our lower elevations. Bigger issue will be
wind Monday afternoon and evening as 50+ kts of mid level wind
induces strong lee side pressure falls prior to a weak Pacific
wave. Have upped winds at Livingston and Nye during this time
period, and have introduced messaging for travel impacts for high
profile vehicles on I-90. Stronger wind event is possible
Tuesday...see extended discussion for that.

Temperatures will continue to run well above normal with highs in
the 50s to near 60F, along with relatively mild nights.


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

There are two weather events that we`re watching in the long term
period. The first is potentially windy conditions along the
foothills and lower elevations west of Billings and Roundup on
Tuesday afternoon. The second weather event features a noticeable
change to cooler conditions and a chance for snow late in the

Southwest flow aloft will prevail over the region as a broad
trough of low pressure over the Western US slowly amplifies.
Embedded in this flow a shortwave will quickly eject east into the
Plains on Tuesday. There is considerable differences in the
strength and timing of this shortwave which will change the
impacts for the region. The GFS is the strongest with the pressure
falls and mid-level winds associated with the shortwave which
would lead to stronger winds across western zones. The Euro and
Canadian contain a much weaker wave, thus reducing the wind
impacts. For now took took an even blend between these camps and
have wind gusts around 40 to 50 mph in our western zones and
foothills west of Billings on Tuesday. In addition to the winds,
the downslope flow will be fairly strong across the region. With a
lack of snow cover, Tuesday has a good chance of being the
warmest day of the year as temperatures near the mid 60s. Outside
of windy conditions along the Plains, mountain snow showers and an
isolated chance of rain showers on the Plains will accompany
passage of this wave.

Pressure rises behind Tuesday`s disturbance, and the steady
eastward progress of the broad western US trough, will lead to a
transition day across the region on Wednesday. With weakening
downslope flow, falling mid-level heights, and cooler northerly
flow beginning to take over, conditions will be mostly quiet. As
the trough pushes into Wyoming on Thursday, it will begin to
strengthen and this is when the region will see the best chance
for snow across southern portions of the forecast area. Model runs
over the last few days have trended weaker and further south with
this feature. As of this update, significant snow over our
forecast area doesn`t seem likely, but uncertainty is high and
details are not clear now so stay up to date with our latest
forecasts. I did reduce precipitation chances slighty for
Thursday, but kept temperatures relatively unchanged as model
consensus for cooler temperatures is still good. High temperatures
will mostly be in the 30s on Thursday and Friday of next week as
a broad trough across the northwest US remains in place. While
uncertainty in precipitation chances continue through next
weekend, the broad trough in place will keep temperatures near
normal. Left a slight chance for precipitation through the weekend
to account for these differences. Dobbs



Periods of snow in the high elevations will lead to frequent
mountain obscurations through the TAF period. A few rain showers
could leak into the Plains near KLVM so left a mention of VCSH
through the TAF period there. Otherwise, mostly light west and
southwest winds will prevail over the region today with VFR
conditions expected. Dobbs


    Tdy Mon     Tue     Wed     Thu     Fri     Sat
BIL 058 034/056 040/065 035/050 027/033 020/031 015/032
    1/E 20/B    02/W    12/R    55/S    33/S    22/J
LVM 055 030/052 040/058 029/042 019/029 014/029 011/029
    3/T 22/W    24/W    24/O    55/S    32/S    32/J
HDN 055 030/055 036/064 032/050 024/035 019/033 015/034
    1/E 40/B    02/W    11/B    55/S    32/S    22/J
MLS 052 034/054 035/063 034/050 027/035 019/032 017/034
    0/E 40/U    12/W    11/B    23/S    21/E    12/J
4BQ 059 034/057 035/066 035/050 026/036 018/032 015/033
    1/B 40/U    01/B    11/B    56/S    42/S    12/J
BHK 055 035/052 034/063 034/046 024/032 016/030 014/031
    0/B 51/U    12/W    10/B    24/S    11/E    12/J
SHR 057 030/055 034/064 032/047 023/032 016/029 009/029
    2/W 30/U    01/B    13/R    76/S    43/S    32/J




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