Area Forecast Discussion
Issued by NWS Billings, MT

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266
FXUS65 KBYZ 210124
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
724 PM MDT Wed Sep 20 2017

.UPDATE...

Minor update this evening, primarily to cancel the High Wind
Advisory for Livingston, and the Beartooth Foothills. Winds have
dropped of significantly in and around Livingston this evening.
Winds are expected to become breezy again overnight, but are not
expected to be anywhere near Advisory strength. Associated wind
grids were also updated to better reflect current and expected
winds for the remainder of this evening and overnight.

Finally made some minor adjustments to pops to extend slight pops
across northern zones further east into Forsyth and Miles City
areas. Current echoes in that area do not a appear to be
significant precip reaching the ground, but increasing activity
across the west is spreading quickly eastward toward those areas
at this time. AAG

&&

.SHORT TERM...valid for Thu and Fri...

Winds have gusted to 59 mph in
the Livingston area this afternoon. As a surface trof shifts east
of the Livingston area this evening expect those gusty winds to
trend down quickly. Wind Advisory remains in place through 9 pm.

Cool and unsettled conditions on tap heading into the weekend.
Latest model runs remain in good agreement with an upper trof
developing over the area tonight then stalling out and slowly
filling into early next week. This puts the region in an cool
unstable regime under the trof with periods of stronger energy
pushing through the area. Though precipitation chances continue
through the weekend, tonight through Friday night will bring the
best chances for widespread significant precipitation to the
area. One area of jet energy works across tonight, mainly
impacting western mountains and foothills, but spilling low pops
into the plains as far east as Broadus and Miles City overnight.

By tomorrow afternoon winds turn northeast across much of the
area as Canadian surface high drops south along the spine of the
rockies. This will enhance upslope flow into areas mainly west of
Rosebud county, with that lift interacting with additional broad jet
level divergence to increase precipitation over those areas.
Current forecast has 0.5in to 1.5in of precipitation (heaviest in
the foothills) for areas west of Rosebud county through Saturday
morning, with up to a quarter of an inch over drier SE MT. Some
ensemble members go significantly higher with precipitation
amounts, so could need more QPF as forecast evolves over the next
36 hours.

Snow...Looking at 10 to 20 inches of snow across the
Beartooth/Absaroka mountains over the next couple of days. While
the heaviest snow looks to fall Thursday afternoon into Friday, 4
to 8 inches is possible tonight into tomorrow morning so elected
to start the Winter Storm Warning upgrade tonight. The Beartooth
Pass is still closed as of this writing, and given the forecast
going forward it may stay closed through the weekend. Kept the
Crazy mountains and Bighorn mountains out of the Winter Storm
Warning for now, mainly due to tonights initial snowfall not
impacting those areas much. May still need a highlite for these
areas with the main precipitation push later on Thursday.
Thursday night could also see advisory type snow in the Beartooth
foothills depending on how fast colder Canadian air deepens over
the area. Chambers


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

The trough will be slow to move out of the area which will keep
the precip chances lingering through the weekend. In general the
amounts will be lighter as the through will be filling and
dissipating through the period. Going into Monday, a ridge will
begin to build across the western US which will put the area in
northwest flow. The ECMWF continues to show with the 12z run a
weak shortwave moving through the flow bring another quick chance
for some more rain, Monday and Tuesday. However, the GFS remains
dry. With the downslope flow, expecting a warming trend through
the week, so nudged the temperatures a little closer to raw
guidance. Reimer
&&

.AVIATION...

Expect VFR conditions to continue. Cloud cover continues to
increase across the west, with scattered showers are possible
overnight ,with best potential across the west and southern routes.
Some localized MVFR conditions are possible with any heavier
showers. Some mountain obscurations are expected overnight. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    Thu     Fri     Sat     Sun     Mon     Tue     Wed
-----------------------------------------------------------
BIL 044/054 039/044 035/048 036/052 037/055 039/060 041/062
    32/R    88/R    65/W    33/W    21/B    11/B    10/U
LVM 038/052 034/042 030/046 028/051 029/053 034/057 036/059
    63/R    88/O    63/W    22/W    21/B    12/W    11/U
HDN 045/058 040/049 038/051 036/054 036/057 037/062 039/064
    33/R    86/R    55/W    44/W    31/B    11/B    11/U
MLS 045/061 042/054 038/052 037/054 038/056 038/061 040/065
    22/R    54/R    33/W    44/W    32/W    11/B    11/U
4BQ 046/064 041/055 038/047 037/051 036/052 035/058 037/062
    22/R    23/R    45/W    53/W    31/B    11/B    11/U
BHK 045/064 041/055 038/051 038/053 036/054 035/058 038/064
    11/B    23/R    34/W    54/W    32/W    11/B    11/U
SHR 044/058 038/050 035/045 032/048 032/051 031/056 033/059
    34/R    65/R    56/W    54/W    32/W    21/B    11/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until 6 AM MDT Saturday FOR
      ZONE 67.
WY...None.

&&

$$
weather.gov/billings



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