Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 250248

Area Forecast Discussion...Updated
National Weather Service Billings MT
848 PM MDT Mon Oct 24 2016

Showers have spread into the southwest mountains this evening and
were approaching Livingston. The ascent stretched all the way back
into eastern Idaho. This activity lines up with 700mb
frontogenesis combined with coupled jet forcing. Jet forcing will
weaken overnight as the jet weakens and slides eastward into
Wyoming. High resolution models keep the precipitation mostly tied
to the terrain with jet forcing staying south. Have raised pops
west of Billings to account for current activity, with a slower
tapering off period overnight. High elevations were still pretty
warm with 700mb temperatures above 2c. Would not expect to see
much accumulating snow, but a rain and snow mixture is likely,
especially above 8 thousand feet. TWH


.SHORT TERM...valid for Tue and Wed...

Southwest flow was over the area this afternoon with middle to
high level clouds streaming overhead. An upper low off the Pac NW
coast was advecting moisture and energy through the southwest flow
and over the Northern Rockies. As a result, isolated to scattered
showers are possible for western areas late this afternoon and
evening, with the best chances for showers over the southwest
mountains and foothills.

A weak front will move across the area on Tuesday causing winds to
shift out of the northwest. Some showers are possible as well during
the afternoon and evening for areas along and north of a
Livingston-Billings-Miles City line as the aforementioned front
and a weak disturbance provide some forcing. Drier weather is
expected for Wednesday as ridging builds over the region.
Temperatures will continue to be above normal with highs expected
to be in the middle to upper 60s on Tuesday and temperatures a few
degrees cooler on Wednesday. STP

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

The ECMWF ensembles showed uncertainty with the extended pattern
through the period, while the GEFS showed more confidence in the
pattern. Despite the more confident GEFS, there was a lot of
spread amongst various parameters in the GEFS plumes beginning on
Friday. The deterministic models were not in good agreement
through the period, so forecast confidence was not very high.

Jet energy moves into the ridge on Thursday, and the GFS pushes a
strong shortwave into the ridge. A cold front accompanies the GFS
wave. Went ahead and introduced some low mountain PoPs Thu.
afternoon over the western mountains. Despite model differences,
it looked like a warm day with temperatures well into the 60s.
Another wave approaches the area from the W on Fri. with
differences in model timing. The ECMWF was faster with the system
than the GFS. Model blends brought PoPs into the W so have gone
that route. Blended temperatures were in the upper 50s/lower 60s.
Both models had precipitation over the area Fri. night and Sat.
due to the wave, so had slight chance to chance PoPs in the
forecast. Expect slightly lower temperatures on Sat. than on
Friday. Ridging on Sun. gives way to another wave and front for
Monday. Kept PoPs across the area on Monday. Temperatures will be
in the 60s on Sun. and a bit lower for Monday. Arthur



Showers have moved into the southwest mountains obscuring the
Beartooth/Absaroka mountains. Showers will be scattered from KLVM
to west of KBIL. Showers will weaken as the night wears on. The
night should remain mostly VFR with the exception of isolated MVFR
conditions in heavier showers nearest the higher terrain.
Southwest winds have gusted to 25kts at KVLM this evening, but
these winds should weaken through the night. TWH



    Tue     Wed     Thu     Fri     Sat     Sun     Mon
BIL 047/068 044/066 047/069 046/061 041/059 043/063 043/061
    11/B    20/B    00/B    11/B    22/W    11/B    23/W
LVM 045/065 042/066 046/069 043/062 040/061 042/063 041/058
    52/W    21/N    10/N    12/W    32/W    12/W    33/W
HDN 043/070 041/068 042/072 044/063 040/061 040/066 040/062
    11/B    10/B    00/B    11/B    22/W    11/B    13/W
MLS 040/066 043/065 043/069 045/059 039/055 040/061 041/060
    11/B    20/B    00/B    11/B    22/W    11/B    13/W
4BQ 042/069 042/067 042/073 044/063 039/059 040/065 041/066
    01/B    10/B    00/B    11/B    22/W    11/U    14/W
BHK 037/061 040/063 040/068 042/057 034/051 036/060 038/058
    01/B    10/B    00/B    01/B    22/W    11/U    13/W
SHR 039/068 039/067 040/073 042/063 038/064 038/066 038/063
    11/B    10/U    00/B    01/B    21/B    11/B    12/W




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