Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 222121

Area Forecast Discussion
National Weather Service Billings MT
221 PM MST Wed Nov 22 2017

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

High pressure ridging will continue to hold over the forecast
area through Thursday. This will result in dry conditions and well
above normal temperatures. A fast flow aloft will result in
considerable mountain wave activity along the eastern slopes of
the Rockies so periods of clouds will also be likely.

Pressure gradients have slackened a bit today as was expected but
will tighten again tonight and especially Thursday afternoon and
evening along the east slopes of the Rockies as low pressure will
be situated over southern Canada with high pressure across
southwest Wyoming. As a result, expect strong gusty winds to
develop once again across the Livingston area and Beartooth
Foothills tonight and especially Thursday afternoon and evening.

A strong Pacific front moves across the forecast area Thursday
evening bringing an end to the strong gusty winds but will also
bring high chances of rain and snow showers Thursday night into
Friday morning for areas mainly along and west of a Roundup-
Billings- Sheridan line. Overnight lows Thursday night look quite
mild so the precip looks to be mainly be in the liquid form. This
front will flatten the ridge resulting in lowering heights and
cooler temperatures for Friday. Highs Thursday will be around
record levels with readings in the 60s. By Friday, temperatures
cool back into the upper 40s to lower 50s, but this is still about
10 degrees above normal. Hooley

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

Uncertainty continued surrounding the system for the Monday/Mon.
night timeframe. GEFS/ECMWF ensembles showed increased
uncertainty with the pattern during this time, while the
deterministic models differed with the timing and orientation of
the Pacific wave. Thus made a few adjustments to this timeframe
based on latest model compromises.

Otherwise, upper ridging builds over the region Saturday into
Sunday. Pattern gives way to SW flow aloft on Sunday on the more
progressive GFS, while ridging dominates the area on the ECMWF.
Either way, there will be just a slight chance of rain/snow
showers over the SW mountains. Above normal temperatures were on
tap for Sat. and the warmest day was still Sunday with highs now
in the low to mid 60s. Expect the typical gusty winds around KLVM,
Big Timber and Harlowton through Sunday. Faster GFS brings the
cold front more forcibly into the region Sun. night than the
ECMWF. Rain showers and a few snow showers will spread into the
west and central parts of the area with windy conditions in KLVM
ahead of the front. Large model QPF differences for Monday and
Mon. night. Temperatures at 850 mb drop below zero degrees C Mon.
night. Had chances of rain/snow showers across the area, lingering
into Tuesday. Lots of uncertainty regarding Mon. temperatures due
to model differences. Drier weather is expected for Wednesday.
Will need to keep an eye on the Monday system and watch for better
model agreement. Arthur



Surface wind gusts of 40-50 kt will continue over KLVM and in the
nearby foothills tonight through Thursday. LLWS will occur over
KMLS late tonight through Thu. morning. VFR will prevail over the
area, and there will be localized mountain obscurations over the
Beartooths/Absarokas this evening. Arthur



    Thu     Fri     Sat     Sun     Mon     Tue     Wed
BIL 043/065 040/054 032/052 040/063 037/047 029/042 027/042
    00/N    63/W    00/B    10/B    23/W    31/B    00/N
LVM 048/062 038/049 032/051 040/060 034/043 024/038 023/039
    10/N    64/W    01/N    11/N    34/W    31/N    00/N
HDN 039/068 039/056 029/054 036/064 034/049 027/042 024/044
    00/B    43/W    00/U    10/B    23/W    31/B    00/U
MLS 042/066 040/051 029/052 035/062 034/047 026/040 024/042
    00/B    21/N    00/U    10/B    13/W    32/J    00/U
4BQ 041/070 041/054 029/054 037/064 036/051 027/041 024/044
    00/B    22/W    00/U    10/B    12/W    42/J    00/U
BHK 038/065 038/050 027/051 032/062 033/046 022/036 020/039
    00/N    20/N    00/U    00/B    13/W    42/J    00/U
SHR 037/068 038/052 027/054 035/064 033/050 026/042 022/045
    00/B    23/W    00/U    00/B    24/W    31/B    00/U


MT...Wind Advisory in effect until 11 PM MST Thursday FOR ZONES


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