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FXUS65 KBYZ 260929
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
329 AM MDT Wed Sep 26 2018

.SHORT TERM...valid for Tdy and Thu...

High level moisture could be seen spilling over the ridge, that
was centered offshore, into MT early this morning on satellite
imagery. With just some high cloudiness expected today, skies will
be mostly sunny and temperatures will reach 65 to 70 degrees.
Added some patchy frost to the grids through 15Z. Good mixing
will promote breezy NW winds across the area this afternoon. There
were only a couple of areas of 20 percent RH this afternoon,
which will not be a large fire weather concern. Will continue to
headline the breezy conditions in the Fire Weather Forecast.

A NW flow will continue over the forecast area tonight and
Thursday. An upper jet will dive SE in the flow and will push a
backdoor cold front into the region tonight. Moisture was not as
aggressive this model run as previous runs, so have trimmed the
PoPs back NE overnight. Cloud cover will keep lows in the 40s, so
precipitation will be in the form of rain showers. The front will
push further SW into the area on Thursday. Weak frontogenesis and
low-level upslope flow will bring scattered to numerous rain
showers to most of the area. Soundings were too stable for
thunder, and snow levels were quite high...around 11-12K ft...so
a little snow was possible at the highest mountain elevations.
High temperatures will depend upon frontal timing through the
area, but model blends gave highs mainly in the 50s with a few
40s. Arthur

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

High pressure quickly deepens over the area Thursday night as the
baroclinic and upslope precipitation banks up against the
foothills and then settles over the Big Horns before breaking down
Friday afternoon. By the time precipitation changes to snow and
has chance to accumulate it is already trying to end from north to
south. This puts the Big Horns and Burgess Junction area in the
position to most likely see some meaningful accumulations of 2 to
5 inches where as the Beartooth and Absaroka Mountains will see 1
to 2 inches and foothills possibly seeing closer to an inch. Any
other areas may see a rain snow mix for a while but do not
expect accumulations.

Temperatures Friday a challenge as cloud cover may break up over
southeast Montana to permit a bit of diurnal warming and
conversely temperatures along the foothills and Sheridan County
may hold in stronger and keep things a bit cooler. Did not make
much in the way of changes and advertising already temperatures 15
degrees below normal. Drier and warmer Saturday though mixing
will be limited as pressure falls west of the continental divide
keep low level flow easterly.

Sunday an upper level wave dissipates over northwest Montana and
southern Canada getting absorbed by westerly flow aloft in the lee
of a more persistent trough over BC. Cold air over southern Canada
gets dragged into northern Montana but models really differ on how
far south it goes after that. This brings a band of precipitation
which could again be rain or a mix but 850mb temperatures
different by nearly 8 degrees which is a similar disagreement
seen with this Thursday night system and GFS ended up not biting
off on the cold air as much as the ECMWF and that was the correct
course. So have trended towards GFS temperatures and only have
scattered shower activity since it does not look like upslope will
be a strong focusing method.

Rest of the extended has some uncertainty as the moisture from
Tropical Storm Rosa may head up towards the region the middle of
next week but given northerly branch uncertainty do not have any
significant precipitation forecast. borsum

&&

.AVIATION...

VFR will prevail over the area today through this evening. Expect
gusty NW surface winds this afternoon. A backdoor cold front will
push SW into the area tonight, turning winds to the N and NE,
mainly N and NE of KBIL by 12Z Thursday. Scattered rain showers
will accompany the front around KMLS and KBHK with MVFR/IFR
conditions. Arthur

&&

.PRELIMINARY POINT TEMP/POPS...

Tdy Thu Fri Sat Sun Mon Tue
-------------------------------------------------------
BIL 070 046/053 036/052 036/059 039/055 039/067 043/066
0/U 15/W 63/W 11/B 22/W 31/E 12/W
LVM 068 041/060 034/051 035/064 037/056 038/067 039/067
0/N 12/W 43/W 11/B 23/W 31/B 22/W
HDN 070 044/051 036/052 038/061 039/060 039/067 043/067
0/N 16/W 53/W 11/B 23/W 31/E 12/W
MLS 069 044/053 033/052 036/060 039/057 040/066 043/065
0/N 35/W 21/B 11/B 23/W 41/E 12/W
4BQ 069 041/049 032/050 035/061 039/057 040/066 044/068
0/N 15/W 41/E 11/E 23/W 31/B 12/W
BHK 067 041/050 030/049 033/057 036/053 037/064 041/064
0/B 34/W 21/B 11/E 23/W 31/E 12/W
SHR 069 042/056 034/050 035/062 037/061 038/068 041/069
0/U 04/W 74/W 11/B 22/W 31/B 12/W

&&

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

&&

$$
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