FXUS65 KBYZ 080927

Area Forecast Discussion
National Weather Service Billings MT
227 AM MST Fri Dec 8 2023


Today through Saturday...

Satellite imagery shows a trof moving slowly through eastern MT
with dry slotting surging into the far southeast. BLX radar shows
scattered echoes (perhaps light snow/flurries) developing east of
Billings...activity that is dropping from the north. As the trof
continues to move eastward, a trowal will bring a period of snow
to our east today (esp. east of Miles City). This combined with
gusty post-frontal NW winds will produce areas of blowing snow
and poor visibility. Radar trends seem to give credence to models
showing potential for a couple inches of snow to the higher hills
just east of Miles City...so have added Custer County to the
Winter Weather Advisory already issued for Fallon and Carter from
12-00z today. Snow amounts look to be 1-3" (mainly over the higher
terrain as surface temps should hold in the lower 30s), but w/ the
wind there will be wintry impacts to travel, and an overall raw
day for our far east. By late afternoon and evening we should see
some light snow push southward to Lodge Grass and Sheridan. Could
be modest travel impacts over Lame Deer Divide, Camps Pass and
Aberdeen Hill as well.

To the west, there is shortwave energy moving through the northern
great basin. Ascent will stay largely to our south, but cold air
aloft (as cold as -34C over the PacNW at 09z) means lapse rates
will steepen thru the day. Fully expect isolated to scattered snow
showers to develop during the peak heating hours over the west
half of our cwa. Mountains will see a little snow accumulation
today and tonight (1-4"). If there is any NW flow banding before
the PV axis passes (possible w/ the instability), there could be
localized issues w/ icy roads over our west tonight. Something to
keep an eye on.

Saturday will be dry with building heights and drying from the
west. Some flurries could linger into the morning over our east.
Breezy conditions will be felt over our west tomorrow with 30-40
mph gusts at Big Timber & Harlowton, courtesy of another period of
tightening downslope gradients under the anticyclonic NW flow
aloft. Strongest winds along the foothills will be after 00z.

Temps will be pretty seasonable the next two days with highs in
the 30s to lower 40s.

Notable probabilities over the next 36 hours:
2+ inches of snow: Baker 60%, Ekalaka 50%, Miles City 0%
Measurable snow:   Livingston 60%, Billings 10%, Sheridan 65%
35+ mph gusts Sat:  Harlowton 90%, Big Timber 80%, Livingston 60%


Saturday Night through Friday...

Upper ridging builds into the area Saturday night and a strong
pressure gradient forms over south-central MT. Canadian and GFS
Ensemble mean paints the KIDA-KLWT pressure gradient still at
around 18 mph at it's peak (occuring during the night), and with
local guidance painting a 83% chance for winds around Livingston
to gust to 58 mph, will likely create impacts to those traversing
along I-90 through that corridor through Sunday morning. As low
pressure decreases over far eastern MT Sunday morning, the
gradient shifts slightly to favor a more westerly wind, and 700
mb winds out of the northwest at 40-50 kts will assist in shifting
the stronger winds to the Big Timber vicinity, still impacting
I-90 traffic, but also travel along US-191. Local guidance is also
fairly high for them to hit at least 58 mph, giving us a 61%
chance of that occuring Sunday mornings. Winds on all accounts
will then slowly decrease through the afternoon. Expect slightly
above normal temperatures on Sunday.

Slightly unsettled northwest flow looks to occur through Tuesday,
with a couple weak, embedded shortwaves having a high chance to
occur. Mostly likely timing for a cold front and small chance for
rain/snow showers to occur is late Monday into early Tuesday,
though accumulations will be minimal, with at least a 85% chance
for all areas to get less than 0.05" of precip, and at least a 95%
chance to get less than an inch of snow.

After Tuesday there is high confidence for a deep upper low to
slowly cut across the southern CONUS, but prominent ridging to
build across the northern CONUS and Canada, keeping us in the
middle with relatively benign weather. Only item that has a high
chance to pop up is more gap winds across south-central MT for the
latter half of the week.




A period of snow and gusty NW winds will impact southeast MT
today. Look for MVFR-IFR and wind gusts of 25-35 knots (creating
some blowing snow) from KBHK-K97M through the late afternoon. VFR
will prevail to the west with scattered light snow showers at
lower elevations. Mountains will be frequently obscured in snow
showers. VFR is anticipated regionwide tonight as the weather
system moves off to the east. JKL



    Tdy Sat     Sun     Mon     Tue     Wed     Thu
BIL 043 027/041 027/048 032/042 025/042 027/047 029/048
    2/J 20/U    20/N    03/O    31/B    00/U    00/U
LVM 038 020/036 026/043 029/042 026/042 024/047 026/047
    2/J 20/N    22/S    24/O    31/B    00/U    00/U
HDN 041 024/042 022/049 029/044 023/043 021/048 022/049
    3/O 40/U    12/S    12/O    31/B    00/U    00/U
MLS 036 024/038 022/044 026/039 020/039 022/045 023/046
    5/S 20/U    00/B    01/B    11/B    00/U    00/U
4BQ 036 023/038 022/044 029/042 024/041 025/047 026/048
    5/S 30/B    00/E    00/B    11/B    00/U    00/U
BHK 033 016/033 016/039 021/038 015/037 021/044 023/045
    9/S 20/U    00/B    00/B    10/B    00/U    00/U
SHR 039 023/038 017/046 026/044 022/042 020/050 024/050
    2/J 40/U    02/S    02/O    22/S    00/U    00/U


MT...Winter Weather Advisory in effect until 5 PM MST this
      afternoon FOR ZONE 32.
     Winter Weather Advisory remains in effect until 5 PM MST this
      afternoon FOR ZONES 33-37.