235
FXUS65 KBYZ 160150
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
750 PM MDT MON SEP 15 2025
KEY MESSAGES
- PERSISTENT CHANCES FOR SHOWERS AND THUNDERSTORMS THROUGH
TUESDAY. 10-50% CHANCE OF RECEIVING GREATER THAN 0.5 INCHES OF
ADDITIONAL RAIN.
- LIGHT SNOW ACCUMULATIONS IN THE BEARTOOTH MOUNTAINS ABOVE 10KFT
TONIGHT THROUGH WEDNESDAY MORNING. MAY IMPACT TRAVEL OVER THE
HIGHEST ELEVATIONS ALONG THE BEARTOOTH HIGHWAY.
- BECOMING DRIER WITH SEASONAL TEMPERATURES FOR THE END OF THE
WORK WEEK. ABOVE NORMAL TEMPERATURES FOR THE WEEKEND.
UPDATE
UPPER LOW CONTINUES TO EVOLVE SLOWLY OVER NORTHWEST WY. THERE IS
AN AREA OF STRONG-ISH THUNDERSTORMS LIFTING THRU THE FAR SOUTHEAST
CORNER OF MT, OTHERWISE STRONGEST ASCENT AND MAIN AXIS OF SHOWERS
AS OF 0140Z IS DRAPED ACROSS OUR NORTH FROM WEST TO EAST (I.E.
HARLOWTON TO BAKER). MID LEVEL W-NW WINDS ARE PROVIDING SOME
DOWNSLOPE TO THE SOUTH OF THIS AREA. OVER TIME TONIGHT, THE LOW
WILL PIVOT SUCH THAT A COMPONENT OF DRY-SLOTTING WILL IMPACT
SOUTHEAST MT WHILE BACKSIDE PRECIP ASSOCIATED WITH A DEVELOPING
TROWAL WILL BE FOCUSED OVER OUR WEST AND NORTH CENTRAL PARTS, AND
THERE WILL BEGIN TO BE UPSLOPE ENHANCEMENT ALONG THE NORTH ASPECTS
OF THE BEARTOOTH-ABSAROKAS AS WINDS SHIFT NORTHERLY. HAVE MADE
SOME POP/WX/QPF ADJUSTMENTS TO ALIGN WITH THESE TRENDS OVER THE
NEXT 12-18 HOURS. AS FAR AS HIGH ELEVATION SNOW IS CONCERNED,
LATEST MESOANALYSIS SHOWS FREEZING LEVELS OVER OUR WEST AT ~11KFT
CURRENTLY, AND THIS SEEMS CONSISTENT W/ CURRENT TEMP OF 37F AT
QUAD CREEK RAWS (ELEV. 9774 ABOVE VISTA PT). SO ONCE THE TROWAL
PRECIP BEGINS IN THE WESTERN MOUNTAINS LATER TONIGHT WE WILL BE
SEEING WET SNOW ABOVE 10-11KFT. A WINTER WEATHER ADVISORY IS IN
EFFECT FOR THE BEARTOOTH HIGHWAY. JKL
DISCUSSION
A 500 MB PACIFIC TROUGH WILL DROP DOWN TO OUR WEST OVER THE NEXT
FEW DAYS. THIS WILL PUT THE REGION IN A FAVORABLE DEFORMATION ZONE
TODAY BRINGING PRECIPITATION CHANCES OF 40-60% ACROSS THE REGION.
CAPE VALUES <500 J/KG AND 20-30 KTS OF SHEAR WILL KEEP MOST
PRECIPITATION AS SHOWERS AND GENERAL THUNDERSTORMS. THE BEST
CHANCE FOR SEVERE STORMS WILL BE IN LOCATIONS SUCH AS SHERIDAN
COUNTY WY AND SOUTHEAST PORTIONS OF POWDER RIVER AND CARTER
COUNTIES. THE STORM PREDICTION CENTER HAS ISSUED A RISK LEVEL 1 OF
5 FOR SEVERE STORMS FOR THESE LOCATIONS. STEEP LOW LEVEL LAPSE
RATES AND INVERTED V SOUNDINGS MAKE STRONG WIND GUSTS >58 MPH THE
MAIN THREAT WITH THESE STORMS. MODELS ARE INDICATING THAT
CONVECTION COULD CONTINUE THROUGH THE OVERNIGHT HOURS.
UPPER LEVEL FLOW OUT OF THE SOUTHWEST TODAY WILL TRANSITION TO
NORTHEASTERLY FLOW TUESDAY AS MOISTURE WRAPS AROUND THE SYSTEM.
MODELS ARE SHOWING A BAND OF PRECIPITATION SETTING UP OVER
SOUTHEAST MONTANA. THERE IS A LOT OF UNCERTAINTY AS TO WHERE THIS
BAND WILL SET UP LEADING TO A WIDE RANGE OF POTENTIAL
PRECIPITATION AMOUNTS. OVERALL, TODAY THROUGH TUESDAY, MOST
LOCATIONS HAVE A 40-50% CHANCE OF GETTING GREATER THAN 0.5 INCHES
OF PRECIPITATION WITH LOWER CHANCES NEAR THE DAKOTAS BORDER. COOL
700 MB TEMPERATURES NEAR 0C AND UPSLOPE FLOW WITH TUESDAYS BAND OF
PRECIPITATION WILL LEAD TO SNOWFALL ABOVE 10,000 FT. ACCUMULATIONS
ARE EXPECTED TO BE IN THE 1-3 INCH RANGE. THIS HAS THE POTENTIAL
TO IMPACT TRAVEL ON THE BEARTOOTH PASS.
HIGH TEMPERATURES WEDNESDAY ARE EXPECTED TO BE IN THE MID 60S TO
MID 70S F.
CONTINUED UPPER LEVEL TROUGHING OVER THE NORTHERN PLAINS WILL KEEP
WEAK LOW PRESSURE OVER THE CENTRAL AND NORTHERN PLAINS WEDNESDAY
THROUGH FRIDAY. THIS WILL CONTINUE TO WRAP MOISTURE INTO MONTANA
KEEPING PWAT VALUES 100-150% OF NORMAL. THE LOW PRESSURE AND
MOISTURE PLUME WILL DRIFT TO THE EAST DIMINISHING PRECIPITATION
CHANCES EVERY DAY. WEDNESDAY WILL SEE LOCATIONS SOUTH OF A LINE
FROM RED LODGE TO MILES CITY HAVE A 20-50% CHANCE FOR
PRECIPITATION. THURSDAY, CARTER AND FALLON COUNTIES HAVE A 20%
CHANCE FOR PRECIPITATION DECREASING TO <10% FOR FRIDAY. CAPE AND
SHEAR WILL BE LIMITED INDICATING PRECIPITATION THESE DAYS WILL BE
SHOWERS WITH LIMITED THUNDERSTORM CHANCES. THE NBM IS GIVING
LOCATIONS SOUTH OF A LINE FROM RED LODGE TO MILES CITY A 5-30%
CHANCE FOR RECEIVING GREATER THAN 0.25 INCHES OF RAIN DURING THIS
PERIOD.
FOR THE WEEKEND, A MORE ZONAL/RIDGING PATTERN MOVES IN LEADING TO
WARMER AND DRIER CONDITIONS. EARLY NEXT WEEK SOME WPC CLUSTERS
ARE INDICATING UPPER LEVEL TROUGHING COULD MOVE INTO THE REGION
BRINGING COOLER TEMPERATURES BUT THIS IS HIGHLY UNCERTAIN AT THIS
TIME. HIGH TEMPERATURES WEDNESDAY THROUGH FRIDAY ARE EXPECTED TO
BE IN THE HIGH 60S TO HIGH 70S F. TEMPERATURES INCREASE INTO THE
MID 70S TO MID 80S F FOR THE WEEKEND. TORGERSON
AVIATION
PERIODS OF RAIN AND EMBEDDED THUNDER WILL CONTINUE INTO TUESDAY
OVER SOUTH- CENTRAL MONTANA. WITH THIS, MVFR CONDITIONS
(VISIBILITY AND/OR CEILINGS) ARE POSSIBLE, BUT CHANCES REMAIN LOW
TO MODERATE (GREATEST AT 30 TO 60 PERCENT AROUND KLVM AND K6S0).
OVER SOUTH-EASTERN MONTANA THIS EVENING, A FEW STRONGER
THUNDERSTORMS ARE EXPECTED. WITH THIS, BRIEF HEAVY RAIN AND GUSTY
WINDS ARE THE MAIN THREATS. OTHERWISE, LOOK FOR PERIODIC MOUNTAIN
OBSCURATIONS TO OCCUR THROUGH TUESDAY. ARENDS
PRELIMINARY POINT TEMP/POPS
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 052/071 054/075 051/076 049/076 050/083 056/081 053/076
66/T 31/B 00/U 00/U 00/U 01/B 11/U
LVM 045/067 044/073 042/077 042/078 045/082 047/077 043/074
88/T 20/U 00/U 00/U 00/U 12/W 21/U
HDN 049/074 051/075 048/076 046/076 046/083 051/082 049/076
64/T 42/W 10/U 00/U 00/U 01/B 21/U
MLS 055/076 054/077 051/073 049/073 048/079 052/082 052/074
63/T 31/B 11/B 10/B 00/U 00/U 20/U
4BQ 052/070 054/070 051/070 048/069 047/077 053/079 052/073
62/T 43/T 11/B 10/B 00/U 00/U 20/U
BHK 050/076 050/073 047/069 046/068 046/075 048/078 048/073
42/T 32/W 12/W 11/B 00/B 00/U 10/U
SHR 043/069 046/067 042/073 042/073 043/080 048/079 046/074
65/T 65/T 11/U 10/U 00/U 01/U 21/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT MDT TUESDAY
NIGHT FOR ZONE 67.
WY...NONE.
WEATHER.GOV/BILLINGS
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