513
FXUS65 KBYZ 261759
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
1159 AM MDT TUE AUG 26 2025
KEY MESSAGES
- SEASONABLE TEMPERATURES THIS WEEK.
- THE CHANCE OF SHOWERS AND THUNDERSTORMS RETURNS TO THE MOUNTAINS
TUESDAY AND WEDNESDAY (MODERATE CHANCE) AND THE ENTIRE AREA
THURSDAY INTO SATURDAY (MODERATE TO HIGH CHANCE).
- THUNDERSTORMS THURSDAY INTO SATURDAY COULD PRODUCE LOCALLY HEAVY
RAINFALL.
DISCUSSION
TODAY THROUGH WEDNESDAY NIGHT...
CURRENT ANALYSIS SHOWS SOUTHWEST FLOW AND MOISTURE BEGINNING TO
ADVECT INTO SOUTH CENTRAL MT, WHILE EASTERN MT REMAINS UNDER DRY
NORTHWEST FLOW. AS A RESULT, THIS WILL INCREASE PRECIP CHANCES FOR
THE BEARTOOTH/ABSAROKAS THIS AFTERNOON (30-50%). SHOWERS SHOULD
REMAIN OVER THE MOUNTAINS AND FOOTHILLS THROUGH THE PERIOD,
SPREADING ONTO THE PLAINS WEDNESDAY EVENING (15-30% CHANCE). WITH
WEAK INSTABILITY AND SHEAR PRESENT, AN ISOLATED WEAK THUNDERSTORM
CANNOT BE RULED OUT. OTHERWISE, WITH PWATS NEAR 150-200% OF
NORMAL AND THE LACK OF SHEAR, ANY SLOW MOVING STORMS WILL BE
CAPABLE OF PRODUCING HEAVY RAIN. THIS EVENT IS EXPECTED TO LINGER
INTO THE WEEKEND; SEE DISCUSSION BELOW FOR MORE DETAILS. HIGH
TEMPERATURES TODAY WILL BE IN THE UPPER 70S AND UPPER 80S.
TOMORROW, THE WEST WILL BEGIN TO SEE COOLER CONDITIONS AS THE
SHORTWAVE MOVES IN WITH HIGHS IN THE 70S WITH THE EAST REACHING
THE MID 80S. TS
THURSDAY THROUGH TUESDAY...
CONFIDENCE CONTINUES TO INCREASE FOR ANOMALOUSLY HIGH
PRECIPITABLE WATERS AND SLOW-MOVING/WET THUNDERSTORM ACTIVITY
THURSDAY & FRIDAY. ENSEMBLES SUGGEST PWATS OF 1.00-1.20" (1 TO 3
STANDARD DEVIATIONS ABOVE NORMAL) COURTESY OF DEEP MONSOON
MOISTURE SPREADING NORTHWARD. IN ADDITION TO THE MOISTURE, THERE
IS A WEAK SHORTWAVE EMERGING FROM THE SW FLOW PROVIDING ASCENT,
AND MORE ENERGY DROPPING OUT OF CANADA WHICH MAY PHASE WITH THE
INITIAL WAVE, PROLONGING THE CHANCE OF SHOWERS AND WET T-STORMS
INTO SATURDAY...THOUGH THERE IS CONSIDERABLE MODEL SPREAD HERE.
WITH SUCH WEAK FLOW ALOFT THE STORMS WON'T BE SEVERE, BUT THEY
WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY HEAVY RAIN AND GUSTY
OUTFLOW WINDS.
WPC HAS HIGHLIGHTED OUR AREA FOR A MARGINAL RISK OF
EXCESSIVE RAINFALL THURSDAY & FRIDAY, GIVEN THE ABOVE NORMAL
MOISTURE AND WEAK INSTABILITY MENTIONED ABOVE. THE LATEST
PROBABILITIES FOR AT LEAST A HALF INCH OF RAIN ARE 50-70% OVER
THE MOUNTAINS & FOOTHILLS AND 20-50% OVER THE PLAINS, LOWEST
NORTHEAST OF BILLINGS. ACTUAL PRECIP AMOUNTS WILL VARY GREATLY
DUE TO THE CONVECTIVE NATURE. POCKETS OF HEAVY RAIN UNDER
STRONGER STORMS COUPLED WITH SLOW STORM MOTION MAY RESULT IN
SUBSTANTIAL PRECIP ACCUMULATIONS FOR SOME AREAS WHILE NO SHOWERS
OR STORMS DEVELOP OVER OTHERS.
SATURDAY SEEMS TO BE THE TRANSITION DAY TO A DRIER AIR MASS, BUT
AS ALREADY MENTIONED QUITE A BIT OF UNCERTAINTY EXISTS ON THE BACK
SIDE OF THE MAIN TROF. IN ADDITION TO THE ENHANCED PRECIP CHANCES
WILL COME COOLER TEMPS, WITH HIGHS IN THE 70S BY FRIDAY AND
SATURDAY.
SUNDAY & MONDAY LOOK TO TREND WARMER & DRIER WITH ENSEMBLE
CONSENSUS SHOWING SHORTWAVE RIDGING ON THESE DAYS. WITH ABOVE
NORMAL HEIGHTS PERSISTING THIS SHOULD PUSH TEMPS BACK TO THE 80S,
WHICH WOULD BE A LITTLE WARMER THAN NORMAL AS WE MOVE INTO EARLY
SEPTEMBER. THEN, BY THE MIDDLE OF THE WEEK, THERE ARE SIGNS OF THE
UPPER LEVEL PATTERN BECOMING MORE UNSETTLED.
JKL/ARCHER
AVIATION
SCATTERED SHOWERS ARE EXPECTED ACROSS THE ABSAROKA-BEARTOOTH
MOUNTAINS THROUGH THE TAF PERIOD. OTHERWISE, INCREASING MONSOONAL
MOISTURE WILL PRODUCE ISOLATED TO SCATTERED SHOWERS AT TIMES,
MAINLY OVER SOUTH CENTRAL MONTANA AND NORTHWEST WYOMING. VFR
CONDITIONS ARE EXPECTED AT THE TAF SITES BUT CANNOT RULE OUT BRIEF
MVFR CONDITIONS AT KLVM GIVEN THE NEARBY SHOWER/ISOLATED
THUNDERSTORM ACTIVITY OVER THE HIGHER TERRAIN. EASTERLY WINDS WILL
BE ON THE INCREASE JUST ABOVE THE SURFACE TONIGHT INTO WEDNESDAY
AS WEAK LOW PRESSURE MOVES IN FROM THE SOUTHWEST BUT WINDS ARE
EXPECTED TO REMAIN BELOW LLWS CRITERIA. JW/RMS
PRELIMINARY POINT TEMP/POPS
TDY WED THU FRI SAT SUN MON
-------------------------------------------------------
BIL 086 060/083 062/080 059/075 055/078 055/084 056/084
0/B 01/E 24/T 46/T 43/W 11/U 11/U
LVM 085 053/076 052/074 051/073 048/077 048/083 048/082
2/T 24/T 57/T 77/T 54/T 22/T 12/T
HDN 088 057/085 059/083 057/076 053/078 052/084 053/085
0/B 01/E 23/T 45/T 43/W 11/U 11/U
MLS 085 055/086 058/085 060/076 055/076 054/083 055/083
0/B 00/B 01/E 44/W 43/W 21/U 10/U
4BQ 083 059/084 060/080 059/074 055/073 054/080 056/081
0/B 00/B 12/T 55/T 63/W 21/U 11/U
BHK 082 051/084 052/083 056/075 052/074 050/078 051/081
0/B 00/B 00/B 33/T 53/W 21/U 11/U
SHR 086 055/082 055/079 053/074 050/073 049/080 050/081
1/B 12/T 35/T 67/T 65/T 22/T 11/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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