070
FXUS65 KBYZ 261908
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
108 PM MDT TUE AUG 26 2025
KEY MESSAGES
- SEASONABLE TEMPERATURES THIS WEEK.
- THE CHANCE OF SHOWERS AND THUNDERSTORMS RETURNS TO THE MOUNTAINS
TODAY AND WEDNESDAY (MODERATE CHANCE) AND THE ENTIRE AREA
THURSDAY INTO SATURDAY (MODERATE TO HIGH CHANCE).
- SHOWERS AND THUNDERSTORMS THROUGH SATURDAY COULD PRODUCE
LOCALLY HEAVY RAINFALL.
DISCUSSION
THE REST OF TODAY THROUGH WEDNESDAY NIGHT...
ATMOSPHERIC MOISTURE CONTINUES TO MOVE IN FROM THE SOUTHWEST, WITH
PWATS AROUND 150-200% OF NORMAL OVER THE BEARTOOTH/ABSAROKA
MOUNTAINS THIS AFTERNOON. SHOWERS AND THUNDERSTORMS WILL BE
MOSTLY LIMITED TO THE WESTERN MOUNTAINS AND FOOTHILLS INTO
WEDNESDAY (30-50% CHANCE). THEN, AS UPPER LEVEL NORTHWEST FLOW
OVER THE EASTERN HALF OF THE REGION ENDS AND MORE ENERGY MOVES IN,
PRECIPITATION WILL GRADUALLY SPREAD EAST.
TODAY AND TOMORROW, SHEAR AND INSTABILITY OUTSIDE OF THE
MOUNTAINS ARE EXPECTED TO REMAIN FAIRLY LOW, WITH SHEAR GENERALLY
LESS THAN 15 KTS AND MUCAPE GENERALLY LESS THAN 500 J/KG. THAT
SAID, AN ISOLATED WEAK THUNDERSTORM OR TWO MAKING IT ONTO THE
PLAINS DURING THE AFTERNOON/EVENING HOURS CANNOT BE RULED OUT.
WITH THE ABOVE NORMAL MOISTURE, COUPLED WITH LOW SHEAR, ANY
SHOWERS OR STORMS THAT DEVELOP WILL BE SLOW MOVING AND WILL HAVE
THE POTENTIAL TO PRODUCE HEAVY RAIN.
LOW TEMPERATURES TONIGHT WILL BE IN THE 50S TO LOW 60S. THEN,
HIGHS WEDNESDAY WILL RANGE FROM MID 70S OVER THE WEST TO MID 80S
OVER THE NORTHEAST. ARCHER
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
WED THU FRI SAT SUN MON TUE
-----------------------------------------------------------
BIL 060/084 061/079 060/077 057/079 055/085 057/086 057/081
12/E 23/T 55/T 32/W 11/U 11/U 12/W
LVM 055/076 053/071 051/074 048/078 047/083 049/084 049/080
25/T 58/T 77/T 43/T 11/U 12/T 23/T
HDN 057/086 059/080 057/078 053/078 051/085 053/087 054/081
01/E 22/W 55/T 42/W 10/U 11/U 11/B
MLS 054/087 059/084 060/076 056/075 055/082 056/086 058/081
00/B 01/E 34/W 32/T 10/U 11/U 11/B
4BQ 058/084 060/077 059/074 056/073 055/079 055/085 057/081
01/B 12/W 55/T 53/T 11/U 10/U 11/B
BHK 050/084 052/083 055/074 052/074 050/079 052/082 053/081
00/U 00/B 23/W 43/T 21/U 10/U 11/B
SHR 055/081 055/077 053/074 051/074 048/081 050/083 052/078
13/T 35/T 67/T 54/T 11/U 11/U 12/T
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
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