196
FXUS65 KBYZ 130200
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
800 PM MDT FRI SEP 12 2025
KEY MESSAGES
- A GOOD CHANCE FOR PRECIPITATION (30-70% CHANCE >0.5 INCHES FROM
BILLINGS EAST) THROUGH SATURDAY.
- TURNING COOLER FOR SATURDAY (UPPER 60S TO 75).
- DRIER AND WARMER (70S TO LOW 80S) SUNDAY AND MONDAY.
- COOLER TEMPERATURES AND WETTER CONDITIONS WITH STORM SYSTEM
MONDAY NIGHT THROUGH WEDNESDAY.
UPDATE
SATELLITE IMAGERY SHOWS A SHORTWAVE LIFTING THRU NORTHEAST WY,
AND AS EXPECTED, A FAIRLY LARGE AREA OF SHOWERS AND EMBEDDED
T-STORMS IS LIFTING INTO OUR SOUTHEAST (FROM SHERIDAN TO CARTER
COUNTIES) AS OF 0145Z. BULK SHEAR HAS DECREASED AND WHILE A STRONG
STORM OR TWO REMAINS POSSIBLE IN SOUTHEAST MT, THE RISK OF SEVERE
T-STORMS HAS DIMINISHED. PWATS ARE QUITE HIGH AND THESE SLOW-
MOVING STORMS WILL PRODUCE HEAVY RAINFALL. MID LEVEL LOW IS NOTED
IN CENTRAL WY ALSO LIFTING TO THE NORTH, AND AN AREA OF SHOWERS W/
EMBEDDED T-STORMS HAS MOVED NORTH OF LANDER-RIVERTON IN A REGION
OF BACKED/EASTERLY MID LEVEL WINDS. OVER TIME TONIGHT, THESE
SHOWERS (W/ ISOLATED TS) WILL LIFT INTO AND THRU OUR SOUTHERN
FOOTHILLS...SETTING UP AN AREA OF HEALTHY PRECIP OVER OUR CENTRAL
AND PERHAPS INTO OUR WESTERN CWA INTO TOMORROW. THE EXACT TRACK OF
THE MID LEVEL CIRCULATION WILL DICTATE WHERE HEAVIEST PRECIP SETS
UP, AND MODELS REMAIN IN SOME DISAGREEMENT HERE. THAT SAID, MANY
LOCATIONS (INCLUDING BILLINGS) SHOULD AT LEAST SEE A PERIOD OF
MODERATE RAINFALL LATE TONIGHT AND SATURDAY MORNING, SOMEWHAT
UNUSUAL FOR THE TIME OF YEAR. MEANWHILE IN THE EAST ONCE THE
CURRENT ROUND OF CONVECTION PASSES (GIVE IT A FEW HOURS), IT IS
LOOKING LIKE A PERIOD OF DRY-SLOTTING FROM THE SOUTH LATER
TONIGHT INTO SATURDAY. HAVE ADJUSTED POPS/WX PER CURRENT TRENDS,
INCLUDING LOWER POPS IN THE EAST LATER TONIGHT AND HIGHER IN THE
WEST LATE TONIGHT AND SATURDAY MORNING. CURRENT PROBABILITIES FOR
0.50" OR MORE OF RAIN REMAIN HIGHEST EAST OF BILLINGS (40-80%) AND
LOWEST TO THE WEST (10-40%), ALTHOUGH CONFIDENCE OF 0.10-0.40" OF
RAIN OVER OUR WEST HAS INCREASED A BIT. JKL
DISCUSSION
THROUGH SATURDAY NIGHT...
SCATTERED SHOWERS AND THUNDERSTORMS WERE LIFTING THROUGH WESTERN
AREAS, AND OFF THE BIGHORN MOUNTAINS AND AREAS TO THE NORTHEAST
THIS AFTERNOON, AS AN UPPER TROUGH APPROACHED AND A JET MAX NOSED
INTO THE AREA. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO INCREASE
IN COVERAGE OVER CENTRAL AND EASTERN AREAS THIS AFTERNOON AND
EVENING, WITH SOME OF THE THUNDERSTORMS POSSIBLY BECOMING STRONG
TO SEVERE. INSTABILITY IS MODEST WITH MUCAPE UP TO 1500 J/KG AND
SHEAR OF 30-40 KTS, GREATEST OVER THE EAST. THE SPC CURRENTLY HAS
A MARGINAL RISK FOR SEVERE STORMS ACROSS WESTERN AND CENTRAL
AREAS, WITH A SLIGHT RISK OVER THE EAST. MAIN THREATS ARE STRONG
WIND GUSTS AND LARGE HAIL, WITH HEAVY RAIN AS WELL.
THE BEST PERIOD FOR PRECIPITATION IS EXPECTED TO BE OVERNIGHT
TONIGHT INTO SATURDAY MORNING (50-90% CHANCE) AS A MID-LEVEL
CIRCULATION LIFTS INTO THE REGION, WITH MOISTURE AND INSTABILITY
WRAPPING BACK IN FROM THE EAST AND NORTHEAST. PRECIPITATION
CHANCES BEGIN DECREASING SATURDAY AFTERNOON AND EVENING AS THE
UPPER ENERGY SHIFTS NORTH AND EAST. PRECIPITATION TOTALS THROUGH
SATURDAY ARE FORECAST TO RANGE FROM NEAR A COUPLE TENTHS IN THE
FAR WEST, TO AROUND AN INCH NEAR THE DAKOTAS BORDER. PROBABILITIES
FOR HALF AN INCH OR MORE OF PRECIPITATION RANGE FROM AROUND 30%
NEAR BILLINGS, TO NEAR 80% NEAR THE DAKOTAS BORDER.
TEMPERATURES ON SATURDAY WILL DROP INTO THE UPPER 60S TO LOWER
70S, BELOW NORMAL FOR THIS TIME OF YEAR. STP
SUNDAY THROUGH THURSDAY...
TROUGHING IS THE OVERALL PATTERN IN THE LONGTERM FORECAST PERIOD,
ALTHOUGH MODELS DEPICT A BRIEF SHORTWAVE RIDGE MOVING THROUGH
SUNDAY THROUGH MONDAY. THE CHANCE FOR SHOWERS AND THUNDERSTORMS
WILL BE LOW SUNDAY INTO MONDAY, BEFORE INCREASING WITH AN
APPROACHING UPPER TROUGH AND DEVELOPING LOW. THERE IS UNCERTAINTY
WITH THIS SYSTEM, DESPITE ENSEMBLES SHOWING MODERATE AGREEMENT.
THE ECMWF ENSEMBLE DEPICTS THE TROUGH INTERACTING AND MERGING INTO
THE UPPER LOW THAT MOVED THROUGH MONTANA TO END THIS WEEK.
MEANWHILE, THE GEFS SHOWS THE TWO COMBINING INTO A LARGER TROUGH
WITHOUT A DISTINCT UPPER LOW. THE TIMING AND LOCATION OF THIS
SYSTEM WILL PLAY A PART IN THE EXTENT OF THE CHANCE FOR PRECIP.
ANOTHER NOTE ABOUT THE MONDAY THROUGH TUESDAY SYSTEM IS THAT
850MB TEMPERATURE ANOMALIES AROUND -5C ARE DEPICTED BY THE LATEST
ENSEMBLES. THE CURRENT FORECAST DEPICTS LIGHT SNOW ACCUMULATIONS
(UP TO AN INCH) ON THE HIGHEST PEAKS OF THE ABSAROKA/BEARTOOTHS.
THOSE WITH RECREATIONS IN THE HIGH COUNTRY SHOULD BE PREPARED FOR
COOLER AND POTENTIALLY WINTRY CONDITIONS DURING THIS TIMEFRAME.
THE CURRENT FORECAST HAS A LOW CHANCE (10-30%) FOR PRECIPITATION
IN THE SOUTHWESTERN MOUNTAINS AND ALONG THE DAKOTAS BORDER,
SUNDAY. MONDAY AFTERNOON AND EVENING THE CHANCE INCREASES (30-80%)
ACROSS THE AREA, CONTINUING THROUGH TUESDAY. THE THREAT FOR
STRONG THUNDERSTORMS IN THE EXTENDED FORECAST PERIOD IS LOW, WITH
MINIMAL INSTABILITY AND SHEAR.
HIGH TEMPERATURES ARE FORECAST TO BE IN THE 70S AND 80SF SUNDAY
AND MONDAY, COOLING INTO THE 60S TO AROUND 70F TUESDAY, AND 70S ON
WEDNESDAY. MATOS
AVIATION
SCATTERED SHOWERS AND THUNDERSTORMS WILL LIFT NORTH AND EAST
LATE EVENING, BECOMING MORE WIDESPREAD OVERNIGHT. SHOWERS AND
ISOLATED THUNDERSTORMS WILL LINGER INTO SATURDAY AS A DISTURBANCE
MOVES THROUGH THE REGION. IN GENERAL, VFR WILL PREVAIL WITH MVFR
CONDITIONS POSSIBLE UNDER ANY STRONGER THUNDERSTORMS. STP/TS
PRELIMINARY POINT TEMP/POPS
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 057/070 052/080 055/080 054/069 050/073 049/078 052/077
88/T 11/U 03/W 45/T 32/W 00/U 11/B
LVM 046/069 043/078 046/073 042/068 041/074 043/079 044/075
25/T 11/U 15/T 55/T 21/U 00/U 11/B
HDN 056/073 048/081 051/082 051/069 047/073 046/079 049/080
87/T 21/B 01/U 55/T 42/W 10/U 10/B
MLS 059/074 053/077 054/082 054/072 051/072 049/075 051/077
87/T 21/B 11/U 33/T 42/W 10/U 10/U
4BQ 058/074 053/074 053/081 054/070 050/068 048/074 050/077
83/T 21/B 11/U 33/T 43/T 11/U 10/U
BHK 057/074 052/074 052/080 051/074 049/071 046/073 047/074
86/T 33/T 31/B 22/T 42/T 11/U 11/U
SHR 051/073 044/077 047/080 046/067 043/069 042/077 046/079
84/T 21/B 02/W 46/T 53/W 10/U 01/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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