136
FXUS65 KTFX 121739
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1139 AM MDT WED AUG 12 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- COOLER AFTERNOON TEMPERATURES ARE EXPECTED ACROSS THE AREA FOR
THE NEXT FEW DAYS.
- SHOWERS AND THUNDERSTORMS WILL BECOME MORE WIDESPREAD TONIGHT
INTO THURSDAY, FEW AREAS POSSIBLY GETTING OVER A HALF INCH OF
RAINFALL.
- LIGHTNING OVER THE NEXT FEW DAYS COULD START NEW WILDFIRES.
DISCUSSION
/ISSUED 425 AM MDT WED AUG 12 2026/
- METEOROLOGICAL OVERVIEW:
THE CHANGE TO A COOLER WETTER WEATHER PATTERN IS BEGINNING TODAY.
THE FLOW ALOFT IS BECOMING A BIT MORE WESTERLY TODAY, AS THE UPPER
LEVEL RIDGE BREAKS DOWN. ONE DISTURBANCE IS APPROACHING THE AREA
FROM THE NORTH THIS MORNING, WHILE ANOTHER DISTURBANCE IS
APPROACHING SOUTHWEST MT FROM THE SOUTHWEST. OVERALL EXPECT SHOWER
AND THUNDERSTORM ACTIVITY TO START TO INCREASE LATE THIS MORNING
THROUGH THIS AFTERNOON. A FEW STORMS COULD PRODUCE STRONG WIND
GUSTS OR HEAVY RAINFALL THIS AFTERNOON/EVENING. THE LATEST HREF
DOES HAVE ONE STRONG STORM MOVING SOUTHEASTWARD THROUGH NORTH
CENTRAL MT THIS EVENING, WITH THE MAIN IMPACT BEING
LIGHTNING/STRONG WIND GUSTS. OTHERWISE, AFTERNOON TEMPERATURES TO
START TO COOL A BIT EACH DAY THROUGH FRIDAY.
THE CHANCE FOR THUNDERSTORMS WILL INCREASE THU INTO FRIDAY MORNING
AS PRECIPITABLE WATER INCREASES. THUS THE CHANCE FOR ISOLATED
FLASH FLOODING IS POSSIBLE FROM HEAVIER SHOWERS. ADDITIONALLY, A
FEW STORMS COULD PRODUCE STRONG WIND GUSTS ON THURSDAY/FRIDAY,
ESPECIALLY OVER SOUTHWEST MT WHERE IT WILL BE A BIT MORE UNSTABLE.
THE SUMMERTIME UPPER LEVEL RIDGE OF HIGH PRESSURE WILL TRY TO
REBUILD OVER THE NORTHERN ROCKIES STARTING THIS WEEKEND. THIS WILL
RESULT IN WARMER, BUT MORE UNSTABLE AIR MOVING BACK INTO THE CWA
THIS WEEKEND. EXPECT DAILY CHANCES FOR SHOWERS/THUNDERSTORMS FROM
SATURDAY THROUGH TUESDAY. AGAIN, THE MAIN CONCERN FROM STORMS OVER
THE WEEKEND WILL BE LIGHTNING AND STRONG WIND GUSTS.
- FORECAST CONFIDENCE & SCENARIOS:
AFTER A FEW DAYS OF COOLER TEMPERATURES, WARMER AIR MOVES BACK
INTO THE CWA THIS WEEKEND. THUS AFTERNOON TEMPERATURES COULD BE A
TOUCH WARMER THAN CURRENTLY FORECAST, ESPECIALLY IF SOME OF THE
SMOKE CLEARS OUT A BIT.
THE MAIN CONCERN FROM THUNDERSTORMS OVER THE NEXT FEW DAYS WILL BE
LIGHTNING, BRIEF HEAVY RAINFALL AND STRONG WIND GUSTS. ANY
LIGHTNING THAT OCCURS AWAY FROM THE MAIN STORM WILL BE CAPABLE OF
PRODUCING NEW WILDFIRES. BRUSDA
AVIATION
12/18Z TAF PERIOD
VFR CONDITIONS WILL GENERALLY PREVAIL THROUGHOUT THIS TAF PERIOD,
WITH THE EXCEPTION OF PERIODS OF MVFR CONDITIONS DUE TO PASSING
THUNDERSTORMS. THUNDERSTORM ACTIVITY IN SOUTHWEST MT WILL BEGIN
AROUND 22Z, MOVING NORTHEAST. THUNDERSTORM ACTIVITY WILL ALSO
BEGIN NEAR KCTB AROUND 23Z, MOVING EAST AND SOUTHEAST. LIGHT RAIN
WILL BEGIN IN NORTH-CENTRAL/CENTRAL MT FOLLOWING THE THUNDERSTORM
ACTIVITY. MOUNTAIN OBSCURATION IS EXPECTED THROUGHOUT THIS TAF
PERIOD, AS IS A DECREASE IN SLANT RANGE VISIBILITY DUE TO SMOKE
FROM REGIONAL WILDFIRES.
FOR KGTF: WHILE SMALL, THERE IS A NON-ZERO CHANCE FOR CROSS WINDS
IN EXCESS OF 15 KTS. HOWEVER, SUSTAINED WINDS AND WIND GUSTS WILL
BE OUT OF THE NORTHEAST, WITH THE EXCEPTION OF PASSING CONVECTION
WHICH COULD CAUSE ERRATIC WINDS. THE LATEST HREF IS CONTINUING TO
SHOW A THUNDERSTORM IN THE GREAT FALLS AREA AROUND 13/02Z. LIGHT
RAIN IS EXPECTED TO FOLLOW THIS CONVECTIVE ACTIVITY. -DZOMBA
FIRE WEATHER
NO FIRE WEATHER STATEMENTS WILL BE ISSUED AT THIS TIME, BUT THE
MAIN CONCERN FROM TODAY THROUGH THIS WEEKEND WILL BE LIGHTNING AND
THUNDERSTORMS THAT PRODUCE STRONG OUTFLOW WIND GUSTS. INITIALLY
THE THUNDERSTORMS WILL BE ON THE WET SIDE TODAY THROUGH FRIDAY,
WITH DRIER THUNDERSTORMS POSSIBLE OVER THE WEEKEND. NOTE ANY
LIGHTNING THAT DOES OCCUR AWAY FROM THE CENTER OF THE STORM WILL
HAVE A HIGHER PROBABILITY OF STARTING A WILDFIRE. BRUSDA
HYDROLOGY
A FLASH FLOOD WATCH HAS BEEN ISSUED FOR THE HORSE GULCH BURN SCAR
AREA, WHICH INCLUDES THE RIVERSIDE CAMPGROUND FROM THIS AFTERNOON
THROUGH THE OVERNIGHT HOURS. SEVERAL CONVECTIVE MODELS HAVE
SHORT/HEAVY PRODUCING RAINFALL STORMS MOVING OVER THE BURN SCAR
THIS EVENING. ANY ONE OF THESE CELLS THAT MOVE OVER THE BURN SCAR
COULD PRODUCE FLASH FLOODING.
IT IS POSSIBLE THAT ADDITIONAL FLOOD STATEMENTS MIGHT BE NEEDED
FOR THE HORSE GULCH BURN SCAR AND THE NEW BURN SCARS IN
BEAVERHEAD COUNTY FOR THURSDAY AND FRIDAY, AS THE
SHOWER/THUNDERSTORM ACTIVITY CONTINUES.
FOR OTHER AREAS ACROSS THE CWA, A MARGINAL RISK OF FLASH FLOODING
IS POSSIBLE FROM TODAY THROUGH FRIDAY FROM ANY STORMS THAT PRODUCE
HEAVY RAINFALL. THE OVERALL PROBABILITY IS GENERALLY LESS THAN 15
PERCENT OF FLASH FLOODING, BUT PRECIPITABLE WATER WILL INCREASE
OVER 1 INCH BY THURSDAY OVER THE EASTERN PORTIONS OF THE CWA,
ALLOWING FOR THAT POTENTIAL OF FLASH FLOODING. BRUSDA
PRELIMINARY POINT TEMPS/POPS
GTF 78 52 70 50 / 0 80 80 70
CTB 65 46 60 44 / 50 80 100 70
HLN 81 53 73 53 / 10 60 40 80
BZN 87 50 77 49 / 10 40 40 80
WYS 79 40 72 39 / 50 40 60 80
DLN 84 49 76 48 / 10 20 70 70
HVR 77 48 69 47 / 20 90 90 60
LWT 78 49 68 47 / 20 90 80 80
TFX WATCHES/WARNINGS/ADVISORIES
FLASH FLOOD WATCH FROM 4 PM MDT THIS AFTERNOON THROUGH LATE
TONIGHT FOR BIG BELT, BRIDGER AND CASTLE MOUNTAINS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page