790
FXUS65 KTFX 130542
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1142 PM MDT WED MAR 12 2025
AVIATION SECTION UPDATED.
KEY MESSAGES
- SNOW, HEAVY AT TIMES, EXPECTED ACROSS SOUTHWESTERN MONTANA ON
THURSDAY.
- NEXT NOTABLE SYSTEM ARRIVES SUNDAY AND MONDAY, BRINGING GUSTY
WINDS AND WIDESPREAD SNOWFALL TO THE AREA.
- QUIETER WEATHER EXPECTED FOR MID NEXT WEEK AS HIGH PRESSURE
SETS UP ACROSS THE AREA.
UPDATE
/ISSUED 855 PM MDT WED MAR 12 2025/
NO UPDATES NEEDED TO THE CURRENT FORECAST FOR THE OVERNIGHT
PERIOD INTO THURSDAY MORNING, AS IT HAS BEEN TRENDING WELL
COMPARED TO WHAT HAS BEEN HAPPENING.
GUSTY SOUTHERLY WINDS WILL REMAIN A CONCERN ACROSS SOUTHWEST
MONTANA THROUGH THURSDAY MORNING AHEAD OF AN APPROACHING PACIFIC
COLD FRONT. THE WIND THREAT WILL THEN SHIFT TO OVER THE PLAINS
DURING THE AFTERNOON, AS GUSTY WESTERLY WINDS THERE WILL SPREAD
EAST BEHIND THE COLD FRONT. HOWEVER, SCATTERED CONVECTIVE RAIN
AND SNOW SHOWERS, POSSIBLY WITH A CHANCE FOR A FEW THUNDERSTORMS,
WILL REMAIN A CONCERN FOR SOUTHWEST MONTANA WITH THE FRONTAL
PASSAGE IN THE AFTERNOON. SOME OF THESE SHOWERS MAY CAUSE
SIGNIFICANT REDUCTIONS IN VISIBILITY, ALONG WITH CAUSING SOME
SLUSHY SNOW COVER OVER MOUNTAIN PASSES. HAVE NOT CHANGED FORECAST
SNOWFALL AMOUNTS, WHICH REMAIN IN THE WINTER WEATHER ADVISORY
CATEGORY, BUT THE LATEST FORECAST MODELS WILL BE FURTHER EVALUATED
OVERNIGHT TO DETERMINE IF THESE AMOUNTS MAY NEED TO BE INCREASED.
-COULSTON
DISCUSSION
/ISSUED 855 PM MDT WED MAR 12 2025/
- METEOROLOGICAL OVERVIEW:
AN UPPER LEVEL RIDGE CURRENTLY SITUATED OVER THE NORTHERN ROCKIES
TODAY WILL GRADUALLY SHIFT EASTWARD AND GIVE WAY TO A SHORTWAVE
TROUGH THAT WILL PUSH ITS WAY THROUGH THE AREA ON THURSDAY. AS
THIS TROUGH PUSHES THROUGH, SOME HIGHER ELEVATION AREAS OF
SOUTHWESTERN MONTANA WILL SEE PERIODS OF MODERATE TO HEAVY
SNOWFALL, WITH SOME BURSTS OF MODERATE TO HEAVY SNOW POSSIBLE AT
THE LOWER ELEVATIONS NEAR AND SOUTH OF I-90. AFTER THIS SYSTEM
CLEARS THE AREA ON FRIDAY, STRONG WESTERLY FLOW WILL REMAIN
ACROSS THE AREA, WHICH WILL RESULT IN BREEZY AND CLOUDY
CONDITIONS ACROSS THE AREA WITH A FEW AREAS OF MOUNTAIN SNOW
SHOWERS. ANOTHER UPPER LEVEL TROUGH WILL PUSH THROUGH THE AREA
SUNDAY AND MONDAY, BRINGING ANOTHER ROUND OF INCREASED WIND AND
WIDESPREAD SNOWFALL TO NORTH CENTRAL AND SOUTHWESTERN MONTANA
BEFORE UPPER LEVEL RIDGING RETURNS FOR MID WEEK.
- FORECAST CONFIDENCE & SCENARIOS:
THURSDAY: AS THE UPPER LEVEL TROUGH PUSHES THROUGH THE AREA,
CONVECTIVE SNOW SHOWERS WILL DEVELOP ACROSS SOUTHWESTERN MONTANA.
GIVEN THE CONVECTIVE NATURE OF THESE SNOW SHOWERS, SNOWFALL
AMOUNTS WILL BE HIGHLY VARIABLE AND HARD TO PIN DOWN, BUT WE CAN
GET SOME IDEAS FOR THE IMPACTS WE EXPECT. FOR STARTERS,
CONVECTIVE SNOW SHOWERS LIKE THESE ARE NOTORIOUS FOR PRODUCING
BRIEF BURSTS OF HEAVIER SNOWFALL THAT CAN RAPIDLY REDUCE
VISIBILITY AND QUICKLY CHANGE ROAD CONDITIONS, AND WITH THE SETUP
TOMORROW I EXPECT WE WILL SEE THIS PLAY OUT ACROSS AREAS ALONG
AND SOUTH OF I-90. SNOWFALL ACCUMULATIONS ACROSS THE HIGHER
ELEVATIONS WILL GENERALLY REACH 6-8 INCHES OR SO, BUT AREAS THAT
SEE TRAINING SNOW SHOWERS COULD SEE LOCALLY HIGHER AMOUNTS, WITH
THE POSSIBILITY OF SOME AREAS SEEING OVER A FOOT, PARTICULARLY
THE PEAKS AND HIGHER PASSES.
SUNDAY THROUGH TUESDAY: OUR NEXT WEATHER SYSTEM WILL ARRIVE EARLY
NEXT WEEK, BRINGING GUSTY WINDS TO SOUTHWESTERN MONTANA, WHERE
THE NBM HAS BEEN GIVING A WIDESPREAD 50% CHANCE OF 55 MPH WIND
GUSTS AT SOME POINT ON SUNDAY. WHILE THIS DOES MEET THE TYPICAL
CRITERIA FOR A HIGH WIND WATCH, WE ARE A BIT FAR OUT FOR THAT TO
BE ISSUED, THOUGH WE WILL NEED TO WATCH THIS CLOSELY OVER THE
NEXT 24 HOURS TO SEE IF THESE PROBABILITIES CONTINUE TO HOLD
FAST. SNOWFALL WILL BE THE OTHER PART OF THIS SYSTEM, WITH
CURRENT OPERATIONAL AND ENSEMBLE BLENDS SHOWING WIDESPREAD
SNOWFALL WITH SOME LOWER ELEVATION RAINFALL SPREADING OVER THE
AREA SUNDAY NIGHT AND MONDAY. THERE DOES REMAIN SOME UNCERTAINTY
WITH HOW FAR NORTH THE SNOWFALL WILL REACH, HOWEVER, AS MOST
MODELS HAVE TENDED TO KEEP THE PRECIPITATION OVER THE MOUNTAIN
VALLEY REGION OF SOUTHWESTERN MONTANA AND ALONG THE CONTINENTAL
DIVIDE IN NORTHERN MONTANA. HOWEVER, THERE IS AROUND 30-40% OF
THE ENSEMBLE SPACE THAT BRINGS THE PRECIPITATION A BIT FURTHER
NORTH, WHICH COULD BRING A LIGHT COATING OF SNOWFALL TO THE
PLAINS. LUDWIG
AVIATION
13/06Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL AT ALL TERMINALS EXCEPT FOR THE KEKS
TERMINAL DURING THE DURATION OF THIS TAF PERIOD. A COLD FRONT WILL
MOVE FROM WEST TO EAST DURING THIS TAF PERIOD REACHING KCTB AT
AROUND 13/17Z. IT WILL REACH KLWT AT AROUND 13/21Z. THIS COLD FRONT
WILL BRING SNOW AND RAIN TO THE KEKS, KBZN, AND KLWT TERMINALS. IT
HAS THE POTENTIAL TO BRING RAIN TO THE KHLN, KGTF, AND KHVR
TERMINALS. THE COLD FRONT WILL SHIFT WINDS FROM THE SOUTH AT ALL
TERMINALS TO BRIEFLY SOUTHWESTERLY AT AROUND FRONTAL PASSAGE. AFTER
FRONTAL PASSAGE WINDS WILL SHIFT TO NORTHWESTERLY. THE SNOW WILL
REDUCE VISIBILITY TO MVFR LEVELS AT THE KEKS TERMINAL BY THE END OF
THIS TAF PERIOD. THERE IS A L5% CHANCE FOR THUNDER AT THE KBZN AND
KEKS TERMINALS BETWEEN 13/18Z AND 13/06Z. ANY THUNDER WOULD CAUSE A
BRIEF RAPID REDUCTION IN VISIBILITY. AT THE KGTF AND KHVR TERMINALS
BETWEEN 13/22Z AND THE END OF THE TAF PERIOD THERE IS A 15% CHANCE
FOR RAIN. THERE WILL ALSO BE ISOLATED INSTANCES OF LOW-LEVEL WIND
SHEAR AND MOUNTAIN WAVE TURBULENCE ACROSS SOUTHWESTERN MONTANA
BETWEEN NOW AND 13/18Z. THERE WILL BE MOUNTAIN OBSCURATION AFTER
13/19Z ACROSS SOUTHWESTERN MONTANA. -IG
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 37 56 31 44 / 10 20 10 10
CTB 29 52 23 39 / 0 10 0 10
HLN 36 52 26 41 / 10 50 30 10
BZN 32 51 21 37 / 0 70 80 20
WYS 28 41 16 31 / 60 70 90 60
DLN 32 47 21 37 / 10 60 50 10
HVR 29 59 24 42 / 0 20 20 10
LWT 33 55 26 38 / 10 60 60 10
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 6 AM THURSDAY TO 6 AM MDT FRIDAY
FOR GALLATIN AND MADISON COUNTY MOUNTAINS AND CENTENNIAL
MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT THURSDAY NIGHT FOR
NORTHWEST BEAVERHEAD COUNTY.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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