559
FXUS65 KMSO 152219
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
319 PM MST SAT FEB 15 2025
DISCUSSION
KEY MESSAGES:
- SNOW RETURNS TO THE REGION TONIGHT.
- A LONG DURATION HEAVY SNOWFALL EVENT IS EXPECTED THROUGHOUT THE
HIGHER TERRAIN ALONG THE IDAHO/MONTANA BORDER WITH SEVERAL FEET
OF SNOW POSSIBLE BY TUESDAY MORNING.
- AN ARCTIC BOUNDARY BRINGING ENHANCED SNOWFALL AND GUSTY WINDS
WILL IMPACT THE GLACIER NP REGION, FLATHEAD & MISSION VALLEY,
MISSOULA VALLEY, NORTHERN BITTERROOT, AND UPPER BLACKFOOT RIVER
VALLEY LATE SUNDAY INTO MONDAY.
A WARM FRONT ASSOCIATED WITH THE NEXT WEATHER SYSTEM IS PRESENTLY
WORKING ITS WAY ACROSS WASHINGTON AND WILL GRADUALLY SPREAD
MOISTURE OVER THE NORTHERN ROCKIES THIS EVENING. LIGHT SNOW IS
EXPECTED FOR MOST LOCATIONS AND THUS A LARGE SWEEP OF WINTER
WEATHER ADVISORIES HAVE BEEN ISSUED ENCOMPASSING MUCH OF THE
NORTHERN ROCKIES.
HOWEVER, FOR MUCH OF THE HIGHER TERRAIN ALONG THE IDAHO/MONTANA
BORDER AND THE SEELEY/SWAN REGION, TONIGHT WILL BEGIN A LONG
DURATION HEAVY SNOW EVENT. ALTHOUGH SNOWFALL WILL BE LIGHT EARLY
ON, IMPRESSIVE LIFTING THROUGH A DEEP AND MOIST DENDRITIC LAYER
WILL BRING SUCCESSIVE BOUTS OF HEAVY SNOW STARTING EARLY SUNDAY
MORNING AND CONTINUING THROUGH MONDAY. WE ELECTED TO GO STRAIGHT
TO WINTER STORM WARNINGS FOR THESE AREAS AND HIGHLIGHT THE
LIKELIHOOD FOR FEET OF SNOWFALL. IN FACT, SOME AREAS IN THE
MISSION, SWAN, AND CLEARWATER MOUNTAINS COULD SEE 2 TO 4 FEET OF
SNOW. HOWEVER, WHERE MOST PEOPLE LIVE IN THESE AREAS THE RANGE
WILL GENERALLY BE 6 TO 10 INCHES WITH UPWARDS OF 16 INCHES
POSSIBLE IN SOME AREAS. PLEASE REFER TO THE WARNING OR OUR WEBSITE
FOR MORE DETAILED INFORMATION.
SNOWFALL ACROSS NW MONTANA (KOOTENAI/CABINET REGION) WILL BE
LIGHT, BUT PERSISTENT, STARTING TONIGHT AND LASTING INTO MONDAY
EVENING. ACCUMULATIONS WILL BE LIGHTEST TOWARDS THE IDAHO BORDER
AND INCREASE AS ONE MOVES EAST AND SOUTH ACROSS THE LINCOLN
COUNTY. PLACES SUCH AS THE YAAK AND LIBBY WILL GENERALLY SEE 4 TO
6 INCHES WITH MORE FAVORED AREAS, SUCH AS THE BULL LAKE, HAPPY'S
INN, PLEASANT VALLEY, AND MARION WILL SEE SEVERAL INCHES MORE. THE
KEY VARIABLE TO PAY ATTENTION IN THESE AREA WILL BE THE WESTWARD
PROGRESSION OF THE ARCTIC BOUNDARY AND HOW IT HELPS TO ENHANCE THE
SNOW PRODUCTION OVER THESE AREAS.
SNOWFALL ACROSS THE FLATHEAD, MISSION, MISSOULA AND NORTHERN
BITTERROOT VALLEY (NORTH OF STEVI) WILL BE HIGHLY LINKED TO THE
TIMING AND STRENGTH OF THE FORECASTED ARCTIC BOUNDARY. MODELS
BRING THIS BOUNDARY THROUGH BAD ROCK CANYON LATE SUNDAY AFTERNOON
BUT THE WINDS REALLY DON'T START HOWLING THROUGH THE NORTHERN
FLATHEAD UNTIL SUNDAY NIGHT WITH THE PEAK IMPACT POTENTIAL
(COMBINATION OF WIND AND SNOW) COMING MONDAY. THE TIMING OF THIS
FRONT WILL STILL QUITE VARIABLE IN THE MODELS AND THUS FURTHER
REFINING OF THE WINTER STORM WATCH MAY BE NECESSARY BY SUCCESSIVE
SHIFTS. THIS LOGIC ALSO APPLIES TO THE MISSION VALLEY WHERE THE
IMPACTS FROM SNOW AND WIND WILL LOGICALLY FOLLOW THOSE OF THE
FLATHEAD VALLEY BY A FEW HOURS AS THE ARCTIC BOUNDARY SAGS SOUTH.
THINGS ARE EVEN MORE COMPLEX FOR THE MISSOULA AND BITTERROOT
VALLEY, BUT STILL FOLLOWING A VERY SIMILAR STORY AS DESCRIBED
ABOVE FOR THE FLATHEAD. IMPACTS ATTRIBUTED TO WIND AND HEAVY
SNOWFALL WILL BE LINKED TO THE TIMING OF THE ARCTIC BOUNDARY AND
ITS INTERACTION WITH PERSISTENT MOIST FLOW ACROSS THE REGION.
AT PRESENT WE ANTICIPATE IT TO ENTER THE MISSOULA VALLEY LATE
MONDAY AFTERNOON WITH ENHANCED SNOW AND SOME BLOWING SNOW
POTENTIALLY IMPACTING THE MONDAY EVENING COMMUTE. THE HEAVIEST
SNOWFALL IS LIKELY TO FOCUS JUST AHEAD OF AND ALONG THE ARCTIC
BOUNDARY AS IT SAGS SOUTH INTO THE BITTERROOT VALLEY. HOWEVER, HOW
FAR SOUTH IT PROGRESSES REMAINS HIGHLY VARIABLE IN THE MODELS.
THUS SNOWFALL AMOUNTS DRAMATICALLY DROP OFF SOUTH OF FLORENCE. BUT
THIS COULD SIGNIFICANTLY CHANGE AS MODELS COULEES ON THE FINER
DETAILS OF THE ARCTIC BOUNDARY OVER THE NEXT 24 HOURS.
FINALLY, WE OPTED FOR A WINTER STORM WATCH ACROSS THE
BUTTE/BLACKFOOT REGION. HOWEVER, THE MOST SIGNIFICANT AND
POTENTIALS WARNING LEVEL IMPACTS WILL BE ACROSS THE NORTHERN PART
OF THIS AREA, GENERALLY THE UPPER BLACKFOOT RIVER AREA AND US-12
EAST OVER MACDONALD PASS. SOUTH OF GARRISON JUNCTION IMPACTS WILL
BE SIGNIFICANTLY LESS UNTIL THE ARCTIC BOUNDARY SAGS THIS FAR
SOUTH EARLY TUESDAY MORNING.
NOT MUCH ATTENTION WAS PLACED UPON THE FORECAST BEYOND TUESDAY
EXCEPT TO KEEP TEMPERATURES MUCH COOLER THROUGH THE ENTIRE
WEEK WITHIN THE VALLEYS OF THE LOWER HELLS CANYON AREA. THE MODEL
BIAS CORRECTION HAS BEEN PLACING VALUES UPWARDS OF 10 DEGREES TOO
WARM. THIS IS LIKELY BECAUSE THE MODELS ARE NOT CORRECTLY
ACCOUNTING FOR THE ANOMALOUSLY HIGH SNOWFALL ON THE GROUND
THROUGHOUT THIS AREA. ELSEWHERE THE REST OF THE WEEK CAN BE
SUMMARIZED AS COLD WITH THE POTENTIAL FOR VERY COLD AROUND MIDWEEK
DEPENDING UPON CLOUDS. THEN PERHAPS SOME MORE LIGHT SNOW TO ROUND
OUT THE WEEK BEFORE HIGH PRESSURE ENTERS THE FORECAST FOR THE
WEEKEND.
AVIATION
SATELLITE IMAGERY THIS AFTERNOON SHOWS INCREASING
MOISTURE MOVING IN FROM THE SOUTHWEST. THIS MOISTURE IS EXPECTED
TO REACH CENTRAL IDAHO BY THIS EVENING AND WESTERN MONTANA BY
TONIGHT, BRINGING SNOW, LOWERING CEILINGS, AND REDUCED
VISIBILITY. A PROLONGED SNOW EVENT IS ANTICIPATED CROSS THE
NORTHERN ROCKIES, LASTING FROM TONIGHT THROUGH AT LEAST MONDAY
NIGHT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY FROM 2 AM SUNDAY TO 11 PM MST MONDAY FOR
KOOTENAI/CABINET REGION.
WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO 11 AM MST MONDAY FOR
WEST GLACIER REGION.
WINTER STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING
FOR FLATHEAD/MISSION VALLEYS...WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 2 AM SUNDAY TO 11 AM MST MONDAY FOR
FLATHEAD/MISSION VALLEYS.
WINTER STORM WARNING FROM 2 AM SUNDAY TO 9 AM MST TUESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...LOWER CLARK FORK REGION.
WINTER WEATHER ADVISORY FROM 2 AM SUNDAY TO 2 PM MST MONDAY FOR
MISSOULA/BITTERROOT VALLEYS.
WINTER STORM WATCH FROM MONDAY AFTERNOON THROUGH TUESDAY MORNING
FOR BUTTE/BLACKFOOT REGION...MISSOULA/BITTERROOT VALLEYS.
WINTER WEATHER ADVISORY FROM 5 AM SUNDAY TO 2 PM MST MONDAY FOR
BUTTE/BLACKFOOT REGION.
WINTER STORM WARNING FROM 5 AM SUNDAY TO 9 AM MST TUESDAY FOR
POTOMAC/SEELEY LAKE REGION.
ID...WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 PM PST MONDAY
FOR NORTHERN CLEARWATER MOUNTAINS.
WINTER STORM WARNING FROM 10 PM THIS EVENING TO 10 PM PST MONDAY
FOR SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST
MONDAY FOR LOWER HELLS CANYON/SALMON RIVER REGION...
OROFINO/GRANGEVILLE REGION.
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