142
FXUS65 KMSO 161045
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
345 AM MST SUN FEB 16 2025
DISCUSSION
KEY MESSAGES:
- SNOW HAS RETURNED 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.
FOR MUCH OF THE HIGHER TERRAIN ALONG THE IDAHO/MONTANA BORDER AND
THE SEELEY/SWAN REGION, LAST NIGHT WAS THE BEGINNING OF 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 TODAY AND
CONTINUING THROUGH TOMORROW. 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 CONTINUE
TO BE LIGHT, BUT PERSISTENT, THROUGH 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 AREAS 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 THIS AFTERNOON
BUT THE WINDS REALLY DON'T START HOWLING THROUGH THE NORTHERN
FLATHEAD UNTIL TONIGHT WITH THE PEAK IMPACT POTENTIAL (COMBINATION
OF WIND AND SNOW) COMING TOMORROW. THE TIMING OF THIS FRONT IS
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
A WARM FRONT MOVING ACROSS THE REGION TONIGHT IS CAUSING LIGHT
SNOW. THIS IS THE BEGINNING OF A LONG TERM WINTER STORM THAT WILL
LAST THROUGH TUESDAY, AND EVEN THEN ANOTHER ROUND OF SNOW LOOKS TO
BE ON THE WAY FOR LATE IN THE WEEK. WITH INCREASING SOLAR
RADIATION AS WE MOVE INTO LATE FEBRUARY AND DAYTIME TEMPERATURES
CLIMBING INTO THE LOW 30S, DAYTIME MELTING AND REFREEZING AT NIGHT
WILL BECOME MORE OF A CONCERN FOR ICE AT REGIONAL TERMINALS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY FOR
FLATHEAD/MISSION VALLEYS.
WINTER WEATHER ADVISORY UNTIL 11 PM MST MONDAY FOR
KOOTENAI/CABINET REGION.
WINTER WEATHER ADVISORY UNTIL 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 STORM WARNING UNTIL 9 AM MST TUESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...LOWER CLARK FORK REGION.
WINTER WEATHER ADVISORY UNTIL 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 UNTIL 2 PM MST MONDAY FOR
BUTTE/BLACKFOOT REGION.
WINTER STORM WARNING UNTIL 9 AM MST TUESDAY FOR POTOMAC/SEELEY
LAKE REGION.
ID...WINTER STORM WARNING UNTIL 4 PM PST MONDAY FOR NORTHERN
CLEARWATER MOUNTAINS.
WINTER STORM WARNING UNTIL 10 PM PST MONDAY FOR SOUTHERN
CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 10 AM PST MONDAY FOR LOWER HELLS
CANYON/SALMON RIVER REGION...OROFINO/GRANGEVILLE REGION.
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