744
FXUS65 KMSO 162100
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
200 PM MST MON DEC 16 2024
DISCUSSION
KEY MESSAGES:
- LIGHT SNOWFALL ACROSS WESTERN MONTANA AND NORTH CENTRAL IDAHO
TODAY
- MIXED PRECIPITATION, INCLUDING FREEZING RAIN POSSIBLE TUESDAY
NIGHT INTO WEDNESDAY MORNING
- HIGH PRESSURE LATE IN THE WEEK INTRODUCES FOG AND LOW STRATUS
LIGHT TO MODERATE SNOWFALL WILL CONTINUE TO TRACK ACROSS THE
NORTHERN ROCKIES THROUGH THIS EVENING. ONLY LIGHT ACCUMULATIONS
ARE EXPECTED IN THE VALLEYS OF WESTERN MONTANA, WITH A TRACE TO 2
INCHES EXPECTED. BEHIND THE FRONT, LIGHT SNOWFALL WILL BECOME
SHOWERY IN NATURE, THAT WILL HAVE THE POTENTIAL TO COALESCE INTO
WEAK BANDS AROUND THE COMMUTE HOURS IN WEST-CENTRAL AND SOUTHWEST
MONTANA THIS EVENING.
SNOW LEVELS WILL BEGIN TO RISE DURING TUESDAY NIGHT INTO
WEDNESDAY, PEAKING WEDNESDAY AFTERNOON AT BETWEEN 5000 TO 6000
FEET. AT THE SAME TIME, A PLUME OF MOISTURE ASSOCIATED WITH AN
ATMOSPHERIC RIVER WILL BE DIRECTED OVER THE REGION. PRECIPITATION
WILL GRADUALLY TRANSITION IN THE VALLEYS TUESDAY NIGHT INTO
WEDNESDAY FROM SNOW TO RAIN. AS THIS IS OCCURRING, A PERIOD OF
FREEZING RAIN WILL BE POSSIBLE (10-15 PERCENT CHANCE) FOR VALLEYS
THAT SEE COLD TEMPERATURES TRAPPED AT THE SURFACE. THE BIGGEST
THREAT FOR THIS TO OCCUR IS ACROSS NORTHWEST MONTANA WHERE THE
BEST PLUME OF MOISTURE IS DIRECTED AND GROUND TEMPERATURES ARE THE
COLDEST. MEANWHILE, HEAVY WET SNOW WILL BE FALLING IN THE HIGHER
ELEVATIONS. IN FACT, CURRENT FORECAST MODELS SHOW A 60 TO 70
PERCENT CHANCE OF 6 INCHES OR MORE FALLING ABOVE 5000 FEET IN
NORTHWEST MONTANA IN THE 24 HOURS ENDING 5PM WEDNESDAY.
A STRONG JET STREAM ASSOCIATED WITH THE WEATHER SYSTEM ON
WEDNESDAY IS ALSO BRINGING AN INCREASED THREAT FOR GUSTY WESTERLY
WINDS IN ALL OF WESTERN MONTANA. CURRENTLY, THERE IS A 50-70
PERCENT PROBABILITY FOR THE VALLEYS TO SEE WIDESPREAD GUSTS IN
EXCESS OF 30 MPH DURING THE AFTERNOON AND EVENING HOURS. THERE IS
A 20 TO 30 PERCENT PROBABILITY GUSTS WILL EXCEED 40 MPH IN THE
BITTERROOT VALLEY AND BUTTE/ANACONDA REGIONS.
A RIDGE OF HIGH PRESSURE IS STILL ON TRACK TO BUILD OVER THE
NORTHERN ROCKIES THURSDAY AND FRIDAY, THAT WILL BRING A CONCERN
FOR THE DEVELOPMENT OF FOG AND/OR STRATUS EACH DAY. 65% OF
ENSEMBLE FORECAST MODELS KEEP A FORM OF THE RIDGE IN PLACE INTO
CHRISTMAS EVE. IF THIS OCCURS, A LONG LASTING RIDGE OF HIGH
PRESSURE IMPACTING HOLIDAY TRAVEL WILL BECOME A CONCERN. OTHER
FORECAST MODELS HAVE A TROUGH OF LOW PRESSURE ENTERING THE REGION
BRING MOUNTAIN SNOW AND A RAIN/SNOW MIX IN THE VALLEYS.
AVIATION
LIGHT TO MODERATE SNOWFALL WILL CONTINUE TO TRACK ACROSS THE
NORTHERN ROCKIES THROUGH THIS EVENING. KGPI IS EXPECTED TO SEE
VISIBILITY REDUCTIONS DUE TO THE SNOW BETWEEN 16/2200Z-17/0300Z
THIS EVENING. SIMILAR TIMING IS EXPECTED FOR KMSO AND KHRF, WITH
THE POTENTIAL FOR ISOLATED SNOW BANDS BETWEEN 16/2300Z-17/0200Z.
SNOW ACCUMULATIONS WILL BE LIGHT, BETWEEN A TRACE TO 2 INCHES IN
THE VALLEYS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 9 AM MST TUESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...FLATHEAD/MISSION VALLEYS...
KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION...
POTOMAC/SEELEY LAKE REGION...WEST GLACIER REGION.
ID...WINTER WEATHER ADVISORY UNTIL 8 AM PST TUESDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
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