428
FXUS65 KMSO 161017
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
317 AM MST MON DEC 16 2024
DISCUSSION
KEY MESSAGES:
-LIGHT SNOWFALL ACROSS WESTERN MONTANA AND NORTH CENTRAL IDAHO
TODAY INTO TUESDAY MORNING
-MIXED PRECIPITATION, INCLUDING FREEZING RAIN POSSIBLE TUESDAY
NIGHT INTO WEDNESDAY MORNING
-HIGH PRESSURE LATE IN THE WEEK INTRODUCES FOG AND LOW STRATUS
THE NEXT WEAK WEATHER SYSTEM IS QUICKLY APPROACHING THIS MORNING,
AND WILL BEGIN TO SPREAD PRECIPITATION INTO NORTH CENTRAL IDAHO
THIS MORNING, AND THEN INTO WESTERN MONTANA BY MID DAY.
TEMPERATURES REMAIN COLD ENOUGH THAT VIRTUALLY ALL LOCATIONS,
OTHER THAN THE LOWEST VALLEYS OF NORTH CENTRAL IDAHO, SHOULD SEE
PRECIPITATION FALL AS SNOW. NUMEROUS WINTER WEATHER ADVISORIES ARE
IN PLACE TO ACCOUNT FOR SLICK ROADS DUE TO LIGHT SNOW
ACCUMULATIONS INTO TUESDAY MORNING. STRONGER CONVECTIVE SNOW
SHOWERS ARE LOOKING MORE LIKELY BY THIS AFTERNOON, WHICH COULD
CAUSE MORE OF A THREAT FOR THE MISSOULA/BITTERROOT VALLEYS TOWARDS
THE EVENING COMMUTE TIME FRAME.
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 (20-30 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 RIDGE OF HIGH PRESSURE IS ANTICIPATED TO BUILD IN BEHIND THIS
WEATHER SYSTEM, WITH THE MAIN CONCERN SHIFTING TO THE DEVELOPMENT
OF LOW CLOUDS AND FOG THURSDAY INTO THE WEEKEND. THE TEMPERATURE
FORECAST IN THIS TIMEFRAME IS CHALLENGING FOR VALLEY LOCATIONS AS
INVERSIONS WILL LIKELY DEVELOP. VALLEYS THAT DO SEE INVERSIONS
WILL LIKELY SEE TEMPERATURES COLDER THAN THE CURRENT FORECAST.
FORECAST MODELS DIFFER IN HOW LONG THE RIDGE WILL REMAIN IN PLACE
OVER THE REGION. A LONGER LASTING, MORE AMPLIFIED RIDGE COULD BE
CRITICAL FOR AVIATION TRAVEL FOR THE CHRISTMAS HOLIDAY DUE TO LOW
CLOUDS AND FOG. AROUND 60 PERCENT OF MODEL SOLUTIONS FAVOR SOME
SORT OF RIDGING REMAINING OVER THE REGION WHILE THE OTHER 40
PERCENT START TO WEAKEN THE RIDGE AND BRING THE NEXT WEATHER
SYSTEM IN BY NEXT TUESDAY.
AVIATION
ANOTHER WEAK WEATHER SYSTEM WILL MOVE THROUGH THE
REGION TODAY FROM WEST TO EAST, STEADILY INTRODUCING LOW CLOUDS
AND SNOWFALL FROM NORTH CENTRAL IDAHO EARLY THIS MORNING,
SPREADING INTO WESTERN MONTANA BY MID DAY. EXPECT THE HIGHER
TERRAIN TO BE OBSCURED WITH PERIODS OF LOWERED VISIBILITY DUE TO
SNOWFALL POSSIBLE AT ALL TERMINAL LOCATIONS. NORTHWEST MONTANA,
INCLUDING KGPI, AND THE HIGHER TERRAIN OF IDAHO WILL RECEIVE THE
MOST STEADY SNOWFALL, MAINLY BETWEEN 16/1800Z AND 17/0600Z.
CONVECTIVE SHOWERS THIS AFTERNOON COULD LEAD TO LOCALLY HEAVY
SNOWFALL RATES.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 9 AM MST TUESDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY FROM 8 AM THIS MORNING TO 9 AM MST
TUESDAY FOR KOOTENAI/CABINET REGION...LOWER CLARK FORK
REGION.
WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 9 AM MST
TUESDAY FOR FLATHEAD/MISSION VALLEYS...POTOMAC/SEELEY LAKE
REGION...WEST GLACIER REGION.
ID...WINTER WEATHER ADVISORY UNTIL 8 AM PST TUESDAY FOR NORTHERN
CLEARWATER MOUNTAINS...SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 8 AM PST THIS MORNING FOR
OROFINO/GRANGEVILLE REGION.
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