984
FXUS65 KMSO 032035
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
135 PM MST WED DEC 3 2025
DISCUSSION
KEY MESSAGES:
- A PROLONGED PERIOD OF WINTER WEATHER STARTS ON THURSDAY LASTING
THROUGH THE WEEKEND
- HEAVY MOUNTAIN SNOW, ALONG WITH A WINTRY MIX IN THE VALLEYS
WILL MAKE FOR DIFFICULT TRAVEL CONDITIONS
- UNSETTLED WINTER WEATHER WILL CONTINUE INTO NEXT WEEK
SATELLITE IMAGERY THIS AFTERNOON IS SHOWING A REGION OF HIGH
PRESSURE OFF THE WEST COAST AND A LOW PRESSURE CIRCULATION
SPINNING OVER THE ALEUTIAN ISLANDS. THESE TWO FEATURES ARE WORKING
TOGETHER TO SEND PACIFIC MOISTURE INTO WESTERN CANADA AND THE
NORTHWESTERN U.S. FROM THE NORTHWEST. SOME OF THAT MOISTURE WILL
REACH NORTHWEST MONTANA AS EARLY AS THIS AFTERNOON AND TONIGHT IN
THE FORM OF SNOW.
THE ALEUTIAN LOW AND PACIFIC HIGH DON’T MOVE MUCH IN THE COMING
DAYS, KEEPING A STEADY STREAM OF MOISTURE POINTED AT THE NORTHERN
ROCKIES. THE RESULT WILL BE A PROLONGED PERIOD OF UNSETTLED WINTER
WEATHER LASTING THROUGH THE WEEKEND. THERE IS HIGH CONFIDENCE FOR
SIGNIFICANT MOUNTAIN SNOW. THERE IS LESS CERTAINTY FOR VALLEY
SNOW, AND EVEN SOME CHANCE FOR FREEZING RAIN ON FRIDAY AND
SATURDAY MORNINGS FOR THE WESTERN MONTANA VALLEYS.
- MOUNTAIN SNOW: THIS SYSTEM WILL VERY MUCH FAVOR THE HIGHER
ELEVATIONS. SNOW WILL START TONIGHT IN NORTHWEST MONTANA OVER
THE CABINETS, MISSIONS, SWANS, AND ALONG THE CONTINENTAL DIVIDE
IN THE GLACIER PARK REGION. COVERAGE WILL SPREAD SOUTH INTO
THE CLEARWATER AND BITTEROOT RANGES ON THURSDAY THROUGH
SATURDAY. SEVENTY-TWO HOUR SNOW-WATER EQUIVALENT NUMBERS LOOK
IMPRESSIVE, WITH MAJOR MOUNTAIN RANGES RECEIVING 0.75 – 1 INCH
ON THE LOW END, TO ABOUT 2 INCHES ON THE HIGH END BY THE END OF
THE DAY ON SATURDAY. TRAVEL OVER MOUNTAIN PASSES SUCH AS
LOOKOUT, LOLO, LOST TRAIL, AND MARIAS PASSES WILL BE IMPACTED.
EXPECT WINTER TRAVEL CONDITIONS ON THESE ROADWAYS. A WINTER
STORM WATCH WILL GO INTO EFFECT ON FRIDAY MORNING FOR MOST
MOUNTAIN PUBLIC FORECAST ZONES.
- VALLEY SNOW: VALLEY SNOW AMOUNTS WILL BE THE FORECAST
CHALLENGE. THERE IS LIMITED COLD AIR COMING WITH THIS SYSTEM.
HOWEVER, THERE IS COLD AIR TRAPPED IN THE VALLEYS. IF THE
VALLEY COLD POOLS ERODE, PRECIPITATION MAY BE IN THE FORM OF A
WINTRY MIX. THE CURRENT THINKING FOR THIS FORECAST PERIOD IS TO
KEEP VALLEY SNOW AMOUNTS ON THE LOW SIDE. EXPECT SNOW ON
THURSDAY TO TRANSITION TO A WINTRY MIX ON FRIDAY INTO SATURDAY
MORNING.
- FREEZING RAIN: SORRY ABOUT THIS, BUT THERE IS A CHANCE FOR
FREEZING RAIN IN THE VALLEYS OF WESTERN MONTANA AND, TO A
LESSER EXTENT, WESTERN IDAHO, ON FRIDAY AND SATURDAY MORNINGS.
MODEL SOUNDINGS INDICATE A DRY LAYER OVER LOW-LEVEL MOISTURE,
WHICH IS CONDUCIVE TO FREEZING RAIN. CHANCES FOR FREEZING RAIN
ARE LOW (ABOUT 15%), BUT WORTH MENTIONING. IF YOU HAVE TRAVEL
PLANS ON FRIDAY OR SATURDAY MORNING, PLEASE DOUBLE CHECK THE
FORECAST AND ROAD CONDITIONS BEFORE DEPARTING.
THERE IS GOOD AGREEMENT IN LONG TERM MODEL SOLUTIONS TO KEEP THE
NORTHERN ROCKIES UNDER MOIST NORTHWEST FLOW ALOFT WELL INTO NEXT
WEEK. WINTER IS HERE.
AVIATION
STABLE CONDITIONS TODAY WILL LEAD TO PERSISTENT
STRATUS ACROSS MUCH OF NORTH-CENTRAL IDAHO AND WEST-
CENTRAL/NORTHWEST MONTANA. MOUNTAINS WILL REMAIN OBSCURED.
CONDITIONS HAVE BRIEFLY IMPROVED THIS AFTERNOON BETWEEN KSMN,
KHRF, AND KBTM, BUT CLOUDS WILL INCREASE OVERNIGHT. AN INCOMING
SYSTEM THURSDAY WILL BRING WIDESPREAD MOUNTAIN OBSCURATION AND A
RETURN TO MVFR/IFR VISIBILITY WITH SNOW DEVELOPING DURING THURSDAY
MORNING.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH SATURDAY
AFTERNOON FOR BITTERROOT/SAPPHIRE MOUNTAINS...LOWER CLARK
FORK REGION...POTOMAC/SEELEY LAKE REGION...WEST GLACIER
REGION.
ID...WINTER STORM WATCH FROM LATE THURSDAY NIGHT THROUGH SATURDAY
AFTERNOON FOR NORTHERN CLEARWATER MOUNTAINS...SOUTHERN
CLEARWATER MOUNTAINS.
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