464
FXUS65 KMSO 241030
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
330 AM MST WED DEC 24 2025
DISCUSSION
KEY MESSAGES:
- STRONG COLD FRONT FRIDAY WILL BRING SNOW, ESPECIALLY IN THE
MOUNTAINS, THROUGH SATURDAY.
- BEHIND THE COLD FRONT SATURDAY, EXPECTED WIND GUSTS 20-35 MPH
ACROSS THE REGION.
- SUNDAY THROUGH EARLY NEXT WEEK A RIDGE BUILDS OVER THE REGION
CAUSING STABLE CONDITIONS.
LOTS OF MOISTURE OVER THE LAST 24 HOURS HAS LEFT THE BOUNDARY
LAYER SATURATED CAUSING A LOT OF FOG AND MIST. WITH RISING
PRESSURE LEVEL HEIGHTS AND INCREASING STABILITY THIS MORNING,
EXPECT SOME OF THAT TO LINGER FOR A WHILE TODAY. AN INCREASING
EASTERLY PRESSURE GRADIENT WILL PREVENT IT FROM REMAINING DENSE
ALL DAY, BUT IT WON'T BE ENOUGH TO CLEAR IT OUT MUCH UNTIL THIS
AFTERNOON.
ANOTHER COLD FRONT IS HEADED OUR WAY FOR FRIDAY INTO SATURDAY. AS
WITH ALL THE SYSTEMS SO FAR THIS WINTER, THERE IS CONSIDERABLE
UNCERTAINTY IN THE SNOW LEVELS AND SNOW AMOUNTS AT AREA PASSES
RANGE FROM 2 TO OVER 9 INCHES OF SNOW IN 24 HOURS. EVEN ON THE
HIGH END OF THE RANGE OF FORECASTS, VALLEYS ARE EXPECTED TO PICK
UP LESS THAN AN INCH OF SNOW BY SATURDAY MORNING. THIS FRONT WILL
ALSO BRING ANOTHER ROUND OF WIND BEHIND IT WITH SATURDAY AFTERNOON
GUSTS RANGING FROM 20 TO 35 MPH IN THE VALLEYS ACROSS THE REGION.
SOME OF THE TYPICALLY WINDIER LOCATIONS LIKE GRANGEVILLE WILL SEE
GUSTS APPROACHING 40 MPH.
SUNDAY INTO EARLY NEXT WEEK A RIDGE BUILDS OVER THE REGION AGAIN.
IT WILL BE A DIRTY RIDGE, WHICH JUST MEANS THERE WILL BE QUITE A
BIT OF MOISTURE FLOWING THROUGH THE RIDGE, SO THERE WILL BE PLENTY
OF CLOUD COVER. STILL, IT WILL CAUSE INCREASING STABILITY AT A
TIME WHEN THE SUN ANGLE IS VERY LOW, SO IF THERE'S MUCH MOISTURE
AVAILABLE IN THE BOUNDARY FROM MELTING SNOW, FOG WILL ONCE AGAIN
RETURN EARLY NEXT WEEK.
AVIATION
THE REMNANTS OF THE ATMOSPHERIC RIVER THAT HAS BEEN
IMPACTING CALIFORNIA ARE MOVING THROUGH OUR REGION IN SOUTHWEST
FLOW. DUE TO RECENT RAINS AND MELTING SNOW, THE BOUNDARY LAYER IS
SATURATED AND THIS IS CAUSING SOME FOG AND MIST. AN EASTERLY
PRESSURE GRADIENT THIS MORNING IS HELPING TO BREAK IT UP AND
PREVENTING THE FOG FROM BECOMING DENSE, BUT WITH RISING HEIGHTS, A
LOW SUN ANGLE, AND PLENTY OF MID AND HIGH CLOUD COVER IT WILL BE
MID-AFTERNOON BEFORE IT CAN CLEAR OUT THE LARGER VALLEYS AROUND
MOST TERMINALS. AND THEN, WITH SO MUCH RECENT MOISTURE IN THE
BOUNDARY LAYER, FOG AND MIST WILL MOST LIKELY RETURN AGAIN
TONIGHT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...DENSE FOG ADVISORY UNTIL 8 AM MST THIS MORNING FOR
MISSOULA/BITTERROOT VALLEYS.
ID...DENSE FOG ADVISORY UNTIL 5 AM MST /4 AM PST/ EARLY THIS MORNING
FOR EASTERN LEMHI COUNTY...OROFINO/GRANGEVILLE REGION.
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