485
FXUS65 KMSO 130820
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
120 AM MST THU NOV 13 2025
DISCUSSION
KEY MESSAGES:
- DENSE FOG THIS MORNING: A DENSE FOG ADVISORY IS IN EFFECT UNTIL
10 AM MST FOR THE FLATHEAD AND MISSION VALLEYS, AS WELL AS
ALONG HIGHWAY 200 AND I-90 WEST OF MISSOULA. EXPECT VISIBILITY
BELOW ONE-QUARTER MILE IN THESE AREAS.
- ONE MORE WARM DAY: TODAY WILL BE UNSEASONABLY MILD BEFORE A
COLD FRONT ARRIVES TONIGHT.
- ACTIVE, UNSETTLED PATTERN: A CHANGE IN THE WEATHER PATTERN WILL
BRING COOLER TEMPERATURES AND CHANCES FOR PRECIPITATION,
STARTING TONIGHT AND CONTINUING THROUGH THE WEEKEND.
A STABLE AIRMASS HAS ALLOWED FOR THE DEVELOPMENT OF WIDESPREAD
DENSE FOG IN OUR WESTERN MONTANA VALLEYS THIS MORNING. A DENSE FOG
ADVISORY IS IN EFFECT UNTIL 10 AM MST FOR THE FLATHEAD AND
MISSION VALLEYS (INCLUDING KALISPELL) AND FOR THE TRANSPORTATION
CORRIDORS OF HIGHWAY 200 AND I-90 WEST OF MISSOULA. PLEASE USE
EXTREME CAUTION IF TRAVELING, AS VISIBILITY MAY DROP RAPIDLY TO
NEAR ZERO. THIS FOG SHOULD BEGIN TO LIFT BY LATE MORNING.
OUTSIDE OF THE FOG, HIGH PRESSURE WILL GIVE US ONE MORE
UNSEASONABLY MILD DAY, WITH HIGH TEMPERATURES RUNNING 10 TO 15
DEGREES ABOVE AVERAGE FOR MID-NOVEMBER.
THE MAIN WEATHER STORY CHANGES TONIGHT AS A COLD FRONT MOVES INTO
THE REGION FROM THE PACIFIC NORTHWEST. THIS FRONT WILL BRING AN
INCREASE IN WINDS AND WIDESPREAD CLOUDS. PRECIPITATION WILL
ACCOMPANY THE FRONT, ESPECIALLY IN THE MOUNTAIN OF NORTH-CENTRAL
IDAHO AND NORTHWEST MONTANA. EXPECT SCATTERED RAIN SHOWERS IN THE
VALLEYS AND RAIN CHANGING TO SNOW FOR THE MOUNTAINS, WITH SNOW
LEVELS STARTING HIGH BEFORE FALLING TO AROUND 4,500-5,500 FEET BY
SATURDAY MORNING.
THE LONG-RANGE FORECAST SHOWS A "SPLIT-FLOW" PATTERN, MEANING THE
MAIN STORM TRACK MAY DIVIDE, WITH ONE BRANCH STAYING TO OUR NORTH
AND A MORE SIGNIFICANT, MOISTURE-FILLED SYSTEM DIVING SOUTH INTO
CALIFORNIA. WHILE THIS SETUP REDUCES OUR CHANCES FOR A MAJOR,
WIDESPREAD PRECIPITATION EVENT, IT WILL KEEP US IN AN UNSETTLED
NORTHWEST FLOW. THIS PATTERN FAVORS PERIODS OF LIGHT MOUNTAIN SNOW
AND VALLEY RAIN-OR-SNOW SHOWERS. CONFIDENCE IN THE EXACT TIMING
AND STRENGTH OF THESE SMALLER SYSTEMS IS LOW, BUT THE KEY TAKEAWAY
IS THAT THE MILD WEATHER IS OVER, AND A MORE TYPICAL LATE-FALL
PATTERN WILL SETTLE IN WITH VALLEY SNOW CHANCES BY MIDWEEK.
AVIATION
WIDESPREAD IFR TO LIFR CONDITIONS ARE IMPACTING
NORTHWEST MONTANA VALLEY TERMINALS THIS MORNING DUE TO DENSE FOG.
A DENSE FOG ADVISORY IS IN EFFECT UNTIL 17Z (10 AM MST) FOR KGPI
AND AREAS SURROUNDING KMSO. CONDITIONS ARE EXPECTED TO IMPROVE TO
MVFR AND THEN VFR AFTER 17-18Z AS THE FOG SLOWLY LIFTS AND
DISSIPATES. CONFIDENCE IS HIGH THAT DENSE FOG WILL BE AN ISSUE
THIS MORNING, BUT THE EXACT TIMING OF ITS DISSIPATION COULD VARY.
SOME VALLEYS MAY STAY SHROUDED IN LOW CLOUDS LONGER THAN OTHERS.
AFTER AROUND 00Z THIS EVENING, AN APPROACHING COLD FRONT WILL
BRING INCREASING MID-LEVEL CLOUDS. WIDESPREAD SHOWERS AND
INCREASING WINDS ARE EXPECTED TONIGHT AND THROUGH FRIDAY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...DENSE FOG ADVISORY UNTIL 10 AM MST THIS MORNING FOR
FLATHEAD/MISSION VALLEYS...LOWER CLARK FORK REGION.
ID...NONE.
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