106
FXUS65 KMSO 301943
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
143 PM MDT THU OCT 30 2025
DISCUSSION
KEY MESSAGES:
- VALLEY FOG IS SLOW TO MIX OUT. INCREASING CLOUD COVER TONIGHT
WILL LIMIT OVERALL EXTENT OF FOG REDEVELOPMENT FOR FRIDAY
MORNING.
- A VERY MILD AND BREEZY WEEKEND IS ON TAP. WIND GUSTS TO 40+ MPH
POSSIBLE IN HIGHER TERRAIN, ESPECIALLY NEAR THE CONTINENTAL
DIVIDE, SATURDAY AFTERNOON INTO SUNDAY MORNING.
- SHOWER CHANCES INCREASING SATURDAY INTO SUNDAY. HIGH SNOW
LEVELS (ABOVE 7,000 FT) BEFORE DROPPING TO NEAR 5,000 FT SUNDAY
EVENING INTO MONDAY MORNING. MINOR IMPACTS TO PASSES EXPECTED.
PERSISTENT VALLEY FOG HAS BEEN SLOW TO BURN OFF TODAY IN FAR
WESTERN MONTANA AND NORTH-CENTRAL IDAHO. MOST LOCATIONS WILL SEE
THE FOG MIX OUT THROUGH THE REST OF THE AFTERNOON, THOUGH
ISOLATED LOCATIONS MAY SEE FOG PERSIST OVERNIGHT INTO FRIDAY.
A WEAK DISTURBANCE WITH ELEVATED MOISTURE MOVES OVERHEAD TONIGHT.
THIS WILL CREATE CLOUD COVER THAT SHOULD ACT AS A BLANKET AND
LIMIT THE OVERALL POTENTIAL FOR WIDESPREAD FOG REDEVELOPMENT FOR
FRIDAY MORNING, YET USUAL SUSPECT AREAS FOR FOG CANNOT BE RULED
OUT COMPLETELY. LITTLE TO NO PRECIPITATION IS EXPECTED, WITH ANY
LIGHT PRECIP CONFINED TO THE HIGHEST PEAKS OF NORTHWEST MONTANA.
HALLOWEEN IS LOOKING GOOD AS A WHOLE. EXPECT SEASONABLE
TEMPERATURES WITH SKIES BECOMING MOSTLY CLOUDY BY THE AFTERNOON
AND EVENING. TEMPERATURES COOL INTO THE 40S AND 30S FOR ANY LATE-
EVENING PLANS SO DRESS ACCORDINGLY.
ON SATURDAY, INCREASING SOUTHWESTERLY WINDS WILL BRING IN MUCH
WARMER AIR, WITH DAYTIME HIGHS EXPECTED TO BE 10-15 DEGREES ABOVE
NORMAL. SHOWER CHANCES WILL INCREASE THROUGH THE DAY AND INTO
SATURDAY NIGHT.
A VERY LOW-PROBABILITY (BUT NON-ZERO) CHANCE FOR MINOR FREEZING
RAIN IMPACTS EXISTS EARLY SATURDAY MORNING IN FAR NW MONTANA (LIKE
THE YAAK, LIBBY, US-93 NORTH OF KALISPELL) BEFORE THESE WARMER
WINDS SCOUR OUT THE VALLEY COLD POOLS.
WIDESPREAD WIND GUSTS OF 15-25 MPH ARE LIKELY ON SATURDAY WITH
STRONGER WINDS, NEARING OR EXCEEDING 40 MPH, EXPECTED ON THE
HIGHEST RIDGELINES (ESPECIALLY NEAR THE CONTINENTAL DIVIDE) FROM
SATURDAY EVENING THROUGH SUNDAY MORNING.
OVERALL, PRECIPITATION AMOUNTS LOOK RATHER LIGHT. THE HIGHEST
TOTALS (70% CHANCE FOR > 0.25") WILL BE ALONG THE MT-ID BORDER AND
POINTS WEST, FROM THE CANADIAN BORDER SOUTH TOWARD THE CENTRAL
BITTERROOT RANGE.
SNOW LEVELS WILL REMAIN HIGH (ABOVE 7,000 FT) THROUGH MOST OF THE
EVENT. BY SUNDAY EVENING INTO MONDAY MORNING, TEMPERATURES WILL
COOL AND SNOW LEVELS DROP TO NEAR 5,000 FT WHICH COULD CAUSE SOME
MINOR ISSUES OVER THE HIGHEST PASSES AS WET ROADS BEGIN TO FREEZE
UP AND/OR LIGHT SNOW ACCUMULATES.
TEMPORARY DRYING IS EXPECTED ON MONDAY MORNING BEFORE A MILD,
SHOWERY PATTERN REACTIVATES FOR MUCH OF NEXT WEEK.
AVIATION
A HIGH-PRESSURE INVERSION IS CAPPING MOST OF THE
VALLEYS ACROSS NORTH-CENTRAL IDAHO AND WESTERN MONTANA, TRAPPING
MOISTURE AND REDUCING DAYTIME HEATING. THE LOW OCTOBER SUN ANGLE
IS NOT STRONG ENOUGH TO BREAK THIS INVERSION. AS A RESULT, NARROW
VALLEYS REMAIN IN FOG THIS AFTERNOON. FORECAST SOUNDINGS SUGGEST
THAT THE FOG WILL LIFT A DECREASE IN COVERAGE THROUGH THE
AFTERNOON, BUT A FULL RETURN TO VFR IS NOT EXPECTED UNTIL LATE IN
THE DAY, IF AT ALL IN THE NARROW VALLEYS OF NORTHWEST MONTANA.
THIS STAGNANT PATTERN MEANS THIS FOG AND LOW CLOUDINESS WILL
LIKELY RE-FORM QUICKLY TONIGHT, LEADING A BROADER AREA OF IFR/LIFR
CONDITIONS BY FRIDAY MORNING, INCLUDING AT KMSO AND KGPI.
LOCATIONS WITHOUT FOG CAN EXPECT MOSTLY SUNNY SKIES AND GENERALLY
LIGHT WINDS IN THE VALLEYS AND A SLIGHT INCREASE IN RIDGETOP WINDS
FRIDAY AFTERNOON.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page