840
FXUS65 KMSO 050928
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
228 AM MST WED NOV 5 2025
DISCUSSION
KEY MESSAGES:
- PACIFIC SYSTEM ARRIVES LATE AFTERNOON THROUGH TONIGHT, WITH
HIGH ELEVATION SNOW (6,000+ FEET) AND BREEZY WINDS.
- A SECOND SYSTEM ON THURSDAY NIGHT - FRIDAY WILL BRING MOUNTAIN
SNOW (4,000-4,500 FEET) AND GUSTY WESTERLY WINDS.
- HIGH PRESSURE BUILDS THIS WEEKEND; RISK FOR FOG AND LOW CLOUDS
BY SUNDAY MORNING.
A PACIFIC SYSTEM WILL MOVE ACROSS THE NORTHERN ROCKIES LATE THIS
AFTERNOON AND EVENING THROUGH THURSDAY. MILD PACIFIC AIR WILL
MOVE IN ALOFT, WITH SNOW LEVELS RISING TO 6000-7000 FEET MSL FOR MOST
AREAS, EXCEPT ACROSS NORTHWEST MONTANA WHERE THE LEVELS COULD BE
AS LOW AS 5500 FEET WEDNESDAY AFTERNOON. SNOW LEVELS FALL TO 5000
TO 6000 FEET BY THURSDAY MORNING. SNOW SHOWERS COULD PRODUCE
PERIODS OF SLUSH ON THE ROADS AT MARIAS PASS. THIS WILL BE A WET
PATTERN WITH THE MOUNTAINS RECEIVING 0.25 TO 0.75 INCHES OF
PRECIPITATION THROUGH THURSDAY MORNING, SOME MOUNTAIN SITES
EXCEEDING 1.00", SPECIFICALLY THE UPSLOPE AREAS ALONG THE
IDAHO/MONTANA BORDER, AND IN THE MISSION AND SWAN RANGES. THIS
COULD EQUATE TO 5 TO 10 INCHES OF WET SNOW IN THE HIGH COUNTRY
ABOVE 5500-6000 FEET. SO MAKE SURE YOU PLAN ACCORDINGLY IF YOU
ARE HUNTING OR RECREATING AT THOSE ELEVATIONS. GUSTY WESTERLY
WINDS DEVELOP ON THURSDAY, MAINLY FELT IN THE MOUNTAINS, BUT A FEW
VALLEY LOCATIONS COULD EXPERIENCE GUSTS OVER 25 MPH...I.E. ALONG
THE DIVIDE AND ACROSS SOUTHWEST MONTANA. THE STRONGER GUSTS OVER
35 MPH WILL MAINLY BE OVER THE DIVIDE.
ANOTHER PACIFIC TROUGH PASSAGE WILL TAKE PLACE THURSDAY NIGHT INTO
FRIDAY, WITH SNOW LEVELS TRENDING LOWER (AROUND 4000-4500 FEET).
PRECIPITATION FORECASTS ARE SIMILAR WITH 0.25 TO 0.75 INCHES IN
THE MOUNTAINS. AGAIN, WESTERLY WINDS WILL DEVELOP AND COULD GUST
WELL OVER 40 MPH IN THE MOUNTAINS AND HIGH VALLEYS ALONG AND WEST
OF THE DIVIDE. A COUPLE INCHES OF SNOW WILL ACCUMULATE ON LOOKOUT,
LOST TRAIL, AND MARIAS PASS BY FRIDAY MORNING.
A BUILDING RIDGE CONTINUES TO BE EXPECTED OVER THE WEEKEND.
LEFTOVER CLOUD COVER AND A FEW SHOWERS ARE POSSIBLE SATURDAY
MORNING ACROSS NORTHWEST MONTANA, BUT EXPECT PARTIAL CLEARING.
AREAS OF LOW CLOUDS AND FOG COULD DEVELOP BY SUNDAY MORNING IN THE
VALLEYS, AS STABLE HIGH PRESSURE DEVELOPS(AROUND 1027 MILLIBARS).
THERE COULD BE A FAIR AMOUNT OF HIGH CLOUDS THAT MOVE OVER THE
REGION SUNDAY, REDUCING SOLAR INSOLATION WHICH WILL HELP TO
MAINTAIN VALLEY INVERSIONS.
THE NEXT FORECAST QUESTIONS AND CHALLENGES ARE: HOW LONG WILL
THIS RIDGE LAST; AND HOW MUCH MOISTURE WILL BE MOVING AROUND IT?
LOOKING UPSTREAM, THE PACIFIC JET IS QUITE ACTIVE AND VERY
"BUCKLED". THERE CONTINUES TO BE PLENTY OF TROPICAL ACTIVITY IN
THE WESTERN EQUATORIAL PACIFIC, INCLUDING A TYPHOON THAT COULD
CONTINUE TO EXCITE AND EXTEND THE EAST ASIAN JET/PACIFIC JET NOV.
11-13. THIS COULD HAVE A DOMINO EFFECT AND IN A SENSE, SHIFT OUR
RECENT "BUCKLED" PATTERN EASTWARDS, PLACING LOWER HEIGHTS/TROUGHS
OVER THE WESTERN U.S. ENSEMBLES ARE DEPICTING REMNANTS OF A PLUME
OF MOISTURE AIMED AT SOUTHWESTERN BRITISH COLUMBIA TO SHIFT OVER
US BY MONDAY THE 10TH AND 11TH. THE CAVEAT WITH THIS PROPOSED
PATTERN IS THAT THE MODELS PREDICTED THIS SIMILAR TYPE OF PATTERN
FOR YESTERDAY (NOV 3), BUT A SUBTLE SHORTWAVE KEPT THE RIDGE
FLATTER THEREFORE KEEPING IT MUCH COLDER OVER NORTHWEST MONTANA
LEADING TO THE SNOWFALL IN THE VALLEYS! IF WE ARE ABLE TO GET A
PATTERN CHANGE LATER IN THE SECOND WEEK OF NOVEMBER, THEN TROUGHS
COULD DIG A LITTLE FURTHER SOUTH, PLACING US IN THE COLDER SIDE OF
THE JET...MEANING A COOLER AND ACTIVE PATTERN FOR US...MORE MOUNTAIN
SNOW! THE ENSEMBLES AND EVEN EXTENDED MODELS ARE HINTING AT THIS.
STAY TUNED!
AVIATION
A WEAK WARM FRONT IS PUSHING NORTHWARD ACROSS THE
NORTHERN ROCKIES AIRSPACE THIS MORNING, WITH REGIONAL RADAR
IMAGERY HIGHLIGHTING LIGHT SHOWER ACTIVITY. AREAS OF VALLEY FOG
AND STRATUS HAVE BEEN IMPACTING KGPI/KMSO/KHRF, AND THE CAMAS
PRAIRIE NEAR GRANGEVILLE. STABLE CONDITIONS WILL REMAIN IN PLACE
THROUGH THIS MORNING, WITH IMPROVED MIXING AND A BREAKUP OF
STRATUS AND FOG BETWEEN 05/1600-1800Z. A PACIFIC SYSTEM WILL
ARRIVE LATE THIS AFTERNOON AND EVENING, WITH WIDESPREAD
PRECIPITATION FOCUSING ALONG THE ID/MT BORDER AND AREA MOUNTAIN
RANGES, WITH WIDESPREAD TERRAIN OBSCURATIONS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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