815
FXUS65 KMSO 240815
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
115 AM MST MON NOV 24 2025
DISCUSSION
KEY MESSAGES:
- WINTER DRIVING CONDITIONS RETURN THIS MORNING ON PASSES:
RAPIDLY CHANGING VISIBILITY AND ROAD CONDITIONS ARE EXPECTED ON
PASSES. LOCALIZED ICY SPOTS, ESPECIALLY IN SOUTHWEST MONTANA.
- BACKDOOR COLD FRONT: ALONG THE CONTINENTAL DIVIDE THIS
AFTERNOON/EVENING PRODUCING HEAVY MOUNTAIN SNOW, COOLING
TEMPERATURES, AND WIND SHIFT TO NORTHEASTERLY.
- UNSETTLED HOLIDAY TRAVEL (WEDNESDAY & THANKSGIVING): LIGHT SNOW
RETURNS TUESDAY NIGHT/WEDNESDAY MORNING. SNOW LEVELS RISE AND
PRECIPITATION TRANSITIONS TO A RAIN/SNOW MIX LATER ON WEDNESDAY
FOR MOST VALLEYS.
- POTENTIAL ARCTIC INTRUSION LATE WEEK (NOV 28-29): PLEASE
MONITOR THE FORECAST CLOSELY IF YOU HAVE POST-THANKSGIVING
TRAVEL PLANS.
TODAY AND TONIGHT:
AREAS OF PRECIPITATION ARE ONGOING THIS MORNING WITH SNOW LEVELS
NEAR 5500 FEET. A SIGNIFICANT COLD FRONT WILL TRAVERSE THE ENTIRE
NORTHERN ROCKIES BY LATE MORNING, DROPPING SNOW LEVELS TO VALLEY
FLOORS. WHILE VALLEY ACCUMULATIONS WILL REMAIN VERY LIGHT,
PRECIPITATION WILL TURN SHOWERY BEHIND THE FRONT; BRIEF HEAVY
SHOWERS MAY REDUCE VISIBILITY AND CAUSE RAPIDLY CHANGING
CONDITIONS ON PASSES. WESTERLY WIND GUSTS OF 30-40 MPH ARE ALSO
EXPECTED POST- FRONTAL. THE PRIMARY IMPACT WILL BE TO TRAVELERS
OVER MOUNTAIN PASSES, WHERE BRIEF SLICK CONDITIONS ARE POSSIBLE
THIS MORNING, THOUGH ROAD TEMPERATURES JUST ABOVE FREEZING MAY
LIMIT EXTENDED PERIODS OF SNOW-COVERED ROADWAYS. AN ADDITIONAL
CONCERN IS THE POTENTIAL FOR ICY PATCHES ON ROADS ACROSS SOUTHWEST
MONTANA THIS MORNING.
AS THE DISTURBANCE EXITS THIS AFTERNOON, A PUSH OF MODIFIED ARCTIC
AIR WILL MOVE INTO THE GLACIER NATIONAL PARK REGION, GENERATING
MODERATE TO HEAVY SNOW, PARTICULARLY NEAR THE CONTINENTAL DIVIDE.
ESSEX TO MARIAS PASS IS EXPECTED TO RECEIVE 7 TO 11 INCHES OF NEW
SNOW, WITH ADJACENT VALLEYS SEEING 1 TO 3 INCHES BY LATE THIS
EVENING.
TUESDAY THROUGH THANKSGIVING DAY (THURSDAY):
TUESDAY BEGINS AS A QUIET WEATHER DAY. HOWEVER, A STREAM OF SUB-
TROPICAL MOISTURE WILL ENTER NORTH-CENTRAL IDAHO AND FAR NORTHWEST
MONTANA BY THE AFTERNOON, GRADUALLY SPREADING LIGHT SNOW ACROSS
THE REST OF THE NORTHERN ROCKIES INTO WEDNESDAY MORNING. SNOW
LEVELS WILL RISE ABOVE VALLEY FLOORS ON WEDNESDAY AFTERNOON,
THOUGH COLD AIR MAY REMAIN TRAPPED IN THE VALLEYS OF NORTHWEST
MONTANA UNTIL THURSDAY MORNING. SNOW ACCUMULATIONS LOOK LIGHT
GENERALLY LESS THAN AN INCH FOR VALLEYS AND 2 TO 5 INCHES ON THE
PASSES THROUGH THURSDAY MORNING BUT ENOUGH TO CAUSE MINOR TRAVEL
IMPACTS OVER PASSES. MOISTURE WILL CONTINUE TO STREAM OVERHEAD
INTO THURSDAY NIGHT, BRINGING ADDITIONAL LIGHT TO MODERATE RAIN/SNOW.
FRIDAY THROUGH NEXT WEEK:
WE ARE CLOSELY MONITORING THE FRIDAY/SATURDAY TIMEFRAME. MOST
GUIDANCE SUGGESTS MODIFIED ARCTIC AIR WILL CROSS THE DIVIDE AND
INTERACT WITH MOISTURE STREAMING OVERHEAD TO PRODUCE AREAS OF
SNOW. WHILE CONSIDERABLE UNCERTAINTY REMAINS REGARDING EXACT
TIMING OF COLD AIR AND PRECIPITATION AMOUNTS, CONFIDENCE IS
INCREASING THAT THIS WILL BE THE COLDEST AIR OF THE FALL SEASON SO
FAR.
CURRENT PROBABILITIES INDICATE A 60-80% CHANCE OF LOWS DIPPING
INTO THE SINGLE DIGITS (OR COLDER) ALONG THE DIVIDE BY SUNDAY
MORNING, WITH A 30-50% CHANCE FOR THE REMAINING WESTERN MONTANA
VALLEYS. THIS PERIOD WARRANTS CLOSE MONITORING DUE TO THE
POTENTIAL FOR WIDESPREAD TRAVEL IMPACTS. LOOKING TOWARD NEXT WEEK
(NOV 30-DEC 5), AN ACTIVE NORTHWEST FLOW PATTERN CONTINUES,
BRINGING CONSIDERABLE SNOW CHANCES AND ADDITIONAL EPISODES OF
ARCTIC AIR POTENTIALLY SPILLING OVER THE DIVIDE INTO WESTERN
MONTANA.
AVIATION
WIDESPREAD PRECIPITATION, MOUNTAIN OBSCURATIONS, AND LOWERED
CEILINGS/VISIBILITY ARE EXPECTED THIS MORNING AS A COLD FRONT MOVES THROUGH
THE NORTHERN ROCKIES. SNOW LEVELS, CURRENTLY AROUND 5500 FEET, WILL FALL TO
VALLEY FLOORS BEHIND THE FRONT BY MID-TO-LATE MORNING. PRECIPITATION WILL
TRANSITION TO SHOWERS BEHIND THE FRONT; WHILE THIS LIMITS VALLEY SNOW
ACCUMULATIONS, BRIEF MVFR AND IFR CONDITIONS REMAIN LIKELY IN HEAVIER
SHOWERS.
WESTERLY WINDS WILL INCREASE BEHIND THE FRONT, GUSTING 25-35 KTS
AT TERMINALS, BEFORE DIMINISHING QUICKLY AROUND SUNSET. SHOWERS
WILL ALSO TAPER OFF THIS EVENING, WITH THE EXCEPTION OF THE
GLACIER PARK REGION WHERE A BACKDOOR COLD FRONT WILL MAINTAIN
LIGHT TO MODERATE SNOW FROM US 93 EASTWARD. DRIER WEATHER AND
MOSTLY VFR CONDITIONS ARE EXPECTED FOR TUESDAY.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR WEST
GLACIER REGION.
ID...WINTER WEATHER ADVISORY UNTIL 11 AM PST MONDAY FOR SOUTHERN
CLEARWATER MOUNTAINS.
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