869
FXUS65 KMSO 131759
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1159 AM MDT SUN SEP 13 2026
DISCUSSION
KEY MESSAGES:
- CONSIDERABLE SHOWERS CONTINUE WITH MOUNTAIN SNOW ABOVE 6,500
FEET LATE TONIGHT INTO EARLY MONDAY, MAINLY THROUGH CENTRAL
IDAHO AND NORTHWEST MONTANA.
- DRYING AND WARMING CONDITIONS BY MID-WEEK.
- TRENDING WETTER LATE THURSDAY INTO FRIDAY.
AN UPPER LOW MOVING THROUGH EASTERN WASHINGTON WILL TRACK INTO
NORTHWEST MONTANA TONIGHT, CONTINUING TO BRING PERIODIC SHOWERS,
ISOLATED THUNDERSTORMS, AND GUSTY SOUTHWEST WINDS ACROSS MUCH OF
THE NORTHERN ROCKIES.
THE HEAVIEST PRECIPITATION WILL TARGET NORTH-CENTRAL IDAHO AND
NORTHWEST MONTANA, WHERE MOUNTAIN LOCATIONS COULD RECEIVE UP TO AN
INCH OF TOTAL PRECIPITATION, WITH LIGHTER AMOUNTS IN THE VALLEYS.
SNOW LEVELS WILL FALL NEAR 6,500 FEET TONIGHT, BRINGING LIGHT
SNOW ACCUMULATIONS ALONG THE CONTINENTAL DIVIDE SOUTHWARD TO THE
BITTERROOTS. THESE COLD, RAW CONDITIONS WILL CREATE A HEIGHTENED
HYPOTHERMIA RISK FOR BACKCOUNTRY RECREATIONISTS. FARTHER SOUTH AND
EAST, INCLUDING MISSOULA, RAINFALL WILL REMAIN LIGHT AND SPOTTY.
IN CONTRAST, SOUTHWEST MONTANA WILL STAY MOSTLY DRY WITH STRONG,
GUSTY WINDS, DRIVING CRITICAL FIRE WEATHER CONDITIONS THROUGH THIS
EVENING (RED FLAG WARNING).
THE SYSTEM EXITS BY TUESDAY MORNING, CLEARING THE WAY FOR A
BRIEFLY WARMER AND DRIER PATTERN THROUGH MID-WEEK, THOUGH SHOWER
CHANCES LINGER NEAR THE CANADIAN BORDER. CLEARING SKIES EARLY
TUESDAY WILL BRING CHILLY TEMPERATURES TO AREAS ALONG AND SOUTH OF
I-90. SUB- FREEZING TEMPERATURES ARE ANTICIPATED IN THE HIGHER
VALLEYS OF SOUTHWEST MONTANA AND ALONG THE DIVIDE, WHILE FROST
WILL LIKELY IMPACT THE TYPICAL COLDER LOCATIONS IN THE MISSOULA,
BITTERROOT, AND CLEARWATER VALLEYS.
A TREND IN THE ENSEMBLE GUIDANCE POINTS TOWARD ANOTHER UPPER-
LEVEL LOW CUTTING OFF ALONG THE PACIFIC COAST WEDNESDAY NIGHT
BEFORE DRIFTING ACROSS WESTERN MONTANA AND NORTH-CENTRAL IDAHO
THURSDAY INTO FRIDAY. A MONSOONAL MOISTURE TAP APPEARS TO BE
INTERACTING WITH THE LOW CAUSING PRECIPITATION CHANCES TO TREND
UPWARD LATE IN THE WEEK. APPROXIMATELY 60 PERCENT OF ENSEMBLE
SOLUTIONS SUPPORT THIS WETTER SCENARIO, THOUGH OVERALL CONFIDENCE
IN EXACT TIMING AND LOCAL DETAILS REMAIN LOW.
AVIATION
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL
CONTINUE ACROSS THE NORTHERN ROCKIES THIS AFTERNOON, WITH
COVERAGE TAPERING OFF SOUTH ACROSS SOUTHWEST MONTANA AND LEMHI
COUNTY. HEAVIER CONVECTIVE CELLS WILL BRIEFLY DEGRADE CEILINGS AND
VISIBILITIES TO MVFR, ACCOMPANIED BY LOCALIZED MOUNTAIN
OBSCURATIONS. SOUTHWEST SURFACE WINDS WILL GUST 20-25 KTS THROUGH
EARLY EVENING, CREATING LOCALIZED MECHANICAL TURBULENCE.
WRAP-AROUND MOISTURE ASSOCIATED WITH A PASSING UPPER-LEVEL LOW
WILL MAINTAIN WIDESPREAD LIGHT PRECIPITATION TONIGHT INTO MONDAY
MORNING ACROSS NORTH-CENTRAL IDAHO AND NORTHWEST MONTANA, BECOMING
INCREASINGLY TERRAIN-FORCED FARTHER SOUTH. WIDESPREAD MOUNTAIN
OBSCURATIONS WILL PERSIST WELL INTO MONDAY MORNING ALONGSIDE GUSTY
WESTERLY WINDS OF 15-25 KTS LATE MONDAY MORNING AND AFTERNOON.
MSO WATCHES/WARNINGS/ADVISORIES
MT...RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR EAST BEAVERHEAD.
ID...NONE.
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