282
FXUS65 KMSO 111918
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
118 PM MDT SUN OCT 11 2026
DISCUSSION
KEY MESSAGES:
- WINTER STORM CONTINUES THROUGH EARLY MONDAY, PASS LEVEL/HIGHER
VALLEY TRAVEL IMPACTS
- HARD FREEZE IN WESTERN MONTANA VALLEYS EARLY THIS WEEK
- RIDGING WITH DAYTIME TEMPERATURES TO ABOVE AVERAGE BY LATE THIS
WEEK
WINTER IMPACTS: AN UPPER-LEVEL TROUGH OVER THE PACIFIC NORTHWEST
WILL CONTINUE TO PUSH MOISTURE OVER THE ENTRENCHED COLD AIR MASS
ACROSS WESTERN MONTANA. THIS SYNOPTIC SETUP WILL YIELD
ACCUMULATING SNOW THROUGH EARLY MONDAY, PRIMARILY ABOVE 4,000
FEET. EXPECT PERIODIC TRAVEL IMPACTS OVER MOUNTAIN PASSES
INCLUDING ROGERS, MACDONALD, HOMESTAKE, AND LOST TRAIL AS WELL AS
VALLEY ROADWAYS IN SOUTHWEST MONTANA. WHILE LOWER VALLEYS IN
WESTERN MONTANA MAY SEE A LIGHT DUSTING ON GRASSY SURFACES,
IMPACTS THERE WILL REMAIN LIMITED. FURTHER WEST INTO NORTH-CENTRAL
IDAHO, RELATIVELY WARMER AIR AND LIMITED MOISTURE WILL PRECLUDE
SIGNIFICANT WINTER IMPACTS. SNOW WILL BE DIMINISHING AREA-WIDE
EARLY MONDAY MORNING BUT A FEW SHOWERS WILL CONTINUE THROUGHOUT
THE DAY.
EASTERLY WINDS: GUSTY EASTERLY WINDS WILL PERSIST OVER FLATHEAD
LAKE THROUGH EARLY MONDAY, PARTICULARLY ALONG THE EASTERN SHORE.
AS WINDS HAVE DIMINISHED IN THE BROADER FLATHEAD AND MISSION
VALLEYS, THE LARGER SCALE WIND ADVISORY HAS BEEN REPLACED WITH A
MORE FOCUSED LAKE WIND ADVISORY. CHOPPY WATERS WILL CONTINUE AND
LOCALIZED TREE DAMAGE REMAINS A POSSIBILITY WITH OCCASIONAL GUSTS
OF 40-50 MPH.
EARLY WEEK FREEZE: HIGH CONFIDENCE REMAINS FOR A WIDESPREAD HARD
FREEZE ACROSS WESTERN MONTANA VALLEYS EARLY THIS WEEK, ACCOMPANIED
BY NEAR-FREEZING TEMPERATURES IN THE LOWER ELEVATIONS OF NORTH-
CENTRAL IDAHO. WHILE MONDAY MORNING HAS TRENDED CLOUDIER LIMITING
RADIATIONAL COOLING AND LIKELY KEEPING TEMPERATURES SLIGHTLY
WARMER THAN PROBABILISTIC GUIDANCE SUGGESTS, TUESDAY MORNING WILL
BE SEVERAL DEGREES COLDER. RESIDENTS SHOULD FINALIZE WINTERIZATION
PREPARATIONS REGARDLESS OF WHICH MORNING WILL BE COLDEST. PROTECTIVE
MEASURES FOR SENSITIVE VEGETATION ARE SUGGESTED FOR THE LOWER
VALLEYS OF NORTH-CENTRAL IDAHO. ONE CAVEAT FOR TUESDAY AND
WEDNESDAY MORNINGS IS POSSIBLE STRATUS FORMATION FOR SOME VALLEYS,
THIS WOULD KEEP LOW TEMPERATURES WARMER THAN CURRENTLY FORECAST.
EXTENDED OUTLOOK: ENSEMBLES STRONGLY AGREE THAT UPPER-LEVEL
RIDGING WILL QUICKLY REBUILD ACROSS THE REGION LATER IN THE WEEK.
BY LATE WEEK, EXPECT AFTERNOON HIGH TEMPERATURES TO REBOUND INTO
THE 60S ACROSS WESTERN MONTANA AND THE 70S ACROSS THE LOWER
ELEVATIONS OF CENTRAL IDAHO. DRY AIR AND LIGHT WINDS WILL ALLOW
OVERNIGHT LOWS TO REMAIN QUITE CHILLY. THE NEXT CHANCE OF
WIDESPREAD PRECIPITATION LOOKS TO BE AROUND OCT 20TH BUT LOW
CONFIDENCE AT THIS POINT.
AVIATION
AN UPPER-LEVEL TROUGH OVER THE PACIFIC NORTHWEST IS DRAWING
MOISTURE ACROSS THE NORTHERN ROCKIES, INTERACTING WITH A COLD AIR
MASS ENTRENCHED OVER WESTERN MONTANA. THIS SYNOPTIC SETUP WILL
BRING EARLY WINTER-LIKE CONDITIONS ACROSS THE AIRSPACE. EXPECT
PERIODIC PRECIPITATION TO RESULT IN DEGRADED FLIGHT CATEGORIES
(MVFR TO LOCALIZED LIFR), PRIMARILY DRIVEN BY LOWERED CEILINGS,
REDUCED VISIBILITIES, AND WIDESPREAD MOUNTAIN OBSCURATION. SNOW
WILL TAPER OFF MONDAY MORNING, FOLLOWED BY A PARTIAL CLEARING OF
LOW CLOUDS BY THE AFTERNOON. EASTERLY SURFACE WINDS OF 10-20 KTS
WILL GRADUALLY SUBSIDE TONIGHT.
* KBTM (BUTTE): EXPECTED TO SEE THE MOST SIGNIFICANT AVIATION
IMPACTS. PERIODS OF ACCUMULATING SNOW WILL DRIVE SUDDEN DROPS
IN VISIBILITY LEADING TO IFR AND OCCASIONAL LIFR CONDITIONS.
* REGIONAL TERMINALS: SURROUNDING TERMINALS WILL PRIMARILY
SEE PRECIPITATION FALL AS LIGHT RAIN OR WET, NON-ACCUMULATING
SNOW, KEEPING IMPACTS COMPARATIVELY LOWER.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 6 AM MDT MONDAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS...POTOMAC/SEELEY LAKE
REGION...WEST GLACIER REGION.
LAKE WIND ADVISORY UNTIL 6 AM MDT MONDAY FOR FLATHEAD/MISSION
VALLEYS.
WINTER STORM WARNING UNTIL 6 AM MDT MONDAY FOR BUTTE/BLACKFOOT
REGION.
ID...NONE.
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