107
FXUS65 KMSO 250820
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
120 AM MST THU DEC 25 2025
DISCUSSION
KEY MESSAGES:
- LOCALIZED SLICK CONDITIONS CHRISTMAS MORNING: EXPECT AREAS OF
FOG AND LOCALIZED ICY SPOTS IN VALLEYS THROUGH MID-MORNING AS
TEMPERATURES HOVER NEAR FREEZING.
- SNOW IMPACTS TRAVEL: FRIDAY THROUGH SATURDAY, DEFINITELY ON
PASSES BUT VALLEYS MAY ALSO BE PROBLEMATIC BEGINNING FRIDAY
NIGHT.
- HIGH WIND/OUTAGE RISK (FRIDAY): SOUTHWESTERLY GUSTS OF 30-40
MPH (VALLEYS) AND 60+ MPH (MOUNTAINS) ARRIVE FRIDAY AFTERNOON.
SATURATED SOILS WILL MAKE TREES MORE PRONE TO FALLING,
INCREASING THE RISK OF POWER OUTAGES.
- SATURDAY ARCTIC PUSH: FLASH FREEZE POTENTIAL AS BITTERLY COLD
AIR AS MOVES WEST OF THE DIVIDE SATURDAY MORNING. STRONG
NORTHEAST WINDS WILL DEVELOP IN PRONE CANYONS AND GAP AREAS
(E.G., BAD ROCK CANYON).
CHRISTMAS DAY THROUGH FRIDAY MORNING:
WIDESPREAD PRECIPITATION WILL TAPER OFF EARLY THIS MORNING; HOWEVER,
LINGERING LOW-LEVEL MOISTURE AND A WEAK PRESSURE GRADIENT WILL
MAINTAIN AREAS OF FOG AND LOW CLOUDS THROUGH MUCH OF CHRISTMAS
MORNING. TRAVELERS SHOULD WATCH FOR LOCALIZED SLICK SPOTS, AS MORNING
TEMPERATURES ARE HOVERING NEAR FREEZING IN MANY VALLEYS.
LOW CLOUDS WILL GRADUALLY SCATTER THROUGHOUT THE DAY, THOUGH ELEVATED
INSTABILITY WILL SUPPORT OCCASIONAL SCATTERED SHOWERS. A WEAK COLD
FRONT ARRIVING LATE THIS EVENING INTO EARLY FRIDAY WILL ENHANCE SHOWER
ACTIVITY, WITH SNOW LEVELS DROPPING TO APPROXIMATELY 4,000 FEET. MINOR
IMPACTS ARE POSSIBLE AT MOUNTAIN PASSES FRIDAY MORNING DUE TO SLUSHY
ACCUMULATIONS.
FRIDAY AFTERNOON & NIGHT (HIGH IMPACT WINDOW):
A POTENT COLD FRONT WILL ARRIVE FROM THE WEST-NORTHWEST LATE FRIDAY.
WE ARE MONITORING THIS PERIOD CLOSELY FOR WIDESPREAD IMPACTS DRIVEN BY
A COMBINATION OF SNOW AND WIND.
-SNOW/SNOW BANDS: WIDESPREAD PASS LEVEL SNOW IMPACTS LATE
FRIDAY AFTERNOON/EVENING, TRANSITIONS TO SNOW BANDS (MODERATE
CONFIDENCE) FRIDAY NIGHT INTO SATURDAY MORNING. VALLEY COULD
ALSO SEE SLICK ROADS UNDER THESE BANDS.
-WIND SPEEDS: VALLEYS CAN EXPECT SOUTHWESTERLY GUSTS OF 30-40
MPH (LOCALLY OVER 50+ MPH IN STRONG SHOWERS), WHILE MOUNTAINS
AND RIDGES SEE GUSTS RANGING FROM 50-65+ MPH.
-TREE/POWER IMPACT: DUE TO MULTIPLE RECENT WIND EVENTS AND
PROLONGED SOIL SATURATION WEAKENING ROOT SYSTEMS, THE RISK FOR
DOWNED TREES AND POWER OUTAGES IS UNUSUALLY HIGH FOR A WIND
EVENT OF THIS MAGNITUDE.
SATURDAY (ARCTIC INTRUSION):
FOLLOWING THE INITIAL PACIFIC FRONT, MUCH COLDER AIR (NEAR 0F)
WILL SLIDE SOUTH ALONG THE EAST SIDE OF THE CONTINENTAL DIVIDE.
THIS ARCTIC AIR WILL EVENTUALLY SEEP WESTWARD THROUGH GAPS SUCH AS
MARIAS PASS AND INTO NORTHWESTERN MONTANA THROUGHOUT SATURDAY.
-WINDS: EXPECT A SHARP WIND SHIFT TO THE NORTH/NORTHEAST. WINDS
WILL ACCELERATE THROUGH PRONE CANYONS, SPECIFICALLY AFFECTING
THE BAD ROCK CANYON AND NORTHERN FLATHEAD VALLEY AREAS.
-FLASH FREEZE: AS TEMPERATURES PLUMMET OVER WET OR SLUSHY
SURFACES, FLASH FREEZE CONDITIONS ARE A SIGNIFICANT CONCERN.
RAPID ICING ON ROADWAYS IS POSSIBLE WHERE RECENT PRECIPITATION
HAS FALLEN, WITH LINGERING SNOW SHOWERS PERSISTING THROUGH
LATE SATURDAY.
-UNCERTAINTY: THE EXACT SOUTH AND WESTWARD EXTENT OF THIS
ARCTIC AIR REMAINS A KEY DETAIL THAT REQUIRES FURTHER
REFINEMENT IN FUTURE MODEL RUNS.
SUNDAY INTO NEXT WEEK:
A DOMINANT RIDGE OF HIGH PRESSURE WILL BUILD ACROSS THE PACIFIC
NORTHWEST, USHERING IN CALMER AND DRIER CONDITIONS. HOWEVER, WITH THE
RIDGE AXIS POSITIONED TO OUR WEST, THE REGION WILL REMAIN UNDER A COOL
NORTHWESTERLY FLOW. THIS PATTERN MAY ALLOW MINOR DISTURBANCES TO
"CLIP" THE REGION, MAINTAINING A POTENTIAL FOR SCATTERED PRECIPITATION
THROUGH THE FIRST HALF OF THE WEEK. FOG AND LOW STRATUS MAY ALSO
BE A CONCERN AT TIMES. CONFIDENCE DECREASES FOR THE SECOND HALF
OF NEXT WEEK AS SOME MODELS SHOW AN ATMOSPHERIC RIVER NOSING INTO
THE REGION.
AVIATION
SOUTHWEST FLOW WILL PERSIST THROUGH FRIDAY MORNING AS A
SERIES OF WEAK DISTURBANCES MAINTAIN OCCASIONAL SHOWER ACTIVITY. WHILE
WIDESPREAD PRECIPITATION IS TAPERING OFF THIS MORNING, RESIDUAL
LOW-LEVEL MOISTURE WILL SUPPORT AREAS OF FOG AND LOW STRATUS THROUGH
18Z, PARTICULARLY ACROSS NORTHWEST MONTANA (INCLUDING KGPI). EXPECT
AREAS OF MVFR/IFR CONDITIONS, WITH WIDESPREAD MOUNTAIN
OBSCURATION.
CONDITIONS ARE EXPECTED TO IMPROVE TOWARD VFR THIS AFTERNOON AS CLOUD
COVER SCATTERS, THOUGH ELEVATED INSTABILITY WILL KEEP ISOLATED SHOWERS
IN THE VICINITY OF TERMINALS. A WEAK COLD FRONT ARRIVING LATE THIS
EVENING INTO EARLY FRIDAY MORNING WILL BRING A RENEWED CHANCE FOR
SHOWERS AND LOWER CEILINGS. THE PRIMARY AVIATION CONCERN SHIFTS
LATE FRIDAY MORNING TO INCREASINGLY GUSTY SOUTHWESTERLY SURFACE
WINDS AND POTENTIAL LOW-LEVEL TURBULENCE.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...WINTER WEATHER ADVISORY UNTIL 5 AM MST EARLY THIS MORNING FOR
EASTERN LEMHI COUNTY...WESTERN LEMHI COUNTY.
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