460
FXUS65 KMSO 051955
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
155 PM MDT SUN OCT 5 2025
DISCUSSION
KEY MESSAGES:
- WIDESPREAD FROST/FREEZE FOR MONDAY AND TUESDAY MORNINGS.
- DRY WITH SEASONABLE TEMPERATURES THROUGH MIDWEEK
THE WEATHER DISTURBANCE THAT BROUGHT SEVERAL INCHES OF SNOW TO THE
MOUNTAINS ALONG THE CONTINENTAL DIVIDE WILL CONTINUE TO MOVE SOUTH
AND EAST OF THE REGION THROUGH THIS AFTERNOON. PARTLY CLOUDY
CONDITIONS AND COOL TEMPERATURES WILL SETTLE IN ACROSS THE REGION
THIS AFTERNOON. CLEARING SKIES AND A DRY AIRMASS WILL SETTLE IN
OVER THE NORTHERN ROCKIES OVERNIGHT, ESPECIALLY ACROSS NORTHWEST
MONTANA, RESULTING IN WIDESPREAD FREEZING TEMPERATURES IN AREA
VALLEYS. CURRENTLY, THERE IS AN 80 TO 90 PERCENT PROBABILITY THAT
TEMPERATURES WILL DROP TO FREEZING OR BELOW IN THE VALLEYS OF
WESTERN MONTANA TOMORROW MORNING. THERE IS A 60 TO 70 PERCENT
PROBABILITY THAT TEMPERATURES WILL LOWER TO 25F OR BELOW IN THE
FLATHEAD VALLEY. THE PROBABILITY FOR A HARD FREEZE IN THE MISSOULA
AND BITTERROOT VALLEYS HAS LOWERED COMPARED TO 24 HOURS AGO, NOW
STANDING AT 30 TO 50 PERCENT. THIS IS LIKELY DUE TO THE LATEST
GUIDANCE NOT DRYING OUT THE LOWER ATMOSPHERE AS QUICKLY AS
PREVIOUS PROJECTIONS. CURRENTLY, HIGH-RESOLUTION GUIDANCE ONLY HAS
THE DEWPOINTS LOWERING INTO THE LOW TO MID-30S. IT IS ALSO
SUGGESTING THE DEVELOPMENT OF STRATUS AND/OR FOG, WHICH WOULD
LIMIT TEMPERATURES FROM FALLING INTO THE 20S. WE WILL BE
MONITORING THE AFTERNOON DEWPOINTS TO DETERMINE IF WIDESPREAD
FREEZE WARNINGS WILL BE WARRANTED FOR MONDAY MORNING. TUESDAY MAY
END UP BEING THE COLDEST MORNING THIS WEEK.
ENSEMBLE MODEL SOLUTIONS ARE KEEPING A RIDGE OF HIGH PRESSURE OVER
THE NORTHERN ROCKIES THROUGH ABOUT MIDWEEK, FEATURING DRY
CONDITIONS AND SEASONABLE TEMPERATURES. MOST MEMBERS ARE
INDICATING UNSETTLED WEATHER ARRIVING LATER IN THE WEEK, THOUGH
TIMING AND INTENSITY ARE STILL RATHER UNCERTAIN.
AVIATION
PERIODS OF MVFR IN LINGERING SHOWERS WILL CONTINUE
THIS AFTERNOON, ACCOMPANIED BY EXTENSIVE MOUNTAIN OBSCURATION.
THESE SHOWERS WILL TAPER OFF AS CLOUD COVER CLEARS FROM NORTH TO
SOUTH THIS EVENING, LEADING TO IMPROVING CONDITIONS. THE PRIMARY
POTENTIAL AVIATION HAZARD WILL THEN BECOME THE FORMATION OF LOW
CLOUDS OVERNIGHT INTO MONDAY MORNING. A PERSISTENT, LIGHT
NORTHERLY TO NORTHWESTERLY FLOW IS EXPECTED WITHIN THE VALLEYS.
THIS GENTLE WIND TYPICALLY PROVIDES ENOUGH MIXING TO LIFT THE
SATURATED LAYER, FAVORING THE DEVELOPMENT OF A LOW STRATUS DECK
RATHER THAN SURFACE-BASED FOG. WIDESPREAD MVFR CEILINGS MAY
DEVELOP AFTER 08Z MONDAY, WITH THE POTENTIAL FOR LOCALIZED IFR,
PARTICULARLY IN THE FLATHEAD VALLEY (KGPI). CONDITIONS WILL
IMPROVE TO VFR BY TUESDAY AFTERNOON AS A DRIER ATMOSPHERE BUILDS
OVER THE REGION.
MSO WATCHES/WARNINGS/ADVISORIES
MT...FREEZE WARNING FROM 3 AM TO 10 AM MDT MONDAY FOR
FLATHEAD/MISSION VALLEYS...MISSOULA/BITTERROOT VALLEYS.
ID...FROST ADVISORY FROM 2 AM TO 9 AM PDT MONDAY FOR
OROFINO/GRANGEVILLE REGION.
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