565
FXUS65 KMSO 120651
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1251 AM MDT SUN APR 12 2026
DISCUSSION
KEY MESSAGES:
- TODAY: PATCHY MORNING FOG GIVES WAY TO AFTERNOON SHOWERS AND
ISOLATED THUNDERSTORMS. MAIN THREATS: GUSTY WINDS TO 40 MPH AND
SMALL HAIL.
- TONIGHT-MONDAY: TRANSITION TO STEADY VALLEY RAIN, SLUSHY SNOW
FOR PASSES ABOVE 5000 FEET.
- WEDNESDAY-THURSDAY: SIGNIFICANT COLD FRONT. SNOW LEVELS
DROPPING TO 1,500-2,000 FT BY THURSDAY MORNING. LIGHT VALLEY
SNOW ACCUMULATIONS AND MODERATE TRAVEL IMPACTS ON MOUNTAIN
PASSES.
TODAY THROUGH TUESDAY:
EARLY MORNING SHOWERS HAVE LARGELY TAPERED OFF, WATCH FOR PATCHY
DENSE VALLEY FOG THROUGH THE MID-MORNING HOURS WHERE CLEARING
OCCURS. THE FOCUS NOW SHIFTS TO A CLOSED UPPER-LEVEL LOW CURRENTLY
MOVING ONTO THE NORTHERN CALIFORNIA COAST. AS THIS SYSTEM MOVES
INLAND, IT IS EXPECTED TO WEAKEN AND FRAGMENT, SENDING A SERIES OF
DISTURBANCES AND A PLUME OF PACIFIC MOISTURE ACROSS THE NORTHERN
ROCKIES.
THIS WILL RESULT IN WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS
DEVELOPING LATE THIS MORNING AND SPREADING SOUTH TO NORTH THROUGH
THE EVENING. PRIMARY THREATS WITH ANY THUNDERSTORMS INCLUDE:
- GUSTY OUTFLOW WINDS UP TO 40 MPH.
- BRIEF HEAVY RAINFALL AND SMALL HAIL.
PRECIPITATION WILL TRANSITION TO A STRATIFORM REGIME TONIGHT INTO
MONDAY MORNING AS A WEAK SURFACE LOW DEVELOPS OVER SOUTHERN IDAHO
AND TRACKS INTO SOUTHWEST MONTANA. A FOCUSED BAND OF PRECIPITATION
IS EXPECTED TO SET UP FROM NORTH-CENTRAL IDAHO INTO WEST-CENTRAL
MONTANA.
- QPF: TOTAL MOISTURE THROUGH MONDAY MORNING WILL RANGE FROM
0.50" TO 1.50" FOR IDAHO AND CLEARWATER COUNTIES, WITH 0.25"
TO 1.00" ACROSS WEST-CENTRAL MONTANA.
- SNOW LEVELS: LEVELS WILL HOVER BETWEEN 5,000 AND 6000 FEET BY
EARLY MONDAY. HIGH-ELEVATION PASSES, INCLUDING LOLO, LOST
TRAIL, HOMESTAKE, ALONG WITH GEORGETOWN LAKE MAY SEE 1-2
INCHES OF SLUSHY SNOW ACCUMULATION.
BY MONDAY AFTERNOON, THE REGION TRANSITIONS TO A WESTERLY (ZONAL)
FLOW THAT WILL PERSIST THROUGH TUESDAY. THIS PATTERN WILL KEEP
LIGHT, TERRAIN-DRIVEN SHOWERS IN THE FORECAST, PARTICULARLY ACROSS
NORTHWEST MONTANA, WHILE LOWER ELEVATIONS REMAIN MOSTLY DRY.
WEDNESDAY THROUGH FRIDAY:
CONFIDENCE REMAINS HIGH THAT A POTENT COLD FRONT AND ASSOCIATED
LOW PRESSURE SYSTEM WILL IMPACT THE NORTHERN ROCKIES BEGINNING
WEDNESDAY. THIS SYSTEM WILL USHER IN AN UNSEASONABLY COLD AIR
MASS, CAUSING TEMPERATURES TO DROP SIGNIFICANTLY BELOW SEASONAL
AVERAGES. SNOW LEVELS ARE PROJECTED TO PLUMMET TO 1,500-2,000 FEET
BY THURSDAY MORNING. LATEST GUIDANCE INDICATES A HIGH PROBABILITY
FOR LIGHT SNOW ACCUMULATIONS AT ALL ELEVATIONS, INCLUDING VALLEY
FLOORS. MOUNTAIN PASSES AND HIGHER-ELEVATION VALLEYS ESPECIALLY
IN SOUTHWEST MONTANA ARE THE MOST LIKELY TO EXPERIENCE MODERATE
TRAVEL IMPACTS FROM ACCUMULATING SNOW DURING THIS PERIOD.
AVIATION
A CLOSED LOW MOVING ONTO THE NORTHERN CALIFORNIA COAST
WILL BREAK APART SENDING SEVERAL DISTURBANCES AND PACIFIC
MOISTURE ACROSS THE NORTHERN ROCKIES INTO MONDAY. A FEW SHOWERS
CONTINUE EARLY THIS MORNING BUT OVERALL A DIMINISHING TREND.
PATCHY DENSE FOG MAY IMPACT TERMINAL SITES WHERE AREAS OF CLEARING
OCCUR EARLY THIS MORNING.
SHOWERS BECOME WIDESPREAD FROM SOUTH TO NORTH LATE THIS MORNING
THROUGH THIS EVENING. THERE IS A POTENTIAL FOR ISOLATED
THUNDERSTORMS MAINLY SOUTH OF I-90. WATCH FOR GUSTY WINDS TO 35
KTS, BRIEF HEAVY RAIN, AND SMALL HAIL WITH ANY THUNDERSTORMS.
PRECIPITATION WILL BECOME STRATIFORM TONIGHT INTO MONDAY MORNING
ALONG A BAND EXPECTED TO STRETCH FROM WEST-CENTRAL MONTANA INTO
NORTH-CENTRAL IDAHO AS A WEAK SURFACE LOW DEVELOPS OVER SOUTHERN
IDAHO AND MOVES INTO SOUTHWEST MONTANA. MVFR AND OCCASIONAL IFR
CONDITIONS ARE LIKELY TO IMPACT TERMINAL SITES TONIGHT INTO MONDAY
MORNING.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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