458
FXUS65 KMSO 130654
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1254 AM MDT MON APR 13 2026
DISCUSSION
KEY MESSAGES:
TODAY: WIDESPREAD PRECIPITATION, LIGHT SNOW ABOVE 5000 FEET.
WEDNESDAY: PASS LEVEL SNOW, POTENTIAL TRAVEL IMPACTS.
WEDNESDAY NIGHT/THURSDAY: STRONG COLD FRONT WITH SNOW LEVELS TO
VALLEY FLOORS BUT LIGHT VALLEY ACCUMULATIONS. MODERATE PASS LEVEL
TRAVEL IMPACTS CONTINUE.
TODAY THROUGH TUESDAY:
A BAND OF STEADY PRECIPITATION CURRENTLY EXTENDS FROM THE BOB
MARSHALL WILDERNESS SOUTHWESTWARD INTO NORTH-CENTRAL IDAHO, DRIVEN
BY AN UPPER-LEVEL LOW SPINNING WEST OF SALMON THIS MORNING. THIS
LOW WILL TRACK SLOWLY EASTWARD TODAY, GRADUALLY SHIFTING THE
PRECIPITATION BAND ACROSS THE REGION AND TRANSITIONING IT INTO
SCATTERED SHOWERS BY THE AFTERNOON. IN NORTHWEST MONTANA, MODEST
INSTABILITY WILL SUPPORT A FEW ISOLATED THUNDERSTORMS THIS
AFTERNOON.
SNOW LEVELS THIS MORNING RANGE FROM 5,000 FEET ALONG AND SOUTH OF
I-90 TO NEAR 6,000 FEET FURTHER NORTH. TRAVELERS SHOULD ALLOW FOR
THE POTENTIAL OF A BRIEF PERIOD OF SLUSHY SNOW ACCUMULATIONS (1-2
INCHES) ON THE ROADWAY AT LOST TRAIL PASS. SHOWERS WILL DIMINISH
THIS EVENING, GIVING WAY TO A BRIEF PERIOD OF ZONAL FLOW ON
TUESDAY. THIS WILL RESULT IN MOSTLY DRY CONDITIONS FOR LOWER
ELEVATIONS, THOUGH ISOLATED, TERRAIN- DRIVEN SHOWERS WILL PERSIST
OVER THE MOUNTAINS.
WEDNESDAY THROUGH THURSDAY (STRONG COLD FRONT):
WIDESPREAD PRECIPITATION RETURNS TUESDAY EVENING ALONG THE ID/MT
BORDER AND SPREADS EASTWARD THROUGH WEDNESDAY MORNING. INITIAL
SNOW LEVELS WILL RANGE FROM 3,500 FEET IN FAR NORTHWEST MONTANA TO
5,000 FEET ACROSS SOUTHWEST MONTANA AND THE GRANGEVILLE AREA.
WINTER DRIVING CONDITIONS ARE EXPECTED FOR MARIAS, LOOKOUT, AND
LOLO PASSES TO START WEDNESDAY, WITH MEAN SNOW TOTALS OF 2-5
INCHES LIKELY BY MIDDAY.
A POWERFUL COLD FRONT WILL CROSS THE REGION WEDNESDAY AFTERNOON
AND EVENING, BRINGING A FOCUSED BAND OF PRECIPITATION AND GUSTY
WINDS. COLDER AIR BEHIND THE FRONT WILL CAUSE SNOW LEVELS TO
PLUMMET TO 1,500-2,000 FEET (ALL VALLEY FLOORS) BY THURSDAY
MORNING. WHILE CURRENT GUIDANCE SUGGESTS THE SYSTEM WILL HAVE
DIMINISHING MOISTURE BEHIND THE FRONT, THIS SCENARIO STILL ALLOWS
FOR SCATTERED VALLEY SNOW SHOWERS BUT WITH LIMITED IMPACTS.
HOWEVER, MODERATE IMPACTS ARE LIKELY AT PASS LEVELS; 50TH
PERCENTILE (NBM) PROJECTIONS INDICATE 3-6 INCHES OF ADDITIONAL
SNOW WEDNESDAY NIGHT THROUGH THURSDAY. HIGHER VALLEYS IN SOUTHWEST
MONTANA MAY ALSO SEE SLICK ROADS AND MODERATE TRAVEL IMPACTS.
CONFIDENCE/ALTERNATIVE SCENARIOS: FORECASTER CONFIDENCE IS HIGH
REGARDING THE FRONTAL TIMING AND TEMPERATURE DROP. WE ARE
MONITORING ONE ALTERNATIVE SCENARIO (<25% PROBABILITY) WHERE A
CLOSED LOW DEVELOPS FURTHER SOUTH, WHICH WOULD SIGNIFICANTLY
INCREASE SNOWFALL TOTALS FOR THE VALLEYS. BUT ONCE AGAIN, THIS IS
A LESS LIKELY SCENARIO.
NEXT WEEKEND (APRIL 18-19):
BRIEF RIDGING IS EXPECTED THIS COMING WEEKEND, LEADING TO A
TEMPORARY WARMING TREND. HOWEVER, LONG-RANGE CPC GUIDANCE FAVORS A
RETURN TO COOL AND SHOWERY WEATHER EARLY NEXT WEEK AS ANOTHER
TROUGH APPROACHES THE PACIFIC NORTHWEST.
AVIATION
AN UPPER-LEVEL LOW CURRENTLY CENTERED WEST OF SALMON, ID,
WILL DRIFT SLOWLY EASTWARD TODAY, SHIFTING A PRIMARY BAND OF
PRECIPITATION ACROSS THE REGION. THIS BAND, CURRENTLY STRETCHING
FROM NORTH-CENTRAL IDAHO INTO THE BOB MARSHALL WILDERNESS, WILL
TRANSITION TO SCATTERED SHOWERS BY THIS AFTERNOON.
CEILINGS/VISIBILITY: WIDESPREAD MVFR CONDITIONS AND FREQUENT
MOUNTAIN OBSCURATIONS WILL PERSIST UNDER THE MAIN PRECIPITATION
BAND THIS MORNING. OCCASIONAL IFR VISIBILITY IS POSSIBLE WITHIN
HEAVIER RAIN/SNOW SHOWERS. CONDITIONS ARE EXPECTED TO IMPROVE TO
VFR FOR MOST TERMINALS BY AFTERNOON AS PRECIPITATION BECOMES
SHOWERY, THOUGH LOCALIZED MVFR WILL REMAIN POSSIBLE NEAR
CONVECTIVE ACTIVITY.
CONVECTION: INCREASING INSTABILITY THIS AFTERNOON WILL SUPPORT
ISOLATED THUNDERSTORMS ACROSS NORTHWEST MONTANA.
SURFACE WINDS: SOUTHWEST WINDS WILL INCREASE THIS AFTERNOON,
SUSTAINED AT 10-15 KTS WITH GUSTS OF 20-25 KTS FOR SOUTHERN
TERMINAL SITES. WINDS ARE FORECAST TO DIMINISH SIGNIFICANTLY
AFTER SUNSET AS THE BOUNDARY LAYER STABILIZES.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page