393
FXUS65 KMSO 181900
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
100 PM MDT WED MAR 18 2026
DISCUSSION
KEY MESSAGES:
- RISES IN SMALL STREAMS AND CREEKS THROUGH TODAY FOR NORTHWEST
MONTANA, ESPECIALLY LINCOLN AND SANDERS COUNTIES
- WELL ABOVE NORMAL TEMPERATURES AND GUSTY WINDS AT TIMES INTO
FRIDAY, ESPECIALLY I-90 SOUTHWARD
- MORE SEASONABLE TEMPERATURES ON SATURDAY WITH A COLD FRONT
PASSAGE
LOW PRESSURE OVER THE GULF OF ALASKA AND A BROAD REGION OF HIGH
PRESSURE OVER THE SOUTHWESTERN US ARE KEEPING THE JET STREAM
DIRECTED OVER THE NORTHWESTERN US, INCLUDING THE NORTHERN ROCKIES.
THAT JET IS BRINGING PACIFIC MOISTURE WITH IT, RESULTING IN
MOUNTAIN PRECIPITATION OVER NORTHWEST MONTANA AND NORTH-CENTRAL
IDAHO. TEMPERATURES ARE WARM, THOUGH, AND SNOW LEVELS WILL REMAIN
ABOVE 7000 FEET GOING INTO THE WEEKEND. RAINFALL OVER NORTHWEST
MONTANA HAS RESULTED IN RISING RIVERS AND STREAMS WITHOUT
WIDESPREAD IMPACTS SO FAR, THUS THE FLOOD WATCH WAS DROPPED FOR THE
REST OF TODAY. EXPECT RAIN TO CONTINUE OVER NORTHWEST MONTANA
TODAY. PRECIPITATION WILL LIGHTEN UP OVERNIGHT TONIGHT AS THE
STRONGEST PART OF THE POLAR JET SHIFTS NORTHWARD. THURSDAY AND
FRIDAY MORNING WILL STILL SEE CHANCES FOR RAIN IN FAR NORTHWEST
MONTANA. THE BIGGER HEADLINE AS WE ROUND OUT THE WEEK WILL BE
TEMPERATURES. DAYTIME HIGH TEMPERATURES FOR WESTERN MONTANA
VALLEYS WILL BE IN THE 60S TO LOWER 70S, LOWER TEMPERATURES IN
THE NORTH, HIGHER IN THE SOUTH. THE BITTERROOT, MISSOULA, AND
MISSION VALLEYS WILL SEE UPPER 60S TO LOW 70S, LOWER FOR THE
FLATHEAD AND NORTHWEST MONTANA. THE FORECAST FOR BUTTE WILL BE
HIGH ENOUGH TO BREAK THE CURRENT RECORD OF 65 DEGREES ON THURSDAY
AND FRIDAY. IN IDAHO, EXPECT 70S TO LOW 80S IN THE LOWER SALMON
AND CLEARWATER VALLEYS, AROUND 70 FOR SALMON.
WEST OR SOUTHWEST WINDS WILL ALSO BE ON THE RISE THROUGH FRIDAY
WITH GUSTS OF 25 TO 35 MPH, ESPECIALLY DURING THE
AFTERNOON/EVENING HOURS. LOCALIZED HIGHER GUSTS ARE POSSIBLE IN
AREAS PRONE TO THE MOUNTAIN WAVE ACTIVITY FAVORED BY THIS PATTERN.
THESE WINDS MAY CREATE CHOPPY CONDITIONS ON AREA LAKES AND COULD
OCCASIONALLY DISRUPT OUTDOOR ACTIVITIES. FIRE WEATHER CONCERNS
WILL ALSO BE HEIGHTENED IN SOUTHWEST MONTANA DUE TO A COMBINATION
OF LOW HUMIDITY AND GUSTY WINDS FOR THE REST OF THIS WEEK.
ON SATURDAY, THERE WILL BE A SHIFT BACK TOWARDS MORE SEASONABLE
CONDITIONS AS A COLD FRONT MOVES THROUGH THE NORTHERN ROCKIES. IN
ADDITION TO COOLER TEMPERATURES, THIS SYSTEM WILL BRING A ROUND OF
LIGHT PRECIPITATION AND GUSTY WINDS. AT THIS TIME, IMPACTS FROM
THIS WEEKEND FRONTAL PASSAGE APPEAR MINIMAL.
AVIATION
AN ATMOSPHERIC RIVER REMAINS DIRECTED AT NORTHWEST MONTANA,
BRINGING LIGHT PRECIPITATION PRIMARILY NORTH OF THE I-90 CORRIDOR
THROUGH FRIDAY. PRECIPITATION RATES WILL GRADUALLY DIMINISH THIS
AFTERNOON WITH THE NEXT PERIOD OF HIGHER RATES ON FRIDAY.
PRECIPITATION WILL REMAIN LARGELY TERRAIN- DRIVEN, WITH SNOW
LEVELS HOVERING NEAR 7,000 FEET, RESULTING IN FREQUENT MOUNTAIN
OBSCURATIONS.
SOUTH OF I-90, VFR CONDITIONS WILL LARGELY PREVAIL AS PERIODIC
MID- TO HIGH-LEVEL CLOUDS STREAM OVERHEAD. EXPECT GUSTY SURFACE
WINDS EACH AFTERNOON AND EVENING, WITH OCCASIONAL GUSTS EXCEEDING
25 KNOTS. WHILE SURFACE WINDS WILL GENERALLY DECOUPLE AND DIMINISH
OVERNIGHT, RIDGETOP WINDS WILL REMAIN ELEVATED AT 25 TO 35 KNOTS.
THIS SETUP WILL INTRODUCE LOCALIZED LOW-LEVEL WIND SHEAR (LLWS)
CONCERNS DURING THE OVERNIGHT AND EARLY MORNING HOURS.
FINALLY, LINGERING LOW-LEVEL MOISTURE COMBINED WITH PARTIAL
CLEARING WILL INTRODUCE THE POTENTIAL FOR VALLEY FOG TONIGHT INTO
THURSDAY MORNING, WITH THE HIGHEST PROBABILITY OF IMPACTS AT KMSO.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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