579
FXUS65 KMSO 221027
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
427 AM MDT FRI MAY 22 2026
DISCUSSION
KEY MESSAGES:
- WARMING AND DRYING TREND EXPECTED THROUGH THE WEEKEND.
- SHOWERS AND THUNDERSTORMS ON MONDAY WITH COLD FRONT MOVING
THROUGH BY TUESDAY.
- TUESDAY COULD BE QUITE THE WET DAY AS A LARGE UPPER LOW BECOMES
SITUATED TO OUR SOUTHWEST. THERE'S A 50 TO 70% PROBABILITY FOR
WIDESPREAD RAINFALL AMOUNTS EXCEEDING 0.25" BY WEDNESDAY
MORNING.
- UPPER LOW KEEPS UNSETTLED WEATHER GOING NEXT WEEK, SO KEEP THAT
RAIN GEAR HANDY!
SCATTERED SHOWERS ARE POSSIBLE THIS AFTERNOON AND EVENING ACROSS
NORTHWEST MONTANA AND ALONG THE DIVIDE. IMPACTS WILL REMAIN
LIMITED TO BRIEF, LOCALIZED RAINFALL AND WIND GUSTS UP TO 30 MPH.
HOWEVER, SUFFICIENT INSTABILITY MAY TRIGGER AN ISOLATED
THUNDERSTORM WITHIN GLACIER NATIONAL PARK.
THIS WEEKEND/WATER SAFETY:
A SIGNIFICANT WARMING TREND WILL BRING SUMMER-LIKE TEMPERATURES TO
THE REGION BY THE WEEKEND. WITH THE WARM AIR TEMPERATURES,
OUTDOOR RECREATION WILL LIKELY INCREASE AROUND AREA LAKES AND
RIVERS. PLEASE BE AWARE THAT LOCAL WATERWAYS CONTINUE TO RUN
EXTREMELY COLD DUE TO ONGOING MOUNTAIN SNOWMELT. PLUNGING INTO
COLD WATER WITHOUT ACCLIMATIZATION CAN INDUCE COLD WATER SHOCK,
WHICH DRASTICALLY ALTERS BREATHING, HEART RATE, AND BLOOD
PRESSURE, CREATING LIFE- THREATENING CONDITIONS. ALWAYS WEAR A
LIFE JACKET TO STAY AFLOAT AND EXERCISE CAUTION. FOR MORE
INFORMATION ON COLD WATER HAZARDS, VISIT
WEATHER.GOV/SAFETY/COLDWATER.
ENSEMBLE WEATHER MODELS HAVE SURPRISINGLY BECOME MORE INLINE WITH
EACH OTHER FOR MONDAY'S WEATHER. A LARGE UPPER LEVEL LOW WILL
DROP SOUTH AND EAST OVER THE PACIFIC NORTHWEST BY MONDAY. THIS
PLACES US IN SOUTHWEST TO SOUTHERLY FLOW ALOFT WHICH IS A GOOD
MAP-TYPE FOR SHOWERS AND THUNDERSTORMS. INSTABILITY IS MARGINAL WHICH
COULD SUPPORT GUSTY WINDS, LIGHTNING AND SMALL HAIL. AS THE FLOW
TURNS MORE SOUTHERLY LATER MONDAY, THAT WILL PROVIDE A LOT OF
CLOUD COVER, THEREBY LIMITING INSTABILITY A BIT.
BY MONDAY NIGHT,AS THE COLD FRONT MAKES ITS WAY INTO WESTERN
MONTANA, THE WRAP-AROUND MOISTURE BEGINS TO KICK IN. ALL THE
ENSEMBLE CLUSTERS SHOW OUR REGION UNDER GENERAL RISING MOTION AS
THE UPPER LEVEL LOW WOBBLES AND MEANDERS OVER OREGON, IDAHO AND
NEVADA THROUGH TUESDAY NIGHT. THIS IS THE PERIOD THAT THE NATIONAL
BLEND OF MODELS HAS THE HIGHEST PROBABILITIES FOR WIDESPREAD
RAINFALL. THE PROBABILITIES SHOW 50 TO 70 PERCENT OF EXCEEDING
0.25", 48 HOURS ENDING WEDNESDAY MORNING. AS SUCH, TUESDAY COULD
BE THE COOLEST DAY OF THE WEEK FOR SOME WITH HIGHS RANGING FROM
THE 50S TO 60S, 5 TO 10 DEGREES COOLER THAN AVERAGE.
AS THE CUTOFF MEANDERS TO OUT SOUTH AND WEST, THERE IS THE
POTENTIAL FOR GULF MOISTURE TO GET ADVECTED NORTHWARDS OVER THE
PLAINS INTO THE MONTANA REGION BY WEDNESDAY AND THURSDAY.
ENSEMBLES SHOW +2 TO +3 STANDARD DEVIATIONS OR 150+ PERCENT OF
NORMAL MOISTURE(PRECIPITABLE WATER). WITH THAT KIND OF ALMOST
"HUMID" AIR FOR OUR REGION, COULD RESULT IN HEAVY RAIN-PRODUCING
SHOWERS OR THUNDERSTORMS. BY THURSDAY, THE ENSEMBLE CLUSTERS
DEPICT SOME EASTWARD MOVEMENT WITH THE MEAN SOLUTION PUTTING THE
UPPER LOW OVER NORTHERN NEVADA. BY FRIDAY THE ENSEMBLE MEANS ALL
SHOW THIS LOW STARTING TO MOVE A LITTLE FASTER, THE ECMWF HAS IT
EJECTING TOWARDS THE YELLOWSTONE REGION WHILE THE GFS ENSEMBLE IS
FURTHER SOUTH.
AVIATION
SUFFICIENT INSTABILITY MAY SUPPORT AN ISOLATED
THUNDERSTORM NEAR GLACIER NATIONAL PARK THIS AFTERNOON. EXPECT
LOCALIZED WIND GUSTS OF 20-25 KNOTS NEAR ANY THUNDERSTORM OR
STRONGER SHOWER ACTIVITY WHICH IMPACT KGPI. OTHERWISE, LIGHT AND
DIURNALLY DRIVEN WINDS WILL CONTINUE AT ALL TERMINAL SITES.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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