239
FXUS65 KMSO 221042 CCA
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 MEMORIAL DAY(MONDAY). ANY LIGHTNING,
SUDDEN WIND, OR RAPID TEMPERATURE DROP COULD BE IMPACTFUL TO
OUTDOOR RECREATIONALISTS. COLD FRONT MOVES THROUGH BY TUESDAY
MORNING.
- 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 IN LINE 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. BOATERS AND PADDLERS ON AREA LAKES
SHOULD BE READY FOR SUDDEN SHIFTS IN WIND AND CHOPPY WATERS.
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 INCHES OF RAIN
OVER THE 48-HOUR PERIOD 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 OUR 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). THIS UNUSUALLY MUGGY AIRMASS FOR OUR
REGION WILL INCREASE THE POTENTIAL FOR 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. WHILE
LOW MOUNTAIN SNOWPACK MEANS OUR LARGER MAINSTEM RIVERS HAVE PLENTY OF
ROOM TO HANDLE THIS RAIN, SMALLER CREEKS AND STREAMS COULD BE HIGHLY
SENSITIVE. THIS IS SOMETHING TO BE WATCHED.
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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