276
FXUS65 KTFX 231650
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1050 AM MDT TUE JUN 23 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- TEMPERATURES TREND CLOSER TO AVERAGE HEADING TOWARDS THE END OF
THE WORKWEEK.
- DAILY ROUNDS OF SHOWERS AND THUNDERSTORMS BECOME MORE WIDESPREAD
BY THURSDAY AND FRIDAY AND WILL BE MOST IMPACTFUL FOR OUTDOOR
RECREATION.
- BREEZY TO WINDY CONDITIONS WILL ALSO IMPACT OUTDOOR RECREATION
ACROSS SOUTHWEST MONTANA ON FRIDAY.
- COOL AND WET CONDITIONS RETURN THIS WEEKEND INTO EARLY NEXT WEEK
WITH SOME INSTANCES OF HIGH MOUNTAIN SNOW.
DISCUSSION
/ISSUED 514 AM MDT TUE JUN 23 2026/
- METEOROLOGICAL OVERVIEW:
WEAK RIDGING ALOFT WILL MOVE OVER THE NORTHERN ROCKIES FOR THE NEXT
FEW DAYS AND BRING WARMER TEMPERATURES AND AND AT LEAST A DAY WITH
LIMITED SHOWER AND THUNDERSTORM ACTIVITY. THE PRIMARY CONCERN FOR
THIS MORNING WILL BE LOW STRATUS AND SOME PATCHY FOG OVER CENTRAL
AND NORTH-CENTRAL MT THIS MORNING AND PERHAPS AN ISOLATED STORM OVER
THE MOUNTAINS THIS AFTERNOON. A WEAK SHORTWAVE MOVES IN AND BRINGS
AT LEAST ISOLATED SHOWERS AND THUNDERSTORMS ON WEDNESDAY BEFORE A
STRONGER SHORTWAVE MOVES IN ON THURSDAY AND INTERACTS WITH ML CAPE
LEVELS IN THE 400 TO 600 J/KG RANGE FOR INCREASED THUNDERSTORM
COVERAGE AND INTENSITY. ANOTHER WAVE OF SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS WILL MOVE THROUGH THE FORECAST AREA ON
FRIDAY GIVEN SOUTHWESTERLY FLOW ALOFT BECOMING MORE ESTABLISHED
AHEAD OF A LARGER SCALE TROUGH MOVING INTO THE PACIFIC NW. A SLIGHT
INCREASE IN BOTH ML CAPE AND BULK SHEAR FROM WARMING SURFACE
TEMPERATURES AND THE STRONGER FLOW ALOFT MAY ENCOURAGE MORE OF THESE
STORMS TO BECOME STRONG TO SEVERE DEPENDING ON TIMING. H700 TO H500
WINDS WILL REACH THE 20 TO 40 KT RANGE BY LATE FRIDAY AND WILL BRING
SOME GUSTY NON-THUNDERSTORM WINDS TO THE HIGHER MOUNTAIN PEAKS AND
THE NARROW SOUTH TO NORTH ORIENTED VALLEYS OF SOUTHWEST MT.
THE AFOREMENTIONED PACIFIC NW TROUGH WILL MOVE EASTWARD AND BRING
WIDESPREAD RAIN SHOWERS AND EMBEDDED THUNDERSTORMS FOR THE FIRST
HALF OF THE WEEKEND FOLLOWED BY GENERAL STRATIFORM RAIN HEADING INTO
EARLY NEXT WEEK. THIS WILL BE A SLOW MOVING TROUGH WITH MOISTURE
LEVELS ABOUT ON PAR OR SLIGHTLY ABOVE CLIMATOLOGY, BUT IT'S COLD
CORE ALOFT WILL HAVE TEMPERATURES RUNNING 2 TO 3 STANDARD DEVIATIONS
BELOW AVERAGE FOR THIS TIME OF YEAR. EVEN THOUGH IT APPEARS THE MAIN
AREA OF FORCING WILL BE CLOSE ENOUGH TO BRING WIDESPREAD RAINFALL TO
MOST LOCATIONS, THE SHEARING AND TRANSFORMATION OF THIS SYSTEM MAKES
IT DIFFICULT TO DECIPHER THE PRECISE AREAS OF HEAVIER RAINFALL.
OVERALL, EXPECT A COOL, WET WEEKEND, ESPECIALLY SUNDAY INTO MONDAY.
THERE WILL ALSO BE HIGH MOUNTAIN SNOW, PRIMARILY FOR ELEVATIONS
ABOVE 7000 FT DURING THE OVERNIGHT AND EARLY MORNING HOURS.
CURRENTLY, THIS LOOKS TO SET UP OVER THE SOUTHWESTERN MOUNTAINS, BUT
THIS MAY CHANGE IF THE POSITIONING THE COLD CORE ALOFT CHANGES AND
IF OTHER AREAS OF DYNAMIC COOLING SET UP. GUSTY WINDS MAY ALSO
DEVELOP ON THE BACK SIDE OF THE SYSTEM ON MONDAY DEPENDING ON THE
STRENGTH AND POSITION OF THE H700 LOW. - RCG
- FORECAST CONFIDENCE & SCENARIOS:
INCREASED SHOWER AND THUNDERSTORM ACTIVITY WEDNESDAY THROUGH
FRIDAY...
SHORTWAVE ENERGY INTERACTING WITH A SEASONABLY UNSTABLE ATMOSPHERIC
PROFILE WILL RESULT IN INCREASED SHOWER AND THUNDERSTORM ACTIVITY
DURING THE SECOND HALF OF THE WORKWEEK. WEDNESDAY'S STORMS LOOK TO
BE THE MOST BENIGN OF THE THREE DAYS WITH SHOWERS AND STORMS MOSTLY
CONFINED TO AND NEAR THE HIGHER TERRAIN OF CENTRAL AND SOUTHWEST MT.
INSTABILITY INCREASES ON THURSDAY FOR MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS, BUT THERE ARE SOME DISAGREEMENTS ON THE STRENGTH AND
EVOLUTION OF THE SHORTWAVE AND THE SHEAR IT WILL BRING TO THE TABLE.
MOST MEMBERS FAVOR A WEAKER WAVE WITH LESS FORCING AND SHEAR
AVAILABILITY FOR WIDESPREAD STRONG TO SEVERE STORMS, THOUGH THE
FORCING LOOKS SUFFICIENT FOR MORE WIDESPREAD PRECIPITATION. ON
PAPER, FRIDAY LOOKS TO HAVE THE BEST OVERALL ENVIRONMENT FOR
STRONGER STORMS GIVEN INCREASED INSTABILITY AND ADDED SHEAR/FORCING
FROM THE APPROACHING PACIFIC NW TROUGH; HOWEVER, THERE'S NOTHING
REALLY STANDING OUT AS UNUSUALLY STRONG OR INTENSE FOR THIS TIME OF
YEAR. IMPACTS FOR ALL THREE DAYS WILL BE MOSTLY FOR THOSE WITH
OUTDOOR RECREATION PLANS AND WILL INCLUDE LOCALIZED STRONG GUSTY
WINDS, HAIL, DOWNPOURS IN ADDITION TO LIGHTNING.
STRONG AND GUSTY WINDS OVER SOUTHWEST MT ON FRIDAY...
THE COMBINATION OF DEEP LAYER MIXING AND THE STRENGTHENING
SOUTHWESTERLY FLOW MAY BRING GUSTY TO STRONG WINDS TO SOUTHWEST MT,
PARTICULARLY OVER THE HIGHER TERRAIN AND THE SOUTH TO NORTH ORIENTED
VALLEYS. ENSEMBLES SEEM TO BE TRENDING WITH THE STRONGER WINDS ALOFT
DEVELOPING TO THE EAST OF THE FORECAST AREA, THOUGH THE SET UP STILL
FAVORS BREEZY TO WINDY CONDITIONS OVER THE AFOREMENTIONED AREAS. THE
LATEST NBM PROBABILITIES FOR WIND GUSTS OVER 50 MPH, FOR MOST AREAS
SOUTH OF THE I-90 CORRIDOR, HAVE FALLEN SLIGHTLY TO THE 20 TO 50%
RANGE AND THE PROBABILITY FOR 40 MPH + SUSTAINED WINDS HAVE LARGELY
FALLEN BELOW 15% AT THIS TIME. THIS TREND TOWARDS LIGHTER WINDS IS
FAIRLY NEW AND WILL BE MONITORED IN THE COMING DAYS. IT IS ALSO
IMPORTANT TO NOTE THAT ANY SHOWERS OR THUNDERSTORMS THAT DEVELOP ON
FRIDAY WILL HELP TRANSFER STRONGER WIND GUSTS TO THE SURFACE. GIVEN
INCREASED SUMMER TRAFFIC ACROSS THE AREA AND MORE PEOPLE RECREATING
IN THE MOUNTAINS, STRONGER WINDS WILL BE MORE IMPACTFUL THAN THE
WINDS NORMALLY OBSERVED DURING THE COOLER SEASON.
COOL CONDITIONS WITH WIDESPREAD PRECIPITATION AND HIGH MOUNTAIN SNOW
THIS WEEKEND...
WIDESPREAD RAIN SHOWERS AND EMBEDDED THUNDERSTORMS ARE IN THE
FORECAST FOR THE FIRST HALF OF THE WEEKEND WITH PERIODS OF MODERATE
TO HEAVY STRATIFORM RAIN AND EVEN HIGH MOUNTAIN SNOW SUNDAY INTO
MONDAY. THE LATEST NBM PROBABILITY FOR 1 INCH OF RAIN OVER THE 72
HOUR PERIOD ENDING 6 AM TUESDAY IS NOW RUNNING ABOVE 60% FOR
VIRTUALLY THE ENTIRE FORECAST AREA WITH ROUGHLY 15 TO 30% CHANCES
FOR 2 INCHES OR MORE OVER MOST LOWER ELEVATIONS DURING THE SAME
PERIOD. MOUNTAIN SNOW WILL DEPEND ON WHERE THE COLD CORE ALOFT SETS
UP AND WHERE ANY CONVECTIVE OR HEAVIER BANDS OF PRECIPITATION
ARTIFICIALLY LOWER SNOW LEVELS WITH DYNAMIC COOLING. THE COLD CORE
LOOKS TO SETTLE OVER THE SOUTHWESTERN MOUNTAINS SUNDAY INTO MONDAY,
BUT THE HIGHER TERRAIN ALONG THE CONTINENTAL DIVIDE AND EVEN THE
CENTRAL RANGES WILL NEED TO BE MONITORED FOR TEMPORARY LOWERING OF
SNOW LEVELS FROM DYNAMIC COOLING. SNOW LEVELS DURING THIS ENTIRE
EVENT SHOULD RANGE BETWEEN 7000 TO 9000 FEET, LOWEST DURING THE
OVERNIGHT AND EARLY MORNING HOURS SATURDAY NIGHT THROUGH MONDAY
MORNING. ANYONE WITH OUTDOOR PLANS SHOULD PLAN FOR COOL AND DAMP
CONDITIONS THAT MAY BE DANGEROUS TO THOSE NOT PROPERLY DRESSED. ALSO
FOREST AND RURAL ROADS MAY BECOME MUDDY OR EVEN IMPASSIBLE FROM THE
WET CONDITIONS. - RCG
AVIATION
23/18Z TAF PERIOD
PRIMARY CONCERN THIS TAF PERIOD WILL BE FOR SOME EARLY AFTERNOON
CUMULUS BRIEFLY RESULTING IN ISOLATED MVFR CEILINGS. AS DAYTIME
MIXING CONTINUES CLOUD BASES SLOWLY RISE WHICH WILL MITIGATE LOW
CLOUD CONCERNS. WINDS WILL REMAIN ON THE LIGHTER SIDE THROUGH THE
TAF PERIOD. -AM
PRELIMINARY POINT TEMPS/POPS
GTF 71 48 75 49 / 0 0 0 10
CTB 69 45 73 47 / 0 0 0 10
HLN 76 50 79 52 / 0 0 10 30
BZN 77 46 78 47 / 0 0 10 20
WYS 77 39 76 39 / 0 0 30 20
DLN 78 47 79 47 / 0 0 30 30
HVR 71 44 75 48 / 0 0 0 0
LWT 66 42 69 45 / 0 0 10 10
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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