223
FXUS65 KTFX 201705
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1105 AM MDT WED MAY 20 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- A COLD FRONT BRINGS A ROUND OF SCATTERED TO NUMEROUS SHOWERS AND
EMBEDDED THUNDERSTORMS TODAY, MOSTLY OVER CENTRAL AND NORTH-
CENTRAL MONTANA.
- THIS ACTIVITY WILL TRANSITION TO GENERAL AREAS OF RAIN AND MOUNTAIN
SNOW AS IT MOVES INTO SOUTHWEST MONTANA TONIGHT INTO THURSDAY
MORNING.
- THE PRECIPITATION DECREASES IN COVERAGE BY THURSDAY AFTERNOON,WITH
MUCH WARMER AND DRIER CONDITIONS MOVING IN FOR MOST IF NOT ALL
OF THE HOLIDAY WEEKEND.
- AN APPROACHING COLD FRONT WILL BRING BREEZY TO WINDY CONDITIONS
AND INCREASED SHOWER AND THUNDERSTORM ACTIVITY MONDAY INTO
TUESDAY FOLLOWED BY A PERIOD OF COOLER TEMPERATURES, MOUNTAIN
SNOW, AND LOWER ELEVATION RAIN.
UPDATE
/ISSUED 517 AM MDT WED MAY 20 2026/
EARLY MORNING UPDATE HAS BEEN PUBLISHED, WITH THE ONLY CHANGE
BEING TO POPS WHICH WAS TO INCREASE CHANCES ACROSS NORTH CENTRAL
MONTANA WHERE RADAR RETURNS SHOW SHOWER ACTIVITY INCREASING.
OTHERWISE THE REMAINDER OF THE FORECAST REMAINS ON TRACK AND NO
OTHER CHANGES WERE NEEDED. - MOLDAN
DISCUSSION
/ISSUED 517 AM MDT WED MAY 20 2026/
- METEOROLOGICAL OVERVIEW:
SCATTERED SHOWERS OVER THE PLAINS HAVE CONTINUED WELL INTO THE
EVENING HOURS DESPITE THE LOSS OF DIURNAL HEATING. THE BIGGEST
CONCERN WITH THESE SHOWERS HAVE BEEN LOCALIZED GUSTY WINDS, WITH A
TOP WIND GUST OF 50 MPH REPORTED NEAR THE BIG SANDY AREA.
NORTHWESTERLY FLOW ALOFT WILL MAINTAIN THESE ISOLATED SHOWERS
THROUGH AROUND 1 OR 2 AM.
OTHERWISE, THE FOCUS SHIFTS TO A TROUGH AND ATTENDANT COLD FRONT
THAT WILL DIVE SOUTHEASTWARD AND INITIATE A ROUND OF SCATTERED TO
NUMEROUS SHOWERS AND EMBEDDED THUNDERSTORMS OVER NORTH-CENTRAL AND
CENTRAL MT LATER THIS MORNING AND AFTERNOON. COOLER SURFACE
TEMPERATURES WITH ML CAPE STRUGGLING TO REACH A COUPLE HUNDRED J/KG
WILL REDUCE THE OVERALL IMPACT FROM THIS ACTIVITY, THOUGH ISOLATED
INSTANCES GUSTY WINDS OVER 40 MPH, SMALL HAIL/GRAUPEL, AND
PRODUCTIVE DOWNPOURS WILL BE PRESENT WITH THE STRONGER CORES.
THE FORCING FROM THE TROUGH PUSHES THIS ACTIVITY INTO SOUTHWEST MT
TONIGHT INTO THURSDAY MORNING, WITH H700 TEMPERATURES FALLING TO
AROUND -5C AND SUPPORTING ACCUMULATING SNOW DOWN TO 6000 FT. SNOW
IMPACTS FOR THURSDAY MORNING LOOK TO THE BE GREATEST OVER THE HIGHER
TERRAIN OF MADISON AND GALLATIN COUNTIES AND WILL MOSTLY BE IN THE
FORM OF COLD AND WET OUTDOOR CONDITIONS.
TEMPERATURES WILL RUN A FEW DEGREES BELOW AVERAGE ON THURSDAY BEFORE
WEAK RIDGING ALOFT WARMS THINGS UP HEADING INTO THE WEEKEND.
WESTERLY FLOW ALOFT WILL BE STRONG ENOUGH TO MIX GUSTY WINDS TO THE
SURFACE SUNDAY AND MONDAY WHILE TEMPERATURES WARM WELL INTO THE 70S
AND 80S. THE NEXT TROUGH AND COLD FRONT WILL USHER IN A MORE
UNSTABLE SOUTHWESTERLY FLOW ALOFT EARLY NEXT WEEK FOR INCREASED
SHOWER AND THUNDERSTORM ACTIVITY AND MORE BREEZY TO WINDY
CONDITIONS, WINDIEST OVER SOUTHWEST MT. SOME STORMS MAY BECOME
STRONG TO SEVERE DEPENDING ON THE TROUGHS'S TIMING, STRENGTH AND
WHETHER IT UNDERGOES SHEARING OR SPLITTING.
NOTE THAT CLOSED LOWS SUCH AS THIS ONE OFTEN RUN A LITTLE SLOWER
THAN MODEL GUIDANCE. THIS MAY RESULT IN HOTTER AND DRIER WEATHER ON
MONDAY IF THE COLD FRONT RUNS LATE AND ARRIVES ON TUESDAY. THERE
WILL BE AT LEAST A PERIOD OF COOLER TEMPERATURES AND MORE WIDESPREAD
PRECIPITATION/MOUNTAIN SNOW ON THE BACKSIDE OF THIS SYSTEM HEADING
TOWARDS MID-WEEK, PARTICULARLY IF THE MAIN CIRCULATION STAYS CLOSE
ENOUGH TO EXERT A STRONGER INFLUENCE OVER THE NORTHERN ROCKIES. -
RCG
- FORECAST CONFIDENCE & SCENARIOS:
TODAY'S SHOWERS AND THUNDERSTORMS WILL TRANSITION TO AREAS OF RAIN
AND MOUNTAIN SNOW TONIGHT INTO THURSDAY MORNING...
SCATTERED TO NUMEROUS SHOWERS AND EMBEDDED THUNDERSTORMS DEVELOP
OVER CENTRAL AND NORTH-CENTRTAL MT BY THE LATE MORNING HOURS. THIS
ACTIVITY WILL BRING MORE PRODUCTIVE RAINFALL THAN THOSE OF THE LAST
COUPLE OF DAYS. ALTHOUGH SEVERE WEATHER IS NOT EXPECTED WITH THE
COOLER TEMPERATURES BEHIND THE FRONT, THERE MAY BE LOCALIZED
INSTANCES OF GUSTY WINDS OVER 40 MPH, SMALL HAIL OR GRAUPEL, AND
HEAVY DOWNPOURS OVER A QUARTER INCH WITH THE STRONGER CORES.
THIS ACTIVITY WILL EXPAND IN COVERAGE AND BECOME MORE STRATIFORM AS
IT SLIDES SOUTHWARD INTO SOUTHWEST MT TONIGHT INTO THURSDAY MORNING.
H700 TEMPERATURES FALLING TO AROUND -4 TO -7C COMBINED WITH
LINGERING CONVECTIVE PROCESSES MAY DROP SNOW LEVELS AS LOW AS 5000
FT AT TIMES, THOUGH ACCUMULATING SNOW LOOKS TO PRIMARILY BE CONFINED
TO AREAS ABOVE 6000 TO 6500 FT AND EVEN HIGHER. SNOWFALL AMOUNTS
LOOK TO BE MOST SIGNIFICANT OVER THE NORTHERN PORTIONS OF THE
MADISON/GALLATIN RANGES WHERE THE PROBABILITIES FOR 3 INCHES OF SNOW
OR MORE ARE CURRENTLY RUNNING ABOVE 70% TONIGHT THROUGH THURSDAY
MORNING. OTHER MOUNTAIN AREAS OF THE SOUTHWEST, ALONG THE
CONTINENTAL DIVIDE, AND OVER THE CENTRAL ISLAND RANGES WILL
GENERALLY SEE TRACE AMOUNTS UP TO AROUND AN INCH OR TWO ON THE HIGH
END. OVERALL, COLD AND WET OUTDOOR RECREATION WILL BE THE PRIMARY
IMPACT WITH THIS SYSTEM. TOTAL RAINFALL/LIQUID EQUIVALENT AMOUNTS
WILL GENERALLY RANGE BETWEEN A TENTH TO A QUARTER INCH FOR MOST
LOWER ELEVATION LOCATIONS WITH A SHARP DECREASING GRADIENT TO JUST A
FEW HUNDRETHS OR SO ALONG THE HI-LINE AND THE DRIER SOUTHWEST
VALLEYS ALONG AND WEST OF I15. OF COURSE RAINFALL AMOUNTS IN EXCESS
OF A HALF INCH WILL BE MORE COMMON FOR AREAS OVER AND NEAR HIGHER
TERRAIN. PRECIPITATION DIMINISHES AND BECOMES MORE SCATTERED IN
NATURE BY THURSDAY AFTERNOON. - RCG
AVIATION
20/18Z TAF PERIOD
A COLD FRONT WORKING THROUGH THE REGION WILL CONTINUE TO RESULT IN
WIND SHIFTS TO A MORE NORTHERLY DIRECTION THROUGH THE AFTERNOON AND
EVENING. NUMEROUS SHOWERS WILL DEVELOP ACROSS THE REGION THIS
AFTERNOON, WITH GREATEST COVERAGE SLOWLY SHIFTING SOUTHWARD INTO
THE EVENING BEFORE PRECIPITATION BECOMES MORE STRATIFORM IN NATURE
NEAR SUNSET. SCATTERED THUNDERSTORMS WILL BE AROUND THIS
AFTERNOON, BUT OVERALL COVERAGE WAS TOO LOW CONFIDENCE TO WARRANT
MENTION IN TAFS AT THIS TIME.
PRECIPITATION DIMINISHES FROM NORTH TO SOUTH LATE AFTERNOON THROUGH
THE NIGHT, BUT LOW CLOUDS WILL REMAIN INTO THURSDAY MORNING.
MOUNTAINS WILL BECOME INCREASINGLY OBSCURED AS LOW CLOUDS DEVELOP
THROUGH THE REMAINDER OF THE DAY. -AM
PRELIMINARY POINT TEMPS/POPS
GTF 56 36 60 37 / 90 60 20 0
CTB 54 33 62 37 / 70 20 10 0
HLN 63 36 61 37 / 60 90 20 0
BZN 61 33 56 31 / 30 90 50 0
WYS 56 28 51 23 / 20 90 40 0
DLN 61 33 58 32 / 20 80 30 0
HVR 61 34 65 35 / 50 10 20 0
LWT 56 33 55 33 / 80 60 40 0
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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