640
FXUS65 KTFX 230044
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
644 PM MDT SAT AUG 22 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON CAPABLE OF
BRIEFLY HEAVY RAINFALL AND GUSTY WINDS.
- ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORMS SUNDAY AFTERNOON AND
EARLY EVENING AHEAD OF A COLD FRONT BRINGING DRIER AND BREEZY
CONDITIONS.
- COOLER IN MOST AREAS MONDAY BEFORE TEMPERATURES TREND CLOSER
TO, IF NOT ABOVE AVERAGE BY MID-WEEK. A FEW SHOWERS AND
THUNDERSTORMS WILL BE AROUND MOST DAYS NEXT WEEK, PRIMARILY
ACROSS SOUTHWEST MT.
DISCUSSION
/ISSUED 1243 PM MDT SAT AUG 22 2026/
- METEOROLOGICAL OVERVIEW:
HIGH AMPLITUDE UPPER LEVEL RIDGING IS SLIPPING EAST OF THE REGION
THIS AFTERNOON AHEAD OF AN UPPER LEVEL TROUGH MOVING ONSHORE ACROSS
THE PACIFIC NW. RESULTING FLOW ALOFT IS SOUTHWESTERLY, WHICH IN
COMBINATION WITH AN EMBEDDED WAVE LIFTING NORTHEASTWARD FROM THE BASE
OF THE UPPER TROUGH WILL RESULT IN QUITE A FEW SHOWERS AND
THUNDERSTORMS TODAY. THIS ACTIVITY LOOKS TO DEVELOP ACROSS SW MT
INITIALLY, SPREADING NORTHEASTWARD INTO CENTRAL MT AND VICINITY WITH
TIME. PWATS ARE ELEVATED, SIGNALING THE RISK FOR SOME HEAVY
RAINFALL IN THE STRONGEST THUNDERSTORMS. MODEST INVERTED-V PROFILES
SUGGEST STRONG WIND GUSTS WILL BE THE PRIMARY CONCERN FROM A SEVERE
WEATHER PERSPECTIVE TODAY, SHOULD THUNDERSTORMS BE ABLE TO CONGEAL
INTO AT LEAST A BROKEN LINE. LOOKING TOWARD TONIGHT FORCING
INCREASES, ESPECIALLY WEST OF THE CONTINENTAL DIVIDE, AS THE CORE OF
THE UPPER TROUGH APPROACHES THE NORTHERN ROCKIES. THERE LOOKS TO BE
QUITE A BIT OF SHOWERS OR THUNDERSTORMS THAT DEVELOP WEST OF THE
CONTINENTAL DIVIDE AS A RESULT, WITH A FEW OF THESE LEAKING EAST OF
THE DIVIDE THROUGH THE OVERNIGHT.
FORCING AND FLOW ALOFT INCREASES FURTHER FOR SUNDAY AS THE UPPER
LEVEL SYSTEM MOVES OVERHEAD AND EVENTUALLY EAST OF THE REGION SUNDAY
NIGHT. A COLD FRONT MOVES THROUGH ASSOCIATED WITH THIS SYSTEM,
BRINGING COOLER TEMPERATURES, MUCH DRIER AIR, AND GUSTY WINDS. AHEAD
OF THIS FRONT THERE LOOKS TO BE AMPLE INSTABILITY, FORCING, AND
MARGINAL KINEMATICS TO RESULT IN AT LEAST A FEW LOOSELY ORGANIZED
THUNDERSTORMS SUNDAY AFTERNOON. BOTH STRONG WIND GUSTS AND LARGE
HAIL WILL BE A CONCERN IN THE MOST ROBUST THUNDERSTORMS. THIS
ACTIVITY LARGELY LOOKS TO DEVELOP EAST OF I-15 AND CONTINUE EASTWARD
SUNDAY.
HEADING INTO NEXT WEEK THE TREND IS FOR WEAK RIDGING NOW ACROSS THE
NW CONUS, WHICH WILL KEEP A SLIGHTLY ANTICYCLONIC FLOW ALOFT IN
PLACE. THIS LOOKS TO INHIBIT SHOWERS AND THUNDERSTORMS FOR A DAY OR
TWO IN MOST AREAS, THOUGH MONSOONAL MOISTURE STUCK IN THE SOUTHERN
PERIPHERY OF THE RIDGE WILL STILL RESULT IN A FEW SHOWERS AND
THUNDERSTORMS IN SW MT NEAR THE IDAHO BORDER. THE RIDGE AXIS SLOWLY
SLIPS EAST THROUGH THE WEEK, WITH FLOW ALOFT BECOMING SLIGHTLY MORE
CYCLONIC EACH DAY AS ANOTHER PACIFIC TROUGH BEGINS TO APPROACH THE
PACIFIC NW. SHOWERS AND THUNDERSTORMS GRADUALLY INCREASE IN COVERAGE
MID-WEEK ONWARDS, FOCUSED MOSTLY IN THE AFTERNOON AND EVENING. -AM
- FORECAST CONFIDENCE & SCENARIOS:
THUNDERSTORMS TODAY:
CLEARING IS BEING NOTED ON LATEST SATELLITE IMAGERY ACROSS MUCH OF
ID AND INTO SW MT. THIS WILL RESULT IN AT LEAST WEAK INSTABILITY
THROUGH THE REMAINDER OF THE AFTERNOON AND EVENING. THE DEGREE TO
WHICH THE AREA DESTABILIZES WILL PLAY A LARGE ROLE IN HOW WIDESPREAD
THE RISK WILL BE FOR STRONG WIND GUSTS. LONGER PERIODS OF SUNNY
SKIES WOULD INCREASE THIS RISK OVER SHORTER PERIODS OF SUNSHINE.
PRECIPITABLE WATER (PWAT) VALUES NEAR AND IN EXCESS OF AN INCH WILL
YIELD AT LEAST A LOCALIZED RISK FOR BRIEFLY HEAVY RAINFALL TODAY IN
THE STRONGEST THUNDERSTORMS. SHOULD A STRONG THUNDERSTORM MOVE
ACROSS AN URBAN AREA OR A BURN SCAR, EXCESSIVE RAINFALL LEADING TO
FLASH FLOODING WILL BE A CONCERN. OVERALL, THE RISK FOR THIS ACROSS
ANY SPECIFIC AREA IS TOO LOW TO WARRANT ANY FLASH FLOOD WATCHES.
ALTHOUGH THIS IS THE CASE, THOSE IN URBAN AREAS AND NEAR BURN SCARS
SHOULD BE AWARE OF THIS RISK TODAY.
THUNDERSTORMS SUNDAY:
STRONGER FLOW ALOFT ARRIVES WITH HE CORE OF THE UPPER LEVEL
DISTURBANCE AHEAD OF THE COLD FRONT SUNDAY. LINGERING MOISTURE AHEAD
OF THE COLD FRONT LOOKS TO COMBINE WITH DAYTIME DESTABILIZATION TO
RESULT IN MODEST INSTABILITY BY THE EARLY AFTERNOON ACROSS MANY
AREAS. FORCING DOES NOT LOOK TO BE LACKING SUNDAY, WITH THE PRIMARY
LIMITING FACTOR ON ORGANIZED THUNDERSTORMS BEING SLIGHTLY SUB-
OPTIMAL SHEAR (CLOSER TO 30KTS THAN 40KTS). THAT SAID, AT LEAST
LOOSELY ORGANIZED THUNDERSTORMS LOOK TO DEVELOP SUNDAY, MAINLY EAST
OF I-15, WHICH WILL BE CAPABLE OF STRONG WIND GUSTS AND LARGE HAIL.
SHOULD SHEAR TREND MUCH HIGHER, CONCERN WOULD INCREASE FOR LONGER
LASTING, MORE ORGANIZED SEVERE THUNDERSTORMS.
MID TO LATE WEEK:
GUIDANCE HAS BEEN INCONSISTENT WITH RESPECT TO THE PROGRESSION OF
PACIFIC TROUGHING MOVING IN MID TO LATE WEEK. THERE IS A ROUGHLY
50/50 SPLIT IN CLUSTER GUIDANCE MEMBERS FOR ABOVE AVERAGE HEIGHTS
(WARMER TEMPS) VS BELOW AVERAGE HEIGHTS (COOLER TEMPS) ACROSS THE
REGION BY THE END OF THE WEEK. -AM
AVIATION
23/00Z TAF PERIOD
SHRA AND TSRA WILL CONTINUE TO LIFT TOWARDS THE NORTHEAST THIS
EVENING AS MONSOONAL MOISTURE WORKS INTO THE AREA. WHILE ANY SHRA
OR TSRA COULD PRODUCE SOME SMALL HAIL OR WIND GUSTS TO 40KTS WILL
BE POSSIBLE. SHRA AND TSRA SHOULD DISSIPATE AFTER 6Z FOR THE
OVERNIGHT. A COLD FRONT WILL PUSH THROUGH THE AREA ON SUNDAY,
BRINGING INCREASED WESTERLY WINDS AND ANOTHER ROUND OF TSRA EAST
OF INTERSTATE 15, AND ANY OF THESE STORMS COULD PRODUCE LARGE HAIL
AND/OR WIND GUSTS IN EXCESS OF 55KTS. LUDWIG
FOR KGTF: THUNDERSTORMS ARE EXPECTED TO BEGIN MOVING OVER KGTF AS
EARLY AS 03Z, AND WILL BE CAPABLE OF PRODUCING GUSTY, ERRATIC
WINDS GREATER THAN 40 KT, FREQUENT LIGHTNING, BRIEF, HEAVY
DOWNPOURS AND HAIL. THUNDERSTORMS ARE EXPECTED TO EXIT THE AREA
AROUND 06Z. OUTSIDE OF ANY GUSTY, ERRATIC WINDS A THUNDERSTORM MAY
PRODUCE, THE CHANCE OF A CROSS-WIND GREATER THAN 15 KTS IS LESS
THAN 10% DUE TO A SOUTHWESTERLY DIRECTION. WHILE NOT EXPLICITLY
MENTIONED IN THE TAF, WESTERLY WINDS TO INCREASE AROUND 21Z, WHICH
WILL BRING NEAR CERTAIN CROSSWINDS OVER 15KTS THROUGH 2Z MONDAY.
LUDWIG
-DZOMBA
FIRE WEATHER
ALTHOUGH PRECIPITABLE WATER IS ABOVE AVERAGE TODAY, A FEW
LIGHTNING IGNITIONS CANNOT BE RULED OUT IN LOCALLY DRY AREAS,
PARTICULARLY IN TERRAIN.
THE MOST CONCERNING FIRE WEATHER DAY WILL BE ON SUNDAY WHEN A
SURFACE FRONT BRINGS GUSTY WESTERLY WINDS AMID CONTINUED VERY WARM
AND DRY CONDITIONS. THE TIMING OF THIS FRONT WILL ULTIMATELY
DETERMINE HOW LONG THE DRY AND WINDY CONDITIONS PERSIST. THE
LATEST NBM PROBABILISTIC GUIDANCE CONTINUES TO HIGHLIGHT LARGE
AREAS OF NORTH- CENTRAL AND PORTIONS OF SOUTHWEST MONTANA WITH
OVER A 70% CHANCE FOR WIND GUSTS OVER 30 MPH. ALTHOUGH THE FUELS
AREN'T QUITE AS DRY AS THEY WERE IN EARLIER IN THE MONTH, ELEVATED
FIRE CONDITIONS WILL BE PRESENT AND THE WIND MAY BE ENOUGH TO
IGNITE ANY LIGHTNING CAUSED HOLD OVER FIRES FROM FRIDAY AND
SATURDAY'S STORMS. IN ADDITION TO THE WINDS, THERE WILL BE MORE
WIDELY SCATTERED SHOWERS AND THUNDERSTORMS, SOME WITH STRONG,
ERRATIC WIND GUSTS. -AM/RCG
HYDROLOGY
THE COMBINATION OF INCREASED MONSOONAL MOISTURE ALOFT AND LOWER
LEVEL MOISTURE MOVING IN FROM THE EAST TODAY WILL RESULT IN A 10%
CHANCE FOR LOCALIZED HEAVY THUNDERSTORM RAINS PRODUCING FLASH
FLOODING OVER AND NEAR BURN SCARS, URBAN AREAS, AND OTHER NORMALLY
FLOOD PRONE LOCATIONS. WHILE THIS ACTIVITY WILL BE MONITORED FOR THE
AFOREMENTIONED FLASH FLOODING, A FLASH FLOOD WATCH WILL ISSUED WITH
THIS FORECAST PACKAGE PER THE MORE SCATTERED NATURE OF HIGHER
RAINFALL RATES AND PROGRESSIVE STORM MOTION. THE MOISTURE PROFILE
BEGINS THIN ON SUNDAY, WHICH WILL REDUCE THE THREAT FOR EXCESSIVE
RAINFALL THROUGH EARLY NEXT WEEK. - RCG
PRELIMINARY POINT TEMPS/POPS
GTF 62 89 54 81 / 20 20 0 0
CTB 58 81 50 77 / 20 20 0 0
HLN 57 87 50 85 / 60 20 0 0
BZN 54 86 49 85 / 50 40 20 0
WYS 46 78 40 79 / 50 30 20 0
DLN 52 85 47 84 / 40 20 0 0
HVR 62 93 56 82 / 10 40 20 0
LWT 60 89 53 79 / 20 50 30 0
TFX WATCHES/WARNINGS/ADVISORIES
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