622
FXUS65 KTFX 230518
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1118 PM MDT WED JUL 22 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- SHOWERS AND THUNDERSTORMS ARE EXPECTED EACH AFTERNOON THROUGH
SATURDAY.
- ISOLATED THUNDERSTORMS IN SOUTHWESTERN MONTANA HAVE THE
POTENTIAL TO PRODUCE LOCALIZED FLASH FLOODING THIS
AFTERNOON/EVENING.
- TEMPERATURES WILL GRADUALLY WARM UP THROUGH SATURDAY AND STAY
WARM THROUGH EARLY NEXT WEEK.
DISCUSSION
/ISSUED 359 PM MDT WED JUL 22 2026/
- METEOROLOGICAL OVERVIEW:
THIS AFTERNOON THERE IS AN UPPER-LEVEL RIDGE OVER NORTH-CENTRAL,
CENTRAL, AND SOUTHWESTERN MONTANA. AN UPPER-LEVEL SHORTWAVE WILL
MOVE THROUGH THE UPPER-LEVEL FLOW AND BRING SHOWER AND THUNDERSTORMS
PRIMARILY SOUTH OF I-90 WEDNESDAY AFTERNOON AND EVENING. DUE TO AN
INCREASE IN MONSOONAL MOISTURE THE THUNDERSTORMS WILL PRODUCE HEAVY
RAINFALL. THERE IS A LACK OF STEERING FLOW SO THE THUNDERSTORMS WILL
ALSO BE SLOW MOVING. THIS HAS THE POTENTIAL TO LEAD TO SOME
LOCALIZED FLOODING. SEE THE HYDROLOGY SECTION FOR DETAILS. ON
WEDNESDAY ISOLATED AND SHOWERS HAVE THE POTENTIAL TO MAKE IT FURTHER
NORTH BUT STAY SOUTH OF AN AUGUSTA TO GREAT FALLS TO LEWISTOWN LINE.
ON THURSDAY THE UPPER-LEVEL RIDGE REMAINS OVER NORTH-CENTRAL,
CENTRAL, AND SOUTHWESTERN MONTANA. ANOTHER UPPER-LEVEL SHORTWAVE
MOVES THROUGH THE FLOW. THIS WILL BRING ANOTHER DAY OF HOT WEATHER
WITH ISOLATED SHOWERS AND THUNDERSTORMS. ON FRIDAY THE UPPER-LEVEL
RIDGE REMAINS OVER NORTH-CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA.
THIS WILL INCREASE TEMPERATURES TO WELL-ABOVE SEASONAL AVERAGES.
WINDS WILL INCREASE DUE TO LOW-LEVEL AND MID-LEVEL WINDS INCREASING.
THIS WILL DRY OUT THE AREA AND BRING ELEVATED FIRE WEATHER
CONDITIONS TO NORTH-CENTRAL MONTANA. SEE THE FIRE WEATHER SECTION
FOR DETAILS. ON SATURDAY THE UPPER-LEVEL RIDGE REMAINS OVER NORTH-
CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA. IT WILL BE THE HOTTEST
OUT OF THIS FORECAST PERIOD ACROSS THE AREA ON SATURDAY WITH WELL-
ABOVE SEASONAL AVERAGE TEMPERATURES. ON SUNDAY A WEAK UPPER-LEVEL
TROUGH MOVES THROUGH WHICH WILL SLIGHTLY COOL DOWN TEMPERATURES AND
BRING SOME WINDY CONDITIONS TO THE AREA. ON MONDAY AND TUESDAY THE
UPPER-LEVEL RIDGE REMAINS OVER NORTH-CENTRAL, CENTRAL, AND
SOUTHWESTERN MONTANA. THIS WILL ALLOW WARM AND DRY CONDITIONS TO
PERSIST. -IG
- FORECAST CONFIDENCE & SCENARIOS:
ON WEDNESDAY THERE IS A 40 - 60% CHANCE FOR THUNDERSTORMS ACROSS
SOUTHWESTERN MONTANA. ON WEDNESDAY THERE IS A 15 - 35% CHANCE FOR
THUNDERSTORMS ACROSS MOST OF NORTH-CENTRAL AND CENTRAL MONTANA. ON
THURSDAY THERE IS A 20 - 40% CHANCE FOR THUNDERSTORMS ACROSS NORTH-
CENTRAL, CENTRAL, AND SOUTHWESTERN MONTANA. ON FRIDAY THERE IS A 25 -
30% CHANCE FOR THUNDERSTORMS ACROSS SOUTHWESTERN MONTANA. ON
SATURDAY THERE IS A 25 - 50% CHANCE FOR THUNDERSTORMS ACROSS
SOUTHWESTERN MONTANA.
ON FRIDAY THERE IS A 20 - 60% CHANCE FOR HIGH TEMPERATURES OF 100
DEGREES OR GREATER ACROSS MOST OF NORTH-CENTRAL MONTANA. ON SATURDAY
THERE IS GREATER THAN A 60% CHANCE FOR HIGH TEMPERATURES OF 100
DEGREES OR GREATER ACROSS NORTH-CENTRAL MONTANA. ON SATURDAY ACROSS
PORTIONS OF FERGUS, HILL, AND BLAINE COUNTIES THERE IS A GREATER
THAN A 70% CHANCE FOR HIGH TEMPERATURES GREATER THAN 105 DEGREES.
THIS COMBINED WITH LOW TEMPERATURES IN THE UPPER 60S TO LOW 70S
ACROSS PORTIONS OF FERGUS, HILL, AND BLAINE COUNTY ON SATURDAY AND
SUNDAY MORNING LED TO AN EXCESSIVE HEAT WATCH BEING ISSUED FOR THOSE
AREAS FROM FRIDAY AFTERNOON THROUGH SUNDAY EVENING. ON SATURDAY
THERE IS A 40 - 60% CHANCE FOR HIGH TEMPERATURES OF 100 DEGREES OR
GREATER FROM THE HELENA VALLEY THROUGH THE CANYON FERRY AREA TO
TOWNSEND TO THE THREE FORKS TO BOZEMAN AREA. -IG
AVIATION
23/06Z TAF PERIOD
LINGERING SHOWERS ACROSS CENTRAL AND SOUTHWEST MONTANA WILL
DIMINISH BY AROUND 23/09Z. IMPACTS ARE GENERALLY NOT EXPECTED AT
ANY OF THE TERMINALS OUTSIDE OF KWYS WHICH WILL HAVE CONTINUE TO
RECEIVE SOME LIGHT RAIN BEFORE TAPERING OFF.
THERE IS A HIGH CHANCE FOR FOG DEVELOPING AT KWYS OVERNIGHT WITH
SLIGHTLY LESSER CONFIDENCE IN KEKS THAT WILL DEPEND ON WHETHER THE
CLOUDS ARE ABLE TO FULLY CLEAR OUT. THE FOG WILL START TO LIFT
AFTER 23/15Z AS THE NEXT SHORTWAVE TROUGH STARTS TO MOVE INTO THE
REGION BRINGING ANOTHER MID-LEVEL CLOUD DECK AND A CHANCE FOR
PRECIPITATION.
ANOTHER ROUND OF ISOLATED TO SCATTERED THUNDERSTORMS ARE POSSIBLE
THURSDAY AFTERNOON ALTHOUGH CONFIDENCE IN IMPACTS TO ANY ONE
TERMINAL REMAINS RATHER LOW. THE HIGHEST CONFIDENCE FOR IMPACT
WILL BE ACROSS SOUTHWEST MONTANA INCLUDING KBZN, KEKS, AND KWYS
WHICH ALL HAVE PROB30 GROUPS FOR THE CONVECTIVE TIMEFRAME. FOR ALL
OTHER TERMINALS, CONFIDENCE WAS LESS THAN 10% AND THUS TOO LOW TO
INCLUDE IN THE TAF AT THIS TIME. THE MAIN CONCERNS FOR ANY
THUNDERSTORM THAT DEVELOPS WILL BE MOUNTAIN OBSCURATION,
LIGHTNING, AND GUSTY WINDS.
WILDFIRE SMOKE WILL CONTINUE TO IMPACT SLANTWISE VISIBILITY
THROUGH THE PERIOD. THERE ARE SOME HINTS IN THE HI-RES MODELS THAT
CONDITIONS MIGHT WORSEN THURSDAY AFTERNOON/EVENING TOWARDS THE END
OF THE TAF PERIOD BUT THERE IS STILL DISAGREEMENT IN THE MODELS AS
TO HOW MUCH SURFACE VISIBILITY AND CEILINGS WILL BE IMPACTED.
-THOR
FIRE WEATHER
HOT, DRY, AND WINDY CONDITIONS ARE EXPECTED THROUGH THE WEEKEND
WHICH WILL LEAD TO ELEVATED FIRE WEATHER CONCERNS ACROSS MUCH OF THE
REGION. THE MAIN LIMITING FACTOR WILL BE THE POTENTIAL FOR WETTER
SHOWERS AND THUNDERSTORMS BOTH THIS AFTERNOON/EVENING AND
THURSDAY.
THERE IS A CONCERN THAT MOST OF THE WETTER SHOWERS WILL NOT MAKE IT
NORTH OF A LINE BETWEEN HELENA AND WHITE SULPHUR SPRINGS WHICH WOULD
PUT NORTH-CENTRAL MONTANA AT A MUCH HIGHER RISK FOR ELEVATED FIRE
WEATHER CONDITIONS THROUGH THE WEEKEND. ADDITIONALLY, IF THE WETTER
STORMS ON WEDNESDAY AND THURSDAY ARE UNABLE TO MATERIALIZE, OR THEY
ARE A LOT MORE ISOLATED THAN WHAT IS CURRENTLY EXPECTED, THEN THAT
COULD ALSO ELEVATE FIRE WEATHER CONCERNS FOR CENTRAL AND SOUTHWEST
MONTANA.
AS IT STANDS THERE IS A GENERALIZED CONCERN FOR ELEVATED FIRE
WEATHER CONDITIONS STARTING ON FRIDAY BUT MUCH OF THE THREAT WILL
NOT BE DETERMINED UNTIL THURSDAY EVENING WHEN IT BECOMES CLEAR WHICH
LOCATIONS WERE ABLE TO PICK UP SOME WETTING RAIN AHEAD OF THE
INCOMING HOT, DRY, AND WINDY CONDITIONS. -IG/THOR
HYDROLOGY
TODAY THE WEATHER PREDICTION CENTER (WPC) HAS ISSUED A SLIGHT
RISK (15% CHANCE FOR FLASH FLOODING WITHIN 25 MILES OF A POINT)
FOR FLASH FLOODING ACROSS MOST OF SOUTHWESTERN MONTANA. BETWEEN
THE I-90 CORRIDOR AND A LINE BETWEEN AUGUSTA TO GREAT FALLS TO
LEWISTOWN WPC HAS ISSUED A MARGINAL RISK (5% CHANCE FOR FLASH
FLOODING WITHIN 25 MILES OF A POINT)FOR FLASH FLOODING TODAY. IN
ADDITION ACROSS THE MOUNTAINS OF SOUTHWESTERN MONTANA THERE IS A
50 - 70% CHANCE FOR RAINFALL RATES IN EXCESS OF ONE HALF INCH PER
HOUR TODAY. IN ADDITION THERE IS AROUND A 50% CHANCE FOR RAINFALL
RATES IN EXCESS OF THREE QUARTER OF AN INCH PER HOUR ACROSS THE
MOUNTAINS OF SOUTHWESTERN MONTANA TODAY. THERE IS A 20 - 40%
CHANCE FOR AN INCH OF RAIN OR GREATER ACROSS THE MOUNTAINS OF
SOUTHWESTERN MONTANA TODAY. AS A RESULT A FLASH FLOOD WATCH
REMAINS IN EFFECT FOR THE MOUNTAINS SOUTH OF I-90 THROUGH MIDNIGHT
TONIGHT. -IG
PRELIMINARY POINT TEMPS/POPS
GTF 62 96 64 99 / 10 20 20 10
CTB 58 93 61 92 / 0 20 20 0
HLN 62 94 63 98 / 20 20 20 10
BZN 58 90 60 97 / 60 30 20 0
WYS 50 80 50 87 / 70 50 30 0
DLN 55 87 57 93 / 60 20 20 0
HVR 60 99 65 102 / 0 20 20 0
LWT 57 90 61 95 / 10 20 20 10
TFX WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WATCH FROM FRIDAY AFTERNOON THROUGH SUNDAY EVENING
FOR BEARS PAW MOUNTAINS AND SOUTHERN BLAINE-FERGUS COUNTY BELOW
4500FT-HILL COUNTY-NORTHERN BLAINE COUNTY.
FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR GALLATIN AND MADISON
COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS-NORTHWEST BEAVERHEAD
COUNTY-RUBY MOUNTAINS AND SOUTHERN BEAVERHEAD MOUNTAINS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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