429
FXUS65 KTFX 201718
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1118 AM MDT MON JUL 20 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- A COLD FRONT WILL BRING NORTHERLY BREEZES, A BRIEF COOLDOWN,
AND MOSTLY DRY CONDITIONS TODAY.
- SUMMER HEAT BUILDS AGAIN AND DAILY ROUNDS OF SHOWERS AND
THUNDERSTORMS RETURN DURING THE MIDDLE AND END OF THE WORKWEEK
WITH SOME STORMS CONTAINING STRONG WIND GUSTS, HAIL, AND
TORRENTIAL DOWNPOURS CAPABLE OF LOCALIZED FLOODING.
- DRIER AND WINDIER CONDITIONS MOVE IN FOR NEXT WEEKEND AND
INCREASE FIRE WEATHER CONCERNS DEPENDING THE QUALITY OF
RAINFALL DURING THE MIDDLE OF THE WEEK.
DISCUSSION
/ISSUED 559 AM MDT MON JUL 20 2026/
- METEOROLOGICAL OVERVIEW:
A TROUGH RUNNING ALONG THE CANADIAN BORDER WILL SEND A CANADIAN
SURFACE FRONT THROUGH THE FORECAST AREA AND WILL BRING A NORTHERLY
WIND SHIFT AND A BRIEF COOLDOWN TONIGHT INTO MONDAY. MOISTURE
WITHIN THE WESTERLY FLOW ALOFT WILL MAINTAIN VARIABLE MIDDLE AND
HIGHER LEVEL CLOUDINESS AND PERHAPS A FEW SPOTTY LIGHT SHOWERS.
RIDGING ALOFT STRENGTHENS AND BRINGS A RETURN TO HOT CONDITIONS
HEADING TOWARDS THE MIDDLE OF THE WEEK. EMEBEDDED SHORTWAVES ALONG
THE RIDGE ARE EXPECTED TO INTERACT WITH THE MONSOONAL MOISTURE
LEADING TO DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS ACROSS THE
REGION, ESPECIALLY IN SOUTHWEST MONTANA. THE MAIN CONCERN,
ESPECIALLY FOR WEDNESDAY, WILL BE AN ELEVATED CHANCE FOR HEAVY
RAINFALL WHICH MAY LEAD TO LOCALIZED FLASH FLOODING.
TOWARDS THE WEEKEND, THE RIDGE AXIS MOVES EASTWARD ALLOWING FOR
DRIER AIR TO FILTER IN AND TEMPERATURES TO WARM ACROSS THE REGION.
THERE ARE HINTS IN THE MODELS THAT THIS RIDGE COULD BREAK DOWN
TOWARDS THE WEEKEND WHICH WOULD HELP MODERATE SOME OF THE
CURRENTLY FORECASTED HIGHS BUT IT WOULD COME AT THE PRICE OF
WINDIER CONDITIONS WHICH MAY STILL LEAD TO INCREASE FIRE WEATHER
CONCERNS. -THOR
- FORECAST CONFIDENCE & SCENARIOS:
THUNDERSTORM POTENTIAL WEDNESDAY THRU FRIDAY:
AFTERNOON SHOWERS AND THUNDERSTORMS ARE EXPECTED BOTH ON
WEDNESDAY AND THURSDAY. THE SEVERE POTENTIAL LOOKS A BIT MARGINAL
AT THE MOMENT AND WILL LARGELY HINGE ON THE TIMING OF THE TROUGH.
THERE IS A CONCERN THAT PWATS ARE RUNNING A BIT HIGH (>1.25"
ACROSS MUCH OF THE REGION) WHICH HAS BEEN FURTHER CONFIRMED BY THE
STRONG SIGNAL ON THE NAEFS. THE MAIN IMPACT FROM THIS WOULD BE
LOCALIZED FLASH FLOODING AS WELL AS THE STANDARD THUNDERSTORM
THREATS OF LIGHTNING, HAIL, AND STRONG WINDS.
TOWARDS FRIDAY, THE THREAT FOR THUNDERSTORMS CONTINUES BUT THE
MOISTURE CONTENT GOES DOWN QUITE A BIT COMPARED TO WEDNESDAY AND
THURSDAY. THIS OPENS THE DOOR FOR MORE OF A THREAT FOR DRIER
THUNDERSTORMS WHICH, COMBINED WITH HOTTER TEMPERATURES AND LOWER
MINIMUM RH VALUES, MAY INCREASE THE FIRE WEATHER CONCERNS FOR THAT
AFTERNOON. -THOR
GUSTY WINDS AND ELEVATED FIRE WEATHER CONDITIONS ON FRIDAY AND
SATURDAY...
CROSS BARRIER FLOW WILL BEGIN TO INCREASE THROUGH THE END OF THE
WORK WEEK AND INTO THE WEEKEND AS UPPER LEVEL RIDGING FLATTENS,
WITH H700 WINDS INCREASING TO BETWEEN 25-35KTS WHICH IS 1 TO
NEARLY 2 STANDARD DEVIATIONS ABOVE NORMAL FOR THE ROCKY MOUNTAIN
FRONT. NBM5.0 PROBABILITIES SUPPORT A 35-70% CHANCE FOR WIND GUSTS
TO EXCEED 34KTS ON BOTH DAYS, WITH A 10-30% CHANCE TO EXCEED
43KTS. THESE GUSTY WINDS COMBINED WITH HOT TEMPERATURES WILL LEAD
TO ELEVATED FIRE WEATHER CONDITIONS ALONG THE ENTIRE ROCKY
MOUNTAIN FRONT, MOST NOTABLY ACROSS FIRE WEATHER ZONES 112.
- MOLDAN
AVIATION
20/18Z TAF PERIOD
A COLD FRONT CONTINUES TO PUSH SOUTH ACROSS CENTRAL AND INTO
SOUTHWEST MONTANA LATE THIS MORNING, WITH THE FRONT PROVIDING SOME
IMPROVED VIS FROM THE HAZY CONDITIONS AS OF LATE. WITH THAT BEING
SAID REDUCED SLANTWISE VIS UPON ASCENT/DESCENT CAN BE EXPECTED
THROUGHOUT THE TAF PERIOD, ESPECIALLY ACROSS SOUTHWEST MONTANA
PRIOR TO THE AFOREMENTIONED FRONTS PASSAGE. VFR CONDITIONS WILL
LARGELY PREVAIL OVER THE NEXT 24 HOURS, BUT SOME PASSING SHOWERS
ACROSS SOUTHWEST MONTANA ALONG AND SOUTH OF THE I-90 COULD MAY
TEMPORARY REDUCE CIGS TO LOW-VFR AND LEAD TO MOUNTAIN OBSCURATION.
- MOLDAN
PRELIMINARY POINT TEMPS/POPS
GTF 84 61 86 60 / 10 10 0 0
CTB 80 57 81 57 / 0 10 0 0
HLN 87 61 88 63 / 10 0 20 10
BZN 90 58 89 59 / 0 0 10 10
WYS 90 50 87 52 / 10 10 50 40
DLN 87 55 84 57 / 10 10 20 20
HVR 86 58 86 60 / 0 0 0 10
LWT 82 55 82 55 / 0 0 10 0
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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