438
FXUS65 KTFX 180011
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
ISSUED BY NATIONAL WEATHER SERVICE MISSOULA MT
611 PM MDT FRI JUL 17 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL MOVE IN A
SOUTHWEST TO NORTHEAST FASHION LATER THIS AFTERNOON THROUGH THE
EARLY OVERNIGHT HOURS.
- THUNDERSTORM HAZARDS WILL INCLUDE STRONG, GUSTY WINDS, HAIL,
AND TORRENTIAL DOWNPOURS CAPABLE OF LOCALIZED FLOODING.
- WARMER TEMPERATURES AND SLIGHTLY DRIER CONDITIONS MOVE IN FOR
THE WEEKEND, ALTHOUGH THERE WILL STILL BE WIDELY SCATTERED
SHOWER AND THUNDERSTORM ACTIVITY.
DISCUSSION
/ISSUED ISSUED BY NATIONAL WEATHER SERVICE MISSOULA MT/
A SHORTWAVE EMBEDDED WITHIN A SOUTHWESTERLY FLOW ALOFT WILL
INTERACT WITH MONSOON MOISTURE AND AN UNSTABLE PROFILE FOR THE
DEVELOPMENT OF CLUSTERS TO BROKEN LINES OF THUNDERSTORMS MOVING
IN A SOUTHWEST TO NORTHEAST FASHION THIS AFTERNOON INTO TONIGHT.
THE MOST ROBUST CAPE OVER 1,500 J/KG WILL BE SLIGHTLY FARTHER EAST
OF THE 30 +KT BULK SHEAR AREA, BUT THERE WILL CERTAINLY ENOUGH
OVERLAP FOR AT LEAST SCATTERED STRONG TO SEVERE THUNDERSTORMS.
ADDITIONALLY, ANOMALOUSLY HIGH PWATS, GENERALLY BETWEEN AN INCH
AND AN INCH AND A HALF, WILL BE CAPABLE OF PRODUCING BRIEF PERIODS
WITH RAINFALL RATES IN THE HALF TO ONE INCH RANGE AND EVEN HIGHER
IN THE STRONGER CORES. A FLASH FLOOD WATCH WAS SENT OUT AGAIN FOR
THE HORSE GULCH BURN SCAR FOR THIS AFTERNOON AND EVENING. URBAN
AREAS THAT RECEIVE THESE HEAVIER RAINFALL RATES WILL ALSO BE
SUSCEPTIBLE TO LOCALIZED FLOODING, ESPECIALLY OVER CENTRAL AND
NORTH-CENTRAL MT, THOUGH CONFIDENCE WAS NOT QUITE HIGH ENOUGH FOR
ADDITIONAL FLOOD PRODUCTS AT THIS TIME.
SLIGHTLY DRIER AIR MOVES IN FOR THE WEEKEND AS THE FLOW ALOFT
BECOMES MORE WESTERLY AND PUSHES THE RICHEST MOISTURE OFF TO THE
EAST. THERE WILL BE ANOTHER SHORTWAVE THAT PASSES THROUGH AGAIN
ON SATURDAY, BUT IT WILL HAVE LESS CAPE AND MOISTURE TO INTERACT
WITH. THE WIDELY SCATTERED SHOWERS AND STORMS THAT DO DEVELOP
WILL CONTAIN GUSTY, TO LOCALLY STRONG WINDS WITH RH'S DROPPING
BACK DOWN TO THE TEENS SATURDAY AFTERNOON. SIMILAR CONDITIONS
PREVAIL FOR SUNDAY, THOUGH STORM COVERAGE MAY BE EVEN LESS THAN
SATURDAY.
ASIDE FROM A BRIEF COOLDOWN ON MONDAY THANKS TO A PASSING COLD
FRONT, TEMPERATURES WILL BE ON THE RISE THANKS TO HIGH PRESSURE
ALOFT BUILDING OVER THE GREAT BASIN AREA. THE NORTHERN ROCKIES
WILL STILL BE FAR ENOUGH NORTH FOR SHORTWAVES AND MOISTURE TO
COMPROMISE THE HIGH AND BRING AT LEAST WIDELY SCATTERED SHOWER AND
THUNDERSTORM ACTIVITY. - RCG
AVIATION
18/00Z TAF PERIOD
SHOWERS REMAIN IN THE AREA WITH THUNDERSTORMS LINGERING OVER THE
LEWIS RANGE AND PUSHING EASTWARD. EASTERLY WINDS AT THE SURFACE
FROM KGTF EASTWARD THIS EVENING WILL SHIFT TO WEST SOUTHWEST AS
THE FRONTAL BOUNDARY MOVES THROUGH. EXPECT SHOWERS AND
THUNDERSTORMS TO PUSH TO THE NORTH NORTHEAST. SHOWERS AND
THUNDERSTORMS WILL BE THE MOST WIDESPREAD UNTIL AROUND 06Z SUN
WHEN HIGH RESOLUTION MODELS SHOW THEM BECOMING MORE SCATTERED AND
DISSIPATING TO THE NORTH. RADAR SHOWS SOME GUSTY OUTFLOW
BOUNDARIES STEMMING FROM THE BULK OF THE STORMS WHICH MAY IMPACT
AREAS AROUND KGTF AND KHLN THROUGH 02Z SAT. TEMPORARY STRONG
NORTHWEST WINDS POSSIBLE WITH THESE STORMS. OVERNIGHT, SKIES WILL
CLEAR SLOWLY WHICH WILL INCREASE RADIATIONAL COOLING. AREAS THAT
RECEIVED RAIN AND THEN CLEAR WILL SEE SOME PATCHY FOG, BUT
WIDESPREAD DENSE FOG IS LESS OF A CONCERN THIS EVENING. THERE IS
AROUND A 10-15% CHANCE OF IFR CIGS AROUND KCTB FROM 08Z-14Z SAT,
WHICH IS ONE AREA THAT MODELS ARE HIGHLIGHTING. A RETURN OF
SHOWERY CONDITIONS IS POSSIBLE AFTER 20Z SAT, BUT NOT EXPECTED TO
BE AS WIDESPREAD AS THIS EVENING. -MUESSLE
PRELIMINARY POINT TEMPS/POPS
GTF 95 61 95 61 / 20 90 10 20
CTB 90 60 91 57 / 30 70 10 0
HLN 94 62 93 61 / 50 70 30 30
BZN 93 57 92 57 / 30 70 20 20
WYS 85 48 87 48 / 50 80 20 10
DLN 88 55 89 55 / 70 70 20 10
HVR 98 64 97 63 / 0 70 20 20
LWT 90 56 89 57 / 10 60 20 20
TFX WATCHES/WARNINGS/ADVISORIES
FLASH FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR BIG BELT,
BRIDGER AND CASTLE MOUNTAINS.
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