906
FXUS65 KTFX 062018
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
218 PM MDT SUN SEP 6 2026
KEY MESSAGES
- SCATTERED TO WIDESPREAD SHOWERS AND THUNDERSTORMS DEVELOP THIS
EVENING ALONG AND NORTH OF HIGHWAY 200, WITH ISOLATED LARGE
HAIL POSSIBLE.
- PERIODS OF WIDESPREAD RAINFALL MONDAY AND TUESDAY, WITH PERIODS
OF MODERATE TO HEAVY RAINFALL ACROSS ROCKY MOUNTAIN FRONT AND
SWEET GRASS HILLS.
- DRIER CONDITIONS WEDNESDAY AND THURSDAY.
- ANOTHER ROUND OF PRECIPITATION FOR NEXT WEEKEND.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
A PASSING SHORTWAVE WILL DEVELOP SCATTERED TO WIDESPREAD SHOWERS
AND THUNDERSTORMS MAINLY NORTH OF THE MT HIGHWAY 200 CORRIDOR
LATE THIS AFTERNOON THROUGH THE EVENING. THE INCOMING TROUGH
BRINGS A GOOD SYNOPTIC ENVIRONMENT FOR THE THREAT OF A FEW SEVERE
THUNDERSTORMS ACROSS NORTH-CENTRAL MT, WITH HAIL AS THE PRIMARY
THREAT. HIGH PWATS NEARING AN INCH THIS AFTERNOON WILL BRING AN
ISOLATED FLASH FLOOD THREAT TO WHERE SOILS HAVE BEEN SATURATED
FROM RECENT PRECIPITATION. BEHIND THIS SYSTEM, A VERTICALLY
STACKED LOW PRESSURE SYSTEM WILL MOVE INTO THE AREA MONDAY MORNING
THROUGH TUESDAY MORNING, BRINGING PERIODS OF WIDESPREAD RAIN FOR
MAINLY NORTH-CENTRAL MT. BASED ON THE CURRENT LOW TRACK, PERIODS
OF MODERATE TO HEAVY RAINFALL WILL BE POSSIBLE FOR THE ROCKY
MOUNTAIN FRONT AND US HIGHWAY 2 CORRIDOR. THIS SYSTEM WILL ALSO
BRING IN COOLER FALL-LIKE TEMPERATURES MONDAY AND TUESDAY. MONDAY
NIGHT INTO TUESDAY MORNING, LOW TO MID LEVEL WINDS INCREASES
AROUND THE CLOSED LOW. THIS RESULTS IN BREEZY TO WINDY CONDITIONS
ACROSS NORTH-CENTRAL MT.
AFTER THE SYSTEM EXITS DURING THE DAY TUESDAY, DRIER CONDITIONS
MOVE IN FOR WEDNESDAY AND MOST OF THURSDAY. 700MB WINDS INCREASING
ALONG THE ROCKY MOUNTAIN FRONT THURSDAY WILL ALSO INCREASE
SURFACE WINDS, THOUGH CONFIDENCE IS LOW FOR HIGH WINDS.
HEADING INTO LATE THURSDAY NIGHT INTO FRIDAY, A COLD FRONT WILL
RE-INTRODUCE LOW END CHANCES FOR PRECIPITATION. THOUGH, BETTER
CHANCES FOR PRECIPITATION ARRIVED WITH THE NEXT INCOMING TROUGH
SATURDAY AND SUNDAY. ENSEMBLES HINT AT A COOLER SYSTEM INCOMING
NEXT WEEKEND WITH SNOW LEVELS FALLING TO AT LEAST THE HIGHER
MOUNTAIN PEAKS. THOUGH DETAILS AND CONFIDENCE IN THIS NEXT SYSTEM
IS LOW.
- FORECAST CONFIDENCE & SCENARIOS:
THE BIGGEST QUESTION MARK OF THE DAY TODAY WAS CLOUD COVER AND
INSTABILITY LIMITING SEVERE THUNDERSTORM POTENTIAL TODAY. THE
SYNOPTICS PROVIDING BOTH DIRECTIONAL AND SPEED SHEAR (40-50KTS)
BRING A FAVORABLE ENVIRONMENT FOR THUNDERSTORMS TO BECOME SEVERE
ACROSS NORTH-CENTRAL MT. THE MORNING CLOUD COVER AND FOG COULD'VE
LIMITED INSTABILITY DEVELOPMENT, BUT THERE LOOKS TO BE A FEW
BREAKS IN THE CLOUDS EARLY THIS AFTERNOON TO KEEP AN EYE ON
ISOLATED SEVERE STORMS. SINCE ALL THE INSTABILITY WILL BE
ELEVATED, THE STORMS WILL BE ELEVATED AND THEREFORE A PRIMARY HAIL
THREAT, WITH A LOW END SEVERE WIND GUST THREAT. THE BEST WINDOW
FOR SEVERE THUNDERSTORMS TO DEVELOP WILL BE BETWEEN 6-10PM WITH
THE BEST SPATIAL CORRIDOR ALONG AND NORTH FROM THE HELENA TO
LEWISTOWN LINE. A LIMITING FACTOR LATE TONIGHT AS STORMS GET
CLOSER TO THE HI-LINE IS THE DROP OFF OF INSTABILITY AND INCREASE
IN SATURATED PROFILES. THEREFORE, IT SEEMS LIKE THOSE INITIAL
STORMS IN THE EARLY TO MID EVENING WILL BE THE STORMS TO WATCH.
MODELS HAVE BEEN CONSISTENTLY SHOWING ADDITIONAL 1-3" RAIN
ACCUMULATIONS ALONG THE ROCKY MOUNTAIN FRONT AND THE SWEET GRASS
HILLS. HOW FAR EAST ALONG US HIGHWAY 2 DOES THIS EXTEND REMAINS
UNCERTAIN, BUT THIS NORTHWEST SHIFT IN THE LOW TRACK FAVORS THE
ROCKY MOUNTAIN FRONT FOR THE CORRIDOR OF HEAVIEST PRECIPITATION.
WITH THUNDERSTORMS TODAY AND TOMORROW, SOME HIGH-RES GUIDANCE SHOW
UP TO ISOLATED 4" IF THAT AREA GETS GOOD CONVECTIVE RAIN RATES.
RAINFALL AMOUNTS DROP OFF SIGNIFICANTLY SOUTH OF THE MT HIGHWAY
200 CORRIDOR TO LESS THAN A QUARTER OF AN INCH. -WILSON
AVIATION
06/18Z TAF PERIOD
LOW CLOUDS/LIGHT PRECIP WILL AFFECT PORTIONS OF NORTH CENTRAL MT
EARLY THIS AFTERNOON. THEN A WAVE OF STRONG STORMS WILL MOVE FROM
SOUTHWEST TO NORTHEAST THROUGH THE CENTRAL AND NORTH CENTRAL MT
THIS EVENING AND OVERNIGHT. EXPECT STRONG WINDS AND SOME HAIL WITH
THIS WAVE. THE STRONGER STORMS TRANSITION TO MORE OF A STRATIFORM
RAIN BY MONDAY MORNING OVER NORTH CENTRAL MT. SOME RAIN LIKELY IN
SOUTHWEST MT BY MONDAY MORNING, BUT PRECIP WILL NOT BE AS HEAVY
OVER THE SOUTHWEST. EXPECT MOUNTAINS/PASSES TO BE OBSCURED AT
TIMES ACROSS THE CWA BY LOW CLOUDS/PRECIP.
FOR KGTF: MAIN CONCERN WILL BE THUNDERSTORM POTENTIAL BETWEEN 00Z
AND 03Z THIS EVENING. SOME STORMS COULD HAVE STRONG ERRATIC WIND
GUSTS OR HAIL. GIVEN CURRENT CONDITIONS, KEPT HAIL OUT OF THE
FORECAST FOR NOW. EXPECT LOW CLOUDS/LIGHT RAIN MONDAY MORNING,
WITH SOME IMPROVING CONDITIONS TOWARDS MID DAY MONDAY. BRUSDA
HYDROLOGY
AREAS ALONG THE ROCKY MOUNTAIN FRONT HAVE RECEIVED 0.75" TO 1.5"
OF RAINFALL OVER THE PAST DAY. THERE HASN'T BEEN MUCH OF A
RESPONSE IN CREEKS/STREAMS YET DUE TO THE DRIER GROUNDING SOAKING
ALL THE RAIN UP. THE MAIN CONCERN IS ANOTHER ADDITIONAL
WIDESPREAD 1 TO 3 INCHES AND ISOLATED 4 INCHES THROUGH TUESDAY
MORNING ON A MORE SATURATED GROUND. AREAS THAT GET THE HIGHER END
3 TO 4 INCH TOTALS MAY SEE MINOR OVERFLOW IN CREEKS/STREAMS ALONG
WITH MUDDIED RURAL ROADS. THE WET CONDITIONS CAN ALSO CAUSE
ROCK/DEBRIS SLIDES IN THE HIGHER TERRAIN. THEREFORE, A FLOOD WATCH
WAS ISSUED FROM THIS AFTERNOON THROUGH TUESDAY. FARTHER EAST
ACROSS NORTH-CENTRAL MT WILL SEE WETTING RAIN, BUT CONFIDENCE FOR
THOSE HIGHER END TOTALS REMAIN LOW. ONE THING TO WATCH FOR IS ANY
EASTERN SHIFT OF THESE AMOUNTS FARTHER EAST ALONG US HIGHWAY 2
TOWARDS HILL COUNTY. -WILSON
PRELIMINARY POINT TEMPS/POPS
GTF 51 64 47 66 / 90 100 40 50
CTB 46 56 44 60 / 90 100 100 80
HLN 51 66 44 70 / 80 100 20 10
BZN 48 69 40 71 / 30 80 10 0
WYS 41 60 30 64 / 90 40 10 0
DLN 46 66 36 71 / 90 50 0 0
HVR 51 68 45 64 / 90 100 90 90
LWT 50 68 44 64 / 90 90 20 30
TFX WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH THROUGH TUESDAY MORNING FOR EAST GLACIER PARK REGION-
EASTERN GLACIER, WESTERN TOOLE, AND CENTRAL PONDERA-EASTERN
PONDERA AND EASTERN TETON-EASTERN TOOLE AND LIBERTY-NORTHERN
HIGH PLAINS-SOUTHERN HIGH PLAINS-SOUTHERN ROCKY MOUNTAIN FRONT.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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