450
FXUS65 KTFX 132059
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
ISSUED BY NATIONAL WEATHER SERVICE MISSOULA MT
259 PM MDT MON JUL 13 2026
KEY MESSAGES
- HOT TEMPERATURES PERSIST THROUGH THE REST OF THE DAY WITH A
CHANCE FOR ISOLATED SHOWERS AND THUNDERSTORMS THIS EVENING.
- MONSOONAL MOISTURE ARRIVES TUESDAY AND WEDNESDAY WITH MORE
SHOWERS AND THUNDERSTORMS EXPECTED; A FEW MAY PRODUCE HEAVY
RAINFALL, GUSTY WINDS, AND HAIL.
DISCUSSION
TODAY WILL BE THE LAST DAY OF EXCESSIVE HEAT FOR NOW. TEMPERATURES
WILL COOL OFF TUESDAY THROUGH THURSDAY AS SOUTHWESTERLY FLOW
STARTS TO TAKE OVER AND BRING MORE CLOUDS AND RAIN INTO THE
REGION. TOWARDS THE WEEKEND, ANOTHER UPPER-LEVEL RIDGE WILL START
TO BUILD BRINGING THE POTENTIAL FOR MORE 90+ DEGREE WEATHER
THROUGH NEXT WEEKEND.
SHOWER/THUNDERSTORM POTENTIAL: THERE IS A CHANCE FOR ISOLATED
THUNDERSTORMS THIS AFTERNOON AND EVENING ACROSS PORTIONS OF
SOUTHWEST AND CENTRAL MONTANA. THESE THUNDERSTORMS WILL BE ON THE
DRIER SIDE TOWARDS SOUTHWEST MONTANA AND TREND WETTER AS THEY HEAD
NORTH. THE MAIN CONCERNS WILL BE STRONG, GUSTY WINDS WITH SMALL
HAIL POSSIBLE.
THINGS WILL TREND WETTER HEADING INTO TUESDAY AND WEDNESDAY WITH
THE ADDITIONAL THREAT OF HEAVY RAIN ENTERING THE PICTURE WITH ANY
SHOWER OR THUNDERSTORM THAT DEVELOPS. HI-RES GUIDANCE HIGHLIGHTS
THE POTENTIAL FOR HEAVY TOTAL RAINFALL AND HEAVY RAINFALL RATES
ACROSS THE REGION. WITH WIDESPREAD PRECIPITABLE WATER VALUES IN
THE 1-1.5" RANGE, THERE IS A CONCERN FOR HEAVY RAIN AND FLASH
FLOODING WITH ANY THUNDERSTORM THAT DEVELOPS. THUS, A FLASH FLOOD
WATCH HAS BEEN ISSUED FOR PORTIONS OF NORTH-CENTRAL, CENTRAL, AND
SOUTHWEST MONTANA. POOR DRAINAGE AND URBAN AREAS AS WELL AS BURN
SCARS WILL BE THE MOST AT RISK FOR FLOODING. THOSE RECREATING
OUTDOORS SHOULD BE PREPARED TO SEEK HIGHER GROUND IF NEEDED TO
AVOID FLOOD-PRONE AREAS.
WEDNESDAY WILL HAVE A SIMILAR SET UP BUT WITH LESS CONFIDENCE ON
WHICH AREAS WILL BE AT GREATEST RISK, THE DECISION WAS MADE TO
START WITH ISSUING THE WATCH FOR TUESDAY AND SEEING HOW FUTURE
MODEL RUNS PLAY OUT TO DETERMINE THE THREAT LEVEL AND SPREAD FOR
WEDNESDAY. -THOR
AVIATION
13/12Z TAF PERIOD
A SOUTHWESTERLY FLOW ALOFT STREAMS VARIABLE MID TO HIGH LEVEL
CLOUDS AND MOISTURE ACROSS THE REGION WITH VFR CONDITIONS
PREVAILING. WIDELY SCATTERED HIGH-BASED SHOWERS AND THUNDERSTORMS
DEVELOP ACROSS SOUTHWEST MT IN THE AFTERNOON WITH GUSTY
SHOWERS/THUNDERSTORMS TRACKING NORTHEAST INTO CENTRAL/NORTH-
CENTRAL MT THIS EVENING. GENERALLY LIGHT SURFACE WINDS THIS
MORNING BECOME EAST TO SOUTHEASTERLY THIS AFTERNOON. HOENISCH
FIRE WEATHER
INITIALLY HIGH-BASED SHOWER AND THUNDERSTORM DEVELOPMENT THIS
AFTERNOON WILL BRING A RISK FOR GUSTY DOWNDRAFT/OUTFLOW WINDS AS
WELL AS ISOLATED LIGHTNING. HIGH RESOLUTION MODEL ENSEMBLES FOCUS
THE GREATEST RISK FOR LIGHTNING AND ISOLATED STRONG WIND GUSTS
ALONG AN AXIS FROM SOUTHWEST THROUGH CENTRAL MT LATE THIS
AFTERNOON AND EVENING. WETTING PRECIPITATION CHANCES WITH
CONVECTION INITIALLY TODAY REMAINS LOW AND RECENT HEAT/DRYNESS
HAS LIKELY MADE VEGETATION IN SOME AREAS MORE RECEPTIVE TO
LIGHTNING IGNITION, ESPECIALLY ACROSS SOUTHWEST MT. HOENISCH
HYDROLOGY
THE INFLUX OF MONSOON-RELATED MOISTURE INTO THE REGION BY TUESDAY
WILL INCREASE THE RISK FOR LOCALLY INTENSE PRECIPITATION/HEAVY
DOWNPOURS WITH THUNDERSTORM ACTIVITY THROUGH THURSDAY.
PRECIPITABLE WATER AMOUNTS OF 1.50" OR MORE ARE FORECAST, WHICH
IS AT OR ABOVE THE 90TH PERCENTILE OF CLIMATOLOGY. THERE IS A
MARGINAL (5-15%) RISK FOR EXCESSIVE RAINFALL ACROSS THE AREA
TUESDAY AND WEDNESDAY WITH POTENTIAL FOR PRECIPITATION RATES THAT
COULD CAUSE LOCALIZED FLASH FLOODING, PARTICULARLY IN
SENSITIVE/STEEPER TERRAIN AREAS OR BURN SCARS. HOENISCH
PRELIMINARY POINT TEMPS/POPS
GTF 63 91 60 84 / 40 20 70 60
CTB 61 82 58 80 / 20 30 70 50
HLN 65 91 64 87 / 30 10 70 60
BZN 59 94 60 87 / 20 10 50 70
WYS 50 94 53 85 / 10 10 10 30
DLN 57 90 57 86 / 30 10 40 40
HVR 65 95 61 85 / 30 20 70 60
LWT 58 91 56 82 / 10 10 70 60
TFX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 9 PM MDT THIS EVENING FOR BEARS PAW
MOUNTAINS AND SOUTHERN BLAINE-CANYON FERRY AREA-CASCADE COUNTY
BELOW 5000FT-EASTERN PONDERA AND EASTERN TETON-EASTERN TOOLE AND
LIBERTY-FERGUS COUNTY BELOW 4500FT-GALLATIN VALLEY-GATES OF THE
MOUNTAINS-HELENA VALLEY-HILL COUNTY-JUDITH BASIN COUNTY AND
JUDITH GAP-MADISON RIVER VALLEY-MISSOURI HEADWATERS-NORTHERN
BLAINE COUNTY-SOUTHERN HIGH PLAINS-WESTERN AND CENTRAL CHOUTEAU
COUNTY.
FLOOD WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY EVENING FOR
BEARS PAW MOUNTAINS AND SOUTHERN BLAINE-BIG BELT, BRIDGER AND
CASTLE MOUNTAINS-CANYON FERRY AREA-CASCADE COUNTY BELOW 5000FT-
ELKHORN AND BOULDER MOUNTAINS-FERGUS COUNTY BELOW 4500FT-
GALLATIN VALLEY-GALLATIN AND MADISON COUNTY MOUNTAINS AND
CENTENNIAL MOUNTAINS-GATES OF THE MOUNTAINS-HELENA VALLEY-JUDITH
BASIN COUNTY AND JUDITH GAP-LITTLE BELT AND HIGHWOOD MOUNTAINS-
MEAGHER COUNTY VALLEYS-MISSOURI HEADWATERS-SNOWY AND JUDITH
MOUNTAINS-SOUTHERN HIGH PLAINS-SOUTHERN ROCKY MOUNTAIN FRONT-
UPPER BLACKFOOT AND MACDONALD PASS-WESTERN AND CENTRAL CHOUTEAU
COUNTY.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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