546
FXUS65 KTFX 010607
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1207 AM MDT TUE SEP 1 2026
KEY MESSAGES
- MARGINAL RISK FOR SEVERE THUNDERSTORMS OVER THE PLAINS OF
CENTRAL AND NORTH CENTRAL MONTANA TODAY, WITH THE PRIMARY RISK
BEING DAMAGING WINDS.
- ABOVE NORMAL TEMPERATURES TODAY FALLING NEAR TO BELOW NORMAL
FOR THE REMAINDER OF THE WEEK.
- STRONG AND GUSTY WINDS ON WEDNESDAY AND THURSDAY, ESPECIALLY
WITHIN THE NORTH-SOUTH ORIENTATED VALLEYS OF SOUTHWEST MONTANA.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
LONGWAVE TROUGHING OVER THE WESTERN CONUS, WITH SOUTH TO SOUTHWEST
FLOW ALOFT ACROSS THE NORTHERN ROCKIES, WILL DOMINATE THE UPCOMING
WEEK. SHORTWAVES EJECTING FROM THE BASE OF THE TROUGH AXIS AND
LIFTING NORTH TO NORTHEAST WITHIN THE AFOREMENTIONED FLOW REGIME
WILL BRING MULTIPLE OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS TO
SOUTHWEST THROUGH NORTH CENTRAL MONTANA, MOST NOTABLY TODAY AND
WEDNESDAY WHEN THE AREAL COVERAGE PRECIPITATION WILL BE GREATEST.
HIGH TEMPERATURES, WITH THE EXCEPTION OF TODAY WHEN HIGHS WILL
GENERALLY BE 5 TO 10 DEGREES ABOVE NORMAL, WILL MOSTLY RANGE FROM
NEAR TO BELOW NORMAL. PERIODS OF STRONG AND GUSTY WINDS WILL OCCUR
OVER THE NEXT WEEK, ESPECIALLY ON WEDNESDAY AND THURSDAY WITHIN THE
NORTH-SOUTH ORIENTATED VALLEYS OF SOUTHWEST MONTANA WHERE FREQUENT
GUSTS IN EXCESS OF 45 MPH ARE LIKELY TO OCCUR. - MOLDAN
- FORECAST CONFIDENCE & SCENARIOS:
STRONG WINDS ON WEDNESDAY AND THURSDAY...
ECMWF EFIS WITH RESPECT TO WINDS CONTINUE TO SUPPORT THE POTENTIAL
FOR AN UNUSUAL TO VERY UNUSUAL WIND EVENT, FOR EARLY SEPTEMBER,
THROUGH THE PERIOD ALONG AND SOUTH OF THE I-90 CORRIDOR; MOST
NOTABLY WITHIN THE MADISON RIVER VALLEY. SOUTHERLY H700 WINDS PER
NAEFS ANALYSIS ACROSS SOUTHWEST MONTANA ARE PROG'D TO INCREASE TO
BETWEEN 30-40KTS BY 18Z WEDNESDAY, AND REMAIN SO THROUGH 00Z FRIDAY
BEFORE DECREASING. THESE 2 TO 2.5 STANDARD DEVIATION WIND SPEEDS
ALIGNED WITH THE NORTH-SOUTH TERRAIN IN SOUTHWEST MONTANA,
SPECIFICALLY THE MADISON RIVER VALLEY, COMBINED WITH DEEP MIXING
BETWEEN 16Z TO 02Z EACH DAY WILL SUPPORT AN IDEAL SCENARIO FOR AN
EARLY SEASON HIGH WIND EVENT. GIVEN THAT NBM5.0 PROBABILITIES WITHIN
THE MADISON RIVER FOR SUSTAINED WIND SPEEDS TO EXCEED 40 MPH RANGE
BETWEEN A 60-70% CHANCE (WEDNESDAY) AND 30-40% CHANCE (THURSDAY),
CONFIDENCE REMAINS HIGH ENOUGH TO CONTINUE THE HIGH WIND WATCH WITH
THIS FORECAST PACKAGE. THE MAIN REASON FOR NOT UPGRADING THE HIGH
WIND WATCH WAS UNCERTAINTY WITH RESPECT TO WEDNESDAY NIGHT'S INTO
THURSDAY'S WINDS, WHICH AT THIS POINT IN TIME APPEAR TO BE SLIGHTLY
WEAKER THAN DURING THE DAYLIGHT HOURS ON WEDNESDAY. ADDITIONALLY, I
WAS UNABLE TO FIND A (6-9 HOUR) PERIOD IN WHICH WIND SPEEDS AND/OR
GUSTS DECREASE SIGNIFICANTLY ENOUGH IN ORDER TO BREAK-UP THE EVENT
INTO TWO (2) DISTINCT WIND EVENTS, THUS THE WATCH FROM 18Z WEDNESDAY
THROUGH 03Z FRIDAY REMAINS IN EFFECT FOR THE MADISON RIVER VALLEY.
LISTED BELOW ARE THE NBM5.0 PROBABILITIES FOR WIND GUSTS TO EXCEED
35, 45, AND 55 MPH FOR SELECT LOCATIONS ACROSS NORTH CENTRAL,
CENTRAL, AND SOUTHWEST MONTANA.
WEDNESDAY'S WIND GUSTS PROBABILITIES
LOCATION > 35 MPH | > 45 MPH | > 55 MPH
BROWNING 95% | 50% | 5%
CUT BANK 95% | 60% | 15%
HAVRE 80% | 40% | 5%
GREAT FALLS 90% | 60% | 20%
LEWISTOWN 60% | 10% | <5%
HELENA 80% | 45% | 15%
BOZEMAN 90% | 65% | 15%
DILLON 90% | 70% | 25%
ENNIS 100% | 85% | 30%
WEST YELLOWSTONE 95% | 60% | 0%
THURSDAY'S WIND GUSTS PROBABILITIES
LOCATION > 35 MPH | > 45 MPH | > 55 MPH
BROWNING 90% | 65% | 20%
CUT BANK 90% | 65% | 20%
HAVRE 75% | 35% | <5%
GREAT FALLS 80% | 45% | 5%
LEWISTOWN 70% | 5% | 0%
HELENA 75% | 25% | 0%
BOZEMAN 85% | 50% | 5%
DILLON 100% | 60% | 10%
ENNIS 95% | 70% | 5%
WEST YELLOWSTONE 85% | 40% | 0%
SEVERE THUNDERSTORM RISK FOR WEDNESDAY...
A MARGINAL RISK FOR SEVERE THUNDERSTORMS, MAINLY CAPABLE OF
PRODUCING DAMAGING WINDS, EXISTS ON WEDNESDAY ALONG AND NORTHWEST OF
A HELENA, TO MONARCH, TO WINIFRED LINE. SHOWERS AND THUNDERSTORMS
LIFTING NORTHEAST FROM IDAHO AND WESTERN MONTANA ARE EXPECTED TO
OVERSPREAD THE AFOREMENTIONED AREA THROUGH THE AFTERNOON HOURS, WITH
BUFKIT SOUNDING DEPICTING INVERTED-V'S BENEATH CLOUDBASES OF
10000KFT. THESE HIGH CLOUD BASES COMBINED WITH ALREADY ANOMALOUS LOW
LEVEL WIND SPEEDS WILL SUPPORT THE POTENTIAL FOR A FEW SEVERE
THUNDERSTORM/SHOWER WIND GUSTS ACROSS PORTIONS OF CENTRAL AND NORTH
CENTRAL MONTANA. - MOLDAN
AVIATION
01/06Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL THROUGHOUT THIS TAF PERIOD, WITH
PERIODS OF MVFR CONDITIONS AND MOUNTAIN OBSCURATION POSSIBLE DUE
TO PASSING SHOWERS OVER THE SOUTHWEST TERMINALS FROM AROUND 14Z TO
18Z. WINDS WILL GENERALLY REMAIN LIGHT BEFORE INCREASING IN THE
AFTERNOON/EVENING HOURS. KEKS WILL SEE THE STRONGEST WINDS, WITH
GUSTS UP TO 25 KTS FROM THE SOUTH.
FOR KGTF: THERE IS A NEAR ZERO CHANCE OF A CROSS-WIND EXCEEDING
15 KTS UNTIL 00Z, DUE TO THE LIGHT NATURE OF THE WIND. THE WIND
WILL TRANSITION FROM SOUTHEAST TO SOUTHWEST BETWEEN 00Z AND 03Z,
IN WHICH THERE IS A 40% CHANCE OF A CROSS-WIND EXCEEDING 15 KTS.
ONCE THIS WIND BECOMES PREDOMINATELY SOUTHWEST, THERE IS A LESS
THAN 10% CHANCE FOR A CROSS-WIND EXCEEDING 15 KTS. VFR CONDTIONS
WILL PREVAIL THROUGHOUT THIS TAF PERIOD. -DZOMBA
PRELIMINARY POINT TEMPS/POPS
GTF 85 56 81 48 / 0 10 50 20
CTB 83 52 77 45 / 0 10 70 50
HLN 86 51 78 48 / 10 40 60 10
BZN 82 49 77 45 / 20 40 20 0
WYS 69 37 64 33 / 40 60 20 0
DLN 81 45 74 42 / 30 50 60 10
HVR 88 54 87 49 / 0 0 50 60
LWT 83 54 82 48 / 10 10 30 10
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
EVENING FOR MADISON RIVER VALLEY.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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