944
FXUS65 KTFX 280618
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1218 AM MDT FRI AUG 28 2026
KEY MESSAGES
- DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS THROUGH THE
WEEKEND, WITH THE POTENTIAL FOR SOME MINOR MOUNTAIN SNOW ON
SUNDAY.
- BREEZY AND GUSTY WINDS ON SUNDAY, ESPECIALLY ALONG THE ROCKY
MOUNTAIN FRONT.
- WELL BELOW NORMAL TEMPERATURES BY SUNDAY.
DISCUSSION
CLOSED UPPER LEVEL LOW OVER GULF OF ALASKA AND ASSOCIATED UPPER
LEVEL TROUGH OVER THE EASTERN PACIFIC WILL DIG SOUTH TO OVER THE
PACIFIC NORTHWEST BY SATURDAY MORNING BEFORE LIFTING AND PIVOTING
EAST NORTHEAST OVER THE NORTHERN ROCKIES THROUGH THE DAY ON SUNDAY.
SOUTHWESTERLY FLOW ALOFT AHEAD OF THE APPROACHING UPPER LEVEL TROUGH
WILL CONTINUE TO TRANSPORT PACIFIC MOISTURE NORTH AND EAST OVER THE
NORTHERN ROCKIES THROUGH THE TIMEFRAME, WHICH COMBINED WITH SURFACE
HEATING DURING THE DAYLIGHT HOURS AND SUBTLE WAVES LIFTING NORTHEAST
WITHIN THE OVERALL FLOW WILL SUPPORT SHOWERS AND THUNDERSTORMS
ACROSS PORTIONS OF SOUTHWEST THROUGH NORTH CENTRAL MONTANA. WHILE AN
ISOLATED STRONG THUNDERSTORM CAN'T BE RULED OUT THROUGH SUNDAY,
ESPECIALLY ON TODAY AND SATURDAY, MOST THUNDERSTORMS WILL BE OF THE
GARDEN VARIETY AND PRODUCE GUSTY AND ERRATIC WINDS. HIGH
TEMPERATURES IN THE UPPER 70S TO UPPER 80S TODAY WILL FALL TO THE
60S TO LOW 70S BY SUNDAY AS THE UPPER LEVEL TROUGH MOVES OVERHEAD,
WITH INCREASING WEST WINDS DURING THE DAY ON SUNDAY.
AN ACTIVE PATTERN LOOKS TO STAY IN PLACE ACROSS THE WESTERN CONUS
BEYOND SUNDAY AS LONGWAVE TROUGHING LOOKS TO REMAIN OVER THE EASTERN
PACIFIC, WITH SOUTHWESTERLY FLOW OVER THE NORTHERN ROCKIES HELPING
TO MAINTAIN NEAR TO BELOW NORMAL TEMPERATURES AND DAILY CHANCES FOR
SHOWERS AND STORMS. - MOLDAN
- FORECAST CONFIDENCE & SCENARIOS:
STRONG AND GUSTY WINDS ON SUNDAY...
CLIMATE ANOMALY INDICATORS ARE SUGGESTING AN UNUSUAL, WITH RESPECT
TO LATE AUGUST WIND CLIMATOLOGY, WIND EVENT ALONG THE ROCKY MOUNTAIN
FRONT AS CROSS BARRIER FLOW INCREASES IN WAKE OF A DEPARTING UPPER
LEVEL WAVE. H700 FLOW PER NAEFS ANALYSIS IS PROG'D TO INCREASE TO
BETWEEN 40-50KTS ALONG THE ROCKY MOUNTAIN FRONT DURING THE DAY ON
SUNDAY, WHICH IS 1 TO NEARLY 2 STANDARD DEVIATIONS ABOVE NORMAL FOR
THIS TIMEFRAME. THESE VALUES COMBINED WITH DEEP MIXING DURING THE
AFTERNOON HOURS ON SUNDAY IN WAKE OF THE DEPARTING UPPER LEVEL WAVE
WILL HELP TO SUPPORT BREEZY AND GUSTY WINDS FOR MOST LOCATIONS
ACROSS THE PLAINS OF CENTRAL AND NORTH CENTRAL MONTANA, MOST NOTABLY
ALONG AND WEST OF THE I-15 CORRIDOR WHERE NBM5.0 PROBABILITIES
CURRENTLY SUPPORT A 90% OR GREATER CHANCE FOR WIND GUSTS TO EXCEED
35 MPH, WITH THE EXCEPTION OF THE SOUTHERN HIGH PLAINS ZONE WHERE
PROBABILITIES GENERALLY RANGE FROM A 60-75% CHANCE. THE TABLE BELOW
LISTS THE NBM5.0 PROBABILITIES FOR WIND GUSTS TO EXCEED 45, 55 AND
65 MPH DURING THE DAY ON SUNDAY.
SUNDAY'S WIND GUSTS PROBABILITIES
LOCATION > 45 MPH | > 55 MPH | > 65 MPH
BABB 60% | 20% | 5%
EAST GLACIER 70% | 20% | 5%
BROWNING 70% | 15% | 0%
CUT BANK 70% | 20% | <5%
SHELBY 30% | <5% | 0%
HEART BUTTE 75% | 25% | 5%
CHOTEAU 10% | <5% | 0%
AUGUSTA 20% | <5% | 0%
LIGHT MOUNTAIN SNOWFALL ON SUNDAY...
SNOW LEVELS ARE EXPECTED TO FALL TO AS LOW AS 7500FT DURING THE DAY
ON SUNDAY ACROSS THE EAST GLACIER PARK REGION AS THE CLOSED LOW
ASSOCIATED WITH THE UPPER LEVEL TROUGH PIVOTS OVERHEAD. THESE
LOWERED SNOW LEVEL WOULD RESULT IN SOME MOUNTAIN PASSES IN THE
BACKCOUNTRY OF GLACIER NATIONAL PARK POTENTIALLY SEEING SOME MINOR
SNOWFALL, WITH THE LATEST NBM5.0 PROBABILITIES INDICATING A 10-20%
CHANCE FOR SNOWFALL ACCUMULATIONS TO EXCEED 0.1" DURING THE DAY ON
SUNDAY. WHAT REMAINS UNCERTAIN WITH RESPECT TO SUNDAY IS HOW MUCH
PRECIPITATION WILL BE LEFT OVER ACROSS THE NORTHERN ROCKIES AS SNOW
LEVELS FALL TO THEIR MINIMUMS FOR THE DAY; WITH LATEST GUIDANCE
SUGGESTING THAT MOST IF NOT ALL OF THE PRECIPITATION WILL FALL PRIOR
TO SNOW LEVELS "BOTTOMING OUT", WHICH WOULD RESULT IN LITTLE TO NO
SNOWFALL OVERALL. - MOLDAN
AVIATION
28/06Z TAF PERIOD
THUNDERSTORMS WILL LINGER IN THE FIRST FEW HOURS OF THIS TAF
PERIOD AROUND KHVR AND KLWT. RAIN SHOWERS WILL BEGIN IN SOUTHWEST
MT AROUND 12Z, MOVING IN A NORTHEAST FASHION THROUGH KWYS, KEKS
AND KBZN. THUNDERSTORM CHANCES RETURN AROUND 22Z IN CENTRAL MT,
WITH CONVECTIVE ACTIVITY INCREASING IN THE FOLLOWING HOURS IN
SOUTHWEST MT AND EAST OF KCTB. THE MAIN THREAT WITH THESE
THUNDERSTORMS WILL BE GUSTY, ERRATIC WINDS AND FREQUENT LIGHTNING.
OVERALL, VFR CONDITIONS WILL PREVAIL THROUGHOUT THIS TAF PERIOD,
ALTHOUGH MOUNTAIN OBSCURATION WILL OCCUR WITH PASSING SHOWERS AND
THUNDERSTORMS.
FOR KGTF: WINDS WILL BE AROUND 09KT FROM THE SOUTHWEST, BEFORE
BECOMING LIGHT AND VARIABLE AROUND 11Z. WHILE THERE IS A CHANCE
FOR THUNDERSTORM ACTIVITY STARTING AROUND 22Z, CONFIDENCE IN EXACT
TIMING AND LOCATION IS LOW AT THIS TIME, HENCE THE BROAD PROB30
GROUP. ANY THUNDERSTORM THAT DEVELOPS WILL BE CAPABLE OF PRODUCING
GUSTY, ERRATIC WINDS, BRIEF, HEAVY DOWNPOURS, AND FREQUENT
LIGHTNING. DUE TO THE PREDOMINATE SOUTHWEST DIRECTION OF THE WIND
DURING THIS TAF PERIOD, THERE IS A LESS THAN 10% CHANCE OF A
CROSS-WIND EXCEEDING 15 KT OUTSIDE OF A THUNDERSTORM. -DZOMBA
FIRE WEATHER
ELEVATED FIRE WEATHER CONDITIONS WILL EXIST ACROSS PORTIONS OF
FIRE WEATHER ZONE 112 TODAY AS SOUTHWEST WINDS PEAK BETWEEN 15-20
MPH DURING THE AFTERNOON AND EVENING HOURS, WITH GUSTS NEAR 30
MPH. THE BREEZY WINDS COMBINED WITH MINIMUM RELATIVE HUMIDLY
VALUES OF 15-20% WEST OF THE I-15 CORRIDOR RAISES CONCERNS FOR THE
POTENTIAL OF NEW FIRES TO SPREAD RAPIDLY; HOWEVER, WITH LESS THAN
HALF OF THE FIRE WEATHER ZONE EXPECTED TO SEE WIND GUSTS NEAR 30
MPH WE WILL CONTINUE TO HOLD OFF ON ANY FIRE WEATHER PRODUCTS. -
MOLDAN
PRELIMINARY POINT TEMPS/POPS
GTF 85 57 77 49 / 20 20 60 80
CTB 81 50 73 46 / 0 10 40 40
HLN 82 54 76 50 / 30 20 70 90
BZN 78 51 75 46 / 30 50 60 90
WYS 67 41 65 36 / 90 80 90 90
DLN 77 50 75 43 / 30 50 70 80
HVR 89 56 83 50 / 0 20 30 60
LWT 82 54 76 47 / 20 20 50 70
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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