988
FXUS65 KTFX 290236
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
736 PM MST TUE JAN 28 2025
KEY MESSAGES
- COLD TEMPERATURES WILL CONTINUE TO AFFECT THE VALLEYS OF
SOUTHWEST MT THROUGH THURSDAY, WITH WARMING TEMPERATURES ON
FRIDAY.
- WINDY CONDITIONS DEVELOP ON WEDNESDAY AND CONTINUE INTO THURSDAY
IN THE BROWNING AND CUT BANK AREAS.
- SNOW DEVELOPS ON FRIDAY MORNING IN GLACIER PARK AND THE MARIAS
PASS AREA.
- STRONG COLD FRONT MOVES SOUTHWARD THROUGH THE CWA STARTING ON
SATURDAY.
- ACCUMULATING SNOWFALL SHIFTED SOUTHWARD INTO SOUTHWEST MT THIS
WEEKEND.
UPDATE
SINCE THE FORECAST IS LARGELY ON TRACK, NO MAJOR CHANGES TO THE
FORECAST HAVE BEEN MADE ASIDE FROM SOME TWEAKS TO THE HOURLY
TEMPERATURES. LUDWIG
DISCUSSION
/ISSUED 448 PM MST TUE JAN 28 2025/
- METEOROLOGICAL OVERVIEW:
H500 HEIGHTS WILL CONTINUE TO FALL THROUGH THE REMAINDER OF THE WORK
WEEK AS UPPER LEVEL RIDGING, WITH ITS RIDGE AXIS OVER THE EASTERN
PACIFIC, IS FLATTENED BY A SERIES OF SHORTWAVE TROUGHS. THIS
FLATTENING OF THE UPPER LEVEL RIDGE WILL LEAD TO UPPER LEVEL FLOW
BACKING FROM THE NORTHWEST TO WEST THROUGHOUT THE REMAINDER OF THE
WORK WEEK, WITH SURFACE HIGH PRESSURE WEST OF THE CONTINENTAL DIVIDE
GRADUALLY WEAKENING THROUGH FRIDAY MORNING. LEE-SIDE TROUGHING THROUGH
THIS SAME TIMEFRAME WILL LEAD TO A STRONG PRESSURE GRADIENT ALONG
THE ROCKY MOUNTAIN FRONT, NORTHERN FOOTHILLS OF THE CENTRAL MONTANA
ISLAND RANGES, AND ALONG THE I-90 CORRIDOR (MAINLY THURSDAY
NIGHT/FRIDAY). THIS STRONG PRESSURE GRADIENT COMBINED WITH
INCREASING WESTERLY FLOW WILL LEAD TO STRONG TO AT TIMES HIGH WINDS
OVER PORTIONS OF CENTRAL AND NORTH CENTRAL MONTANA PLAINS THROUGH
THE REMAINDER OF THE WORK WEEK, MOST NOTABLY FROM WEDNESDAY MORNING
THROUGH THURSDAY MORNING. HIGH TEMPERATURES OVER THE PLAINS OF
CENTRAL AND NORTH CENTRAL MONTANA WILL WARM INTO THE MID-30S TO NEAR
50 DEGREES THANKS TO THESE WINDS, BUT IN THE DECOUPLED VALLEYS OF
SOUTHWEST AND CENTRAL MONTANA WHERE A STRONG INVERSION WILL REMAIN
READINGS WILL REMAIN WELL BELOW NORMAL AND IN THE 20S.
BIG CHANGES REMAIN ON TRACK FOR THE WEEKEND AS LONGWAVE TROUGHING
DIGS SOUTH FROM OVER WESTERN CANADA TOWARDS THE PACIFIC NORTHWEST,
WITH AN ARCTIC FRONT PUSHING SOUTH FROM CANADA AND ACROSS THE
NORTHERN ROCKIES SATURDAY NIGHT/SUNDAY MORNING. THIS WILL LEAD TO
INCREASING CHANCE FOR ACCUMULATING SNOW, INITIALLY ALONG THE
CONTINENTAL DIVIDE FRIDAY NIGHT BEFORE EXPANDING FURTHER EAST
THROUGH THE WEEKEND, WITH THE HIGHEST ACCUMULATIONS FOCUSED ALONG
THE CONTINENTAL DIVIDE THROUGH THE WEEKEND. ADDITIONALLY,
TEMPERATURES WILL TUMBLE IN WAKE OF THE ARCTIC FRONT, WITH HIGH
TEMPERATURES REMAINING WELL BELOW NORMAL FROM SUNDAY AND THROUGH THE
FIRST HALF OF THE UPCOMING WORK WEEK. - MOLDAN
- FORECAST CONFIDENCE & SCENARIOS:
TEMPERATURES (IN THE VALLEYS OF SOUTHWEST MONTANA) THROUGH THURSDAY :
A DENSE, AND FAIRLY DEEP (~3000FT TO 5000FT), COLD AIR MASS WITHIN
THE HELENA, MISSOURI RIVER, GALLATIN, AND MADISON VALLEYS OF
SOUTHWEST MONTANA WILL PERSIST THROUGH AT LEAST FRIDAY MORNING PRIOR
TO A WEAK PACIFIC COLD FRONT, WHICH WILL THEN HELP TO BREAK THE
INVERSION OVER THE VALLEYS AND MIXOUT THE STUBBORN COLD AIR. THESE
INVERTED VALLEYS WILL CONTINUE TO RUN WELL BELOW DETERMINISTIC
FORECAST GUIDANCE GIVEN THEIR (MODELS) BIAS IN ERODING THESE COLD
AIR MASSES TOO QUICKLY; THUS AN OVERALL PERSISTENCE FORECAST WILL
CONTINUE TO BE EMPLOYED THROUGH THURSDAY ACROSS THESE VALLEY
LOCATIONS WITH A COUPLE DEGREES OF WARMING EACH DAY.
HIGH WINDS FROM WEDNESDAY MORNING THROUGH THURSDAY MORNING :
CONFIDENCE IN A FAIRLY NON-TRADITIONAL HIGH WIND EVENT HAS RISEN TO
THE POINT WHERE THE HIGH WIND WATCH FOR THE EASTERN GLACIER, WESTERN
TOOLE, AND CENTRAL PONDERA COUNTIES ZONE WAS UPGRADED TO A HIGH WIND
WARNING; WITH THE ADDITION OF NORTHERN HIGH PLAINS ZONE AS WELL.
WITH RESPECT TO THE ACTUAL EVENT ITSELF, PROBABILISTIC GUIDANCE
SUPPORTS A 60-90% CHANCE FOR WIND GUSTS IN EXCESS OF 48KTS IN THE
CUT BANK AND BROWNING AREAS AND A 20-40% CHANCE FOR GUSTS IN EXCESS
OF 64KTS. WHILE THESE PROBABILITIES FOR GUSTS ARE RATHER
UNIMPRESSIVE FOR THE CUT BANK AND BROWNING AREAS THE PROBABILITIES
FOR SUSTAINED SPEEDS IN EXCESS OF 34KTS AND 43KTS RANGE FROM 60-90%
AND 25-70% RESPECTFULLY. BUFKIT SOUNDINGS AND THE STRONG PRESSURE
GRADIENT FOCUSED ALONG THE ROCKY MOUNTAIN FRONT SUPPORT A SCENARIO
IN WHICH HIGH WINDS ARE ACHIEVED VIA A HIGH SUSTAINED SCENARIO VS
ACTUAL GUSTS BEING REALIZED; HOWEVER, AN OCCASIONAL GUST OR TWO MAY
OCCUR BENEATH ANY STRONG MOUNTAIN WAVE THAT PROPAGATES EASTWARD.
THESE WINDS WILL BE ESPECIALLY STRONG IN THE BADGER CREEK AND TWO
MEDICINE RIVER VALLEYS ALONG AND WEST OF THE US HWY 89 CORRIDOR. -
MOLDAN
ACCUMULATING SNOW AND TEMPERATURES THIS WEEKEND THROUGH EARLY NEXT
WEEK:
FOR GLACIER PARK, THERE IS A 75 PERCENT CHANCE OF A SNOWFALL OVER 6
INCHES FROM FRIDAY INTO FRIDAY NIGHT. SNOWFALL OF A FEW INCHES
LOOK LIKELY OVER SOUTHWEST MT SATURDAY INTO SATURDAY NIGHT, WITH
THE MAIN CONCERN BEING AN HOUR OR TWO OF HEAVY SNOWFALL. FOR NEXT
WEEK, THERE IS A 30 PERCENT CHANCE OF 4 INCHES OF SNOWFALL FROM
GREAT FALLS TO LEWISTOWN WITH THE POTENTIAL OVERRUNNING SNOWFALL
MON INTO TUE.
WITH THE SNOW COVER DECREASING OVER NORTH CENTRAL MT AND NOT MUCH
SNOW EXPECTED THIS WEEKEND, TEMPERATURES OVER THE NORTH WILL BE
TRICKY, AS IT MIGHT NOT GET AS COLD AS ONE WOULD THINK WITH THIS
AIRMASS AND AREAS OVER NORTH CENTRAL MT THAT HAVE NO SNOW COVER.
BRUSDA
AVIATION
29/00Z TAF PERIOD
VFR CONDITIONS WILL CONTINUE OVER THE NEXT 24 HOURS. MAIN CONCERN
WILL BE INCREASING WINDS ALOFT AND AT THE SURFACE LATE TONIGHT,
WHICH WILL EVENTUALLY TRANSLATE TO GUSTY SURFACE WINDS AND SOME
MOUNTAIN WAVE TURBULENCE. LUDWIG
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 23 46 31 45 / 0 0 0 0
CTB 24 45 31 40 / 0 0 0 0
HLN 11 27 11 31 / 0 0 0 0
BZN 0 25 2 29 / 0 0 0 0
WYS -9 30 -6 27 / 0 0 0 0
DLN 6 25 6 28 / 0 0 0 0
HVR 19 40 20 36 / 0 0 0 0
LWT 21 47 23 43 / 0 0 0 0
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WARNING FROM 3 AM WEDNESDAY TO 6 AM MST THURSDAY FOR
NORTHERN HIGH PLAINS.
HIGH WIND WARNING FROM 6 AM WEDNESDAY TO 6 AM MST THURSDAY FOR
EASTERN GLACIER, WESTERN TOOLE, AND CENTRAL PONDERA.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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