963
FXUS65 KTFX 181713
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1013 AM MST WED DEC 18 2024
KEY MESSAGES
- STRONG WINDS ACROSS MUCH OF THE REGION ARE EXPECTED THROUGH
THIS EVENING.
- HEAVY SNOW AND AREAS OF BLOWING AND DRIFTING SNOW ARE EXPECTED
TODAY ALONG THE NORTHERN ROCKY MOUNTAIN FRONT.
- MILD AND GENERALLY DRY CONDITIONS RETURN BY THE WEEKEND.
UPDATE
MORNING UPDATE HAS BEEN PUBLISHED, WITH THE MAIN ADJUSTMENT BEING
TO ADD BLOWING DUST ACROSS PORTIONS OF THE CENTRAL MONTANA
PLAINS, MAINLY ALONG AND WITHIN 50 MILES (NORTH/SOUTH) OF THE
MONTANA HWY 200 CORRIDOR BETWEEN GREAT FALLS AND LEWISTOWN, AND IN
THE MADISON RIVER VALLEY IN SOUTHWEST MONTANA. DRY CONDITIONS
SINCE MID-FALL ACROSS THESE AREAS COMBINED WITH THE STRONG WINDS
IN EXCESS OF 60 MPH HAS THE POTENTIAL TO PRODUCE BLOWING DUST,
WHICH WOULD LEAD TO REDUCTIONS IN VISIBILITY. RECENT WIND EVENTS
WITHIN THE PAST 5 YEARS THAT HAD SIMILAR DRY CONDITIONS PRECEDING
THE EVENT (I.E. FEBRUARY 1, 2020 AND MARCH 3, 2020) PRODUCED
SIGNIFICANT REDUCTIONS IN VISIBILITY ALONG MT HWY 200 BETWEEN BELT
AND GREAT FALLS AND ON US HWY 87 FROM GREAT FALLS TO FORT BENTON.
WHILE IT IS STILL UNCERTAIN TO WHAT MAGNITUDE BLOWING DUST WILL
OCCUR, THE POTENTIAL IMPACTS ARE HIGH GIVE THE IMPACTS TO
VISIBILITY. OTHERWISE THE REMAINDER OF THE FORECAST REMAINS ON
TRACK, WITH WINDS ALREADY BEGINNING TO SPREAD FURTHER EAST AND
OVER THE PLAINS. WINDS ALONG THE ROCKY MOUNTAIN FRONT HAVE ALREADY
BEEN GUSTING ANYWHERE FROM 60 TO 80 MPH, WITH THESE GUSTS
EXPECTED TO INCREASE FURTHER HERE. TRAVELERS SHOULD EXERCISE
EXTREME CAUTION IF TRAVELING TODAY, ESPECIALLY FROM THE EARLY
AFTERNOON THROUGH EARLY EVENING HOURS. CONSIDER DELAYING TRAVEL
DURING THIS TIMEFRAME AS THIS IS WHEN THE MOST INTENSE WIND SPEEDS
AND GUSTS WILL OCCUR. - MOLDAN
DISCUSSION
/ISSUED 948 AM MST WED DEC 18 2024/
- METEOROLOGICAL OVERVIEW:
A FAST MOVING CLIPPER SYSTEM WILL DEVELOP AND EJECT ACROSS THE
STATE TODAY BRINGING PERIODS OF HEAVY SNOW TO THE NORTHERN ROCKY
MOUNTAIN FRONT AND VERY STRONG WINDS ACROSS MUCH OF STATE. BLOWING
AND DRIFTING SNOW WILL CONTINUE TO BE A CONCERN FOR THIS REGION AS
WINDS CONTINUE TO PICK UP THROUGH THE MORNING HOURS. STRONG WINDS
WILL SLOWLY SPREAD ACROSS MUCH OF THE STATE THROUGH THE LATE
MORNING INTO THE EARLY AFTERNOON MAKING FOR A DANGEROUS, AT TIMES,
SITUATION FOR HIGH-PROFILE VEHICLES TRAVELING IN THE AREA. DAYTIME
MIXING ALONG WITH A VORT MAX DEVELOPING ROUGHLY ALONG THE HWY 200
CORRIDOR WILL ALLOW FOR POTENTIALLY HIGH-END WINDS TO REACH THE
SURFACE FROM GREAT FALLS TO LEWISTOWN THIS AFTERNOON. WINDS WILL
SLOWLY START TO LET UP LATER IN THE EVENING AND THE STRONGEST
WINDS ARE EXPECTED TO DIMINISH BY MIDNIGHT. TOWARDS THE WEEKEND,
RIDGING WILL BUILD OVER THE WESTERN CONUS WHICH WILL KEEP THINGS
GENERALLY ABOVE NORMAL THROUGH THE START OF NEXT WEEK WITH PASSING
DISTURBANCES ALONG THE RIDGE WILL PERIODICALLY BRINGING SOME
RAIN/SNOW THE REGION DURING THIS TIME.
- FORECAST CONFIDENCE & SCENARIOS:
SNOW/FREEZING RAIN POTENTIAL TODAY: EVALUATING THE CHANCES FOR
FREEZING RAIN, THE PROBABILITIES REMAIN LESS THAN 40% FOR PORTIONS
OF THE HI-LINE EAST OF HAVRE. IN GENERAL, THE MAIN THREAT EXTENDS
FURTHER INTO NORTHEASTERN MONTANA BEYOND THE CWA AND, AS SUCH,
THERE IS NO IMPACTFUL THREAT EXPECTED AT THIS TIME. SO THE
DECISION WAS MADE TO HOLD OFF ON ISSUING ANY WINTER WEATHER
PRODUCTS.
WHEN LOOKING AT UPDATED SNOW AMOUNTS AND PROBABILITIES, THE
OVERWHELMING MAJORITY OF THE THREAT IS STILL CONFINED TO THE EAST
GLACIER PARK REGION THAT IS ALREADY UNDER A WINTER STORM WARNING.
THERE ARE PROBABILITIES ABOVE 60% FOR 3 INCHES OR MORE ALONG THE
SOUTHERN ROCKY MOUNTAIN ZONE, HOWEVER, MUCH OF THAT IS ABOVE PASS
LEVEL AND AWAY FROM IMPACT AREAS THAT WOULD NORMALLY RAISE
CONCERNS. AS A RESULT, THE DECISION WAS MADE TO KEEP THE WARNING
FOR THE NORTHERN ROCKIES THE SAME AND REFRAIN FROM ADDING ANY
ADDITIONAL PRODUCTS WITH THIS FORECAST.
HIGH WINDS: THERE IS STILL NEAR-UNANIMOUS AGREEMENT IN THE MODELS
FOR A WIDESPREAD HIGH WIND EVENT FOR CENTRAL AND NORTH-CENTRAL
MONTANA TODAY. THERE IS ALSO GROWING CONCERN FOR THE POTENTIAL OF
GUSTS ABOVE 70 MPH ACROSS PORTIONS OF THE SOUTHERN ROCKY MOUNTAIN
FRONT INTO CASCADE AND JUDITH BASIN COUNTIES. MOST OF THIS CONCERN
COMES FROM A JET STREAK COMING THROUGH THE AREA DURING THE MID-
AFTERNOON HOURS WHICH COULD HELP PRODUCE THE HIGHEST WIND GUSTS
RIGHT ALONG CENTRAL MONTANA.
THE MAIN CHANGE WITH THIS FORECAST UPDATE WAS ADDRESSING THE
PREVIOUS HIGH WIND WATCH. PROBABILITIES OF GUSTS OVER 50 MPH ARE
GENERALLY LESS THAN 60% FOR THE HIGHER ELEVATIONS AND LESS THAN
40% FOR MOST OF THE VALLEYS OF SOUTHWEST MONTANA, WITH THE
EXCEPTION OF ENNIS. WHILE GUSTY WINDS ARE STILL VERY MUCH A THREAT
THIS AFTERNOON, HIGH WINDS ARE NOT EXPECTED FOR BEAVERHEAD AND
WESTERN PORTIONS OF MADISON COUNTY. THUS, THE HIGH WIND WATCH FOR
MOST OF SOUTHWEST MONTANA WAS CANCELLED. THE EXCEPTION WAS THE
ZONE INCLUDING THE MADISON AND GALLATIN RANGES. THE SOUTHERN HALF
OF THE ZONE HAS A LESS THAN 50% PROBABILITY OF EXCEEDING 55 MPH.
BUT THE CONCERN STARTS AROUND BIG SKY AND ALONG THE NORTHERN HALF.
THERE IS A BIT OF CONCERN FOR THOSE TRAVELING BETWEEN BOZEMAN AND
BIG SKY ON US-191 AS WELL AS ANYONE RECREATING IN THE NEARBY
MOUNTAINS. WITH THE PROBABILITY OF WINDS OVER 55 MPH ABOVE 70% FOR
THE AREAS OF CONCERN, THE DECISION WAS MADE TO ADD THE MADISON
AND GALLATIN RANGE ZONE INTO THE HIGH WIND WARNING AND TIME MATCH
IT TO WHEN THE REST OF SOUTHWEST MONTANA INCLUDING THE I-90
CORRIDOR. -THOR
AVIATION
18/18Z TAF PERIOD
THE PRIMARY CONCERN THIS TAF PERIOD WILL BE FOR A PERIOD OF STRONG
WINDS ACROSS THE REGION THROUGH THE REMAINDER OF THE DAY. AHEAD OF
THE STRONG SURFACE WINDS, LLWS WILL BE COMMON ACROSS THE REGION.
STRONG SURFACE WINDS WILL SLOWLY SPREAD ACROSS THE REGION THROUGH
THE DAY TODAY, PEAKING THIS AFTERNOON AND EARLY EVENING. MOUNTAIN
WAVE TURBULENCE, LLWS, LOW-LEVEL TURBULENCE AND ALL ASSOCIATED
HAZARDS WILL BE POSSIBLE THROUGH 06Z OR SO. WINDS GRADUALLY DIMINISH
THIS EVENING AND TONIGHT, LEADING TO MORE BENIGN VFR CONDITIONS
HEADING INTO THURSDAY. MOUNTAINS WILL BE OBSCURED AT TIMES,
ESPECIALLY ALONG THE CONTINENTAL DIVIDE. -AM
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 53 23 44 33 / 20 10 0 20
CTB 47 17 37 26 / 30 20 0 20
HLN 53 31 42 28 / 40 20 0 0
BZN 48 23 40 21 / 20 10 0 0
WYS 33 12 32 11 / 70 30 10 0
DLN 47 20 40 24 / 10 0 0 0
HVR 43 3 21 10 / 90 50 10 10
LWT 49 23 40 27 / 40 40 10 0
TFX WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING UNTIL MIDNIGHT MST TONIGHT FOR EAST GLACIER
PARK REGION.
HIGH WIND WARNING UNTIL MIDNIGHT MST TONIGHT FOR CASCADE COUNTY
BELOW 5000FT-EAST GLACIER PARK REGION-EASTERN GLACIER, WESTERN
TOOLE, AND CENTRAL PONDERA-EASTERN PONDERA AND EASTERN TETON-
EASTERN TOOLE AND LIBERTY-GATES OF THE MOUNTAINS-JUDITH BASIN
COUNTY AND JUDITH GAP-MADISON RIVER VALLEY-NORTHERN HIGH PLAINS-
SOUTHERN HIGH PLAINS-SOUTHERN ROCKY MOUNTAIN FRONT-UPPER
BLACKFOOT AND MACDONALD PASS-WESTERN AND CENTRAL CHOUTEAU COUNTY.
HIGH WIND WARNING UNTIL 5 AM MST THURSDAY FOR BEARS PAW
MOUNTAINS AND SOUTHERN BLAINE-FERGUS COUNTY BELOW 4500FT-HILL
COUNTY-NORTHERN BLAINE COUNTY-SNOWY AND JUDITH MOUNTAINS.
HIGH WIND WARNING UNTIL MIDNIGHT MST TONIGHT FOR BIG BELT,
BRIDGER AND CASTLE MOUNTAINS-CANYON FERRY AREA-ELKHORN AND
BOULDER MOUNTAINS-GALLATIN VALLEY-GALLATIN AND MADISON COUNTY
MOUNTAINS AND CENTENNIAL MOUNTAINS-HELENA VALLEY-LITTLE BELT AND
HIGHWOOD MOUNTAINS-MEAGHER COUNTY VALLEYS-MISSOURI HEADWATERS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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