333
FXUS65 KTFX 300411
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
911 PM MST WED JAN 29 2025
KEY MESSAGES
- WINDY OVER THE PLAINS TODAY THROUGH AT LEAST TONIGHT,
ESPECIALLY ON THE ROCKY MOUNTAIN FRONT.
- COLD AIR WILL LINGER IN THE VALLEYS OF CENTRAL AND SOUTHWEST
MONTANA THROUGH AT LEAST THURSDAY.
- A PACIFIC WEATHER SYSTEM WILL BRING SNOW TO THE MOUNTAINS ON
THE CONTINENTAL DIVIDE FRIDAY THROUGH SATURDAY, WHICH WILL
SPREAD OVER MUCH OF THE AREA OVER THE WEEKEND AND INTO EARLY
NEXT WEEK.
- ANOTHER ROUND OF WINDY CONDITIONS ARE POSSIBLE ON SATURDAY
AHEAD OF A STRONG COLD FRONT, WHICH WILL BRING MUCH COLDER
TEMPERATURES STARTING ON SUNDAY.
UPDATE
ASIDE FROM HOURLY TEMPERATURES, THE FORECAST REMAINS LARGELY ON
TRACK THIS EVENING. NO MAJOR CHANGES HAVE BEEN MADE TO THE
EXISTING FORECAST. LUDWIG
DISCUSSION
/ISSUED 435 PM MST WED JAN 29 2025/
- METEOROLOGICAL OVERVIEW:
A HIGH PRESSURE RIDGE EXTENDING WEST TO EAST FROM THE PACIFIC
NORTHWEST COAST WILL KEEP THE AREA MOSTLY DRY WITH BREEZY WINDS
OVER THE PLAINS THROUGH AT LEAST FRIDAY. DISTURBANCES MOVING OVER
THIS RIDGING WILL CONTINUE TO INCREASE WESTERLY WINDS ALOFT TODAY
THROUGH TONIGHT, INCREASING DOWNSLOPING WINDS OVER THE PLAINS.
THIS WILL BE ESPECIALLY TRUE ON THE ROCKY MOUNTAIN FRONT AND
ADJACENT PLAINS, WHERE THE PRESSURE GRADIENT WILL BE STRONGEST
ALONG A SURFACE TROUGH TO THE LEE OF THE ROCKIES. AREAS ALONG THE
MT HIGHWAY 200 CORRIDOR FROM WEST OF GREAT FALLS EAST TO EDDIE'S
CORNER AND SOUTH TO JUDITH GAP COULD SEE GUSTS UP TO 50 MPH AT
TIMES, BUT GUSTS OF 60 TO 75 MPH ARE POSSIBLE ON THE ROCKY
MOUNTAIN FRONT AND ADJACENT PLAINS EAST TO THE CUT BANK AREA.
GUSTS ELSEWHERE ON THE PLAINS WILL MOSTLY BE IN THE 30 TO 40 MPH
RANGE. WINDS WILL DECREASE SOMEWHAT THURSDAY INTO FRIDAY BUT
REMAIN BREEZY. THESE WINDS OVER THE PLAINS WILL KEEP TEMPERATURES
THERE AROUND 10 DEGREES ABOVE NORMAL. HOWEVER, THE HIGH PRESSURE
RIDGING WILL MAINTAIN TEMPERATURE INVERSIONS IN THE VALLEYS OF
CENTRAL AND SOUTHWEST MONTANA, KEEPING TEMPERATURES THERE AT LEAST
10 DEGREES BELOW NORMAL, WITH LOWS IN SOME VALLEYS FALLING BELOW
ZERO AGAIN TONIGHT AND THURSDAY NIGHT, SIMILAR TO THE LAST NIGHT
OR TWO.
A PACIFIC LOW PRESSURE TROUGH WITH AN ASSOCIATED STRONG COLD
FRONT IS FORECAST TO APPROACH THE AREA ON FRIDAY, INITIALLY
BRINGING LIGHT MEASURABLE SNOW TO THE MOUNTAINS ALONG THE
CONTINENTAL DIVIDE FRIDAY THROUGH SATURDAY. HOWEVER, AHEAD OF THE
COLD FRONT MOVING SOUTH OUT OF CANADA, WESTERLY WINDS MAY BECOME
STRONG ONCE AGAIN ON THE ROCKY MOUNTAIN FRONT. MORE SOUTHERLY
WINDS BLOWING THROUGH THE VALLEYS OF SOUTHWEST MONTANA AHEAD OF
THIS FRONT MAY HELP SCOUR OUT SOME OF THE COLD AIR THERE. THE
PASSAGE OF THIS COLD FRONT SATURDAY NIGHT OVER NORTH CENTRAL AND
CENTRAL MONTANA WILL SHIFT WINDS MORE NORTHERLY THERE, USHERING IN
COLD ARCTIC AIR THAT COULD BRING A PERIOD OF HIGHS IN THE SINGLE
DIGITS ABOVE AND BELOW ZERO AND LOWS IN THE SINGLE DIGITS AND
TEENS BELOW ZERO. IRONICALLY, CONSIDERING THE COLD AIR CURRENTLY
TRAPPED IN THE SOUTHWEST VALLEYS, THIS BITTER COLD AIR IS NOT
FORECAST TO MOVE COMPLETELY IN THERE WITH THIS SYSTEM. REGARDLESS,
THE SYSTEM IS TAPPING INTO A GOOD FEED OF PACIFIC MOISTURE, SO IT
SHOULD BRING PERIODS OF LIGHT TO MODERATE SNOW TO MUCH OF THE
FORECAST AREA SATURDAY THROUGH NEXT WEDNESDAY; HOWEVER, FORECAST
MODELS CONTINUE TO KEEP THE MAIN FOCUS FOR SNOW OVER SOUTHWEST AND
CENTRAL MONTANA. -COULSTON
- FORECAST CONFIDENCE & SCENARIOS:
WINDS TODAY:
CONFIDENCE REMAINS STEADY IN THE CURRENT AREAL AND TEMPORAL
COVERAGE OF THE HIGH WIND WARNING. THE STRONGEST WINDS ARE STILL
EXPECTED TO TAPER OFF THURSDAY MORNING. THUS NO CHANGES WERE MADE
TO THE EXISTING HEADLINES.
SNOW:
CONFIDENCE HAS CONTINUED TO INCREASE IN THE POTENTIAL FOR
SIGNIFICANT IMPACTS ALONG PORTIONS OF CENTRAL AND SOUTHWEST
MONTANA. WHILE MOST OF THE REGION IS EXPECTED TO EXPERIENCE
IMPACTS AT SOME POINT THIS WEEKEND INTO THE MIDDLE OF NEXT WEEK,
THE FIRST CONCERN FOR NOW IS THE NORTHERN ROCKIES AND NORTHWEST
BEAVERHEAD COUNTY. GIVEN THE EXPECT SNOW AMOUNTS AND THE POTENTIAL
FOR SIGNIFICANT BLOWING SNOW ALONG THE NORTHERN ROCKIES, THE
DECISION WAS MADE TO ADD THESE ZONES TO A WINTER STORM WATCH.
IT IS VERY CRUCIAL TO STRESS THAT THIS IS A LONG DURATION EVENT
INVOLVING MULTIPLE ROUNDS OF HEAVY SNOW WITH SHORT PERIODS OF
LIGHT TO NO SNOW POSSIBLE IN BETWEEN. LULLS IN THE SNOW ARE
EXPECTED TO LAST BETWEEN 3 AND 6 HOURS BEFORE HEAVIER SNOW RETURNS
TO THE REGION. AS OF RIGHT NOW THERE IS STILL SOME UNCERTAINTY IN
THE TIMING OF THESE LULLS AND IT IS STILL POSSIBLE THAT THE LULLS
MAY NOT HAPPEN AT ALL. THUS THIS WAS BEHIND THE DECISION TO EXTEND
OUT ONE WINTER STORM WATCH TO COVER THE DURATION OF THE EVENT.
ANOTHER MAJOR IMPACT EXPECTED ALONG THE NORTHERN ROCKIES WILL BE
BLOWING SNOW. WINDS UP TO 65 MPH, IN COMBINATION WITH HEAVY
SNOWFALL, WILL CAUSE A POTENTIALLY DANGEROUS SITUATION ALONG THE
GLACIER PARK REGION INCLUDING MARIAS PASS. SNOW DRIFTS MAY CAUSE
LANE BLOCKAGES AND SIGNIFICANTLY REDUCE VISIBILITY AT TIMES.
TRAVEL CONCERNS WILL BE THE GREATEST FRIDAY AND SATURDAY WITH
LINGERING IMPACTS POSSIBLE THROUGH THE START OF NEXT WEEK.
THERE ARE MULTIPLE WILD CARDS WITH THIS EVENT. THE FIRST BEING ANY
POTENTIAL ADDITIONAL ZONES THAT MAY NEED TO BE ADDED TO THE WINTER
STORM WATCH. THIS INCLUDES ROGERS PASS AND THE LINCOLN AREA, WEST
YELLOWSTONE, AND AT A LATER DATE INCLUDES THE MOUNTAIN RANGES OF
CENTRAL MONTANA INCLUDING THE LITTLE BELTS AND SNOWIES. IN THE
CASE OF THE CENTRAL MONTANA MOUNTAINS, THERE IS TOO MUCH
UNCERTAINTY THIS FAR OUT TO DETERMINE THE HOW MUCH IS EXPECTED.
BUT FOR ROGERS PASS AND WEST YELLOWSTONE, THERE IS GROWING CONCERN
AND CONFIDENCE THAT MORE SIGNIFICANT IMPACTS COULD OCCUR.
ANOTHER WILD CARD IS THE ACCUMULATING IMPACT FACTOR. THIS IS WHERE
A SITUATION DEVELOPS IN WHICH NO INDIVIDUAL PORTION OF THE EVENT
IS OVERLY SIGNIFICANT BUT THE COMBINATION OF MULTIPLE LOWER END
FACTORS COMBINE TO MAKE A SIGNIFICANT AND POTENTIALLY SEVERE
IMPACT. FOR EXAMPLE, 2 INCHES OF SNOW BY ITSELF WOULD NOT BE
CONSIDERED A MAJOR IMPACT. BUT 2 ADDITIONAL INCHES OF SNOW ON TOP
OF THE 6 INCHES THAT HAVE ALREADY FALLEN IN COMBINATION WITH
DETERIORATING ROAD CONDITIONS MAY CREATE A DOMINO EFFECT THAT
PUTS SIGNIFICANT STRAIN AND STRESS ON ROAD CREWS TRYING TO KEEP
THE ROADS OPEN AND MAINTAINED.
FOR NOW, THESE WILL BE ITEMS TO WATCH WITH FUTURE FORECASTS. AS
WE GET CLOSER TO THE EVENT, ADDITIONAL ADVISORIES AND
MODIFICATIONS TO THE WATCHES MAY BE NEEDED TO FULLY REFLECT THE
FULL NATURE OF THIS EVENT.
SNOW ACCUMULATION PROBABILITIES:
- MARIAS PASS
- 8+ INCHES: GREATER THAN 80%
- 12+ INCHES: 70 TO 80%
- 18+ INCHES: 20 TO 40%
- ROGERS PASS
- 8+ INCHES: 30 TO 50%
- 12+ INCHES: 15 TO 30%
- 18+ INCHES: 10 TO 20%
- CHIEF JOSEPH PASS
- 8+ INCHES: GREATER THAN 80%
- 12+ INCHES: 50 TO 70%
- 18+ INCHES: 10 TO 30%
COLD TEMPERATURES:
BEHIND THE COLD FRONT, TEMPERATURES ARE EXPECTED TO BE MUCH COLDER
THAN NORMAL BUT THERE IS UNCERTAINTY REMAINING AS TO EXACTLY HOW
COLD IT WILL GET. COMPARED TO EARLIER FORECASTS, THERE IS STILL
SOME DISAGREEMENT BETWEEN THE ENSEMBLE CLUSTERS ON WHERE THE
ANOMALOUS LOW PRESSURE VERSUS THE ANOMALOUS HIGH PRESSURE SETS UP
WITH MINOR CHANGES IN THE PLACEMENT OF THIS SETUP POTENTIALLY
HAVING BIG IMPACTS TO THE FORECAST. THIS WILL BE MONITORED WITH
FUTURE FORECASTS. -THOR
AVIATION
30/00Z TAF PERIOD
VFR CONDITIONS PREVAIL THROUGH THE TAF PERIOD. STRONG INVERSIONS
AND LIGHT WINDS IN THE SOUTHWEST VALLEYS WILL KEEP HAZE CONCERNS
THROUGH THE PERIOD FOR KHLN/KBZN. VISIBILITY WILL GENERALLY STAY
VFR, BUT THERE'S A SLIGHT CHANCE IT CAN DROP TO MVFR BRIEFLY.
GUSTY WINDS CONTINUE AT KCTB, WITH BREEZY WINDS ACROSS THE NORTH-
CENTRAL MT PLAINS. WINDS COULD GUST AS HIGH AT 50KT AT TIMES AT
KCTB THROUGH EARLY THURSDAY MORNING. -WILSON
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 42 27 43 32 / 0 0 0 0
CTB 43 26 39 24 / 0 0 0 0
HLN 39 15 38 22 / 0 0 0 0
BZN 38 8 37 17 / 0 0 0 0
WYS 38 -5 33 1 / 0 0 0 0
DLN 38 11 38 17 / 0 0 0 0
HVR 39 20 38 20 / 0 0 0 0
LWT 44 23 43 27 / 0 0 0 0
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WARNING UNTIL 6 AM MST THURSDAY FOR EASTERN GLACIER,
WESTERN TOOLE, AND CENTRAL PONDERA-NORTHERN HIGH PLAINS.
WINTER STORM WATCH FROM FRIDAY MORNING THROUGH MONDAY AFTERNOON
FOR EAST GLACIER PARK REGION-SOUTHERN ROCKY MOUNTAIN FRONT.
WINTER STORM WATCH FROM FRIDAY EVENING THROUGH MONDAY AFTERNOON
FOR NORTHWEST BEAVERHEAD COUNTY.
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