879
FXUS65 KTFX 171032
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
332 AM MST TUE DEC 17 2024
KEY MESSAGES
- WARM FRONT LIFTS THROUGH THE AREA ON WEDNESDAY, BRINGING SOME
BRIEF SNOW BEFORE HIGH WINDS DEVELOP IN THE LATE MORNING AND
AFTERNOON
- WINDS WILL BE STRONGEST ALONG THE ROCKY MOUNTAIN FRONT, BUT
WINDS OVER 60 MPH WILL BE POSSIBLE ACROSS MUCH OF NORTH CENTRAL
AND SOUTHWESTERN MONTANA
- GENERALLY WARMER AND TRANQUIL, IF BREEZY AT TIMES, WEATHER
EXPECTED THROUGH THE REST OF THIS WEEK AS RIDGING BUILDS IN,
THOUGH ACTIVE WEATHER MAY RETURN NEXT WEEK
DISCUSSION
- METEOROLOGICAL OVERVIEW:
UPPER LEVEL RIDGING WILL BEGIN TO BUILD INTO THE AREA TODAY IN
THE WAKE OF A WEAK TROUGH THAT MOVED THROUGH OVERNIGHT. AS THIS
RIDGE BUILDS IN, EXPECT A FAIRLY QUIET WEATHER DAY ACROSS NORTH
CENTRAL AND SOUTHWESTERN MONTANA, THOUGH WEAK HIGH PRESSURE
SLIDING IN ACROSS THE PLAINS WILL KEEP THE PLAINS ON THE COOL SIDE
EVEN AS THE SOUTHWESTERN VALLEYS BEGIN TO WARM UP UNDER THE
RIDGE’S INFLUENCE.
THE RIDGE THAT BUILDS IN TODAY WILL NOT LAST LONG, AS A STRONG,
VIGOROUS SHORTWAVE TROUGH ROARS INTO THE AREA, ALONG WITH IT’S
ASSOCIATED JET STREAK. WHILE SOME LIGHT SNOWFALL (AND ISOLATED
FREEZING DRIZZLE) WILL BE POSSIBLE AS THE SYSTEM’S WARM FRONT
SURGES THROUGH THE AREA, THE BIGGER STORY WILL BE THE STRONG WINDS
ASSOCIATED WITH THIS SYSTEM (MORE ON THAT IN THE CONFIDENCE &
SCENARIOS SECTION). AFTER THIS SHORTWAVE, UPPER LEVEL RIDGING WILL
TAKE A FIRM HOLD ACROSS THE WESTERN CONUS, WHICH WILL RESULT IN
WARMING CONDITIONS AND GENERALLY QUIET WEATHER, THOUGH IT WILL BE
A BIT BREEZY AT TIMES. LOOKING INTO NEXT WEEK, THERE IS FAIRLY
GOOD AGREEMENT IN THE MODELS SUGGESTING A SLIGHTLY ACTIVE, BUT
STILL WARM, WEATHER PATTERN FOR AT LEAST EARLY NEXT WEEK HEADING
INTO CHRISTMAS.
- FORECAST CONFIDENCE & SCENARIOS:
FOR TODAY, CONFIDENCE IS HIGH IN A MOSTLY QUIET DAY, ASIDE FROM
SOME EARLY MORNING FOG AND ISOLATED LIGHT SNOW SHOWER BEFORE HIGH
PRESSURE SLIDES IN FROM THE NORTH.
WEDNESDAY WILL BE THE HIGHEST IMPACT PERIOD OF THIS FORECAST AS
HIGH WINDS IMPACT MOST OF THE AREA. CONFIDENCE CONTINUES TO
STEADILY INCREASE IN A SEASONABLY NOTABLE HIGH WIND EVENT, WITH
MANY AREAS OF NORTH CENTRAL AND SOUTHWESTERN MONTANA NOW HAVING A
50-70%+ CHANCE OF WIND GUSTS OVER 55 MPH, AND AREAS ALONG THE
ROCKY MOUNTAIN FRONT, JUDITH GAP, AND SOME OF THE RIDGES OF
SOUTHWESTERN MONTANA HAVING OVER A 50% CHANCE OF WIND GUSTS OVER
65 MPH, I HAVE ELECTED TO EXPAND THE EXISTING HIGH WIND WATCH TO
MUCH OF SOUTHWESTERN MONTANA, ALONG WITH SOME EXPANSION FURTHER
NORTH ACROSS THE PLAINS. SUPPORTING THIS DECISION ARE TWO THINGS:
EARLIER TIMING AND, IN TURN, ATMOSPHERIC PROFILES MORE FAVORABLE
TO THE TRANSPORT OF THE STRONGEST WINDS TO THE SURFACE THANKS TO
DAYTIME THERMAL MIXING STILL BEING IN PLAY. RECENT ATMOSPHERIC
PROFILES SUGGEST THAT MOST LOW ELEVATION AREAS WILL HAVE ABOUT
APPROXIMATELY A 3-4 HOUR WINDOW FOR WIND GUSTS OVER 60 MPH, NAMELY
BETWEEN NOON AND 4, WHEN THERMAL MIXING WILL BEGIN TO WEAKEN AS
THE SUN SETS. THIS WILL ALSO COINCIDE WITH THE ARRIVAL OF COOLING
ALOFT, WHICH WILL MAKE THE AIR ALOFT EVEN MORE READY TO MIX TO THE
SURFACE VIA MECHANICAL MIXING OF THE AIR. AS CONFIDENCE
INCREASES, I WOULD EXPECT THAT MOST AREAS SEE THE HIGH WIND
WATCHES UPGRADED TO HIGH WIND WARNINGS, THOUGH WE ARE JUST A BIT
OUTSIDE THE TIME WINDOW FOR THE UPGRADES. REGARDLESS OF WHAT
PRODUCT IS OUT AT THE END OF THE DAY TODAY, BE PREPARED FOR A VERY
WINDY DAY ACROSS NORTH CENTRAL AND SOUTHWESTERN MONTANA, AND
ENSURE THAT ANY LOOSE CHRISTMAS/HOLIDAY DECORATIONS ARE SECURED.
BEYOND WEDNESDAY, WITH UPPER LEVEL RIDGING BECOMING ENTRENCHED
ACROSS THE WESTERN US, EXPECT TEMPERATURES TO GRADUALLY WARM, WITH
LITTLE TO NO PRECIPITATION EXPECTED. THIS RIDGE WILL HOLD THROUGH
SATURDAY, THOUGH THERE ARE SOME INDICATIONS THAT OUR WEATHER COULD
BECOME A BIT MORE ACTIVE EARLY NEXT WEEK. LUDWIG
AVIATION
17/06Z TAF PERIOD
A WEAK DISTURBANCE WILL CONTINUE MOSTLY BROKEN TO OVERCAST LOW VFR
AND MVFR CEILINGS, CAUSING SOME MOUNTAIN TOP OBSCURATION. LIGHT
SNOW ASSOCIATED WITH THE DISTURBANCE COULD STILL LOWER CONDITIONS
TO IFR AT TIMES, BUT THE SNOW WILL CONTINUE TO DECREASE FROM THE
WEST THROUGH 12Z. HOWEVER, BREAKS IN THE CLOUDS IN THE WAKE OF THE
DISTURBANCE MAY ALLOW LOWER CLOUDS AND FOG TO FORM, CAUSING MAINLY
IFR CONDITIONS AT TIMES THROUGH 17Z OR SO. BROKEN VFR TO MVFR
SHOULD LINGER THROUGH AT LEAST 18/00Z IN A NORTHWEST FLOW ALOFT,
BUT CEILINGS SHOULD START TO LIFT AFTER 00Z. THE PASSAGE OF THIS
DISTURBANCE WILL ALSO CAUSE SOME MOUNTAIN WAVE TURBULENCE.
-COULSTON
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 27 16 52 21 / 10 40 20 10
CTB 20 10 45 14 / 0 50 40 10
HLN 37 26 52 29 / 10 30 40 10
BZN 36 21 49 22 / 10 20 30 10
WYS 30 16 32 13 / 50 60 60 20
DLN 37 24 46 20 / 10 10 20 0
HVR 19 5 42 6 / 20 50 60 30
LWT 29 14 48 18 / 20 30 30 20
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY NIGHT
FOR EAST GLACIER PARK REGION-EASTERN GLACIER, WESTERN TOOLE, AND
CENTRAL PONDERA-NORTHERN HIGH PLAINS-SOUTHERN HIGH PLAINS-
SOUTHERN ROCKY MOUNTAIN FRONT.
HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
NIGHT FOR BEARS PAW MOUNTAINS AND SOUTHERN BLAINE-EASTERN
PONDERA AND EASTERN TETON-NORTHERN BLAINE COUNTY-WESTERN AND
CENTRAL CHOUTEAU COUNTY.
HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY
NIGHT FOR BIG BELT, BRIDGER AND CASTLE MOUNTAINS-CANYON FERRY
AREA-CASCADE COUNTY BELOW 5000FT-ELKHORN AND BOULDER MOUNTAINS-
FERGUS COUNTY BELOW 4500FT-GALLATIN VALLEY-GALLATIN AND MADISON
COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS-GATES OF THE MOUNTAINS-
HELENA VALLEY-JUDITH BASIN COUNTY AND JUDITH GAP-LITTLE BELT AND
HIGHWOOD MOUNTAINS-MADISON RIVER VALLEY-MEAGHER COUNTY VALLEYS-
MISSOURI HEADWATERS-SNOWY AND JUDITH MOUNTAINS-UPPER BLACKFOOT
AND MACDONALD PASS.
WINTER WEATHER ADVISORY UNTIL 9 AM MST THIS MORNING FOR GALLATIN
AND MADISON COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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