651
FXUS65 KTFX 090527
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1027 PM MST SAT MAR 8 2025
AVIATION SECTION UPDATED.
KEY MESSAGES
- BREEZY TO WINDY AND MILD CONDITIONS ARE EXPECTED THROUGH THE
WEEKEND, WITH THE STRONGEST WINDS ALONG THE ROCKY MOUNTAIN FRONT AND
THE ADJACENT HIGH PLAINS.
- A FAST MOVING PACIFIC WEATHER SYSTEM EXPANDS THE AREA OF STRONG
WINDS DEEPER INTO THE PLAINS SUNDAY NIGHT INTO MONDAY.
- LIGHT MOUNTAIN SNOW IS ALSO EXPECTED MONDAY AND TUESDAY, MOSTLY
OVER THE HIGHER TERRAIN ALONG THE ROCKY MOUNTAIN FRONT.
- THE NEXT CHANCE FOR WIDESPREAD ACCUMULATING SNOW MOVES IN FOR THE
SECOND HALF OF THE WORKWEEK.
UPDATE
/ISSUED 915 PM MST SAT MAR 8 2025/
NO MAJOR CHANGES WERE MADE TO THE FORECAST THIS EVENING. STRONG
700MB WINDS WILL CONTINUE TO MOVE IN TONIGHT OVER THE ROCKY
MOUNTAIN FRONT, AND WILL MIX DOWN THOSE STRONG WINDS TO THE
SURFACE. THESE STRONG WINDS WILL EXPAND EAST FROM THE FOOTHILLS OF
THE ROCKIES TO THE CUT BANK AND CHOTEAU AREAS SUNDAY MORNING.
THERE WILL BE A FEW INSTANCES WHERE IMMEDIATE DOWNWIND AREAS OF
HIGHER TERRAIN (LIKE THE SWEET GRASS HILLS, BEAR'S PAW, HIGHWOODS,
AND LITTLE BELTS) WHERE WINDS TRY TO REACH 40 MPH SUSTAINED AND
GUSTS OF 58 MPH BRIEFLY OVERNIGHT. SINCE MORE WIDESPREAD WINDS ARE
EXPECTED LATE SUNDAY NIGHT/MONDAY MORNING, I'VE HELD OFF ON
EXPANDING THE CURRENT HIGH WIND WARNINGS SINCE THESE INSTANCES
WILL BE MORE LOCALIZED. -WILSON
DISCUSSION
/ISSUED 915 PM MST SAT MAR 8 2025/
- METEOROLOGICAL OVERVIEW:
RIDGING ALOFT REMAINS IN PLACE FOR MUCH OF THE WEEKEND, BUT
WESTERLY FLOW ALOFT WILL STEADILY INCREASE IN ADVANCE OF A FAST
MOVING SHORTWAVE AND ATTENDANT COLD FRONT DUE TO ARRIVE SUNDAY
NIGHT INTO MONDAY. GUSTY TO AT TIMES STRONG WINDS ARE EXPECTED
ALONG THE ROCKY MOUNTAIN FRONT AND PLAINS GIVEN MOUNTAIN WAVE
ACTIVITY AND EFFICIENT DIURNAL MIXING. TEMPERATURES WARM TO 15 TO
25 DEGREES ABOVE AVERAGE OVER THE PLAINS BY SUNDAY, WITH A MORE
MODEST 5 TO 10 DEGREES ABOVE AVERAGE OVER THE SOUTHWEST. THE
AFOREMENTIONED INCREASING WESTERLY FLOW ALOFT WILL BRING PASSING
MID- TO HIGHER LEVEL CLOUDINESS OVER THE REGION AND THERE WILL BE
SOME LOWER STRATUS AND PATCHY FOG TONIGHT INTO SUNDAY MORNING OVER
THE CENTENNIAL VALLEY AND WEST YELLOWSTONE AREA.
THE FAST MOVING PACIFIC SHORTWAVE AND COLD FRONT APPROACH THE
CONTINENTAL DIVIDE SUNDAY NIGHT BEFORE CLEARING THE FORECAST AREA
ON MONDAY. H700 WINDS PEAK IN THE 60 TO 70 KT RANGE SUNDAY
AFTERNOON THOUGH EARLY MONDAY AFTERNOON, WHICH IS ABOUT 3 STANDARD
DEVIATIONS ABOVE AVERAGE ACCORDING THE NAEFS STANDARD ANOMALY
ANALYSIS. MOUNTAIN WAVE ACTIVITY WILL INITIALLY DRIVE THE WINDS
BEFORE ROBUST COLD AIR ADVECTION AND DIURNAL MIXING TAKE OVER BY
MONDAY AFTERNOON. THESE FACTORS WILL EXPAND THE AREA OF STRONGER
WINDS ALONG THE ROCKY MOUNTAIN FRONT DEEPER INTO THE PLAINS. H700
TEMPERATURES DIP TO AROUND -15C WHICH WILL WRING OUT ANY AVAILABLE
MOISTURE IN THE FORM OF SNOW SHOWER ACTIVITY MOVING IN A
NORTHWEST TO SOUTHEAST FASHION. ACCUMULATING SNOW WILL GENERALLY
BE CONFINED TO MOUNTAIN AREAS, WITH THE HIGHER TERRAIN OF GLACIER
NATIONAL PARK SEEING THE LION'S SHARE.
ENSEMBLES ARE IN GOOD AGREEMENT WITH MOIST WESTERLY FLOW ALOFT
REMAINING IN PLACE HEADING TOWARDS THE MID- WEEK PERIOD FOR NEAR
AVERAGE TEMPERATURES AND PERIODS OF BREEZY TO WINDY CONDITIONS.
PASSING DISTURBANCES WILL BRING SOME LOWER END MOUNTAIN SNOW AND
PERHAPS EVEN A FEW SPRINKLES OR FLURRIES OVER LOWER ELEVATIONS
AREAS.
ANOTHER SPLITTING TROUGH APPROACHES THE PACIFIC COAST ON
WEDNESDAY AND HEADS TOWARDS THE INTERIOR WEST TO CLOSE OUT THE
WORK WEEK. WHILE NEARLY ALL ENSEMBLES HIGHLIGHT A SIGNIFICANT
PORTION OF ITS ENERGY AND MOISTURE DIVING SOUTHWARD INTO THE GREAT
BASIN AND THE SOUTHWESTERN US, THERE ARE DISAGREEMENTS ON
SHORTWAVE STRENGTH AND IMPACTS OVER THE NORTHERN ROCKIES.
CURRENTLY ABOUT A THIRD OF ENSEMBLES SUPPORT MORE ROBUST LOWER
ELEVATION SNOWFALL IN EXCESS OF 3 INCHES FOR THE THURSDAY THROUGH
FRIDAY TIMEFRAME WHILE THE REMAINDER ARE MORE MODEST AND KEEP MOST
OF THE IMPACTS IN MOUNTAIN AREAS. - RCG
- FORECAST CONFIDENCE & SCENARIOS:
STRONG WIND POTENTIAL THROUGH MONDAY :
DEEP LAYER MIXING WILL MAINTAIN WIND GUSTS IN THE 30 TO 55 MPH
RANGE ALONG THE ROCKY MOUNTAIN FRONT AND THE PLAINS THIS AFTERNOON
AND EVENING. STRONGER WINDS ALOFT ARRIVE TONIGHT AND BRING THE
POTENTIAL MORE MORE INTENSE MOUNTAIN WAVE ACTIVITY ALONG THE
NORTHERN ROCKY MOUNTAIN FRONT AND ADJACENT HIGH PLAINS. SUSTAINED
WINDS OF 40 MPH AND GUSTS ABOVE 55 MPH (70 TO 90% CHANCE) WILL
BECOME MORE COMMON WITH CHANCES FOR GUSTS EXCEEDING 75 MPH
INCREASING TO AS HIGH AS 70% TOWARDS MORNING. GIVEN THESE
PROBABILITIES AND THE FACT THAT MOUNTAIN WAVES TEND TO ARRIVE
SLIGHTLY AHEAD OF MODEL GUIDANCE, I DECIDED TO UPGRADE THE HIGH
WIND WATCH TO A WARNING AND MOVE ITS START TIME TO 11 PM MST
TONIGHT FOR THE NORTHERN ROCKY MOUNTAIN FRONT AND THE ADJACENT
NORTHERN HIGH PLAINS ZONES.
I ALSO UPGRADED THE REMAINING WESTERN AREAS OF THE HIGH WIND
WATCH TO A WARNING, WITH NO TIMING CHANGES, GIVEN SUNDAY MORNING
STILL LOOKING TO BE THE GATEWAY TO THE MORE WIDESPREAD STRONGER
WINDS. THESE CHANGES REASONABLY MATCH THE CURRENT METEOROLOGICAL
SET UP AND THE RESULTANT 80% PROBABILITIES FOR 40 MPH SUSTAINED
WINDS AND 55 MPH GUSTS. THERE'S A LITTLE MORE TIME TO EVALUATE THE
REMAINDER OF THE WATCH SLATED TO GO IN EFFECT LATE SUNDAY NIGHT
OR MONDAY MORNING. THE PRIMARY QUESTION FOR THESE AREAS WILL BE
THE TEMPORAL HIGHER END WIND PERSISTENCE.
SNOW MONDAY THROUGH WEDNESDAY :
A COLDER AND MORE MOIST WESTERLY FLOW ALOFT IS EXPECTED TO SETTLE
IN THE WAKE OF THE COLD FRONT MONDAY AND TUESDAY. THE HIGHER
TERRAIN OF THE NORTHERN ROCKY MOUNTAIN FRONT WILL BE THE PRIMARY
TARGET FOR ACCUMULATING SNOW. CURRENT PROBABILISTIC GUIDANCE
SUPPORT A 2 TO 4 INCH SNOWFALL IN THE MARIAS PASS AREA AND AMOUNTS
EXCEEDING 6 INCHES OVER THE HIGHER TERRAIN OF GLACIER NATIONAL
PARK. MOST OTHER LOCATIONS WILL ONLY SEE A SHORT OPPORTUNITY FOR
SNOW SHOWER ACTIVITY ON MONDAY WITH LITTLE TO NO ACCUMULATIONS,
THOUGH THE POTENTIAL FOR LOCALIZED AND BRIEF VISIBILITY REDUCTIONS
WILL REQUIRE MONITORING. SNOWFALL WILL BEGIN TO PICK UP ALONG THE
CONTINENTAL DIVIDE ONCE AGAIN ON WEDNESDAY AS PACIFIC MOISTURE
INCREASES AHEAD OF THE LATE WEEK TROUGH.
WIDESPREAD ACCUMULATING SNOW POTENTIAL THURSDAY AND FRIDAY :
AS MENTIONED IN THE METEOROLOGICAL OVERVIEW SECTION, AROUND A
THIRD OF ENSEMBLES SUPPORT LOWER ELEVATION SNOWFALL EXCEEDING 3
INCHES ON WIDESPREAD BASIS. OVERALL SNOWFALL AMOUNTS WILL GREATLY
DEPEND ON THE STRENGTH OF THE NORTHERN PART OF THE TROUGH AND ITS
DEFORMATION ZONE. CURRENT PROBABILISTIC GUIDANCE FAVORS MOUNTAIN
AREAS WITH THE BEST CHANCES (60 TO 90%) FOR 2 INCHES OR MORE OF
SNOW OVER A 48 HOUR PERIOD ENDING FRIDAY AD 6 PM MDT. CONFIDENCE
IS HIGHEST OVER THE GALLATIN AND MADISON RANGES WHERE THERE IS
OVER A 60% CHANCE FOR SNOWFALL AMOUNTS EXCEEDING 6 INCHES. - RCG
AVIATION
09/06Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL AT ALL TERMINALS DURING THIS TAF PERIOD.
IT WILL BE WINDY ACROSS THE NORTH-CENTRAL MONTANA TERMINALS (KCTB,
KHVR, KGTF, AND KLWT) DURING THE DURATION OF THIS TAF PERIOD. THERE
WILL BE INSTANCES OF LOW-LEVEL WIND SHEAR AND MOUNTAIN WAVE
TURBULENCE ACROSS NORTH-CENTRAL MONTANA DURING THE DURATION OF THIS
TAF PERIOD. THERE WILL BE INSTANCES OF LOW-LEVEL WIND SHEAR AND
MOUNTAIN WAVE TURBULENCE FROM 10/02Z ON THROUGH THE END OF THE TAF
PERIOD AT THE KEKS AND KBZN TERMINALS. -IG
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 42 61 43 49 / 0 0 0 10
CTB 36 58 35 36 / 0 0 20 40
HLN 30 56 34 47 / 0 0 0 10
BZN 21 50 29 47 / 0 0 0 10
WYS 11 41 18 39 / 0 0 0 10
DLN 26 51 28 47 / 0 0 0 0
HVR 36 63 37 42 / 0 0 0 10
LWT 34 54 35 43 / 0 0 0 10
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WARNING UNTIL 1 PM MST MONDAY FOR EAST GLACIER PARK
REGION-NORTHERN HIGH PLAINS.
HIGH WIND WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY AFTERNOON
FOR EASTERN TOOLE AND LIBERTY.
HIGH WIND WATCH FROM MONDAY MORNING THROUGH MONDAY AFTERNOON FOR
BEARS PAW MOUNTAINS AND SOUTHERN BLAINE-CASCADE COUNTY BELOW
5000FT-FERGUS COUNTY BELOW 4500FT-HILL COUNTY-JUDITH BASIN
COUNTY AND JUDITH GAP-NORTHERN BLAINE COUNTY-SNOWY AND JUDITH
MOUNTAINS.
HIGH WIND WARNING FROM 6 AM SUNDAY TO 1 PM MST MONDAY FOR
SOUTHERN HIGH PLAINS-SOUTHERN ROCKY MOUNTAIN FRONT.
HIGH WIND WARNING FROM 9 AM SUNDAY TO 1 PM MST MONDAY FOR
EASTERN GLACIER, WESTERN TOOLE, AND CENTRAL PONDERA.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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