729
FXUS65 KTFX 051839
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1239 PM MDT SUN APR 5 2026
KEY MESSAGES
- THE POTENTIAL FOR A WIDESPREAD AND INTENSE WIND EVENT CONTINUES
TO GROW FOR THE DAY ON TUESDAY, WITH THE MOST INTENSE WINDS
CURRENTLY EXPECTED TO OCCUR ALONG AND WEST OF THE I-15
CORRIDOR.
- LIGHT MOUNTAIN SNOW AND LOWER ELEVATION RAIN AND SNOW SHOWERS
DEVELOP TUESDAY NIGHT INTO WEDNESDAY BEHIND A COLD FRONT.
- ANOTHER TROUGH LOOKS TO MOVE IN DURING THE SECOND HALF OF NEXT WEEKEND
FOR ANOTHER COOL DOWN AND INCREASED SHOWER ACTIVITY.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
NORTHWEST TO QUASI-NORTHWEST FLOW ALOFT WILL REMAIN OVER THE
NORTHERN ROCKIES THROUGH MONDAY WHILE A 1040 MB SURFACE HIGH MOVES
SOUTHEASTWARD OUT OF CANADIAN PRAIRIES INTO NORTHERN PLAINS. THIS
WILL BRING A MOIST EASTERLY FLOW IN THE LOW LEVELS FOR CLOUDIER
AND COOLER CONDITIONS, PARTICULARLY FOR CENTRAL AND NORTH-CENTRAL
MT. THERE MAY BE SOME PATCHY FOG AND SPOTTY LIGHT PRECIPITATION,
THOUGH EASTERLY BREEZES SHOULD REDUCE FOG IMPACTS SOME AND
PRECIPITATION AMOUNTS LOOK TO BE NEGLIGIBLE AND MOSTLY
CONCENTRATED ALONG THE HI-LINE.
ON TUESDAY, A COMPACT PACIFIC TROUGH AND ATTENDANT COLD FRONT
WILL BRING A PERIOD OF STRONG GUSTY WINDS TO MUCH OF THE FORECAST
AREA. AN H700/H500 60 TO 80 KT JET, SUPPORTED BY COLD AIR
ADVECTION, LOOKS TO PASS THROUGH DURING LATE MORNING AND AFTERNOON
HOURS WHEN DIURNAL MIXING IS NEAR ITS PEAK. THERE WILL ALSO BE
MOUNTAIN WAVE ACTIVITY THAT WILL CONTRIBUTE TO LOCALIZED STRONGER
GUSTS NEAR AREAS OF HIGHER TERRAIN. THESE FACTORS WILL MAKE THIS
WINDS MORE IMPACTFUL THAN A TYPICAL EVENT. THE MOST PERSISTENT
STRONG WINDS LOOK TO OCCUR ALONG THE ROCKY MOUNTAIN FRONT AND THE
PLAINS ALONG AND WEST OF THE I15 CORRIDOR WHERE MAX GUSTS IN THE
75 TO 90 MPH RANGE WILL BE COMMON. MOST OF THE WINDS WILL OCCUR IN
THE DAYLIGHT HOURS WITH THE EXCEPTION OF FERGUS COUNTY AND AREAS
NEAR THE BEAR'S PAW MOUNTAINS. THESE LOCATIONS WILL SEE THEIR
STRONGEST WINDS LATER IN THE AFTERNOON AND CONTINUING WELL INTO
THE OVERNIGHT HOURS.
LIGHT MOUNTAIN SNOW AND LOWER ELEVATION SCATTERED RAIN AND SNOW
SHOWER ACTIVITY WILL DEVELOP ON THE BACKSIDE OF THIS SYSTEM WITH A
SHORT PERIOD OF BELOW AVERAGE TEMPERATURES FOLLOWING THE COLD
FRONTAL PASSAGE. MILDER CONDITIONS MOVE IN FOR NEXT WEEKEND BEFORE
ANOTHER TROUGH PASSES THROUGH HEADING INTO EARLY NEXT WEEK. WHILE
THIS SYSTEM SHOULD BRING SOME COOLER TEMPERATURES AND INCREASED
SHOWER ACTIVITY, CONFIDENCE IS LOW IN REGARDS TO PRECIPITATION
COVERAGE AND AMOUNTS DUE TO A LARGE PORTION OF THE SAID TROUGH
SHEARING OFF AND MOVING SOUTHEAST TOWARD THE GREAT BASIN AND
SOUTHWESTERN CONUS. - RCG
- FORECAST CONFIDENCE & SCENARIOS:
HIGH WIND POTENTIAL ON TUESDAY...
CONFIDENCE CONTINUES TO RISE FROM SHIFT-TO-SHIFT THAT HIGH WINDS
WILL OCCUR ON TUESDAY ACROSS PORTIONS OF SOUTHWEST, CENTRAL, AND
NORTH CENTRAL MONTANA; HOWEVER, THE AREAL COVERAGE OF THESE HIGH
WINDS STILL REMAINS UNCERTAIN AND THUS THE HIGH WIND WATCHES THAT
WERE ISSUED OVER THE PAST 24 HOURS REMAIN VALID. ADDITIONALLY, THE
HIGH WIND WATCH WAS EXPANDED TO INCLUDE THE GATES OF MOUNTAINS,
HELENA VALLEY, MEAGHER COUNTY VALLEYS, AND ELKHORN AND BOULDER
MOUNTAINS ZONES. WHILE THESE LOCATIONS MAY SEE A SHORTER PERIOD OF
HIGH WINDS AS COMPARED TO OTHER AREAS THE POTENTIAL INTENSITY OF
THESE WINDS WITHIN A SHORTER PERIOD OF TIME NECESSITATED THE FURTHER
EXPANSION OF THE HIGH WIND WATCH.
RUN-TO-RUN VALUES WITHIN THE ECMWF EFIS AND NAEFS CONTINUE TO
INCREASE, WHICH IS GIVING RISE TO INCREASED CONFIDENCE THAT A VERY
UNUSUAL TO POTENTIALLY EXTREME HIGH WIND EVENT, WITH RESPECT TO
APRIL CLIMATOLOGY, MAY OCCUR ACROSS PORTIONS OF THE NORTHERN ROCKIES
ON TUESDAY. ECMWF EFIS WITH RESPECT TO WIND GUSTS HAVE NOW REACHED
AN IMPRESSIVE 0.8 TO 0.99 ACROSS MUCH OF SOUTHWEST THROUGH NORTH
CENTRAL MONTANA, WITH EVEN A SHIFT OF TAILS (SOTS) OF 1 NOW BEING
OBSERVED ACROSS MUCH OF CENTRAL MONTANA. WHILE A SOT OF 1 APPEARING
IS NOT IN ITSELF IMPRESSIVE IT IS WORTH MENTIONING GIVEN THE RUN-TO-
RUN TENDENCY OVER THE PAST 48 HOURS FOR VALUES TO INCREASE.
ADDITIONALLY, EFIS WITH RESPECT TO SUSTAINED WIND SPEEDS NOW RANGE
FROM 0.6 TO 0.9 ACROSS MUCH OF THE SAME AREAS, WHICH IS CONCERNING
AS A PROLONGED PERIOD OF SUSTAINED HIGH WINDS WILL STRESS
INFRASTRUCTURE THAT HAS ALREADY BEEN STRESSED OVER MULTIPLE WIND
EVENTS SINCE OCTOBER 2025. H700 WINDS PER NAEFS ANALYSIS ARE
FORECASTED TO REACH BETWEEN 40-70KTS ON TUESDAY, WITH RETURN
INTERVAL FOR THESE VALUES OCCURRING 1 DAY EVERY 10 YEARS DURING THE
FIRST HALF OF APRIL CLIMATOLOGY. THIS FURTHER HELPS TO STRENGTHEN
CONFIDENCE IN AN IMPACTFUL WIND EVENT, ESPECIALLY CONSIDERING THAT
THE INCREASING APRIL SUN ANGLE WILL CONTRIBUTE TO DEEPER MIXING AS
COMPARED TO DURING THE HEART OF THE WINTER SEASON. AS OF RIGHT NOW
DETERMINISTIC GUIDANCE HAS THE STRONGEST MID-LEVEL WINDS AND TROUGH
AXIS MOVING OVER SOUTHWEST THROUGH NORTH CENTRAL MONTANA FROM THE
MID-MORNING HOURS ON TUESDAY THROUGH THE AFTERNOON HOURS, WHICH
SHOULD ENSURE THAT A PORTION OF THESE WINDS MIX DOWN. WHERE
EXACTLY THE CORE OF STRONGEST WINDS IS AT BETWEEN 18-24Z ON
TUESDAY DURING PEAK MIXING WILL ULTIMATELY DETERMINE WHERE THE
MOST INTENSE WINDS OCCUR, BUT NONE-THE-LESS OTHER AREAS WILL
STILL SEE STRONG WINDS.
THE FOLLOWING TABLE ILLUSTRATES THE NBM10PCT (LOW END SCENARIO),
NBM50PCT (MOST LIKELY SCENARIO), AND NBM90PCT (HIGH END SCENARIO)
FOR MAXIMUM WIND GUSTS (MPH) AND SUSTAINED WINDS SPEEDS (MPH) FOR
SELECT LOCATIONS ACROSS NORTH CENTRAL, CENTRAL, AND SOUTHWEST
MONTANA :
24 HOUR MAXIMUM WIND GUSTS
LOCATION LOW END | MOST LIKELY | HIGH END
BROWNING 60 MPH | 75 MPH | 85 MPH
CUT BANK 60 MPH | 70 MPH | 85 MPH
HAVRE 45 MPH | 50 MPH | 65 MPH
GREAT FALLS 50 MPH | 60 MPH | 75 MPH
LEWISTOWN 40 MPH | 50 MPH | 60 MPH
HELENA 45 MPH | 60 MPH | 75 MPH
WHITE SULPHUR SPRINGS 45 MPH | 50 MPH | 65 MPH
BOZEMAN 50 MPH | 55 MPH | 70 MPH
DILLON 50 MPH | 60 MPH | 70 MPH
ENNIS 40 MPH | 50 MPH | 60 MPH
WEST YELLOWSTONE 35 MPH | 45 MPH | 55 MPH
24 HOUR MAXIMUM SUSTAINED WIND SPEEDS
LOCATION LOW END | MOST LIKELY | HIGH END
BROWNING 40 MPH | 50 MPH | 60 MPH
CUT BANK 40 MPH | 50 MPH | 60 MPH
HAVRE 30 MPH | 35 MPH | 45 MPH
GREAT FALLS 35 MPH | 45 MPH | 50 MPH
LEWISTOWN 25 MPH | 35 MPH | 40 MPH
HELENA 25 MPH | 40 MPH | 50 MPH
WHITE SULPHUR SPRINGS 25 MPH | 35 MPH | 40 MPH
BOZEMAN 30 MPH | 35 MPH | 45 MPH
DILLON 30 MPH | 35 MPH | 45 MPH
ENNIS 30 MPH | 40 MPH | 50 MPH
WEST YELLOWSTONE 15 MPH | 15 MPH | 20 MPH
- MOLDAN
AVIATION
05/18Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL AT THE KBZN, KEKS, AND KHLN TERMINALS
DURING THIS TAF PERIOD WITH LIGHT AND VARIABLE WINDS AND HIGH-LEVEL
CLOUDS AROUND. AT THE REST OF THE TERMINALS THERE WILL BE MVFR LEVEL
CEILINGS AROUND AFTER 06/00Z. THE LOW CEILINGS WILL AFFECT THE KCTB
TERMINAL FIRST BEFORE MOVING TO THE KHVR, KGTF, AND KLWT TERMINALS
TOWARDS THE END OF THIS TAF PERIOD. AT THE KHVR TERMINAL THERE IS A
15 - 25% CHANCE FOR RAIN FROM NOW THROUGH 06/00Z. THERE WILL BE
PERIODS OF MOUNTAIN OBSCURATION AFTER 06/00Z ACROSS NORTH-CENTRAL
MONTANA. MONDAY MORNING THERE IS A LOW CHANCE FOR PATCHY FOG AT THE
KHLN AND KBZN TERMINALS. -IG
PRELIMINARY POINT TEMPS/POPS
GTF 29 56 40 66 / 10 10 10 10
CTB 27 53 37 58 / 10 10 0 40
HLN 35 62 38 68 / 0 10 0 10
BZN 32 61 34 69 / 0 10 10 20
WYS 25 57 25 56 / 0 10 10 30
DLN 35 64 37 67 / 0 0 0 10
HVR 27 51 32 66 / 10 0 10 20
LWT 28 48 34 66 / 10 10 0 30
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING 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 TUESDAY MORNING THROUGH TUESDAY EVENING FOR
BEAVERHEAD AND WESTERN MADISON BELOW 6000FT-BIG BELT, BRIDGER
AND CASTLE MOUNTAINS-CASCADE COUNTY BELOW 5000FT-EASTERN PONDERA
AND EASTERN TETON-EASTERN TOOLE AND LIBERTY-ELKHORN AND BOULDER
MOUNTAINS-GATES OF THE MOUNTAINS-HELENA VALLEY-JUDITH BASIN
COUNTY AND JUDITH GAP-LITTLE BELT AND HIGHWOOD MOUNTAINS-MADISON
RIVER VALLEY-MEAGHER COUNTY VALLEYS-NORTHWEST BEAVERHEAD COUNTY-
UPPER BLACKFOOT AND MACDONALD PASS-WESTERN AND CENTRAL CHOUTEAU
COUNTY.
HIGH WIND WATCH FROM TUESDAY AFTERNOON THROUGH LATE TUESDAY
NIGHT FOR BEARS PAW MOUNTAINS AND SOUTHERN BLAINE-FERGUS COUNTY
BELOW 4500FT-SNOWY AND JUDITH MOUNTAINS.
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