042
FXUS65 KTFX 160544
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1144 PM MDT FRI MAY 15 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- BREEZY THROUGH THE REMAINDER OF THE DAY IN MOST AREAS.
- LOCALLY BREEZY CONDITIONS DEVELOP SATURDAY AHEAD OF A COLDER
SPRING SYSTEM MOVING IN LATE SATURDAY INTO SUNDAY.
- MOUNTAIN SNOW, WITH A MIX OF LOWER ELEVATION RAIN AND SNOW
SATURDAY NIGHT INTO SUNDAY.
UPDATE
/ISSUED 823 PM MDT FRI MAY 15 2026/
MOISTURE WITHIN CONTINUED WESTERLY FLOW ALOFT INCREASES TONIGHT AS
UPPER LEVEL TROUGHING DIGS INTO THE NW US. AN INITIAL SHORTWAVE
DISTURBANCE EJECTING OUT OF THE BROADER TROUGH LIFTS ACROSS NW MT
LATE TONIGHT WITH SHOWERS DEVELOPING ALONG THE CONTINENTAL DIVIDE
AFTER MIDNIGHT. A PACIFIC COLD FRONT CROSSES THE CONTINENTAL
DIVIDE SATURDAY MORNING AND SLOWS AS THE MID-UPPER LEVEL FLOW
TURNS MORE SOUTHWESTERLY. SHOWERS ARE LIKELY TO INCREASE ALONG
THIS BOUNDARY SATURDAY MORNING, AFFECTING AREAS FROM HELENA TO
GREAT FALLS, WITH PRECIPITATION SHIFTING SOUTH AND EASTWARD
THROUGH SATURDAY AFTERNOON. HOENISCH
DISCUSSION
/ISSUED 823 PM MDT FRI MAY 15 2026/
- METEOROLOGICAL OVERVIEW:
ZONAL FLOW ALOFT CONTINUES ACROSS THE REGION THIS AFTERNOON INTO
TONIGHT, WITH A SMALL SHORTWAVE RIDGE MOVING THROUGH TONIGHT
AHEAD OF A ROBUST PACIFIC TROUGH NEAR THE PACIFIC NW COAST
ARRIVING THIS WEEKEND WITH ACTIVE WEATHER. SUFFICIENT INSTABILITY
HAS DEVELOPED TO RESULT IN SOME SHOWERS NEAR THE CANADIAN BORDER
EAST OF I-15/. THIS ACTIVITY, ALONG WITH BREEZY WINDS, CONTINUES
THROUGH THE EARLY EVENING BEFORE SUBSIDING.
AFOREMENTIONED TROUGHING BEGINS TO MOVE IN TOMORROW, WHICH WILL
COMBINE WITH SUFFICIENT DAYTIME HEATING AND COOL AIR ALOFT TO RESULT
IN LOWER ELEVATION SHOWERS AND MOUNTAIN SNOW SHOWERS, PRIMARILY FROM
LATE MORNING THROUGH EARLY EVENING. AS OROGRAPHIC FORCING TAKES OVER
AND SNOW LEVELS FALL TOMORROW AFTERNOON AND EVENING AS THE CORE OF
THE UPPER TROUGH ARRIVES, A STRETCH OF MORE IMPACTFUL SNOW
DEVELOPS SOUTH OF I-90 AND EAST OF I-15, PRIMARILY IN THE TERRAIN
THROUGH SUNDAY MORNING.
MEANWHILE, SURFACE LOW PRESSURE BEING CARVED OUT IN WYOMING AND
SOUTHEAST MONTANA THROUGH THE DAY SATURDAY WILL RESULT IN A
NORTHERLY WINDS DEVELOPING, INITIALLY OVER THE PLAINS LATE AFTERNOON
INTO THE EVENING HOURS SATURDAY. THESE NORTHERLY WINDS, WHICH
WILL BE GUSTY AT TIMES, USHER IN COOLER AIR FROM NORTH TO SOUTH
ACROSS THE REGION SATURDAY NIGHT INTO SUNDAY. THE COOLER AIR
MOVING IN WILL COINCIDE WITH THE BEST OROGRAPHIC AND DYNAMICAL
FORCING, WHICH WILL YIELD AT LEAST A BRIEF OPPORTUNITY FOR SOME
LOWER ELEVATION SNOW SUNDAY. THE COLDEST NIGHT LOOKS TO BE SUNDAY
NIGHT, WHICH WILL FEATURE LOWS INTO THE 20S FOR MANY AREAS.
ATTEMPTS ARE MADE AT A RIDGE BUILDING IN EARLY NEXT WEEK, THOUGH
EMBEDDED WAVES IN THE BUILDING NORTHWEST FLOW ALOFT WILL KEEP
CONDITIONS UNSETTLED AND ON THE COOLER SIDE TO OPEN THE WEEK. THIS
THEME MORE OR LESS PERSISTS THROUGH THE REMAINDER OF THE WEEK, WHICH
WILL KEEP DAILY OPPORTUNITIES FOR SHOWERS AROUND. -AM
- FORECAST CONFIDENCE & SCENARIOS:
SNOW LEVELS SATURDAY AFTERNOON AND EVENING IN SW MT:
PRESENT TIMING OF FALLING SNOW LEVELS SATURDAY AFTERNOON AND EVENING
RESULTS IN SNOW BEGINNING TO MIX IN JUST AFTER SUNSET AT BOZEMAN AND
ENNIS AND ADJACENT AREAS. SHOULD THIS TRANSITION BE QUICKER WITH AN
OVERALL COOLER SOLUTION, SOME MINOR IMPACTS FROM SNOW WOULD DEVELOP
IN THE GALLATIN VALLEY AND MADISON RIVER VALLEY.
AT THIS TIME THE TIMING OF SNOW LEVELS KEEPS IMPACTS FROM THE SNOW
CONFINED TO HIGHER ELEVATION AREAS ACROSS SW MT, PARTICULARLY THE
NORTHERN END OF THE MADISON AND GALLATIN RANGES, WHERE UPSLOPE
ENHANCEMENT WILL OCCUR. OVERALL SNOWFALL AMOUNT AND DURATION
APPEARS TO BE LIGHTER/MORE BRIEF IN NATURE FOR THE BIG BELTS AND
BRIDGERS THROUGH THE NIGHT SATURDAY, BUT TRENDS WILL BE MONITORED
FOR CHANGES IN THINKING.
SNOW SUNDAY:
AS BETTER OROGRAPHIC LEFT AND SYNOPTIC FORCING ARRIVES LATE
SATURDAY NIGHT INTO SUNDAY, ADDITIONAL PERIODS OF SNOW DEVELOP
(SOME RAIN DOES LOOK TO MIX IN AT TIMES AT LOWER ELEVATIONS).
AREAS WHERE CONFIDENCE IS GREATEST IN IMPACTFUL SNOW IS IN THE
LITTLE BELTS AND NEAR GLACIER NP, THOUGH THERE STILL REMAINS
UNCERTAINTY IN OVERALL AMOUNTS AND TIMING. SHOULD SNOW FALL AT
NIGHT, THERE WOULD BE GREATER CONFIDENCE IN IMPACTS, AND VICE
VERSA. -AM
AVIATION
16/06Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL AT MOST TERMINALS DURING THIS TAF
PERIOD. THE EXCEPTIONS ARE KBZN AND KLWT, WHERE MVFR CONDITIONS
ARE POSSIBLE WITH THE ONSET OF PRECIPITATION. LIGHT RAIN SHOWERS
ARE EXPECTED TO BEGIN AROUND 19Z 5/16 FOR KBZN AND KEKS, WITH A
CHANGE TO A RAIN/SNOW MIX AROUND 02Z 5/17. FOR KHLN, THESE LIGHT
RAIN SHOWERS ARE EXPECTED TO BEGIN AROUND 10Z 5/16, WHILE FOR
KGTF AND KLWT THEY ARE EXPECTED TO BEGIN CLOSER TO 14Z 5/16. KWYS
WILL BEGIN TO SEE A RAIN/SNOW MIX AROUND 01Z 5/17. AT THIS TIME
IT IS NOT ANTICIPATED THAT KCTB OR KHVR WILL RECEIVE PRECIPITATION
DURING THIS TAF PERIOD. -DZOMBA
PRELIMINARY POINT TEMPS/POPS
GTF 41 55 33 40 / 10 40 40 90
CTB 34 55 30 38 / 0 10 60 90
HLN 39 50 33 42 / 10 80 40 80
BZN 36 58 29 45 / 10 80 90 30
WYS 30 52 25 40 / 0 30 60 30
DLN 37 57 26 44 / 10 30 40 40
HVR 38 59 35 43 / 10 30 50 80
LWT 38 53 31 39 / 10 80 90 80
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM MIDNIGHT SATURDAY NIGHT TO MIDNIGHT
MDT SUNDAY NIGHT FOR BIG BELT, BRIDGER AND CASTLE MOUNTAINS-EAST
GLACIER PARK REGION-ELKHORN AND BOULDER MOUNTAINS-LITTLE BELT
AND HIGHWOOD MOUNTAINS-SOUTHERN ROCKY MOUNTAIN FRONT-UPPER
BLACKFOOT AND MACDONALD PASS.
WINTER WEATHER ADVISORY FROM 5 PM SATURDAY TO 6 AM MDT SUNDAY
FOR GALLATIN AND MADISON COUNTY MOUNTAINS AND CENTENNIAL
MOUNTAINS.
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