085
FXUS65 KTFX 101129
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
529 AM MDT SAT OCT 10 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- TWO WAVES OF IMPACTFUL SNOWFALL DEVELOP THIS WEEKEND INTO MONDAY
AS TEMPERATURES TREND SIGNIFICANTLY COOLER ACROSS THE REGION.
- INITIAL CONCERN THROUGH THE DAY TODAY AND INTO TONIGHT WILL BE
ALONG THE ROCKY MOUNTAIN FRONT AND ACROSS CENTRAL MONTANA.
- CONCERN FOR HEAVY SNOWFALL EXPANDS FURTHER SOUTH INTO SOUTHWEST
MONTANA SUNDAY INTO SUNDAY NIGHT.
DISCUSSION
/ISSUED 127 AM MDT SAT OCT 10 2026/
- METEOROLOGICAL OVERVIEW:
A COMPLEX EVOLUTION TO THE UPPER LEVEL PATTERN WILL ENSUE TODAY,
INITIALLY WITH A LARGE UPPER LEVEL TROUGH WITH MULTIPLE EMBEDDED
VORT MAXES SINKING SOUTHWARD FROM THE PACIFIC NORTHWEST, ELONGATING
AS IT DOES SO. AT THE SURFACE AN AREA OF LOW PRESSURE CENTERED IN
SOUTHERN SK IS PROPELLING A COLD FRONT SOUTHWARD ACROSS THE PLAINS
EARLY THIS MORNING. THE COMBINATION OF THIS FRONT, FAVORABLE
FORCING, AND AMPLE MOISTURE WILL RESULT IN A ROUND OF PRECIPITATION
DEVELOPING THROUGH THE DAY TODAY. INITIAL PRECIPITATION TYPE LOOKS TO
BE RAIN IN MANY AREAS BEFORE COLD AIR ADVECTION NEAR THE SURFACE
WINS OUT AND FLIPS PRECIPITATION TYPE TO SNOW. CONFIDENCE IS HIGHEST
IN SNOW DEVELOPING EARLY NEAR THE SOUTHERN ROCKY MOUNTAIN FRONT,
WHERE A BAND OF SNOW WILL AID IN FLIPPING PRECIP TYPE TO SNOW BY
EARLY AFTERNOON. SNOW CHARACTERISTIC LOOKS TO BE THE WET AND HEAVY
VARIETY, ESPECIALLY AT LOWER ELEVATIONS, WHICH RAISES CONCERN FOR
TREES WITH LEAVES ON THEM STILL SEEING SNAPPED BRANCHES, POTENTIALLY
IMPACTING POWER LINES.
COLDER AIR CONTINUES TO SINK SOUTHWARD INTO SOUTHWEST MONTANA
HEADING INTO SUNDAY, THOUGH THERE REMAINS SOME UNCERTAINTY WITH
RESPECT TO JUST HOW FAR IT MAKES IT. ALOFT THE COMPLEX EVOLUTION
CONTINUES, WITH THE UPPER LEVEL TROUGHING ELONGATING FURTHER, WHILE
ALSO INTERACTING WITH THE REMNANTS OF RACHEL AS THEY LIFT
NORTHEASTWARD AHEAD OF THE TROUGH AXIS. AMPLE MOISTURE ASSOCIATED
WITH NOT ONLY THE MAIN TROUGHING, BUT THE REMNANTS OF RACHEL WILL
SUPPORT THE EXPANSION OF PRECIPITATION SOUTHWARD INTO SOUTHWEST
MONTANA DURING THE DAY SUNDAY AS AN UPPER LEVEL JET MOVES OVERHEAD.
THE EXTENT OF IMPACTFUL SNOWFALL ACROSS SOUTHWEST MONTANA WILL
FOLLOW WHERE THE COLDEST AIR BOTH ALOFT AND AT THE SURFACE ENDS UP
SETTLING. BANDED PRECIPITATION LOOKS TO PERSISTS INTO MONDAY
MORNING ACROSS PORTIONS OF CENTRAL AND SOUTHWEST MONTANA BEFORE
SUBSIDING THROUGH THE DAY.
THE REGION LOOKS TO DRY OUT FOR AT LEAST A COUPLE DAYS AS THE UPPER
LEVEL TROUGHING CONSOLIDATES ONCE AGAIN ACROSS THE DESERT SOUTHWEST.
UNCERTAINTY GROWS A BIT TOWARD THURSDAY, THOUGH THE MAJORITY OF
ENSEMBLE MEMBERS REMAIN DRY THURSDAY TOWARD THE WEEKEND. -AM
- FORECAST CONFIDENCE & SCENARIOS:
GIVEN MARGINAL THERMODYNAMICS AT TIMES WITH RESPECT TO BOTH THE
ATMOSPHERE AND SURFACE TEMPERATURES, IT MAKES FOR QUITE THE TRICKY
SNOWFALL/ACCUMULATION FORECAST. OVERALL THERE WERE NO CHANGES WITH
THIS FORECAST CYCLE TO ONGOING WINTER HIGHLIGHTS, BUT CONSIDERATION
WAS GIVEN TO UPGRADES IN A FEW AREAS:
- NORTHERN ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS: THIS AREA
LOOKS TO HAVE THE MOST CONSISTENT THERMODYNAMIC ENVIRONMENT
SUPPORTING SNOW (COLD THROUGHOUT), BUT THE GREATEST FORCING LOOKS TO
REMAIN FURTHER SOUTH. GIVEN SNOWFALL AMOUNTS VARY QUITE A BIT FROM
NORTH TO SOUTH ACROSS THESE ZONES, THE WINTER WEATHER ADVISORY WAS
LEFT AS IS. SHOULD AMOUNTS INCREASE MUCH IN THESE ZONES, A WINTER
STORM WARNING MAY BECOME NECESSARY.
- HELENA VALLEY: THE GREATEST UNCERTAINTY IN THE HELENA AREA IS
WITH RESPECT TO JUST HOW QUICKLY PRECIPITATION FLIPS OVER TO SNOW
TODAY/THIS EVENING. EITHER WAY, INITIAL SNOW THAT FALLS WILL NEED TO
OVERCOME WARM PAVEMENT TO BEGIN ACCUMULATING, WHICH LOOKS
QUESTIONABLE THROUGH LATE TONIGHT GIVEN UNCERTAINTY WITH RESPECT TO
SNOWFALL RATES. COLDER AIR CONTINUES TO MAKE INROADS SUNDAY WHICH
WILL ALLOW FOR GREATER SNOWFALL RATES TO RESULT IN MORE
ACCUMULATIONS. GIVEN MARGINAL SNOWFALL FORECAST TOTALS, I ELECTED TO
CONTINUE WITH THE WINTER WEATHER ADVISORY FOR NOW.
- NEAR AND SOUTH OF I-90 SUNDAY INTO SUNDAY NIGHT: AMPLE FORCING
AND MOISTURE MOVING IN WITHIN A DEEP FETCH OF SOUTHWESTERLY FLOW
ALOFT (SUPPORTED BY RACHEL'S REMNANTS) WILL FOSTER SOME BANDED
PRECIPITATION SUNDAY INTO MONDAY. THE AREA OF GREATEST CONCERN WOULD
BE ALONG AND SOUTH OF A LINE FROM DILLON TO BOZEMAN FOR THE GREATEST
PRECIPITATION AMOUNTS. THIS ALSO HAPPENS TO BE THE AREA OF GREATEST
UNCERTAINTY WITH RESPECT TO THE COLDER AIR AT THE SURFACE AND ALOFT.
GIVEN THERE ARE WINTER WEATHER ADVISORIES IN PLACE ALREADY, AND THAT
THERE IS STILL UNCERTAINTY WITH RESPECT TO TEMPERATURES, NO UPGRADES
TO A WINTER STORM WARNING WERE MADE. THIS AREA WILL BEAR MONITORING
FOR ANY TRENDS OVER THE NEXT 24 HOURS OR SO. -AM
AVIATION
10/12Z TAF PERIOD
INITIAL CONCERN THIS TAF PERIOD WILL BE FOR A FRONT MOVING SOUTHWARD
ACROSS THE REGION, BRINGING PRECIPITATION AND LOW CLOUDS. MEANWHILE
FURTHER SOUTH ACROSS SW MT, A FEW SHOWERS HAVE ALREADY RESULTED IN A
FEW WIND GUSTS NEAR 40 KTS. WHILE THESE GUSTS LOOK TO BE ISOLATED,
THEY ARE STILL WORTH A MENTION. ADDITIONAL INSTABILITY MAY ALSO
RESULT IN A FEW THUNDERSTORMS THIS AFTERNOON ACROSS SW MT.
PRECIPITATION SLOWLY SPREADS SOUTHWARD THROUGH THE DAY TODAY,
TRANSITIONING TO SNOW AS COLDER AIR MOVES IN. MOUNTAINS WILL BECOME
INCREASINGLY OBSCURED THROUGH THE TAF PERIOD. -AM
PRELIMINARY POINT TEMPS/POPS
GTF 42 28 33 25 / 90 100 100 90
CTB 36 25 32 21 / 60 80 100 80
HLN 48 28 34 25 / 90 100 100 100
BZN 59 30 35 25 / 80 90 100 100
WYS 56 33 44 27 / 80 100 100 100
DLN 60 28 33 23 / 60 80 100 100
HVR 49 28 39 25 / 70 80 100 90
LWT 50 29 34 25 / 90 100 100 100
TFX WATCHES/WARNINGS/ADVISORIES
WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 AM MDT MONDAY
FOR BIG BELT, BRIDGER AND CASTLE MOUNTAINS-CASCADE COUNTY BELOW
5000FT-EASTERN PONDERA AND EASTERN TETON-ELKHORN AND BOULDER
MOUNTAINS-JUDITH BASIN COUNTY AND JUDITH GAP-LITTLE BELT AND
HIGHWOOD MOUNTAINS-MEAGHER COUNTY VALLEYS-SNOWY AND JUDITH
MOUNTAINS.
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM MDT
MONDAY FOR BEARS PAW MOUNTAINS AND SOUTHERN BLAINE-BEAVERHEAD
AND WESTERN MADISON BELOW 6000FT-CANYON FERRY AREA-EAST GLACIER
PARK REGION-EASTERN GLACIER, WESTERN TOOLE, AND CENTRAL PONDERA-
EASTERN TOOLE AND LIBERTY-FERGUS COUNTY BELOW 4500FT-GALLATIN
VALLEY-GALLATIN AND MADISON COUNTY MOUNTAINS AND CENTENNIAL
MOUNTAINS-HELENA VALLEY-MADISON RIVER VALLEY-MISSOURI HEADWATERS-
NORTHERN HIGH PLAINS-NORTHWEST BEAVERHEAD COUNTY-RUBY MOUNTAINS
AND SOUTHERN BEAVERHEAD MOUNTAINS-WESTERN AND CENTRAL CHOUTEAU
COUNTY.
WINTER STORM WARNING FROM NOON TODAY TO 6 AM MDT MONDAY FOR
GATES OF THE MOUNTAINS-SOUTHERN HIGH PLAINS-SOUTHERN ROCKY
MOUNTAIN FRONT-UPPER BLACKFOOT AND MACDONALD PASS.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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