468
FXUS65 KTFX 260125
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
725 PM MDT SUN OCT 25 2026
KEY MESSAGES
- PATCHY TO AREAS OF DENSE FOG WILL BRING LOCALIZED SHARP
VISIBILITY REDUCTIONS ACROSS SHORT DISTANCES AND ISOLATED
SLIPPERY SPOTS FROM FROST DEPOSITION AGAIN TONIGHT IN MONDAY
MORNING.
- PACIFIC WEATHER SYSTEMS WILL BRING PERIODS OF LIGHT SNOW
THIS WEEK, MOST WIDESPREAD OVER THE HIGHER TERRAIN ALONG THE
CONTINENTAL DIVIDE AND SOUTHWEST MONTANA MONDAY NIGHT INTO
TUESDAY.
- TEMPERATURES WILL GENERALLY REMAIN BELOW AVERAGE HEADING INTO
THE LATTER PART OF OCTOBER.
UPDATE
THE ONLY UPDATE FOR THE EVENING WAS TO INCREASE MENTION OF CLOUD
COVER ACROSS THE VALLEYS OF SW MT. LOW CLOUDS HAVE PERSISTENT
THERE, BUT ARE STILL FORECAST TO LOWER FURTHER AND BECOME FOG
OVERNIGHT TONIGHT. CONSIDERATION WAS GIVEN TOWARD EXPANDING THE
DENSE FOG ADVISORY FURTHER NORTH, BETWEEN THE HELENA AND GREAT
FALLS AREA, BUT HIGH LEVEL CLOUDS MOVING IN WERE A NUDGE TO HOLD
OFF FOR NOW. TRENDS WILL BE MONITORED THROUGH THE NIGHT FOR ANY
ADDITIONAL DENSE FOG ADVISORIES. -AM
DISCUSSION
/ISSUED 525 PM MDT SUN OCT 25 2026/
- METEOROLOGICAL OVERVIEW:
LOW LEVEL EASTERLY FLOW LOOKS TO BRING ANOTHER ROUND LOW STRATUS
AND PATCHY/AREAS OF DENSE FOG AGAIN TONIGHT. AREAS ALONG THE
CONTINENTAL DIVIDE, THE SOUTHWEST VALLEYS, AND THE PLAINS
EAST/NORTHEAST OF THE ROCKY MOUNTAIN FRONT/BIG BELTS WILL SEE THE
GREATEST COVERAGE AND OVERALL VISIBILITY IMPACTS. THE GENERAL FLOW
ALOFT WILL SHIFT SOUTHWESTERLY IN ADVANCE OF A CLOSED LOW MOVING
ONTO THE PACIFIC NW COAST. THIS WILL BRING VARIABLE CLOUDINESS AND
A SLIGHT WARM UP ON MONDAY BEFORE THE LOW HEADS INTO THE NORTHERN
ROCKIES AND SENDS A WAVE OF MOSTLY MOUNTAIN LIGHT SNOW MOVING IN
SOUTHWEST TO NORTHEAST FASHION MONDAY NIGHT INTO TUESDAY.
ACCUMULATIONS IN THE 1 TO 4 INCH RANGE WILL GENERALLY FAVOR THE
HIGHER TERRAIN ALONG THE CONTINENTAL DIVIDE AND THE SOUTHWEST
MOUNTAINS.
ENSEMBLES THEN HIGHLIGHT ANOTHER CLOSED LOW MOVING SOUTHEAST OUT
OF THE GULF OF AK BEFORE SLOWING DOWN AND REMAINING NEAR OR JUST
OFF THE PACIFIC NW COAST FOR MUCH OF THE WEEK. THIS WILL BRING A
SOUTHWESTERLY FLOW ALOFT AGAIN AND SEND A SERIES OF WEAK
SHORTWAVES AND PERIODS OF SPOTTY LIGHT RAIN AND SNOW INTO THE
NORTHERN ROCKIES FOR MUCH OF THE REMAINING WEEK. THIS SYSTEM IS
PROGGED TO MOVE TOWARDS THE GREAT BASIN/SW CONUS BY EARLY NEXT
WEEK. SIMILAR TO MANY SYSTEMS SO FAR THIS FALL, SPLITTING AND
SHEARING WILL MAKE FOR A CHALLENGING FORECAST. A FURTHER NORTH
TRACK WHILE MAINTAINING STRENGTH WOULD FAVOR MORE SNOW AND COLDER
TEMPERATURES HEADING INTO EARLY NEXT WEEK. ROUGHLY HALF OF THE
ENSEMBLES FAVOR THIS. - RCG
- FORECAST CONFIDENCE & SCENARIOS:
..DENSE FOG INCREASING TONIGHT INTO MONDAY MORNING
LOW STRATUS HAS BEEN SLOW TO THIN OUT EARLY THIS AFTERNOON, WITH
ANOTHER NIGHT OF LIGHT WIND AND CONTINUED LINGERING SURFACE
MOISTURE IN THE FORECAST. THE STRATUS LOOKS TO INCREASE IN
COVERAGE AND LOWER AGAIN TONIGHT FOR ANOTHER ROUND OF FOG IN THE
SOUTHWEST VALLEYS. A DENSE FOG ADVISORY WAS ADDED THROUGH MONDAY
AT NOON TO ADDRESS THE IMPACTS FROM VARIABLE VISIBILITY DOWN TO A
QUARTER MILE OR LESS AND FROST DEPOSITION CREATING SLIPPERY SPOTS
ON AREA ROADS.
DENSE FOG LOOKS TO ALSO BE A CONCERN FOR VALLEYS AND PLAINS
LOCATIONS ADJACENT TO THE BIG BELT MOUNTAINS, WITH HREF
PROBABILITIES SUPPORTING HALF MILE VISIBILITY APPROACHING 50% IN
SOME CASES. HELD OFF ISSUING FOG PRODUCTS HERE WITH HIGHER CLOUDS
LOOKING TO BE THICKER AND ARRIVING SOONER THAN THE SOUTHWEST. THIS
AREA WILL CONTINUE TO BE MONITORED FOR FOG PRODUCTS HEADING INTO
THE EVENING HOURS.
..LIGHT MOUNTAIN SNOW MONDAY NIGHT INTO TUESDAY
A COLD CORE ALOFT WILL BRING A PERIOD OF ACCUMULATING SNOW MONDAY
NIGHT INTO EARLY TUESDAY. H700 TEMPERATURES QUICKLY DROP OFF TO
AROUND -5C, WHICH WILL BE SUPPORTIVE OF THE 1 TO 4 INCHES SNOW
BEING DEPICTED BY MODEL GUIDANCE. AREAS ALONG THE CONTINENTAL
DIVIDE AND THE SOUTHWESTERN MOUNTAINS ALONG AND SOUTH OF I90 LOOK
TO SEE THE HEAVIEST SNOWFALL AMOUNTS WITH LIGHTER SNOWS OVER THE
CENTRAL RANGES. IMPACTS WILL MOSTLY BE SLIPPERY PASSES AND REDUCED
VISIBILITY. - RCG
AVIATION
26/00Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL AT THE KHLN, KGTF, KHVR, AND KLWT
TERMINALS DURING THIS TAF PERIOD. AT THE KBZN AND KWYS TERMINAL
THERE WILL BE FOG FROM 26/03Z THROUGH 26/16Z. THIS FOG WILL REDUCE
VISIBILITY TO AT LEAST ONE MILE WITH INTERMITTENT VISIBILITY
REDUCTIONS DOWN TO ONE HALF MILE EXPECTED AT THE KBZN TERMINAL.
DURING THE FIRST 16 HOURS OF THIS TAF PERIOD AT THE KBZN TERMINAL
THERE WILL BE AT LEAST IFR-LEVEL CEILINGS WITH A PERIOD OF LIFR-
LEVEL CEILINGS. DURING THE FIRST 6 HOURS OF THIS TAF PERIOD THERE
WILL BE PERIODS OF MOUNTAIN OBSCURATION ACROSS NORTH-CENTRAL,
CENTRAL, AND SOUTHWESTERN MONTANA. BETWEEN 26/06Z AND 26/18Z THERE
WILL BE MOUNTAIN OBSCURATION ACROSS SOUTHWESTERN MONTANA. -IG
PRELIMINARY POINT TEMPS/POPS
GTF 18 43 30 50 / 0 0 40 40
CTB 19 43 25 50 / 0 0 30 40
HLN 22 48 32 50 / 0 0 80 30
BZN 19 52 28 47 / 0 0 90 60
WYS 17 49 18 38 / 0 10 100 70
DLN 22 52 30 46 / 0 0 90 20
HVR 23 52 28 49 / 0 0 40 70
LWT 22 50 29 45 / 0 0 60 70
TFX WATCHES/WARNINGS/ADVISORIES
DENSE FOG ADVISORY UNTIL NOON MDT MONDAY FOR BEAVERHEAD AND
WESTERN MADISON BELOW 6000FT-CANYON FERRY AREA-ELKHORN AND
BOULDER MOUNTAINS-GALLATIN VALLEY-GALLATIN AND MADISON COUNTY
MOUNTAINS AND CENTENNIAL MOUNTAINS-MADISON RIVER VALLEY-MISSOURI
HEADWATERS-NORTHWEST BEAVERHEAD COUNTY.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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