064
FXUS65 KTFX 131448
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
848 AM MDT THU MAR 13 2025
KEY MESSAGES
- LOCALLY HEAVY SNOW ACROSS SOME SOUTHWEST MONTANA MOUNTAIN RANGES
THROUGH TONIGHT.
- BRIEF BUT INTENSE SHOWERS WITH A PASSING COLD FRONT THIS
AFTERNOON AND EVENING WILL QUICKLY CHANGE TO SNOW THIS EVENING
IN THE GALLATIN AND MADISON VALLEYS.
- ACTIVE WEATHER PATTERN CONTINUES INTO NEXT WEEK WITH
TEMPERATURES REMAINING NEAR SEASONAL AVERAGES AND ADDITIONAL
PRECIPITATION CHANCES
UPDATE
A PACIFIC COLD FRONT ASSOCIATED WITH A SPLITTING UPPER LEVEL TROUGH
WILL PROGRESS ACROSS THE REGION TODAY AND IS JUST STARTING TO CROSS
THE CONTINENTAL DIVIDE IN BEAVERHEAD COUNTY AS OF WRITING THIS
UPDATE. ON THE PLAINS HIGH RESOLUTION GUIDANCE STRUGGLES TO RESULT
IN MUCH PRECIPITATION WITH THE FRONT, BUT DOES OFFER SOME
INSTABILITY IN EASTERN AREAS. GIVEN FAVORABLE TIMING OF FRONTAL
PASSAGE IN THE AFTERNOON, I CAN'T RULE OUT A WEAK THUNDERSTORM EAST
OF US-87 THIS AFTERNOON AND EARLY EVENING.
FURTHER SOUTH ACROSS SOUTHWEST MONTANA IS WHERE THE GREATER CONCERN
LIES TODAY, PRIMARILY FOR SNOW, ALTHOUGH AN OUTSIDE OPPORTUNITY FOR
A RUMBLE OF THUNDER WILL ALSO EXIST LATE AFTERNOON AND EARLY
EVENING. MOISTURE WORKING IN FROM THE SOUTH THIS MORNING IS RESULTING
IN SNOW MOSTLY ALONG THE IDAHO BORDER, BUT EXTENDING NORTH TOWARD
BIG SKY AND VICINITY AS WELL. THE TIMEFRAME FOR THE HEAVIEST SNOW
NEAR THE IDAHO BORDER WILL BE THROUGH THE MORNING BEFORE FOCUS
SHIFTS FURTHER NORTH THIS AFTERNOON AND EVENING TOWARD THE NORTHERN
MADISONS, NORTHERN GALLATINS, AND TOBACCO ROOTS. THE CHANCE FOR SNOW
IN EXCESS OF AN INCH PER HOUR PEAKS AROUND 60% EARLY THIS EVENING IN
THESE RANGES. AT LOWER ELEVATIONS IN THE VICINITY OF THESE MOUNTAINS
A TRANSITION FROM RAIN TO SNOW WILL OCCUR BY EARLY EVENING. THERE
HAS NOT BEEN SIGNIFICANT CHANGE IN THINKING IN FORECAST SNOW
AMOUNTS, RATES OR TIMING FOR THIS EVENT, SO ONGOING WINTER WEATHER
ADVISORIES REMAIN UNCHANGED.
CROSS BARRIER FLOW APPROACHES 40-45 KTS OR SO THIS EVENING ALONG THE
NORTHERN ROCKY MOUNTAIN FRONT BEHIND THE PACIFIC COLD FRONT. GIVEN
THE LACK OF A STRONG PRESSURE GRADIENT AND LACK OF STRONGER MID
LEVEL FLOW, THE RISK FOR HIGH WINDS IN THIS AREA APPEARS LOW FOR THE
EVENING. NONETHELESS, THIS WILL BE A BREEZY PERIOD, EXTENDING OUT TO
THE CUT BANK AREA AND VICINITY.
JUST A FEW MINOR TWEAKS WERE MADE TO THE FORECAST THIS MORNING TO
ACCOUNT FOR LATEST TRENDS. -AM
DISCUSSION
/ISSUED 459 AM MDT THU MAR 13 2025/
- METEOROLOGICAL OVERVIEW:
AN UPPER LEVEL TROUGH DIGGING INLAND ALONG THE WEST COAST THIS
MORNING IS DIRECTING A PLUME OF PACIFIC MOISTURE NORTHWARD INTO SW
MT WHERE OROGRAPHICALLY GENERATED SNOW IS UNDERWAY ALONG THE ID BORDER
AND ADJACENT MOUNTAIN RANGES. THE UPPER TROUGH CONTINUES INLAND
TODAY WITH AN ASSOCIATED PACIFIC COLD FRONT MOVING EAST ACROSS THE
NORTHERN ROCKIES THIS AFTERNOON. RAIN AND MOUNTAIN SNOW SHOWERS WILL
SPREAD EAST OF THE CONTINENTAL DIVIDE BY EARLY THIS AFTERNOON,
BRINGING A SHIFT TO GUSTY WEST WINDS AND COOLER TEMPERATURES WITH
ITS PASSAGE TO MOST OF NORTH-CENTRAL AND CENTRAL MT BY EARLY THIS
EVENING.
ACROSS SW MT, HI-RESOLUTION MODEL GUIDANCE IS CONSISTENT IN SHOWING
A SOMEWHAT SLOWER PROGRESSION OF THE FRONT WITH INCREASED
FRONTOGENIC FORCING, GENERATING A BAND OF ENHANCED POST-FRONTAL
PRECIPITATION THIS EVENING ALONG AN AXIS ROUGHLY FROM MONIDA PASS
NORTHEAST THROUGH BOZEMAN PASS. COOLING AND LOWERING SNOW LEVELS
WILL LEAD TO A FAIRLY QUICK TRANSITION TO SNOW AT LOWER ELEVATIONS
IN THIS AREA, INCLUDING THE GALLATIN VALLEY AND OVER BOZEMAN PASS.
WINTER WEATHER ADVISORIES WERE EXPANDED TO INCLUDE MONIDA PASS, THE
MADISON AND GALLATIN VALLEYS AND BRIDGER RANGE WITH ACCUMULATIONS
AROUND 2 INCHES OR LESS IN THE VALLEYS WITH 2 TO 4 INCHES OVER THE
PASSES.
A FAIRLY ACTIVE WEATHER PATTERN CONTINUES INTO NEXT WEEK WITH A
SERIES OF PACIFIC WEATHER DISTURBANCES MOVING ACROSS THE REGION IN
THE WAKE OF THE INITIAL TROUGH PASSAGE TONIGHT. A SOMEWHAT UNSTABLE
NORTHWESTERLY FLOW IS IN PLACE FRIDAY AND SATURDAY WITH CHANCES FOR
SCATTERED PRECIPITATION MAINLY CONFINED TO THE MOUNTAINS. RIDGING
BRIEFLY DEVELOPS SUNDAY AS THE NEXT PLUME OF PACIFIC MOISTURE BEGINS
TO STREAM INTO THE REGION AHEAD A MORE ORGANIZED UPPER LEVEL TROUGH
TO MOVE THROUGH THE AREA EARLY NEXT WEEK.
- FORECAST CONFIDENCE & SCENARIOS:
THE GALLATIN VALLEY COULD SEE A LARGE SPREAD IN SNOW ACCUMULATION
WITH MINOR ACCUMULATION OF AN INCH OR LESS IN BELGRADE TO SEVERAL
INCHES FROM THE CITY OF BOZEMAN OVER BOZEMAN PASS AND HIGHER AMOUNTS
NEAR GALLATIN GATEWAY. WITH TEMPERATURES IN LOWER 50S TODAY, ROADS
WILL INITIALLY BE WARM AND IMPACTS TO THE THE COMMUTE EARLY THIS
EVENING MAY BE MORE FROM LOWER VISIBILITY, BUT THIS COULD BE
OVERCOME BY HIGHER SNOWFALL RATES WITH LATEST GUIDANCE GIVING THE
BOZEMAN AREA A 30% PROBABILITY OF RATES AS HIGH AS 1/2" PER HOUR AND
10% CHANCE OF RATES AS HIGH AS 1" PER HOUR THIS EVENING.
TEMPERATURES ALSO FALL TO THE 20S BY LATE THIS EVENING WHICH COULD
LEAD TO ADDITIONAL IMPACTS FROM WET ROAD SURFACES BECOMING ICY.
HOENISCH
AVIATION
13/12Z TAF PERIOD
CLOUDS INCREASE WITH LOWERING VFR CLOUD BASES THIS MORNING AS
SOUTHERLY FLOW ALOFT SPREADS INCREASING MOISTURE ACROSS THE AREA.
A COLD FRONT MOVES EAST CROSSING THE CONTINENTAL DIVIDE AROUND
18Z AND SWEEPS ACROSS NORTH-CENTRAL AND CENTRAL MT TERMINALS THIS
AFTERNOON, SHIFTING WINDS TO THE WEST WITH A PERIOD OF MOUNTAIN
OBSCURATION AND SCATTERED SHOWERS. MVFR CONDITIONS DEVELOP AT
KEKS AND KBZN THIS EVENING AS THE FRONT MOVES THROUGH THESE AREAS
WITH PRECIPITATION BEGINNING AS RAIN BUT CHANGING TO SNOW WITH A
BRIEF PERIOD OF MORE INTENSE SNOW AND IFR CONDITIONS POSSIBLE
BETWEEN 00Z AND 04Z. SNOW CONTINUES THROUGH MOST OF THE TAF PERIOD
ACROSS THE MOUNTAINS NEAR THE ID BORDER. HOENISCH
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 57 30 44 22 / 30 10 0 0
CTB 51 25 39 16 / 20 0 10 0
HLN 51 26 41 23 / 60 20 10 0
BZN 51 21 36 19 / 70 90 20 10
WYS 41 15 32 13 / 90 80 50 30
DLN 46 21 37 21 / 80 60 10 0
HVR 59 25 42 16 / 20 10 0 0
LWT 54 27 39 21 / 50 50 0 0
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 6 AM MDT
FRIDAY FOR BIG BELT, BRIDGER AND CASTLE MOUNTAINS-GALLATIN
VALLEY-MADISON RIVER VALLEY.
WINTER WEATHER ADVISORY UNTIL 6 AM MDT FRIDAY FOR GALLATIN AND
MADISON COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS-RUBY MOUNTAINS
AND SOUTHERN BEAVERHEAD MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR NORTHWEST
BEAVERHEAD COUNTY.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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