691
FXUS65 KTFX 281648
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
948 AM MST TUE JAN 28 2025
KEY MESSAGES
- COLD TEMPERATURES WILL CONTINUE TO AFFECT THE VALLEYS OF
SOUTHWEST MT THROUGH ABOUT THURSDAY.
- WINDY CONDITIONS DEVELOP ON WEDNESDAY AND CONTINUE INTO THURSDAY
IN THE BROWNING AND CUT BANK AREAS.
- SNOW DEVELOPS ON FRIDAY MORNING IN GLACIER PARK AND THE MARIAS
PASS AREA.
- STRONG COLD FRONT MOVES SOUTHWARD THROUGH THE CWA STARTING ON
SATURDAY.
- ACCUMULATING SNOWFALL SHIFTED SOUTHWARD INTO SOUTHWEST MT THIS
WEEKEND.
UPDATE
MINIMAL ADJUSTMENTS MADE THIS MORNING, WITH THE ONLY CHANGE BEING
MADE TO TEMPERATURES TO ACCOUNT FOR THE COLD STARTING POINTS IN
SOME OF THE SOUTHWEST MONTANA VALLEYS. OTHERWISE THE PREVIOUS
FORECAST ADDRESSED THE MAIN CONCERN OF THE DAY WELL, WHICH IS THE
STUBBORN COLD AIR MASS ACROSS THE SOUTHWEST MONTANA VALLEYS, WHICH
WILL HELP TO KEEP TEMPERATURES WELL BELOW ANY AVAILABLE
DETERMINISTIC GUIDANCE. THUS A HEAVY BLEND OF PERSISTENCE AND THE
COLDER PROBABILISTIC GUIDANCE (I.E. NBM10TH PERCENTILE) WAS
EMPLOYED. - MOLDAN
DISCUSSION
/ISSUED 447 AM MST TUE JAN 28 2025/
- METEOROLOGICAL OVERVIEW:
AN UPPER LEVEL RIDGE OF HIGH PRESSURE CONTINUES TO RESIDE JUST OF
THE COAST OF THE PACIFIC NORTHWEST, RESULTING IN QUIET WEATHER
CONDITIONS CURRENTLY OVER MT. THE QUIET WEATHER NOW WILL GIVE WAY
TO WINDY CONDITIONS STARTING ON WEDNESDAY AND CONTINUING INTO
THURSDAY IN THE BROWNING/CUT BANK AREAS. WITH A CORE OF 50 KNOT
WINDS BETWEEN 500 AND 1000 FEET ABOVE GROUND LEVEL FROM 6 AM WED
TO 6 AM THU, THERE IS THE POTENTIAL THAT THESE STRONG WINDS COULD
MIX DOWN AT TIMES. THUS A HIGH WIND WATCH HAS BEEN ISSUED FOR THE
CUT BANK ZONE FOR THIS TIME. THERE IS THE POTENTIAL FOR THE STRONG
WINDS TO CONTINUE INTO THU IN THESE SAME AREAS. BY FRIDAY, THE
UPPER LEVEL RIDGE BREAKS DOWN, AND A FAST MOVING WESTERLY FLOW
DEVELOPS ALOFT, THIS WILL RESULT IN SNOW FALLING ALONG THE DIVIDE,
ESPECIALLY UP IN GLACIER PARK. ON SATURDAY, A STRONG CANADIAN COLD
FRONT WILL START TO MOVE SOUTHWARD THROUGH THE CWA. FORECAST
MODELS HAVE SIGNIFICANTLY REDUCED THE SNOWFALL OVER NORTH CENTRAL
MT WITH THIS FRONT, AND NOW SHOW THE BEST LIFT/MOISTURE COLLIDING
OVER SOUTHWEST MT. BY MONDAY MORNING, MID LEVEL WINDS WILL HAVE
SWITCHED TO THE SOUTHWEST, ALLOWING FOR A WIDESPREAD AREA OF
OVERRUNNING SNOWFALL TO DEVELOP OVER SOUTHWEST AND NORTH CENTRAL
MT. BUT AGAIN, SOME FORECAST MODELS DON'T SHOW THE SNOW GOING
VERY FAR NORTH INTO NORTH CENTRAL MT, SO THERE IS SOME
UNCERTAINTY.
IN TERMS OF TEMPERATURES, I DID KEEP THE VALLEYS OF SOUTHWEST MT
COLDER THAN GUIDANCE THROUGH THURSDAY. GENERALLY, WARMING
TEMPERATURES ABOUT 3 TO 5 DEGREES EACH DAY OVER THE NEXT FEW
DAYS. OVERALL NBM TEMPERATURES LOOK REASONABLE OVER NORTH CENTRAL
MT, BUT WITH WINDY CONDITIONS AT NIGHT, OVERNIGHT LOWS MIGHT BE A
BIT WARMER THAN CURRENTLY FORECASTED. BEHIND THE COLD FRONT THIS
WEEKEND, EXPECT THE COLD AIR TO MOVE SOUTHWARD INTO NORTH CENTRAL
MT, BUT THE COLD AIR WILL STRUGGLE TO MAKE IT ALL THE WAY SOUTH
TO LIKE DILLON/WEST YELLOWSTONE AREA.
- FORECAST CONFIDENCE & SCENARIOS:
THERE IS UP TO A 70 PERCENT CHANCE OF WIND GUSTS OVER 60 MPH IN
THE CUT BANK AREA FOR WEDNESDAY AND A 50 PERCENT CHANCE ON
THURSDAY.
FOR GLACIER PARK, THERE IS A 75 PERCENT CHANCE OF A SNOWFALL OVER
6 INCHES FROM FRIDAY INTO FRIDAY NIGHT.
SNOWFALL OF A FEW INCHES LOOK LIKELY OVER SOUTHWEST MT SATURDAY
INTO SATURDAY NIGHT, WITH THE MAIN CONCERN BEING AN HOUR OR TWO
OF HEAVY SNOWFALL.
FOR NEXT WEEK, THERE IS A 30 PERCENT CHANCE OF 4 INCHES OF
SNOWFALL FROM GREAT FALLS TO LEWISTOWN WITH THE POTENTIAL
OVERRUNNING SNOWFALL MON INTO TUE.
WITH THE SNOW COVER DECREASING OVER NORTH CENTRAL MT AND NOT MUCH
SNOW EXPECTED THIS WEEKEND, TEMPERATURES OVER THE NORTH WILL BE
TRICKY, AS IT MIGHT NOT GET AS COLD AS ONE WOULD THINK WITH THIS
AIRMASS AND AREAS OVER NORTH CENTRAL MT THAT HAVE NO SNOW COVER.
BRUSDA
AVIATION
28/12Z TAF PERIOD
VFR CONDITIONS ARE FORECAST TO PERSIST OVER NORTH CENTRAL,
CENTRAL, AND SOUTHWEST MONTANA THROUGH AT LEAST 29/12Z. A HIGH
PRESSURE RIDGE WILL CONTINUE THE NORTHWEST FLOW ALOFT THROUGH THE
PERIOD WITH ONLY PASSING HIGH CLOUDINESS MOVING OVERHEAD. PATCHY
FOG IS POSSIBLE IN SOME VALLEYS OF CENTRAL AND SOUTHWEST MONTANA
UNTIL 17Z TODAY AND AGAIN AFTER 29/08Z, BUT THE PROBABILITY OF
LESS THAN 6SM VISIBILITY IS ONLY GREATER THAN 15 PERCENT IN THE
KBZN AREA (20-30 PERCENT), SO ONLY HAVE A MENTION OF 6SM
VISIBILITY THERE DURING THOSE TIMES.
WINDS WILL REMAIN LIGHT IN THE VALLEYS AND BREEZY OUT OF THE
SOUTHWEST OVER THE PLAINS. HOWEVER, MID-LEVEL WINDS WILL INCREASE
OUT OF THE WEST AFTER 06Z FROM THE NORTHWEST OVER NORTH CENTRAL
AND CENTRAL MONTANA, CAUSING INCREASED MOUNTAIN WAVE TURBULENCE
AND SPREADING SPREADING LOW-LEVEL WIND SHEAR INTO THE KCTB, KGTF,
AND KHVR TERMINAL AREAS. -COULSTON
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 38 23 46 31 / 0 0 0 0
CTB 39 24 45 31 / 0 0 0 0
HLN 23 11 27 11 / 0 0 0 0
BZN 21 0 25 2 / 0 0 0 0
WYS 29 -9 30 -6 / 0 0 0 0
DLN 23 6 25 7 / 0 0 0 0
HVR 36 19 40 20 / 0 0 0 0
LWT 41 21 47 23 / 0 0 0 0
TFX WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM LATE TONIGHT THROUGH LATE WEDNESDAY NIGHT
FOR EASTERN GLACIER, WESTERN TOOLE, AND CENTRAL PONDERA.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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