997
FXUS65 KTFX 210445
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
945 PM MST FRI DEC 20 2024
AVIATION SECTION UPDATED.
KEY MESSAGES
- WINDY CONDITIONS, ESPECIALLY ON SUNDAY AND MONDAY, AND WARMER
WEATHER THROUGH THE WEEKEND AND NEXT WEEK.
- A FEW DISTURBANCES MOVE THROUGH, BRINGING MAINLY LIGHT MOUNTAIN
SNOW AND LOWER ELEVATION RAIN AND A WINTRY MIX.
- WIDESPREAD PRECIPITATION CHRISTMAS EVE TO EARLY CHRISTMAS
MORNING CAN CAUSE MINOR IMPACTS TO HOLIDAY TRAVEL.
UPDATE
/ISSUED 138 PM MST FRI DEC 20 2024/
WINDS REMAIN GUSTY ALONG THE ROCKY MOUNTAIN FRONT, BUT WILL
DIMINISH AS THE NIGHT PROGRESSES. OTHERWISE, GENERAL DRY AND MILD
CONDTIONS ARE EXPECTED UNDER PASSING MID- AND HIGHER LEVEL
CLOUDINESS. THE ONE EXCEPTION TO THIS WILL BE ALONG THE MILK
RIVER VALLEY (NORTHERN HILL/BLAINE) WHERE A THIN LAYER OF COLD AND
MOIST AIR WILL REMAIN IN PLACE. TEMPERATURES WERE LOWERED TOWARDS
THE LOW END OF GUIDANCE FOR TONIGHT AND TOMORROW. PATCHY FOG
DEVELOPMENT IS EXPECTED LATE TONIGHT AND EARLY SATURDAY, BUT THE
AFOREMENTIONED HIGHER CLOUDS MOVING IN SHOULD MITIGATE WIDESPREAD
IMPACTS. THIS AREA WILL ALSO BE MONITORED FOR MIXED PRECIPITATION,
INCLUDING FREEZING DRIZZLE/LIGHT RAIN, SATURDAY NIGHT AND SUNDAY
MORNING. - RCG
DISCUSSION
/ISSUED 849 PM MST FRI DEC 20 2024/
- METEOROLOGICAL OVERVIEW:
AN OVERALL MESSY, PROGRESSIVE PATTERN IS EXPECTED OVER THE NEXT WEEK
ACROSS THE NORTHERN ROCKIES, WITH PERIODS OF TRANSIENT RIDGING AND
FAST MOVING DISTURBANCES LIFTING/SLIDING NORTHEAST/EAST OVER
SOUTHWEST THROUGH NORTH CENTRAL MONTANA. OF PARTICULAR NOTE THE
DISTURBANCES FROM SATURDAY NIGHT THROUGH SUNDAY AFTERNOON AND THEN
TUESDAY THROUGH WEDNESDAY AFTERNOON LOOK TO BRING AT LEAST SOME
IMPACTS TO THE CWA; MAINLY IN THE FORM OF STRONG AND GUSTY WINDS IN
PRONE AREAS AND MOUNTAIN SNOWFALL. ADDITIONAL PERIODS OF STRONG AND
GUSTY WINDS ARE ALSO EXPECTED THROUGH THE UPCOMING WEEK AS THE
PRESSURE GRADIENT ALONG THE ROCKY MOUNTAIN FRONT, MT HWY 200
CORRIDOR IN CENTRAL MONTANA, AND NEAR THE I-90 CORRIDOR IN SOUTHWEST
FLUCTUATES WITH PASSING AREAS OF SURFACE LOW PRESSURE. TEMPERATURES
WILL LARGELY RANGE FROM ABOVE TO WELL ABOVE NORMAL ACROSS SOUTHWEST
THROUGH NORTH CENTRAL MONTANA, WITH A FEW EXCEPTIONS. THESE
EXCEPTIONS INCLUDE NORTHERN PORTIONS OF HILL AND BLAINE COUNTIES IN
NORTH CENTRAL MONTANA, GENERALLY NORTH OF THE US HWY 2 CORRIDOR,
WHERE NEAR NORMAL TEMPERATURES WILL OCCUR AT TIMES AS COOLER AIR
SLOSHES IN AND OUT. - MOLDAN
- FORECAST CONFIDENCE & SCENARIOS:
REST OF TODAY THROUGH SATURDAY... CONFIDENCE REMAINS HIGH THAT MOST
AREAS WILL REMAIN DRY THROUGH THE PERIOD. A WEAK TO MODERATELY
STRONG PRESSURE GRADIENT ALONG THE ROCKY MOUNTAIN FRONT, MT HWY 200
CORRIDOR IN CENTRAL MONTANA, AND SOUTH OF THE I-90 CORRIDOR IN
SOUTHWEST MONTANA THROUGH SATURDAY WILL HELP TO MAINTAIN GUSTY WINDS
ACROSS THESE AREAS, BUT SOME REDUCTIONS IN WINDS GUSTS WILL OCCUR
THIS EVENING AS CROSS BARRIER RELAXES SLIGHTLY ONLY TO INCREASE EARLY
SATURDAY MORNING YET AGAIN. WINDS WILL GENERALLY BE NOT QUITE AS
STRONG ON SATURDAY, LIMITING AT LEAST A 50 PERCENT PROBABILITY OF AT
LEAST 30 MPH WIND GUSTS TO THE ROCKY MOUNTAIN FRONT AND THROUGH THE
MADISON RIVER VALLEY. - MOLDAN/COULSTON
SATURDAY NIGHT THROUGH MONDAY... THE PROBABILITIES FOR WIND GUSTS OF
AT LEAST 50 MPH ARE AT LEAST 50 PERCENT ONLY ALONG THE ROCKY
MOUNTAIN FRONT SATURDAY NIGHT INTO SUNDAY MORNING, AND AGAIN DURING
THE DAY ON MONDAY, WITH LESS THAN AN 40% PROBABILITY OF 75 MPH WIND
GUSTS (HIGH WIND CRITERIA). AM THEREFORE NOT ANTICIPATING A NEED FOR
A HIGH WIND WATCH AT THIS TIME, BUT WILL MONITOR THE SITUATION OVER
THE COMING DAYS. REGARDING SNOWFALL, THE POTENTIAL FOR EVEN MINOR
ACCUMULATION IS LIMITED TO THE MOUNTAINS; 50+ PERCENT PROBABILITIES
OF AT LEAST 2 INCHES IN A GIVEN 24-HOUR PERIOD ARE LIMITED TO AREAS
ABOVE MOUNTAIN PASS LEVEL.
TUESDAY THROUGH NEXT FRIDAY... THE MAIN PERIOD OF CONCERN WILL BE
THE WEDNESDAY NIGHT INTO THURSDAY MORNING FOR HOLIDAY TRAVEL. THE
PROBABILITY FOR AT LEAST 2 INCHES OF SNOWFALL WILL BE AT LEAST 50
PERCENT AT AND ABOVE MOUNTAIN PASS LEVEL, BUT THERE IS LESS THAN A
40 PERCENT PROBABILITY OF AT LEAST 4 INCHES OF SNOWFALL ON THE
MOUNTAIN PEAKS. DURING THIS SAME PERIOD, THERE IS MAINLY A 15 TO 25
PERCENT PROBABILITY OF AT LEAST 0.10 INCHES OF RAIN AND MELTED SNOW
AT LOWER ELEVATIONS ACROSS CENTRAL AND SOUTHWEST MONTANA, BUT THE
BOZEMAN VALLEY AND THE MADISON RIVER VALLEY HAVE A 40 TO 60 PERCENT
PROBABILITY OF GETTING THAT MUCH PRECIPITATION.
-COULSTON
AVIATION
21/06Z TAF PERIOD
GUSTY WINDS ALONG THE ROCKY MOUNTAIN FRONT AND PLAINS WILL
CONTINUE TO DIMINISH TONIGHT WHILE MID- AND HIGHER LEVEL CLOUDS
CONTINUE TO PASS OVERHEAD. RIDGING ALOFT WILL GENERALLY MAINTAIN
VFR CONDITIONS THROUGH 22/00Z; HOWEVER, HI-RES GUIDANCE STILL
HIGHLIGHTS STRATUS/FOG DEVELOPMENT ALONG THE MILK RIVER VALLEY
(KHVR AREA). THE ABUNDANCE OF HIGHER LEVEL CLOUDS IS EXPECTED TO
LIMIT OVERALL COVERAGE/IMPACT AND THIS IS REFLECTED IN THE
IMPACTFUL FOG PROBABILITY BEING LESS THAN 20%. AN APPROACHING
PACIFIC WEATHER SYSTEM THEN BRINGS MOUNTAIN OBSCURING CLOUDS,
LIGHT, MOSTLY MOUNTAIN PRECIPITATION, AND GUSTY WINDS AFTER
22/00Z. - RCG
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 38 55 41 50 / 0 10 20 0
CTB 34 50 36 44 / 10 0 20 0
HLN 32 46 32 47 / 0 0 30 0
BZN 28 49 29 46 / 0 0 30 0
WYS 10 38 19 32 / 0 0 30 30
DLN 29 45 26 42 / 0 0 20 0
HVR 14 38 28 43 / 0 0 50 10
LWT 33 56 34 46 / 0 10 40 20
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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