828
FXUS65 KTFX 201633
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
933 AM MST FRI DEC 20 2024
KEY MESSAGES
- WARMER THAN NORMAL TEMPERATURES ARE EXPECTED ACROSS SOUTHWEST,
CENTRAL, AND NORTH CENTRAL MONTANA THROUGH NEXT WEEK.
- DISTURBANCES MOVING THROUGH THE AREA WILL BRING GUSTY WESTERLY
DOWNSLOPE WINDS AND MAINLY MOUNTAIN PRECIPITATION.
- THE WINDIEST PERIOD WILL LIKELY BE SATURDAY NIGHT INTO SUNDAY,
AND AGAIN ON MONDAY.
- THE MOST FAVORED PERIOD FOR WIDESPREAD LIGHT PRECIPITATION IS
FORECAST TO BE WEDNESDAY NIGHT INTO THURSDAY, WHICH MAY CAUSE
MINOR IMPACTS TO HOLIDAY TRAVEL.
UPDATE
ONLY MINOR CHANGES MADE TO THE ON-GOING FORECAST WITH THE MORNING
UPDATE, WITH THE MAIN CHANGES MADE TO WINDS AND TEMPERATURES TO
ACCOUNT FOR RECENT OBSERVATION AND MODEL TRENDS. 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 WILL HELP TO MAINTAIN GUSTY WINDS THROUGH THE
AFTERNOON HOURS BEFORE DECREASING SLIGHTLY HERE. CROSS BARRIER
FLOW OF 50-70KTS THIS MORNING IN CONJUCTION WITH THIS PRESSURE
GRADIENT WAS LEADING TO WIND GUSTS OF BETWEEN 50-80 MPH ALONG THE
ROCKY MOUNTAIN FRONT, BUT AS THIS CROSS BARRIER FLOW DECREASES
THROUGH THE EARLY AFTERNOON MOST LOCATIONS ALONG THE ROCKY
MOUNTAIN FRONT WILL SEE WIND GUSTS FALL BELOW 50 MPH. OTHERWISE,
ONLY OTHER CONCERN THROUGH THE DAY WILL BE WHEN THE "WARM" AIR
ARRIVES TO THE MILK RIVER VALLEY, WITH LATEST GUIDANCE SUGGESTING
THAT SURFACE WINDS WILL COME AROUND TO THE SOUTHWEST BETWEEN NOON
AND 3 PM MST THIS AFTERNOON, WHICH SHOULD HELP TO MIXOUT THE
STUBBORN COLD AIR SO LONG AS WIND SPEEDS OVER THIS TIMEFRAME ARE
10 MPH OR GREATER. SHOULD WIND SPEEDS REMAIN BELOW 10 MPH WITHIN
THE MILK RIVER VALLEY THEN THE "WARMER" AIR WILL LIKELY HOLD JUST
SOUTH OF THE US HWY 2 CORRIDOR IN HILL AND BLAINE COUNTIES TOADY.
- MOLDAN
DISCUSSION
/ISSUED 354 AM MST FRI DEC 20 2024/
- METEOROLOGICAL OVERVIEW:
TODAY THROUGH SATURDAY... A FRONTAL BOUNDARY FROM CUT BANK TO
LEWISTOWN IS SEPARATING THE COOLER AIRMASS TO THE EAST FROM THE
WARMER AIRMASS TO THE WEST OVER NORTH CENTRAL, CENTRAL, AND
SOUTHWEST MONTANA. AS A RESULT, A WEAK SHORTWAVE TROUGH MOVING
EAST ACROSS NORTH CENTRAL MONTANA WILL BRING A SLIGHT CHANCE OF
LIGHT SNOW AND FREEZING DRIZZLE TO THE CANADIAN BORDER AREAS EAST
OF CUT BANK. OTHERWISE, THE PASSAGE OF THE SHORTWAVE SHOULD HELP
SPREAD THE WARMER AIR WITH ABOVE NORMAL TEMPERATURES AND GUSTY
WESTERLY WINDS EAST OVER THE PLAINS TODAY. WARM AND DRY
CONDITIONS WILL PERSIST INTO SATURDAY UNDER AN UPPER LEVEL HIGH
PRESSURE RIDGE, BUT WITH SLIGHTLY LESS WIND.
SATURDAY NIGHT THROUGH MONDAY... SHORTWAVE TROUGHS WILL MOVE OVER
THE AREA EACH DAY, BRINGING MAINLY MOUNTAIN PRECIPITATION. THE
MORE FAVORED PERIODS FOR PRECIPITATION TO REACH LOWER ELEVATIONS
WILL BE SATURDAY NIGHT AND DURING THE DAY ON MONDAY. HOWEVER,
THESE ARE ALSO THE MORE FAVORED PERIODS FOR POTENTIALLY STRONGER
WESTERLY DOWNSLOPING WINDS, WHICH MAY LIMIT PRECIPITATION
POTENTIAL OVER THE PLAINS, BUT WILL KEEP TEMPERATURES WELL ABOVE
NORMAL.
TUESDAY THROUGH NEXT FRIDAY... A FAIRLY PROGRESSIVE WESTERLY FLOW
PATTERN IS FORECAST TO CONTINUE THROUGH THE WEEK, CONTINUING
MAINLY CHANCES OF MOUNTAIN PRECIPITATION WITH BREEZY PERIODS AND
MILDER THAN NORMAL TEMPERATURES. THE BEST CHANCE FOR PRECIPITATION
TO REACH LOWER ELEVATIONS IS WEDNESDAY NIGHT (CHRISTMAS EVE) INTO
THURSDAY MORNING (CHRISTMAS); THIS IS CURRENTLY FOCUSED MORE SO
OVER SOUTHWEST AND CENTRAL MONTANA AND SHOULD BE A RAIN/SNOW MIX.
- FORECAST CONFIDENCE & SCENARIOS:
TODAY THROUGH SATURDAY... CONFIDENCE IS HIGH THAT MOST AREAS WILL
REMAIN DRY THROUGH THE PERIOD, WITH MOST AREAS ON THE HI-LINE THIS
MORNING HAVING LESS THAN A 20 PERCENT PROBABILITY OF GETTING A
TRACE OF ICING FROM ANY POSSIBLE FREEZING DRIZZLE. ALSO FOR TODAY,
THE MOST WIDESPREAD 50+ PERCENT PROBABILITY FOR WIND GUSTS ACROSS
NORTH CENTRAL AND CENTRAL MONTANA IS 30 MPH, WHILE 50+ PERCENT
PROBABILITIES OF AT LEAST 45 MPH IS LIMITED TO THE ROCKY MOUNTAIN
FRONT AND OVER PORTIONS OF JUDITH BASIN COUNTY. 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.
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
20/12Z TAF PERIOD
THERE IS A SMALL CHANCE FOR A LIGHT SNOW SHOWER THIS MORNING IN
THE HAVRE AREA, OTHERWISE QUIET WEATHER CONDITIONS ARE EXPECTED
OVER THE REMAINDER OF THE CWA. DO EXPECT MID/HIGH LEVEL CLOUDS
OVER THE CWA TODAY. BRUSDA
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 57 38 55 41 / 0 10 10 20
CTB 52 34 50 36 / 0 20 0 20
HLN 48 32 46 32 / 0 10 0 30
BZN 48 28 49 29 / 0 10 0 30
WYS 37 10 38 19 / 0 0 0 30
DLN 47 29 45 26 / 0 10 0 20
HVR 43 21 43 28 / 20 0 0 50
LWT 53 33 56 34 / 20 0 10 40
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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