661
FXUS65 KTFX 201012
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
312 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.
DISCUSSION
- 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
20/06Z TAF PERIOD
MID AND HIGH LEVEL CLOUD COVER CONTINUES TO STREAM ACROSS THE
REGION TONIGHT AS AN UPPER LEVEL RIDGE SHIFTS ACROSS THE NORTHERN
ROCKIES WITH DECREASING CLOUDS EXPECTED ON FRIDAY. CANNOT RULE
OUT SOME PATCHY FOG AND/OR LOW CLOUD-DEVELOPMENT NEAR THE KHVR
TERMINAL OVERNIGHT BUT LATEST FORECAST GUIDANCE HAS A LOW (LESS
THAN 20%) PROBABILITY OF THIS. OTHERWISE, VFR CONDITIONS PREVAIL
WITH GENERALLY LIGHT SURFACE WINDS OVERNIGHT GIVING WAY TO BREEZY
WEST TO SOUTHWEST WINDS ON THE PLAINS FRIDAY. HOENISCH
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 55 36 55 37 / 0 10 0 30
CTB 50 31 50 34 / 0 0 0 20
HLN 48 29 47 32 / 0 0 0 30
BZN 48 25 49 27 / 0 0 0 20
WYS 37 9 39 16 / 0 0 0 20
DLN 47 26 46 26 / 0 0 0 20
HVR 43 22 45 26 / 10 0 0 40
LWT 53 33 56 33 / 10 0 0 30
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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