129
FXUS65 KTFX 212047
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
147 PM MST SAT DEC 21 2024
KEY MESSAGES
- LIGHT MOUNTAIN SNOW AND LOWER ELEVATION RAIN ARRIVES LATE
TONIGHT AND INTO SUNDAY MORNING.
- BREEZY TO GUSTY WINDS ARE EXPECTED ALONG THE PLAINS NEXT WEEK,
PARTICULARLY SUNDAY AND MONDAY.
- THERE'S A SLIGHT CHANCE FOR LIGHT FREEZING RAIN NORTH OF THE
HAVRE TO HARLEM LINE EARLY SUNDAY MORNING.
- DAILY CHANCES FOR LIGHT MOUNTAIN SNOW NEXT WEEK, WITH LOWER
ELEVATION MIXED PRECIPITATION CHRISTMAS EVE INTO CHRISTMAS
MORNING.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
THE REST OF THE AFTERNOON REMAINS DRY ACROSS THE REGION AS THE
UPPER- LEVEL RIDGE SLOWLY EXITS TO THE EAST. AN UPPER-LEVEL TROUGH
MOVES IN THIS EVENING, BRINGING LIGHT MOUNTAIN SNOW AND LOWER
ELEVATION RAIN THROUGH SUNDAY MORNING. ALONG THE HI-LINE, WHERE
SHALLOW COLDER AIR AT THE SURFACE SUNDAY MORNING, CAN ALLOW A
BRIEF FEW HOUR WINDOW FOR LIGHT FREEZING RAIN. THIS WILL BE MAINLY
NORTH OF U.S ROUTE 2 FROM THE HAVRE TO HARLEM CORRIDOR. STRONG
WARM AIR ADVECTION WILL TRANSITION FREEZING RAIN TO RAIN SHORTLY
AFTER. WITH THIS RIDGE BREAKDOWN COMES STRONGER WINDS ALONG THE
ROCKY MOUNTAIN FRONT AND BREEZY WINDS ACROSS THE PLAINS.
NEXT WEEK LOOKS TO BE A MORE ACTIVE PATTERN EFFECTING MOSTLY THE
HIGHER ELEVATIONS. MULTIPLE DISTURBANCES MOVE THROUGH THE REGION,
BRINGING LIGHT, MOUNTAIN SNOW/MIXED PRECIP AT LOWER ELEVATIONS,
AND GUSTY WINDS TO THE PLAINS. BETTER CHANCES FOR WIDESPREAD
PRECIPITATION ARRIVES ON CHRISTMAS EVE TO EARLY CHRISTMAS MORNING
AND LATE FRIDAY NIGHT TO SATURDAY MORNING. DAILY MINOR
ACCUMULATIONS OF SNOW ALONG MOUNTAIN PASSES WILL HAVE A MINOR
IMPACT TO HOLIDAY TRAVEL. TEMPERATURES ALSO REMAIN WELL ABOVE
AVERAGE THROUGH THE WEEK.
- FORECAST CONFIDENCE & SCENARIOS:
IN TERMS OF SNOW TODAY, MARIAS PASS HAS A 20-30% CHANCE FOR 3" OF
SNOW. WITH THIS HIGHER END AMOUNT ONLY HAVING MINOR IMPACTS TO
TRAVEL, I HAVE OMITTED FROM ISSUING A WINTER WEATHER ADVISORY. IN
OTHER MOUNTAIN PASSES, MINOR SNOWFALL AMOUNTS THAT RANGE UP TO
2" LIKELY. THROUGHOUT THE WEEK, THERE'S A 30-40% CHANCE FOR 2" OF
SNOW AT PASS LEVEL DAILY, LEAVING TO MINOR ACCUMULATIONS/ TRAVEL
IMPACTS. LATE FRIDAY TO EARLY SATURDAY MORNING, THERE'S A 30%
CHANCE FOR AREAS ABOVE 7,000FT TO GETTING 4" OF SNOW.
FOR THE WINDS SUNDAY AND MONDAY, VERTICAL PROFILE SOUNDINGS SHOW
35-45KT WINDS MIXING DOWN AT THE CUT BANK AREA. ALONG THE
IMMEDIATE ROCKY MOUNTAIN FRONT AREA, THERE'S A 40% FOR 70MPH WINDS
IN ISOLATED AREAS. STRONG WINDS WILL LIKELY BORDER HIGH WIND
CRITERIA. WITH LESS THAN 80% CONFIDENCE IN THESE WINDS EXCEEDING
CRITERIA, I HAVE ALSO OMITTED HIGH WIND PRODUCTS AT THIS TIME.
GUSTY WINDS CONTINUE THROUGHOUT THE WEEK, BUT ALL LOOK TO STAY
BELOW HIGH WIND CRITERIA.
I HAVE MEDIUM CONFIDENCE IN THE LIGHT FREEZING RAIN CHANCES FOR
AREAS NORTH OF THE HAVRE TO HARLEM LINE SUNDAY MORNING. HIGHER-
RES GUIDANCE GIVES A 20-40% CHANCE FOR 0.01" OF ICE. THIS WINDOW
WILL BE BRIEF, SINCE TEMPERATURES WILL QUICKLY WARM ABOVE
FREEZING IN THE MORNING, TRANSITIONING TO RAIN AND LEAVING
ACCUMULATIONS LIGHT (UP TO A FEW ONE HUNDRETHS).-WILSON
AVIATION
21/18Z TAF PERIOD
VFR CONDITIONS ARE EXPECTED TO CONTINUE OVER NORTH CENTRAL,
CENTRAL, AND SOUTHWEST MONTANA THROUGH AT LEAST 22/18Z.
WITH A HIGH PRESSURE RIDGE OVER THE AREA, ONLY PASSING MID-AND HIGH-
LEVEL CLOUDINESS WILL BE OBSERVED THROUGH AROUND 22/00Z. AN
APPROACHING DISTURBANCE FROM THE PACIFIC NORTHWEST WILL THEN SPREAD
INCREASED WESTERLY WINDS EAST ACROSS THE AREA. THIS WILL RESULT IN
MOUNTAIN WAVE TURBULENCE AND LOW LEVEL WIND SHEAR, AS WELL AS
INCREASING CLOUDINESS AND MAINLY MOUNTAIN PRECIPITATION. HOWEVER,
THE RELATIVELY WARM PRECIPITATION MOVING OVER COLD AIR TRAPPED OVER
THE NORTHEAST PORTION OF NORTH CENTRAL MONTANA (INCLUDING KHVR)
COULD PRODUCE A PERIOD OF FREEZING DRIZZLE/RAIN THERE, MAINLY
BETWEEN 06Z AND 12Z, POSSIBLY WITH PERIODS OF MVFR CONDITIONS. -
BRITTON
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 36 48 33 51 / 20 10 0 0
CTB 34 43 27 46 / 30 10 0 0
HLN 31 45 29 47 / 20 0 0 20
BZN 27 44 26 43 / 30 10 0 50
WYS 18 32 20 34 / 30 10 40 90
DLN 26 41 26 42 / 20 0 10 30
HVR 25 42 24 44 / 70 10 0 0
LWT 32 45 27 48 / 30 10 0 10
TFX WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM MST SUNDAY
FOR HILL COUNTY-NORTHERN BLAINE COUNTY.
HTTP://WWW.WEATHER.GOV/GREATFALLS
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