920
FXUS65 KGGW 172221
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
321 PM MST TUE DEC 17 2024
DISCUSSION
KEY MESSAGES:
- A MESSY WINTRY MIX OF SNOW, SLEET, FREEZING RAIN, AND BLOWING
SNOW WILL SPREAD FROM WEST TO EAST THROUGH NORTHEAST MONTANA
BEGINNING WEDNESDAY MORNING.
- SUSTAINED WINDS OF 35 TO 45 MPH WITH GUSTS UP TO 60 MPH ARE
EXPECTED ACROSS MOST (IF NOT ALL) OF NORTHEAST MONTANA FROM
MID-DAY WEDNESDAY THROUGH THURSDAY AFTERNOON.
- ARCTIC AIR FROM SASKATCHEWAN WILL SPILL OVER THE BORDER AND
COMBINE WITH GUSTY WINDS TO DROP WIND CHILLS DOWN TO 25 DEGREES
BELOW ZERO EARLY THURSDAY MORNING.
WEATHER PATTERN OVERVIEW:
THIS IS A PARTICULARLY COMPLICATED FORECAST WITH MULTIPLE IMPACTS
SPREAD OVER DIFFERENT TIME FRAMES.
A STRONG, EMBEDDED SHORT-WAVE IMPULSE WILL EMERGE FROM THE
CANADIAN ROCKIES LATE TONIGHT AND SET OFF ACCUMULATING
PRECIPITATION THROUGH PORTIONS OF MONTANA BY EARLY WEDNESDAY
MORNING. THE PRECIP WILL BEGIN AS SNOW IN THE NORTH, BUT THROUGH
THE DAY ON WEDNESDAY, COMPETING AIR MASSES WILL MIX IN SOME
FREEZING RAIN AND SLEET FROM THE SOUTH AS THE STORM PUSHES THROUGH
NORTHEAST MONTANA ALL DAY LONG. SNOW ACCUMULATIONS UP TO 3 INCHES
ARE MORE LIKELY IN OUR NE CORNER. FREEZING RAIN IS EXPECTED TO
ACCUMULATE AT LEAST A GLAZE FOR MOST LOCATIONS JUST BEHIND THE
SNOWFALL, LIKELY CREATING A HARD ICE CRUST OVER THE SNOW.
TEMPERATURES BY WEDNESDAY AFTERNOON WILL WARM ENOUGH FROM THE
SOUTH TO MELT SOME OF THIS ICE AND SNOW AND EVEN ALLOW FOR SOME
RAINFALL. BUT IF THE GROUND REMAINS FROZEN OR NEAR FROZEN, THIS
MIXED PRECIPITATION WILL MAKE FOR SOME INSTANTLY SLICK SURFACES. A
WINTER WEATHER ADVISORY FOR THIS WINTRY MIX HAS BEEN ISSUED.
TO COMPLICATE THINGS, A TIGHT PRESSURE GRADIENT AND JET STREAM
ALOFT WILL ALLOW FOR STRONG AND GUSTY WINDS TO REACH THE SURFACE,
MAINLY FROM MID-DAY WEDNESDAY THROUGH THURSDAY AFTERNOON. HREF
MODEL ENSEMBLE WIND DATA INDICATE THAT WIDESPREAD 60 MPH WINDS ARE
POSSIBLE. A HIGH WIND WARNING HAS BEEN ISSUED TO COVER ALL OF
NORTHEAST MONTANA.
AS IF THAT ALL WASN'T ENOUGH, A RE-ENFORCING BACK-SIDE COLD
INTRUSION OF ARCTIC AIR WILL SLIDE DOWN FROM SASKATCHEWAN LATE
WEDNESDAY AND THURSDAY MORNING AND COMBINE WITH THOSE GUSTY WINDS
TO DROP THE APPARENT TEMPERATURE (OR WIND CHILL) DOWN TO NEAR 25
DEGREES BELOW ZERO. WE WILL LET THE NEXT FEW SHIFTS GET A CLOSER
LOOK AT THIS DATA BEFORE ISSUING ANY RELATED HEADLINES.
FRIDAY AND BEYOND, A WARM AND BUILDING RIDGE OF HIGH PRESSURE WILL
ARRIVE FROM THE WEST TO BRING WARMER AND CALMER CONDITIONS TO THE
REGION WHICH ARE EXPECTED TO PERSIST THROUGH THE CHRISTMAS SEASON.
FORECAST CONFIDENCE & DEVIATIONS:
RAISED ALL WIND SPEEDS WEDNESDAY AFTERNOON AND NIGHT AS NBM TENDS
TO UNDER FORECAST WINDS BEHIND A STRONG COLD FRONT AND IS LIKELY
UNDER FORECASTING THIS MIXING OF STRONG WINDS ALOFT. DID NOT
DEVIATE ANYWHERE ELSE FROM THE BASE FORECAST FOR NOW.
THERE IS MODERATE TO HIGH CONFIDENCE MULTIPLE IMPACTS FROM THE
WINTRY MIX AND GUSTY WINDS.
THERE IS MEDIUM TO LOW CONFIDENCE ON THE EXACT AMOUNTS OF
FREEZING RAIN ACCUMULATION.
THERE IS MODERATE CONFIDENCE IN A WARMING TREND ARRIVING THROUGH
THE WEEKEND.
AVIATION
BETWEEN MVFR AND IFR, WITH POSSIBLE LIFR THROUGH THIS TAF CYCLE.
WINTRY MIX OF SNOW, SLEET, FREEZING RAIN, AND RAIN IS LIKELY FROM
12Z WEDNESDAY MORNING THROUGH 00Z WEDNESDAY EVENING.
THIS AFTERNOON THROUGH WEDNESDAY MORNING, WINDS WILL BE LIGHT AND
VARIABLE IF NOT CALM. BY MID-DAY WEDNESDAY, WINDS FROM THE SE AND
S WILL INCREASE TO 15 TO 20 KTS. BY 21Z, WINDS WILL SHIFT AROUND
FROM THE SW AND INCREASE TO 30 KTS WITH GUSTS AROUND 50 KTS
THROUGH WEDNESDAY NIGHT AND INTO THURSDAY MORNING.
GGW WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 4 AM WEDNESDAY TO 5 AM MST THURSDAY
FOR CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-DAWSON-EASTERN ROOSEVELT-GARFIELD-MCCONE-NORTHERN
PHILLIPS-NORTHERN VALLEY-PETROLEUM-RICHLAND-SHERIDAN-SOUTHWEST
PHILLIPS-WESTERN ROOSEVELT.
HIGH WIND WARNING FROM 10 AM WEDNESDAY TO 5 PM MST THURSDAY FOR
CENTRAL AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-
DANIELS-DAWSON-EASTERN ROOSEVELT-GARFIELD-MCCONE-NORTHERN
PHILLIPS-NORTHERN VALLEY-PETROLEUM-PRAIRIE-RICHLAND-SHERIDAN-
SOUTHWEST PHILLIPS-WESTERN ROOSEVELT-WIBAUX.
WEATHER.GOV/GLASGOW
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