931
FXUS65 KGGW 180927
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
227 AM MST WED DEC 18 2024
DISCUSSION
KEY MESSAGES:
- HEADLINES:
WINTER WEATHER ADVISORY: THRU 5 AM THU
HIGH WIND WARNING:THRU 11 AM THU
- GENERALLY EXPECTING SNOWFALL TO BE AS HIGH AS 3" FOR FAR NE MT
THRU THU AM. THIS, IN COMBINATION WITH ICE RISKS AND HIGH WINDS
WILL MAKE FOR DIFFICULT TRAVEL THRU THU
- ABOVE AVERAGE TEMPERATURES BY CHRISTMAS DAY
WEATHER PATTERN OVERVIEW:
LET THE MESS BEGIN!
THE NEXT TROUBLEMAKER... I MEAN DISTURBANCE IS CURRENTLY BRINGING
PRECIPITATION TO CENTRAL MONTANA. AHEAD OF THIS AREA OF
PRECIPITATION, LOW TO MID-LEVELS ARE BEGINNING TO SEE WARM-AIR
ADVECTION AS PER THE LATEST RAP13 MESOANALYSIS. THIS WARM AIR
GLIDING OVER THE COLD POCKET AT THE SURFACE WILL SET UP A SCENARIO
WHERE THE FALLING PRECIPITATION LOOKS TO INITIALLY FALL AS A
SNOW/SLEET MIX TRANSITIONING TO FREEZING LINE ON THE BACK-HALF IN
THE INITIAL PRECIPITATION. FREEZING RAIN WILL THEN GIVE WAY TO
BRIEF DRY CONDITIONS. GIVEN THAT THE ICE ACCUMULATION EXTENT
SPREAD OUT FURTHER INTO NE MONTANA, FELT JUSTIFIED IN ADDING
WIBAUX AND PRAIRIE COUNTIES INTO THE WINTER WEATHER ADVISOR FOR
ICE CONCERNS AGAIN APPROACHING THE I-94 CORRIDOR.
BY TONIGHT, THE WRAP AROUND MOISTURE IS LOOKING TO REMAIN MOSTLY
IN NORTHEAST MONTANA, STARTING OFF AS A RAIN/SNOW MIX. EFFICIENT
WET- BULB COOLING AND COLD-AIR ADVECTION WILL QUICKLY SATURATE
THE MID- LEVELS TO SUPPORT ANOTHER ROUND OF SNOW. GREATEST QPF AND
SNOW VALUES ARE LOOKING TO PRIMARILY MAX OUT IN NORTH DAKOTA, BUT
NORTHEAST ZONES HAVE THE GREATEST CHANCE FOR APPROACHING 3 INCHES
OF FRESH SNOWFALL BY THURSDAY MORNING.
BUT WAIT! THERE'S MORE!
THE PASSAGE OF THIS SYSTEM WILL ALSO BRING WIDESPREAD WIND GUSTS
IN EXCESS OF 50 MPH. MOST OF THIS SHOULD SUBSIDE BY THURSDAY
AFTERNOON, SO SIMPLY EDITED THE HIGH WIND WARNING TO UPDATE THE
EXPIRATION DATE TO 11 AM THU.
BY FRIDAY, WE RETURN TO NORTHWESTERLY FLOW ALOFT. A SHORTWAVE
LOOKS TO REMAIN FAR ENOUGH AWAY IN MANITOBA TO NOT BRING
PRECIPITATION FOR FRIDAY. THIS WILL ALSO ALLOW A WARM UP INTO
CHRISTMAS DAY.
FORECAST CONFIDENCE & DEVIATIONS:
FOR ICE ACCUMULATION, THE BIGGEST FACTOR WILL BE HOW QUICKLY MID-
LEVELS DRY OUT AS THE DRY CONVEYOR BELT OF THE CYCLONE BEGINS TO
WRAPPING IN TO THE CENTER OF THE SURFACE LOW. THE LATEST ICE
ACCUMULATION GRID RESULTED IN HIGHER VALUES THAN WPC GUIDANCE, BUT
WILL NEED TO CAREFULLY EVALUATE THE 12Z SOUNDING FROM KGGW AND
KTFX TO SEE IF ANY TOP-DOWN GRIDS NEED ADDITIONAL EDITING FOR THE
MORNING UPDATE.
- ENRIQUEZ
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 THROUGH THURSDAY AM.
WINDS WILL BE LIGHT AND VARIABLE IF NOT CALM. BY MID-DAY, 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 UNTIL 5 AM 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.
HIGH WIND WARNING FROM 10 AM THIS MORNING TO 11 AM 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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