148
FXUS65 KGGW 211007
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
307 AM MST THU NOV 21 2024
DISCUSSION
KEY MESSAGES:
- FREEZING RAIN CHANCES INCREASE FOR LOCATIONS SOUTH AND WEST OF
FORT PECK LAKE, LEADING TO A RISK FOR A LIGHT GLAZE FROM FRIDAY
NIGHT THROUGH SATURDAY MORNING.
- TREND FOR SNOWFALL AMOUNTS CONTINUE TO INCREASE. PROBABILITIES
OF SNOWFALL AMOUNTS LISTED BELOW. WILL CONTINUE TO MONITOR AND
ISSUE WINTER WEATHER HEADLINES ACCORDINGLY.
- A WELL-BELOW NORMAL PERIOD OF TEMPERATURES ARE IN STORE FROM
MONDAY.
WEATHER PATTERN OVERVIEW:
A DRY THURSDAY IS IN STORE AS EASTERN MONTANA IS PLACED UNDER AN
UPPER-LEVEL RIDGE. THIS WILL BE SHORT LIVED AS A SERIES OF UPPER-
LEVEL PATTERN CHANGES BRINGS SEVERAL BOUTS OF PRECIPITATION FOR
THE REGION.
TODAY, AN ALBERTA CLIPPER WILL DEVELOP, FLATTENING OUT THE UPPER
LEVEL RIDGE. THIS WILL INCREASE CHANCES OF LIGHT SNOW WITH MINIMAL
ACCUMULATIONS TONIGHT. AS THE CLIPPER MOVES TOWARD THE GREAT LAKES
REGION, A SHORTWAVE RIDGE BUILDS IN ITS WAKE ACROSS MONTANA.
CONSEQUENTLY, THIS WARM ADVECTION IN THE LOW LEVELS WILL RESULT IN
A WARM NOSE SETTING UP ACROSS CENTRAL MONTANA AND EXTENDING INTO
NE MONTANA, PRIMARILY SOUTH OF THE MISSOURI. THIS WILL INCREASE
CHANCES FOR FREEZING RAIN AS SURFACE TEMPERATURES ARE EXPECTED TO
BE IN THE 20S. NORTH OF THE MISSOURI, THE FORECAST SOUNDINGS ARE
MORE LIKELY TO SUPPORT FROZEN PRECIPITATION, THUS ALLOWING A QUICK
1-2 INCHES OF SNOWFALL ACCUMULATING BY FRIDAY NIGHT ALONG THE
INTERNATIONAL BORDER.
BY SATURDAY, THE PROMINENT UPPER LEVEL LOW BRINGING AN ATMOSPHERIC
RIVER EVENT TO THE PNW WILL SEE THE LOW BEGIN TO SPLIT OFF A
TROUGH THAT WILL CONTINUE TO PROVIDE THE UPPER-LEVEL DIVERGENCE
TO SUPPORT MODERATE TO HEAVY SNOWFALL THROUGH SUNDAY MORNING.
GIVEN THE LATEST FORECAST TRENDS OF INCREASING SNOWFALL AMOUNTS
NORTH OF THE MISSOURI RIVER WITH EVERY ENSEMBLE RUN, THE
LIKELIHOOD OF WINTER HEADLINES BEING ISSUED LOOKS CERTAIN. WILL
DISCUSS WITH THE DAY CREW AND NEIGHBORS ON HOW WE COLLECTIVELY
PROCEED FOR THIS LATE NOVEMBER WINTER STORM.
FROM MONDAY, FLOW ALOFT WILL BE NORTHWESTERLY, USHERING IN AN
ARCTIC AIRMASS, LEADING TO WELL BELOW NORMAL TEMPERATURES AS WE
ROUND OUT NOVEMBER. WIND CHILL VALUES AT THE NIGHT TIME ARE
EXPECTED TO REMAIN ABOVE -20F FOR THE FORECAST, SO LIKELY NO
HEADLINES FOR COLD WEATHER AS OF YET.
FORECAST CONFIDENCE & DEVIATIONS:
THERE IS A LOW TO MEDIUM CONFIDENCE IN IMPACTS AS A RESULT OF ICE
ACCUMULATIONS FROM THE FREEZING RAIN THREAT FRIDAY AFTERNOON
THROUGH SATURDAY MORNING. AS OF NOW, THE AREA WITH THE GREATEST
THREAT APPEARS TO BE ALONG THE HIGHER TERRAIN SOUTH OF THE
MISSOURI BREAKS.
WITH RESPECT TO SNOWFALL FOR A PERIOD ENDING 5 PM SUNDAY
(ACCORDING TO THE NBM):
CHANCE OF AT LEAST 4" OF SNOWFALL:
- NORTH OF HWY 2: 70-90% CHANCE
- SOUTH OF THE MISSOURI: 20-30% CHANCE (DECREASING TO ZERO NEAR
I-94)
CHANCE OF AT LEAST 6" OF SNOWFALL:
- NORTH OF HWY 2: 50-70% CHANCE
CHANCE OF AT LEAST 8" OF SNOWFALL:
- ALONG HWY 2: 10-30% CHANCE
- ALONG THE INTERNATIONAL BORDER: NEAR 50% CHANCE
- ENRIQUEZ
AVIATION
LAST UPDATED: 0940Z
FLIGHT CAT RANGE: MOSTLY VFR// MVFR-IFR IN THE MORNING DUE TO
PATCHY FREEZING FOG, AND LATER ON THIS EVENING IN SNOW SHOWERS
DISCUSSION: AREAS OF PATCHY FREEZING FOG WILL DECREASE THROUGH THE
MORNING. SCATTERED HIGH CLOUDS WILL BECOME MORE OF MID TO LOW-
CLOUD DECK TONIGHT GENERALLY NORTH OF THE MISSOURI RIVER.
WIND: SE WINDS AT 5-10 KTS TODAY. TONIGHT, WINDS BECOME MORE
NORTHERLY AT 5-10 KTS.
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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