493
FXUS65 KGGW 171015
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
315 AM MST TUE DEC 17 2024
DISCUSSION
KEY MESSAGES:
- LIGHT SNOW OVER THE AREA THIS MORNING WILL DIMINISH BY EARLY
AFTERNOON. MOST OF THE SNOW WILL BE OVER THE SW HALF OF THE
FORECAST AREA.
- WEDNESDAY AND WEDNESDAY NIGHT, ANOTHER ROUND OF SNOWFALL MIXED
WITH FREEZING RAIN WILL MOVE ACROSS THE AREA.
- STRONG WEST TO NORTHWEST WINDS WILL MOVE THROUGH THE AREA LATE
WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. A HIGH WIND WATCH HAS
BEEN ISSUED FOR SW PHILLIPS COUNTY.
WEATHER PATTERN OVERVIEW:
GENERALLY LARGE-SCALE NORTHWEST FLOW ALOFT IS EXPECTED THROUGH
MIDWEEK WITH MULTIPLE EMBEDDED DISTURBANCES MOVING THROUGH THE
NORTHERN ROCKIES AND ADJACENT NORTHERN HIGH PLAINS. AT THE
SURFACE, THIS WILL RESULT IN A FEW SEPARATE ROUNDS OF SNOWFALL: A
WEAKER ONE THIS MORNING, AND A STRONGER ONE ON WEDNESDAY AND
WEDNESDAY NIGHT WITH SNOW MIXED AT TIMES WITH RAIN AND FREEZING
RAIN.
CANADIAN HIGH PRESSURE PUSHES SOUTH THIS AFTERNOON AND EVENING
WITH SUB- ZERO LOW TEMPERATURES TONIGHT IN MOST AREAS NORTH OF US
HIGHWAY 2.
A STRONG LOW PRESSURE SYSTEM WILL TRACK ACROSS THE NORTHERN PART
OF THE FORECAST AREA WEDNESDAY AFTERNOON AND EVENING. AHEAD OF THE
SYSTEM, THERE WILL BE AN AREA OF OVERRUNNING PRECIPITATION MOVING
INTO THE FORECAST AREA WEDNESDAY MORNING WITH A WARM FRONT. IT
WILL BE A MIX OF SNOW, SLEET, FREEZING RAIN, AND RAIN DEPENDING ON
TEMPERATURES AT THE SURFACE AND ALOFT. THE NE CORNER OF THE STATE
WILL STAY COLD ENOUGH FOR ALL SNOW AND THE MOST LIKELY SNOWFALL
AMOUNT AT THIS TIME WILL BE BETWEEN 3 AND 5 INCHES. GOING SOUTH,
SNOWFALL AMOUNTS DIMINISH PARTLY DUE TO MIXED PRECIPITATION AND
PARTLY DUE TO LESS TIME IN THE OVERRUNNING PRECIPITATION. LITTLE
OR NO SNOW ACCUMULATION IS EXPECTED SOUTH OF THE MISSOURI RIVER.
THE TRACK OF THE LOW ON WEDNESDAY WILL CREATE A WIDE RANGE IN
TEMPERATURES ALONG WITH A LOW CONFIDENCE TEMPERATURE FORECAST.
AS THE LOW PASSES WEDNESDAY AFTERNOON AND EVENING, A COLD FRONT
DROPS SOUTH WITH STRONG WEST TO NW WINDS AND RAPID COLD AIR
ADVECTION. MODELS CURRENTLY HAVE 50 TO 60 KNOT WINDS AT 850 MB
WHICH WITH GOOD MIXING WILL PROVIDE A GOOD CHANCE OF REACHING HIGH
WIND WARNING CRITERIA OF 40+ MPH SUSTAINED AND 58+ MPH GUSTS IN
SOME AREAS. AT THE SAME TIME, SNOW NORTH AND MIXED PRECIPITATION
SOUTH WILL LIKELY RESULT IN WINTER WEATHER HEADLINES ON WEDNESDAY.
FOR NOW, WILL ISSUE A HIGH WIND WATCH FOR SW PHILLIPS COUNTY FOR
WEDNESDAY AFTERNOON AND EVENING WHERE THE PROBABILITY OF 55+ MPH
WIND GUST IS AROUND 70%. MOST OF THE REMAINDER OF NE MONTANA HAS A
20-50% CHANCE OF A WIND GUST OF 55+ MPH WEDNESDAY NIGHT. THE NE
PART OF THE FORECAST AREA WILL HAVE BLOWING SNOW WITH THE STRONG
WINDS. HOW MUCH OF THE FORECAST AREA WILL NEED WINTER WEATHER
HEADLINES VERSUS HIGH WIND HEADLINES REMAINS UNCERTAIN AT THIS
POINT.
TEMPERATURES WILL COLD ENOUGH IN THE NORTH LATE WEDNESDAY NIGHT
AND THURSDAY MORNING WITH WIND CHILLS AROUND -25 THAT A COLD
WEATHER ADVISORY MAY BE NEEDED.
AFTER A COLD DAY ON THURSDAY WITH HIGH PRESSURE OVER THE AREA,
TEMPERATURES WARM AS AN UPPER RIDGE PUSHES THE COLD AIR TO THE
EAST ON FRIDAY. THE RIDGE WILL BRING ABOVE NORMAL TEMPERATURES
OVER THE WEEKEND AND EARLY NEXT WEEK.
FORECAST CONFIDENCE & DEVIATIONS:
RAISED WIND SPEEDS WEDNESDAY AFTERNOON AND NIGHT AS NBM TENDS TO
UNDER FORECAST WINDS BEHIND STRONG COLD FRONT AND IS LIKELY UNDER
FORECASTING THE MIXING OF STRONG WINDS ALOFT. DID NOT DEVIATE
ANYWHERE ELSE FROM THE BASE FORECAST FOR NOW.
THERE IS MODERATE CONFIDENCE ON THE SNOW AMOUNTS IN THE NE CORNER
OF THE STATE AND LOW CONFIDENCE ON THE PRECIPITATION TYPES AND
AMOUNTS ALONG WITH TEMPERATURES ON WEDNESDAY AS A SLIGHT CHANGE IN
THE STORM TRACK WILL RESULT IN SIGNIFICANT TEMPERATURE AND PRECIP
TYPE DIFFERENCES. THERE IS MODERATE TO HIGH CONFIDENCE ON THE
STRONG WEST TO NW WINDS WEDNESDAY NIGHT.
AVIATION
BETWEEN VFR, MVFR AND IFR TODAY AND TONIGHT.
MULTIPLE PERIODS OF TRANSITION BETWEEN LOW AND MID AND BACK DOWN
TO LOW LEVEL CLOUDS ARE EXPECTED THROUGHOUT THIS TAF CYCLE.
OCCASIONAL SNOWFALL IS ALSO POSSIBLE UNTIL 18Z TODAY.
LIGHT AND VARIABLE WINDS EARLY WILL BECOME NORTH THIS MORNING AT 5
TO 10 KNOTS. WIND TONIGHT WILL VARY FROM NORTH TO NE TO EAST AT 10
KNOTS OR LESS.
GGW WATCHES/WARNINGS/ADVISORIES
HIGH WIND WATCH FROM WEDNESDAY AFTERNOON THROUGH LATE WEDNESDAY
NIGHT FOR SOUTHWEST PHILLIPS.
WEATHER.GOV/GLASGOW
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