024
FXUS65 KMSO 202051
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
151 PM MST FRI DEC 20 2024
DISCUSSION
KEY MESSAGES:
- RISK FOR FREEZING RAIN, SUNDAY AND MONDAY MORNINGS ACROSS
PORTIONS OF NORTHWEST AND WEST-CENTRAL MONTANA VALLEYS.
- MILD PACIFIC STORM TRACK CONTINUES INTO CHRISTMAS DAY.
- PROLONGED PERIOD OF MOUNTAIN SNOW FOLLOWING CHRISTMAS.
GOES SATELLITE IMAGERY SHOWS A RIDGE OF HIGH PRESSURE AMPLIFYING
ACROSS THE NORTHERN ROCKIES THIS AFTERNOON, WITH A MIX OF SUN AND
HIGH CLOUDS, BRINGING MILD TEMPERATURES.
A SPLIT FLOW WEATHER PATTERN WILL PERSIST THROUGH MONDAY NEXT
WEEK. TWO PACIFIC TROUGHS STAND OUT, WITH THE FIRST SYSTEM
ARRIVING SATURDAY NIGHT INTO SUNDAY MORNING. SNOW LEVELS WILL
CLIMB ABOVE 4,500-5,000 FEET, LEADING THE THREAT OF POCKETS OF
FREEZING RAIN ACROSS VALLEY AREAS, MAINLY ACROSS NORTHWEST AND
WEST-CENTRAL MONTANA, WHERE COLD SUB-SURFACE GROUND TEMPERATURES
ARE MORE PREVALENT. LIGHT TO MODERATE SNOW WILL CONTINUE ACROSS
MOUNTAIN RANGES THROUGH SUNDAY MORNING, WITH GENERALLY OF 3-8
INCHES OF ACCUMULATION. ANOTHER SYSTEM ARRIVES SUNDAY NIGHT INTO
MONDAY MORNING, FOLLOWING A SIMILAR TREND, WITH VALLEY RAIN AND
POCKETS OF FREEZING RAIN AND HIGH ELEVATION MOUNTAIN SNOW.
THE OVERALL PATTERN BEGINS TO SHIFT TUESDAY NEXT WEEK, AS A
BROADER TROUGH APPROACHES THE WEST COAST AND AN ATMOSPHERIC RIVER
COMES ONSHORE IN NORTHERN CA. SOUTHWESTERLY FLOW DURING THE ONSET
OF PRECIPITATION WILL KEEP SNOW LEVELS HIGH, RANGING FROM
4,500-5,500 FEET TUESDAY MORNING. A COLD FRONT WILL MOVE THROUGH
THE NORTHERN ROCKIES TUESDAY NIGHT INTO CHRISTMAS MORNING, WITH
SNOW LEVELS DROPPING TO 3,500 FEET. SNOW WILL ONCE AGAIN FOCUS
ACROSS THE MOUNTAINS, WITH LITTLE TO ANY VALLEY ACCUMULATIONS.
GLOBAL ENSEMBLES CONTINUE TO ADVERTISE A PROGRESSIVE WESTERLY FLOW
FOLLOWING CHRISTMAS DAY, WITH SEVERAL PACIFIC SYSTEMS LEADING TO A
FAVORABLE PATTERN FOR MOUNTAIN SNOW. THIS IS SUPPORTED WELL BY THE
8-14 CLIMATE PREDICTION CENTERS HAZARD OUTLOOK, WHICH HAS THE
NORTHERN ROCKIES UNDER A MODERATE RISK (40-60%) FOR HEAVY SNOW BY
DECEMBER 28. /AL
AVIATION
STABLE AND STAGNANT CONDITIONS WILL CONTINUE UNDER A
RIDGE OF HIGH PRESSURE THROUGH SATURDAY AFTERNOON. SATELLITE
IMAGERY SUGGESTS MID AND UPPER LEVEL CLOUDS WILL INCREASE LATER
THIS EVENING INTO THE OVERNIGHT HOURS, LIMITING THE THREAT FOR
WIDESPREAD VALLEY STRATUS AND FOG. /AL
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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