509
FXUS65 KMSO 200839
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
139 AM MST FRI DEC 20 2024
DISCUSSION
KEY MESSAGES:
- HIGH PRESSURE WILL PERSIST THROUGH SATURDAY
- THE NEXT CHANCE FOR PRECIPITATION WILL BE SATURDAY NIGHT WITH A
POTENTIAL FOR FREEZING RAIN ON SUNDAY MORNING
SATELLITE IMAGERY EARLY THIS MORNING SHOWS A FAST-MOVING SHORTWAVE
DISTURBANCE EXITING THE NORTHERN ROCKIES TO THE EAST. HIGH
PRESSURE WILL RESUME TODAY AND PERSIST THROUGH SATURDAY. THERE
WILL BE ENOUGH MOISTURE ASSOCIATED WITH THE RIDGE TO KEEP
INTERMITTENT CLOUD COVER IN THE FORECAST.
A MORE SIGNIFICANT TROUGH OF LOW PRESSURE REMAINS ON TRACK TO
MOVE THROUGH NORTH-CENTRAL IDAHO AND WESTERN MONTANA SATURDAY
NIGHT INTO SUNDAY. PRE-FRONTAL WARMING WILL RAISE SNOW LEVELS,
LEADING TO A WINTRY MIX IN THE VALLEYS AND THE POTENTIAL FOR
FREEZING RAIN, DEPENDING ON THE THERMAL PROFILE. THE GFS MODEL
SHOWS A FASTER COLD FRONT WITH VALLEY SNOW SUNDAY MORNING, WHILE
THE ECMWF MODEL SUGGESTS SLOWER TIMING AND HIGHER SNOW LEVELS. THE
TIMING OF THE COLD FRONT WILL DETERMINE THE EXTENT OF FREEZING
RAIN.
NEXT WEEK, ENSEMBLE GUIDANCE INDICATES AN ACTIVE WEATHER PATTERN
WITH FLUCTUATING SNOW LEVELS. EXPECT CONTINUED WINTRY MIX IN
VALLEYS AND ACCUMULATING SNOW AT MOUNTAIN PASSES AND HIGHER
ELEVATIONS.
AVIATION
LIGHT AND VARIABLE WINDS UNDER OVERCAST SKIES WILL
PERSIST TODAY UNDER A RIDGE OF HIGH PRESSURE. SOME LOW STRATUS
DOWN TO ABOUT 4000 FT AGL WILL BE POSSIBLE TODAY AT KGPI WITH A
STABLE ATMOSPHERE. EXPECT DECREASING CLOUDS OVERNIGHT TONIGHT WITH
CONTINUED LIGHT AND VARIABLE WINDS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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