271
FXUS65 KMSO 180958
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
258 AM MST TUE FEB 18 2025
DISCUSSION
KEY MESSAGES:
- COLD START TO WEDNESDAY MORNING
- LIGHT SNOW EVENT WEDNESDAY INTO THURSDAY
- NEXT SYSTEM LATE WEEKEND, SNOW LEVELS RISE WELL ABOVE VALLEYS,
POTENTIAL REFREEZE OF WET ROADS, PONDING OF WATER IN LOW LYING/
POOR DRAINAGE AREAS FROM SNOW MELT.
LIGHT SNOW IS CONTINUING AS WELL AS WINTER IMPACTS TO DRIVING,
USE CAUTION DURING YOUR MORNING COMMUTE. LIGHT SNOW WILL BE
POSSIBLE THROUGH AFTERNOON WITH MINOR ACCUMULATIONS. A FEW HIGH
RESOLUTION MODELS CONTINUE TO DEPICT WEAK SNOW BANDS EAST OF
MISSOULA ALONG I-90. THIS AREA MAY SEE PERIODS OF MODERATE SNOW,
LOWERED VISIBILITY FROM BLOWING SNOW, AND RAPIDLY CHANGING ROAD
CONDITIONS.
QUESTIONS REMAIN ON CLOUD COVER OVERNIGHT TONIGHT. ONCE AGAIN
HIGH RESOLUTION MODELS DEMONSTRATE CLEARING AFTER MIDNIGHT, WHICH
COULD ALLOW FOR MODERATE RADIATIONAL COOLING. THE CURRENT
FORECAST HAS SINGLE DIGITS BELOW ZERO ALONG THE CONTINENTAL DIVIDE
WITH SINGLE DIGITS TO TEENS ALONG US-93 FROM NORTH TO SOUTH. IN
MOST CASES THESE TEMPERATURES ARE ONLY 5 DEGREES OR SO BELOW
NORMAL, DO NOT BE SURPRISED IF A FEW OF OUR COLDER LOCATIONS DROP
TO -10 TO -20F BELOW, IF PERFECT CONDITIONS EXIST. NORTH-CENTRAL
ID CAN EXPECT NEAR NORMAL OVERNIGHT LOWS.
WEDNESDAY EVENING LIGHT PRECIPITATION DEVELOPS ACROSS THE REGION
AND SNOW LEVELS SUGGEST ALL SNOW, EXCEPT IN HELLS CANYON ID. LIGHT
ACCUMULATIONS OF UP TO AN INCH IN VALLEYS AND GENERALLY 3 TO 6
INCHES IN THE MOUNTAINS CAN BE EXPECTED AS SNOW ENDS ON THURSDAY.
FRIDAY RISING HEIGHTS FROM AN UPPER LEVEL RIDGE WILL ALLOW FOR
WARMING, WITH HIGH TEMPERATURES IN THE 40S. A STRONG PACIFIC JET
STREAM WILL PUSH THE POLAR BOUNDARY EAST INTO THE DAKOTAS AND SET
THE STAGE FOR RISING SNOW LEVELS AS A WEAK ATMOSPHERIC RIVER
ARRIVES. BY TUESDAY MORNING, MOUNTAINS IN NORTH-CENTRAL ID AND
ALONG THE ID/ MT BORDER HAVE A 50% CHANCE OF RECEIVING GREATER
THAN A INCH AND A HALF OF LIQUID WATER EQUIVALENT. SNOW LEVELS
DURING THIS PERIOD WILL FLUCTUATE BETWEEN 5000 AND 6000 FEET.
IMPACTS EXPERIENCED FROM PREVIOUS EVENTS SIMILAR TO THIS HAVE
BEEN; RIVER ICE-JAM FLOODING, PONDING OF WATER IN LOW LYING AREAS,
AND A REFREEZE OF WET SURFACES OVERNIGHT. MORE TO COME IN FUTURE
FORECASTS AS DETAILS BECOME CLEARER.
AVIATION
LIGHT SNOW IS EXPECTED TO CONTINUE THROUGH AFTERNOON, MAINLY I-90
AND SOUTH. WEAK SNOW BANDS WILL BE POSSIBLE EAST OF KMSO AND BRING
RAPIDLY REDUCED VISIBILITY AND CEILINGS, THESE BANDS SHOULD BE
SHORT-LIVED AND ARE LOW PROBABILITY OF DEVELOPING. GUSTY EAST TO
NORTHEAST WINDS HAVE BEEN SLOW TO MATERIALIZE, YET MAY STILL
CAUSE REDUCED VISIBILITY DUE TO BLOWING SNOW THROUGHOUT THE DAY.
THE POSITION OF THE ARCTIC HIGH PRESSURE WELL EAST OF THE NORTHERN
ROCKIES IS REDUCING THE THREAT OF EAST WINDS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WARNING UNTIL 9 AM MST THIS MORNING FOR
BITTERROOT/SAPPHIRE MOUNTAINS...BUTTE/BLACKFOOT REGION...
FLATHEAD/MISSION VALLEYS...LOWER CLARK FORK REGION...
MISSOULA/BITTERROOT VALLEYS...POTOMAC/SEELEY LAKE REGION...
WEST GLACIER REGION.
ID...WINTER STORM WARNING UNTIL 8 AM PST THIS MORNING FOR NORTHERN
CLEARWATER MOUNTAINS...OROFINO/GRANGEVILLE REGION...
SOUTHERN CLEARWATER MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 9 AM MST THIS MORNING FOR EASTERN
LEMHI COUNTY...WESTERN LEMHI COUNTY.
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