283
FXUS65 KMSO 221057
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
357 AM MST SAT FEB 22 2025
DISCUSSION
KEY MESSAGES:
- INCREASED SNOWMELT AND RUNOFF SATURDAY INTO MONDAY, BRINGING
THE RISK OF MINOR FLOODING TO LOW-LYING AND POOR DRAINAGE AREAS
AND TO SMALL STREAMS AND CREEKS FROM POTENTIAL ICE JAM RELEASES
- WIDESPREAD RAIN AND HIGH ELEVATION MOUNTAIN SNOW, SUNDAY INTO
MONDAY.
- AREAS OF FREEZING RAIN SATURDAY NIGHT THROUGH SUNDAY MORNING
ACROSS WESTERN MONTANA WITH COLD SUBSURFACE GROUND TEMPERATURES
IN PLACE.
NO MAJOR CHANGES THIS UPDATE. LIGHT RAIN AND SNOW HAVE BEEN
REPORTED OVER NORTH-CENTRAL IDAHO. WITH TEMPERATURES NEAR
FREEZING, EXPECT POSSIBLE BLACK ICE IF TRAVELING THIS MORNING.
A LONG DURATION (~48 HOUR) ATMOSPHERIC RIVER EVENT REMAINS ON
TRACK TO IMPACT THE NORTHERN ROCKIES SUNDAY INTO MONDAY,
DELIVERING WIDESPREAD PRECIPITATION AND PUSHING SNOW LEVELS ABOVE
6,000 FEET. WARM, WET, AND BREEZY CONDITIONS IN THE LOWER
ELEVATIONS WILL SET THE STAGE FOR RAPID SNOWMELT, LEADING TO
RUNOFF CONCERNS AND INTRODUCING THE RISK FOR MINOR FLOODING IN
LOW-LYING AND POOR DRAINAGE AREAS ACROSS WESTERN MONTANA AND
NORTH-CENTRAL IDAHO. FURTHERMORE, THE RAPID THAW OF SMALL STREAMS
AND CREEKS MAY LEAD TO ICE JAM RELEASES. GIVEN RISING SNOW LEVELS
AND WIDESPREAD PRECIPITATION, AN ELEVATED RISK ALSO EXISTS FOR
ROCK SLIDES, PARTICULARLY ACROSS NORTH-CENTRAL IDAHO AND ALONG THE
ID- MT BORDER, WHERE CONFIDENCE IS HIGH (90% PROBABILITY) FOR
WIDESPREAD PRECIPITATION TOTALS EXCEEDING ONE INCH. HIGHER PEAKS
ACROSS THE NORTHERN BITTERROOT, NORTHWEST MONTANA MOUNTAINS, AND
CLEARWATER MOUNTAINS WILL SEE THE HIGHEST PRECIPITATION TOTALS OF
2-4 INCHES. FINALLY, GIVEN THE INTENSITY OF THIS SYSTEM AND
CHANGES TO THE SNOWPACK, THOSE PLANNING WINTER RECREATION
ACTIVITIES ARE ENCOURAGED TO MONITOR AVALANCHE FORECASTS AT
AVALANCHE.ORG
ANOTHER CONCERN IS THE RISK OF ICY CONDITIONS, PARTICULARLY OVERNIGHT
SATURDAY NIGHT INTO SUNDAY MORNING. ALTHOUGH AIR TEMPERATURES MAY
RISE ABOVE FREEZING, MANY WESTERN MONTANA VALLEYS STILL HAVE
SUBSURFACE TEMPERATURES BELOW FREEZING. THIS COULD RESULT IN RAIN
FREEZING ON CONTACT, CREATING HAZARDOUS CONDITIONS, ESPECIALLY ON
SECONDARY ROADS WITH LINGERING SNOW COVER. TRAVELERS SHOULD BE
PREPARED FOR SLICK SPOTS, PARTICULARLY ON UNTREATED SURFACES.
WINTER WEATHER ADVISORIES HAVE BEEN ISSUED ACROSS NORTHWEST
MONTANA WHERE OUR CONFIDENCE IS CURRENTLY THE HIGHEST FOR MORE
WIDESPREAD IMPACTS TO OCCUR.
THE NEXT PACIFIC DISTURBANCE IS EXPECTED LATE MONDAY NIGHT INTO
TUESDAY. SNOW LEVELS WILL INITIALLY START AROUND 5000 FEET, BUT
WILL DROP DOWN TO 3500 FEET TUESDAY MORNING AS A COLD FRONT MOVES
THROUGH THE REGION. BY THIS POINT, THE MAIN MOISTURE SOURCE WILL
BE CUT OFF, BUT LINGERING SNOW SHOWERS WILL LIKELY EXIST.
AVIATION
SHOWERS WILL PERSIST ACROSS NORTH-CENTRAL IDAHO AND
NORTHWEST MONTANA THIS MORNING, SO EXPECT PERIODIC MOUNTAIN
OBSCURATION. BY SATURDAY NIGHT AND CONTINUING THROUGH SUNDAY
NIGHT, AN ATMOSPHERIC RIVER WILL BRING RISING SNOW LEVELS AND
WIDESPREAD VALLEY RAIN, LEADING TO A WET AND ACTIVE WEATHER
PATTERN.
MSO WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH FROM 2 PM MST THIS AFTERNOON THROUGH MONDAY
AFTERNOON FOR BITTERROOT/SAPPHIRE MOUNTAINS...
BUTTE/BLACKFOOT REGION...FLATHEAD/MISSION VALLEYS...
KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION...
MISSOULA/BITTERROOT VALLEYS...POTOMAC/SEELEY LAKE REGION...
WEST GLACIER REGION.
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 8 AM MST
SUNDAY FOR FLATHEAD/MISSION VALLEYS...KOOTENAI/CABINET
REGION...WEST GLACIER REGION.
ID...FLOOD WATCH FROM 1 PM PST THIS AFTERNOON THROUGH MONDAY
AFTERNOON FOR LOWER HELLS CANYON/SALMON RIVER REGION...
NORTHERN CLEARWATER MOUNTAINS...OROFINO/GRANGEVILLE
REGION...SOUTHERN CLEARWATER MOUNTAINS.
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