186
FXUS65 KMSO 212015
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
115 PM MST FRI FEB 21 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 MORNING, BECOMING MORE
WIDESPREAD SUNDAY MORNING ACROSS WESTERN MONTANA WITH COLD
SUBSURFACE GROUND TEMPERATURES IN PLACE.
GOES SATELLITE IMAGERY SHOWS A RIDGE OF HIGH PRESSURE BUILDING
OVER THE NORTHERN ROCKIES THIS AFTERNOON, WITH AREAS OF SUNSHINE
ALLOWING FOR TEMPERATURES TO CLIMB WELL ABOVE FREEZING ACROSS
VALLEY AREAS. OUR NEXT PACIFIC DISTURBANCE IS BEGINNING TO PUSH
ONSHORE IN THE PACIFIC NORTHWEST, WITH MOISTURE ARRIVING LATE
TONIGHT INTO SATURDAY MORNING ALONG THE ID-MT BORDER AND IN
NORTHWEST MONTANA. RISING SNOW LEVELS AND MILD TEMPERATURES WILL
FOCUS SNOW ACCUMULATIONS OVER THE HIGHER TERRAIN, WITH MINOR
ACCUMULATIONS OF A TRACE TO UP TO 1 INCH, FOCUSED ACROSS LINCOLN
AND FLATHEAD COUNTIES. POCKETS OF FREEZING RAIN ARE ALSO A CONCERN
INTO SATURDAY MORNING ACROSS NORTHWEST MONTANA GIVEN COLD SUB-
SURFACE GROUND TEMPERATURES IN PLACE.
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 (80% PROBABILITY) FOR
WIDESPREAD PRECIPITATION TOTALS EXCEEDING ONE INCH. HIGHER PEAKS
ACROSS THE NORTHERN BITTERROOT, CABINET, 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 ONCE AGAIN ON 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. IN FACT,
SOME FORECAST MODELS ARE SHOWING A PATTERN THAT COULD BE
CONDUCIVE FOR SNOW BANDS TUESDAY MORNING.
AVIATION
SATELLITE IMAGERY AND WEBCAMS SHOW NORTHWEST MONTANA
TERRAIN STILL OBSCURED BY CLOUDS, WHILE MUCH OF THE REGION ENJOYS
MOSTLY SUNNY SKIES WITH INCREASING HIGH-LEVEL CLOUD COVER.
HOWEVER, MOISTURE IS ON THE RISE FROM THE SOUTHWEST, AND MODEL
CROSS-SECTIONS SUGGEST CLOUDS WILL THICKEN AND LOWER TONIGHT,
PARTICULARLY OVER NORTH-CENTRAL IDAHO AND NORTHWEST MONTANA.
AS MOISTURE BUILDS, HIGH RESOLUTION MODELS INDICATE SHOWERS
DEVELOPING IN THESE AREAS BY SATURDAY MORNING. BY SUNDAY, 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 SATURDAY 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 SATURDAY TO 8 AM MST SUNDAY
FOR FLATHEAD/MISSION VALLEYS...KOOTENAI/CABINET REGION...
WEST GLACIER REGION.
ID...FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY AFTERNOON FOR
LOWER HELLS CANYON/SALMON RIVER REGION...NORTHERN
CLEARWATER MOUNTAINS...OROFINO/GRANGEVILLE REGION...
SOUTHERN CLEARWATER MOUNTAINS.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page