343
FXUS65 KMSO 200951
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
251 AM MST THU FEB 20 2025
DISCUSSION
KEY MESSAGES:
- A WARMER AND WET PERIOD IS EXPECTED LATE THIS WEEKEND INTO
EARLY NEXT WEEK LEADING TO PONDING AND LOCALIZED MINOR FLOODING
PRECIPITATION WILL GRADUALLY DIMINISH ACROSS WESTERN MONTANA AND
NORTH-CENTRAL IDAHO THIS MORNING, WITH LINGERING SCATTERED SHOWERS,
PRIMARILY OVER HIGHER ELEVATIONS. HOWEVER, SLICK ROADS AND ICY PATCHES WILL
PERSIST THROUGH THE MORNING COMMUTE DUE TO A MIX OF SNOW AND REFREEZING
MOISTURE. DRIVERS SHOULD EXERCISE CAUTION ON THE ROADS.
A WEAK RIDGE OF HIGH PRESSURE WILL BRIEFLY SETTLE OVER THE REGION ON
FRIDAY, BRINGING A SHORT-LIVED BREAK FROM PRECIPITATION. HOWEVER, BY
SATURDAY, ANOTHER WEAK DISTURBANCE WILL MOVE IN, TRIGGERING SCATTERED
SHOWERS ACROSS THE NORTHERN ROCKIES. SNOW LEVELS WILL BEGIN TO RISE,
KEEPING SNOWFALL CONFINED TO HIGHER ELEVATIONS, WHILE VALLEYS WILL LIKELY
SEE A WINTRY MIX.
LOOKING AHEAD TO SUNDAY AND MONDAY, FORECAST MODELS INDICATE AN ATMOSPHERIC
RIVER WILL PUSH INTO THE REGION, BRINGING WIDESPREAD PRECIPITATION AND
RAISING SNOW LEVELS ABOVE 5,000 FEET. CLEARWATER COUNTY AND AREAS NEAR THE
MONTANA-IDAHO BORDER COULD SEE SIGNIFICANT RAINFALL, WITH AN 80% CHANCE OF
MORE THAN AN INCH ACCUMULATING OVER 48 HOURS. AND IN FACT, SOME OF
THE HIGHER TERRAIN, PARTICULARLY IN NORTH CENTRAL IDAHO COULD SEE
OVER 2 INCHES OF LIQUID PRECIPITATION.
IN ADDITION TO THE RAIN, TEMPERATURES IN MOST VALLEYS WILL REMAIN ABOVE
FREEZING FROM SATURDAY NIGHT THROUGH TUESDAY, WITH NORTH-CENTRAL IDAHO
VALLEYS HAVING A 70% CHANCE OF STAYING ABOVE 40DEGREES ON SUNDAY
NIGHT. THE COMBINATION OF WARM TEMPERATURES AND PERSISTENT
RAINFALL COULD LEAD TO RAPID MELTING OF LOW-ELEVATION SNOW,
INCREASING THE RISK OF PONDING IN POOR DRAINAGE AREAS, LOCALIZED
MINOR FLOODING, AND ICE BREAKUPS ON SMALL CREEKS AND STREAMS. TO
MITIGATE POTENTIAL IMPACTS, CONSIDER CLEARING SNOW FROM DRAINAGE
AREAS AHEAD OF TIME.
ANOTHER KEY CONCERN WITH THIS SYSTEM IS THE POTENTIAL FOR ICY CONDITIONS AS
RAIN FALLS ON COLD GROUND, ESPECIALLY IN THE OVERNIGHT HOURS
SUNDAY. SUBSURFACE TEMPERATURES IN MANY WESTERN MONTANA VALLEYS
ARE CURRENTLY 2 TO 5 DEGREES BELOW FREEZING, MEANING THAT EVEN IF
AIR TEMPERATURES RISE ABOVE FREEZING, RAIN COULD STILL FREEZE ON
CONTACT. THIS MAY LEAD TO EXTREMELY SLICK CONDITIONS, PARTICULARLY
ON SECONDARY ROADS WHERE LINGERING SNOW COVER FROM RECENT STORMS
REMAINS. TRAVELERS SHOULD USE CAUTION, ESPECIALLY ON UNTREATED
SURFACES.
LOOKING FURTHER AHEAD, ANOTHER DISTURBANCE IS EXPECTED BY MIDWEEK, BRINGING
ADDITIONAL PRECIPITATION. HOWEVER, UNCERTAINTY REMAINS REGARDING HOW MUCH
COOLING WILL ACCOMPANY THIS SYSTEM, MEANING SNOW LEVELS COULD STAY
RELATIVELY HIGH FOR THIS TIME OF YEAR.
AVIATION
PRECIPITATION WILL CONTINUE TO DECREASE THROUGH THE
MORNING HOURS, BECOMING MORE SHOWERY AND FOCUSED OVER THE HIGHER
TERRAIN. WHILE VALLEY LOCATIONS WILL LARGELY SEE PRECIPITATION
END, SOME LINGERING FOG/LOW STRATUS MAY CAUSE LOCALLY LOWERED
CEILINGS AND VISIBILITY. ANTICIPATE THE HIGHER TERRAIN TO BE
OBSCURED AT TIMES. WEAK HIGH PRESSURE WILL BUILD OVER THE REGION
TONIGHT INTO FRIDAY. THIS WILL LEAD TO A DRIER PERIOD, BUT ALSO
MAY ALLOW FOR FOG AND LOW STRATUS TO IMPACT AREA AIRFIELDS ACROSS
WESTERN MONTANA AND NORTH CENTRAL IDAHO.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL 8 AM MST THIS MORNING 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.
ID...WINTER WEATHER ADVISORY UNTIL 8 AM MST /7 AM PST/ THIS MORNING
FOR EASTERN LEMHI COUNTY...LOWER HELLS CANYON/SALMON RIVER
REGION...NORTHERN CLEARWATER MOUNTAINS...
OROFINO/GRANGEVILLE REGION...SOUTHERN CLEARWATER
MOUNTAINS...WESTERN LEMHI COUNTY.
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