836
FXUS65 KMSO 180840
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
240 AM MDT WED MAR 18 2026
DISCUSSION
KEY MESSAGES:
- STREAM AND CREEK FLOODING CONCERNS THROUGH TODAY FOR NORTHWEST
MONTANA, ESPECIALLY LINCOLN AND SANDERS COUNTIES
- WELL ABOVE NORMAL TEMPERATURES AND GUSTY WINDS AT TIMES INTO
FRIDAY, ESPECIALLY I-90 SOUTHWARD
DEEP MOISTURE FROM AN ATMOSPHERIC RIVER WILL BE DIRECTED INTO
THE NORTHERN ROCKIES THROUGHOUT THE WEEK. THE HEAVIEST
PRECIPITATION IS EXPECTED THIS MORNING, WITH A SECONDARY SURGE
ARRIVING ON FRIDAY. HIGH-RESOLUTION GUIDANCE INDICATES MEAN
PRECIPITATION AMOUNTS RANGING FROM 1.50 TO 2.50 INCHES OVER THE
HIGHER TERRAIN OF THE CABINET, WHITEFISH, AND SWAN RANGES THROUGH
EARLY THURSDAY. CONVERSELY, VALLEY LOCATIONS WILL SEE
SIGNIFICANTLY LESS PRECIPITATION, GENERALLY AROUND 0.10 TO 0.30
INCHES. WITH SNOW LEVELS REMAINING UNUSUALLY HIGH AT 7,000 TO
8,000 FEET, ACCUMULATING SNOWFALL WILL BE RESTRICTED TO THE
HIGHEST PEAKS OF NORTHWEST MONTANA.
HYDROLOGICAL & TEMPERATURE IMPACTS: THE COMBINATION OF RAIN AND
WARM TEMPERATURES WILL ACCELERATE MELT FROM A PRIMED SNOWPACK IN
NORTHWEST MONTANA. THERE IS CONCERN FOR RAPIDLY RISING STREAMS AND
CREEKS, ESPECIALLY IN SANDERS AND LINCOLN COUNTIES AS RAIN RATES
PICK UP BY LATE THIS EVENING. ALSO WATCH FOR PONDING OF WATER AND
ROCK/SNOW SLIDES ALONG ROADWAYS. BOTH DAYTIME HIGHS AND NIGHTTIME
LOWS WILL WARM TO NEAR-RECORD LEVELS BY LATE WEEK, RUNNING 10 TO
20 DEGREES ABOVE SEASONAL NORMALS, ESPECIALLY FROM I-90 SOUTHWARD.
THE COMBINATION OF ANOMALOUS WARMTH AND RAIN-ON-SNOW POTENTIAL
WILL LIKELY DEGRADE THE SNOWPACK, LEADING TO WORSENING AVALANCHE
CONDITIONS. BACKCOUNTRY RECREATIONISTS ARE STRONGLY ENCOURAGED TO
MONITOR LOCAL AVALANCHE CENTERS FOR THE LATEST UPDATES THIS WEEK.
WINDS: BREEZY TO LOCALLY WINDY CONDITIONS WILL PERSIST, WITH GUSTS
OF 25 TO 35 MPH, ESPECIALLY DURING THE AFTERNOON/EVENING HOURS.
LOCALIZED HIGHER GUSTS ARE POSSIBLE IN AREAS PRONE TO THE MOUNTAIN
WAVE ACTIVITY FAVORED BY THIS PATTERN. THESE WINDS MAY CREATE
CHOPPY CONDITIONS ON AREA LAKES AND COULD OCCASIONALLY DISRUPT
OUTDOOR ACTIVITIES. FIRE WEATHER CONCERNS WILL ALSO BE HEIGHTENED
IN SOUTHWEST MONTANA DUE TO A COMBINATION OF LOW HUMIDITY AND
GUSTY WINDS THE LATTER HALF OF THIS WEEK.
CHANGES BY SATURDAY: A COLD FRONT IS FORECAST TO SWEEP THROUGH THE
REGION ON SATURDAY. THIS WILL BRING A RETURN TO COOLER, MORE
SEASONABLE TEMPERATURES, ALONG WITH A ROUND OF LIGHT PRECIPITATION
AND GUSTY WINDS. AT THIS TIME, IMPACTS FROM THIS WEEKEND FRONTAL
PASSAGE APPEAR MINIMAL.
AVIATION
AN ATMOSPHERIC RIVER WILL DIRECT MOISTURE ACROSS THE
REGION THE DAY, BRINGING PRECIPITATION PRIMARILY TO AREAS NORTH OF
I-90. THIS PRECIPITATION WILL BE LARGELY TERRAIN-FOCUSED, WITH
SNOW LEVELS REMAINING UNUSUALLY HIGH NEAR 7,000 FEET, RESULTING IN
FREQUENT MOUNTAIN OBSCURATIONS ACROSS NORTHWEST MONTANA.
SURFACE WINDS FROM THE WEST AND SOUTHWEST WILL BECOME GUSTY EACH
AFTERNOON AND EVENING THROUGHOUT THE WEEK, OCCASIONALLY EXCEEDING
25 KNOTS AT VALLEY TERMINALS. WHILE THESE SURFACE WINDS WILL
GENERALLY DECOUPLE AND DIMINISH OVERNIGHT, RIDGE TOP WINDS WILL
REMAIN ELEVATED AT 25 TO 35 KNOTS. THIS WILL INTRODUCE LOCALIZED
LOW-LEVEL WIND SHEAR CONCERNS DURING THE OVERNIGHT AND EARLY
MORNING HOURS.
FINALLY, LINGERING LOW-LEVEL MOISTURE PRESENTS A SLIGHT RISK FOR
PATCHY MORNING FOG. HOWEVER, ABUNDANT CLOUD COVER AND CONTINUED
BOUNDARY LAYER MIXING SHOULD SIGNIFICANTLY LIMIT ITS OVERALL
COVERAGE AND OPERATIONAL IMPACT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...FLOOD WATCH THROUGH THIS AFTERNOON FOR FLATHEAD/MISSION
VALLEYS...KOOTENAI/CABINET REGION...LOWER CLARK FORK REGION.
ID...NONE.
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