448
FXUS65 KMSO 011050 CCA
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
426 AM MDT TUE APR 1 2025
DISCUSSION
KEY MESSAGES:
- WINTER DRIVING CONDITIONS ARE EXPECTED ALONG THE DIVIDE AND IN
SOUTHWEST MT THIS MORNING.
- COOL AND SHOWERY WEDNESDAY/THURSDAY. WET SNOW POSSIBLE AT
MOUNTAIN PASSES, GLACIER REGION AND FLATHEAD VALLEY THURSDAY.
- WARMER AND DRIER CONDITIONS RETURN FRIDAY AND INTO THE WEEKEND.
THE WATER VAPOR IMAGERY DEPICTS A VERY LARGE UPPER LEVEL LOW
ENCOMPASSING THE NORTHWESTERN U.S. EMBEDDED WITHIN THIS FEATURE ARE
SEVERAL COUNTER-CLOCKWISE-MOVING SHORTWAVES. A LONG, CONTINUOUS
STRETCH OF COLDER CLOUD TOPS EXTEND GENERALLY FROM HELENA NORTH AND
WEST INTO LINCOLN COUNTY, MONTANA. THIS ELONGATED FEATURE IS A
RELATIVELY NARROW DEFORMATION ZONE OR WRAP-AROUND PRECIPITATION
SHIELD. MODERATE TO HEAVY SNOW RATES WERE OBSERVED IN THE BUTTE AREA
LAST EVENING, BUT HAVE SINCE LIGHTENED UP BY EARLY THIS MORNING AS
THIS DEFORMATION ZONE HAS SHIFTED NORTHWARDS. WEBCAMS IN NORTHERN
POWELL COUNTY INCLUDING THE AVON AND HELMVILLE AREAS, CONTINUE TO
REPORT SNOW...ALSO SNOWING IN SEELEY LAKE. THE PRECIPITATION BECAME
HEAVY ENOUGH TO SWITCH OVER TO HEAVY WET SNOW IN THE FLATHEAD VALLEY
RIGHT AROUND MIDNIGHT. THE WEBCAMS SHOW SLUSH ON THE ROADWAYS. THIS
DEFORMATION ZONE WILL CONTINUE TO IMPACT PORTIONS OF THE DIVIDE AND
WESTERN MONTANA THROUGH THE MORNING HOURS. WITH THE HEATING OF THE
DAY, THE WIDESPREAD PRECIPITATION WILL BREAK UP INTO SCATTERED
SHOWERS. SHOWERS WILL CONTINUE ON WEDNESDAY, SO EXPECT PERIODIC WET
SNOW ACCUMULATION ON MOUNTAIN PASSES.
THE BACKDOOR COLD FRONT MOVING SOUTH OUT OF CANADA IS STILL ON
TAP TO OCCUR WEDNESDAY NIGHT INTO THURSDAY. BY DAYBREAK THURSDAY,
THERE'S A 95 PERCENT CHANCE THAT SNOW WILL BE FALLING IN THE
GLACIER REGION. AS THE COLDER AIR PUSHES SOUTHWESTWARDS, SNOW IS
POSSIBLE IN THE FLATHEAD VALLEY AND US-2 CORRIDOR WEST OF
KALISPELL TO HAPPY'S INN. THERE'S A 70 PERCENT CHANCE FOR AN INCH
OF SNOW ACCUMULATION IN MARION/KILA/OLNEY, AND A 50 PERCENT CHANCE
IN THE FLATHEAD VALLEY. SNOWFALL RANGES BETWEEN 3 AND 7 INCHES
ARE POSSIBLE IN THE GLACIER REGION, INCLUDING MARIAS PASS.
THERE IS HIGH CONFIDENCE IN A RIDGE OF HIGH PRESSURE BUILDING THIS
WEEKEND INTO EARLY NEXT WEEK, BRINGING WARMER AND DRIER CONDITIONS
TO THE REGION. IN FACT, THERE IS A 20-30 PERCENT CHANCE FOR HIGHS
REACHING NEAR 80 DEGREES IN THE BITTERROOT VALLEY, A 40 PERCENT
CHANCE FOR KAMIAH/KOOSKIA, IDAHO, AND A 60 PERCENT CHANCE FOR THE
SALMON/SNAKE RIVER VALLEYS SOUTH OF GRANGEVILLE TO REACH 80 DEGREES.
AVIATION
WRAP-AROUND RAIN AND SNOW WILL CONTINUE THROUGH 01/1800Z
ACROSS THE DIVIDE AND NORTHWEST MONTANA BEFORE TRANSITIONING TO
SHOWERS THIS AFTERNOON. GIVEN THE RECENT PRECIPITATION, VALLEY FOG
FORMATION IS POSSIBLE TONIGHT. SHOWERS PERSISTS INTO WEDNESDAY WITH
PERIODIC MOUNTAIN OBSCURATIONS EXPECTED.
MSO WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY UNTIL NOON MDT TODAY FOR
BITTERROOT/SAPPHIRE MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR
BUTTE/BLACKFOOT REGION...POTOMAC/SEELEY LAKE REGION.
ID...NONE.
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