417   
FXUS65 KMSO 011026  
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 ARE CONTINUING TO 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 THIS 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  
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/SNOW WILL CONTINUE THROUGH 01/1800Z  
OVER THE DIVIDE AND NORTHWEST MONTANA, THEN TRANSITION TO SHOWERS  
THIS AFTERNOON. WITH THE RECENT PRECIPITATION, VALLEY FOG   
FORMATION IS POSSIBLE TONIGHT. SHOWER ACTIVITY CONTINUES INTO   
WEDNESDAY WITH PERIODIC MOUNTAIN OBSCURATION.   
  
  
   
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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