737  
FXUS65 KMSO 281943  
AFDMSO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MISSOULA MT  
1243 PM MST MON NOV 28 2022  
   
DISCUSSION
 
LIGHT SNOW IS EXPECTED TONIGHT ALONG THE I-90  
CORRIDOR, PARTICULARLY FROM LOOKOUT PASS EASTWARD THROUGH ROUGHLY  
DRUMMOND, AND POINTS SOUTH OF THIS CORRIDOR. THIS INCLUDES MOST OF  
NORTH CENTRAL IDAHO AND THE MISSOULA AND BITTERROOT VALLEYS, LOLO  
PASS, AND LOST TRAIL PASS. SNOW WILL PERSIST THROUGH THIS EVENING  
AND INTO THE OVERNIGHT HOURS BEFORE TAPERING OFF NEAR OR ABOUT  
SUNRISE TUESDAY. WHILE SNOW ACCUMULATIONS WILL GENERALLY BE ON THE  
LIGHTER SIDE (ABOVE 4500 FEET: 2-6 INCHES, BELOW 4500 FEET: 1 TO  
3 INCHES), TRAVEL ON TUESDAY MORNING COULD BE DIFFICULT AS A  
RESULT IN THE AFOREMENTIONED LOCATIONS.  
 
TUESDAY INTO WEDNESDAY WILL BE MOSTLY BENIGN WEATHER DAYS, SAVE  
FOR MOUNTAINOUS TERRAIN ALONG THE MONTANA/IDAHO BORDER. THESE  
AREAS WILL BEGIN TO SEE THE NEXT ROUND OF SNOWFALL STARTING  
WEDNESDAY AFTERNOON (ABOVE 5000 FEET), PERSISTING THEREAFTER  
THROUGH FRIDAY MORNING. THIS STORM WILL MAKE ITS WAY FURTHER OVER  
THE NORTHERN ROCKIES, SPREADING ADDITIONAL SNOWFALL TO BOTH  
MOUNTAINS AND VALLEYS ALIKE ON THURSDAY, WITH FURTHER ENHANCEMENT  
OCCURRING THURSDAY NIGHT THROUGH FRIDAY MORNING AS IT SHIFTS  
TOWARDS THE DIVIDE.  
 
WHAT WE ARE CONFIDENT OF RIGHT NOW IS THAT SNOW WILL BECOME  
WIDESPREAD THURSDAY INTO FRIDAY FOR ALL ELEVATIONS ACROSS WESTERN  
MONTANA AND NORTH CENTRAL IDAHO. WE ALSO FEEL CONFIDENT THAT HEAVY  
SNOWFALL WILL IMPACT TERRAIN ABOVE 4500 FEET, WITH THE HIGHEST  
ACCUMULATIONS LIKELY ALONG THE MONTANA/IDAHO BORDER, AND ACROSS  
NORTHWEST MONTANA, INCLUDING GNP, MARIAS PASS, AND SOUTH TOWARDS  
MACDONALD PASS. STORM TOTAL SNOWFALL OF UP TO A FOOT OR MORE IS  
EXPECTED FROM THIS SYSTEM LATE WEDNESDAY THROUGH EARLY FRIDAY,  
EQUALING BETWEEN 0.75 AND 1.25 INCHES OF WATER EQUIVALENT. AS  
SUCH, DIFFICULT TRAVEL WILL BE LIKELY OVER MOUNTAIN PASSES AND IN  
THE BACKCOUNTRY DURING THIS TIME.  
 
WHAT WE ARE LESS CONFIDENT ABOUT IS VALLEY SNOWFALL AMOUNTS. A  
STRONG JET ALOFT WITH SOUTHWESTERLY FLOW OFTEN DECREASES THE  
AMOUNT OF SNOW THAT MAKES IT DOWN TO VALLEY FLOORS, PARTICULARLY  
IN VALLEYS SUCH AS THE BITTERROOT AND MISSOULA VALLEYS. WE SUSPECT  
THIS WILL BE THE CASE EARLY ON IN THE STORM, BUT BY LATE  
THURSDAY, CONDITIONS WILL BECOME MORE FAVORABLE FOR WIDESPREAD  
VALLEY SNOWFALL TO OVERSPREAD NORTH CENTRAL IDAHO AND WESTERN  
MONTANA VALLEYS (IF IT HASN’T STARTED BEFORE THEN ALREADY).  
 
A RIDGE OF HIGH PRESSURE WILL ATTEMPT TO BUILD IN BEHIND THE  
EXITING WINTER STORM ON SATURDAY, WHICH WOULD POINT TO DRY AND  
COLD CONDITIONS ALONG WITH SOME LINGERING LIGHT SNOW SHOWERS FOR  
NORTHWEST MONTANA MOUNTAINS.  
 

 
   
AVIATION
 
SNOW SHOWERS THIS EVENING WILL INCREASE FROM NORTHWEST  
TO SOUTHEAST ACROSS THE REGION WITH A SHORTWAVE MOVING THROUGH. AN  
INCH OR TWO IS ALL THAT IS EXPECTED AT AREA TERMINALS WITH SOME  
MVFR AND IFR CONDITIONS IN THE LATE OVERNIGHT AND EARLY MORNING  
PERIODS. OVERALL CONDITIONS WILL START IMPROVE BETWEEN 29/12Z AND  
29/18Z.  
 

 
   
MSO WATCHES/WARNINGS/ADVISORIES
 
 
MT... WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 5 AM MST  
TUESDAY FOR LOWER CLARK FORK REGION.  
 
WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 5 AM MST  
TUESDAY FOR BITTERROOT/SAPPHIRE MOUNTAINS...  
MISSOULA/BITTERROOT VALLEYS.  
 
ID...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 4 AM PST  
TUESDAY FOR NORTHERN CLEARWATER MOUNTAINS...  
OROFINO/GRANGEVILLE REGION...SOUTHERN CLEARWATER MOUNTAINS.  
 

 
 

 
 
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