203  
FXUS65 KMSO 222152  
AFDMSO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MISSOULA MT  
252 PM MST TUE JAN 22 2019  
 
...DIFFICULT WINTER DRIVING CONDITIONS EXPECTED TONIGHT THROUGH  
WEDNESDAY...  
   
DISCUSSION
 
A WINTER STORM IS EXPECTED TO DEVELOP THIS EVENING  
AND CONTINUE THROUGH WEDNESDAY. WE FEEL THE HARDEST HIT AREA IN  
TERMS OF HIGH IMPACT WITH MODERATE TO HEAVY SNOW, WILL BE ALONG THE  
HIGHWAY 200 AND INTERSTATE 90 CORRIDORS, ESPECIALLY IN SANDERS  
AND MINERAL COUNTIES. WE HAVE THE HIGHEST CONFIDENCE THAT THE  
MOUNTAINS WILL GET AT LEAST A FOOT OR MORE OF SNOWFALL.  
 
WE HAVE WINTER WEATHER ADVISORIES HOISTED FOR MOST AREAS EXCEPT  
FOR THE RIGGINS AREA IN CENTRAL IDAHO AND LEMHI COUNTY. SNOW WILL  
FALL IN THE VALLEYS OF LEMHI COUNTY, BUT IT WILL BE LIGHT AMOUNTS.  
WILLIAMS CREEK SUMMIT COULD SEE HALF A FOOT OF SNOW SPREAD OUT IN  
A 24 HOUR PERIOD. FOLLOWING SHIFTS WILL REASSESS WHETHER LEMHI  
COUNTY MAY NEED AN ADVISORY OR NOT. THE ADVISORY FOR THE CAMAS  
PRAIRIE, IDAHO WAS A TRICKY ONE IN THAT WE ARE EXPECTING STRONG  
SOUTHERLY WINDS TO DEVELOP LATER TODAY AND CONTINUE THROUGH  
WEDNESDAY MORNING. USUALLY THIS MEANS THAT THESE DOWNSLOPE WINDS  
WILL CAUSE TEMPERATURES TO RISE ABOVE FREEZING, BUT WE THINK THE  
LIGHT TO MODERATE SNOW MAY DELAY THE WARMING UNTIL AFTER DAYBREAK.  
WITH THAT IN MIND, THE SNOW WILL INITIALLY BE MORE DRY AND WILL  
BLOW AROUND ESPECIALLY ALONG PORTIONS OF HIGHWAY 95. THIS WET  
WEATHER WILL ALSO AN ISSUE FOR ANY NEWBORN LIVESTOCK. FOR MORE  
INFORMATION ON SNOW AMOUNTS AND TIMING SEE THE ADVISORIES AND  
WARNING BY VISITING HTTP://WWW.WEATHER.GOV/MSO/  
 
THE NORTHERN ROCKIES WILL BE UNDER NORTHWESTERLY FLOW FOR THE LATTER  
PART OF THE WORK WEEK. A SUBTLE DISTURBANCE WILL BE MOVING THROUGH  
THE REGION THURSDAY NIGHT INTO FRIDAY MORNING. THIS TYPE OF  
FEATURE IN NORTHWESTERLY FLOW IS CONDUCIVE OF WIDESPREAD LIGHT  
SNOW SHOWERS WITH WESTERN MONTANA RECEIVING THE BULK OF THE  
PRECIPITATION. THE VALLEYS HAVE THE POTENTIAL OF PICKING UP AN  
INCH OR TWO OF NEW SNOW. MODERATE CONFIDENCE IN THIS EVENT AS ALL  
MODELS ARE PICKING UP ON THE FEATURE, BUT TIMING IS A LITTLE  
UNCERTAIN AT THIS TIME.  
 
THE REGION WILL REMAIN UNDER THIS NORTHWESTERLY FLOW THROUGH SUNDAY,  
BUT WARMER AIR WILL MOVE INTO THE REGION. THE WARMING ALOFT WILL  
ALLOW FOR THE DEVELOPMENT OF VALLEY INVERSIONS WITH THE  
POSSIBILITYOF PATCHY FREEZING FOG THROUGHOUT THE REGION.  
 
A MORE ROBUST SYSTEM IS EXPECTED TO MOVE INTO THE REGION ON SUNDAY  
NIGHT INTO MONDAY. THIS FEATURE HAS THE POTENTIAL BRINGING COLDER  
AIR INTO THE REGION WITH POTENTIAL OF SIGNIFICANT SNOW ACROSS  
WESTERN MONTANA.  
 

 
   
AVIATION
 
LOW CLOUDS AND SNOW WILL BLANKET THE NORTHERN ROCKIES  
AIR SPACE THROUGH AT LEAST 24/0000Z. ANTICIPATE WIDESPREAD TERRAIN  
OBSCURATIONS IN SNOW AND LOW CLOUDS. LIGHT SNOW WILL REDUCE  
VISIBILITY, CEILINGS AT KGPI AND KMSO AFTER 23/0600Z AND CONTINUE  
THROUGHOUT WEDNESDAY. MODERATE SNOW IS EXPECTED TO CREATE THE  
LOWEST VISIBILITY AND CEILINGS NEAR KGPI AND KMSO 23/1000Z THROUGH  
23/1600Z. CEILINGS AND VISIBILITY WILL ALSO BE REDUCED DUE TO SNOW  
AT KBTM AND KSMN, PEAKING 23/0800Z THROUGH 23/1600Z. NORTHEAST  
WIND GUSTING OVER 20 KNOTS IS ANTICIPATED AT KGPI 23/1800Z THROUGH  
24/0200Z AS WELL.  
 

 
   
MSO WATCHES/WARNINGS/ADVISORIES
 
 
MT...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 5 PM MST  
WEDNESDAY MISSOULA/BITTERROOT VALLEYS.  
 
WINTER STORM WARNING FROM 8 PM THIS EVENING TO 11 AM MST  
WEDNESDAY LOWER CLARK FORK REGION.  
 
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 5 PM MST  
WEDNESDAY FLATHEAD/MISSION VALLEYS.  
 
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 5 PM MST  
WEDNESDAY WEST GLACIER REGION.  
 
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 11 AM MST  
WEDNESDAY KOOTENAI/CABINET REGION.  
 
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 11 PM MST  
WEDNESDAY BITTERROOT/SAPPHIRE MOUNTAINS.  
 
WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 5 PM MST  
WEDNESDAY POTOMAC/SEELEY LAKE REGION.  
 
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 PM MST  
WEDNESDAY BUTTE/BLACKFOOT REGION.  
 
ID...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 4 PM PST  
WEDNESDAY NORTHERN CLEARWATER MOUNTAINS.  
 
WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 4 PM PST  
WEDNESDAY SOUTHERN CLEARWATER MOUNTAINS.  
 
WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO 4 AM PST  
WEDNESDAY OROFINO/GRANGEVILLE REGION.  
 

 
 

 
 
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