829  
FXUS65 KMSO 222149  
AFDMSO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MISSOULA MT  
249 PM MST WED JAN 22 2020  
   
DISCUSSION
 
THE NEXT WEATHER SYSTEM IS APPROACHING FROM THE  
WEST THIS AFTERNOON AND WILL SPREAD WIDESPREAD LIGHT  
PRECIPITATION INTO NORTH CENTRAL IDAHO AND WEST-CENTRAL/NORTHWEST  
MONTANA THIS EVENING INTO FRIDAY MORNING. SNOW LEVELS WILL BE  
GRADUALLY RISING WITH TIME. STEADY SNOWFALL WILL DEVELOP ON  
PASSES, CAUSING SLICK SNOWCOVERED ROADS THROUGH THE WEDNESDAY  
MORNING COMMUTE. IN PARTICULAR, LOOKOUT PASS AND LOLO PASS ARE  
EXPECTED TO SEE THE MOST CONSISTENT SNOWFALL. VALLEYS IN CENTRAL  
IDAHO ARE ANTICIPATED TO LARGELY SEE RAIN OR A RAIN/SNOW MIX. VALLEYS  
OF WESTERN MONTANA WILL INITIALLY SEE SNOW, TRANSITIONING TO RAIN  
AND PATCHES OF FREEZING RAIN TOWARDS THURSDAY MORNING. SNOW  
ACCUMULATIONS IN VALLEYS WILL BE MINIMAL, AND PERHAPS THE BIGGER  
IMPACT WILL BE POTENTIAL FOR ICE TO FORM ON SIDEWALKS, DRIVEWAYS  
AND PARKING LOTS AS OVERNIGHT TEMPERATURES HOVER NEAR FREEZING.  
 
FRIDAY THROUGH NEXT WEDNESDAY, A SERIES OF WEAK STORM SYSTEMS ARE  
ANTICIPATED TO MOVE ACROSS THE NORTHERN ROCKIES. SIMILAR TO  
RECENT WEATHER OBSERVED IN THE REGION, LIGHT SNOWFALL AT HIGH  
ELEVATIONS AND A WINTRY MIX OF RAIN, SNOW, AND FREEZING RAIN AT  
LOW ELEVATIONS ARE ANTICIPATED DURING THE EVENING THROUGH MORNING  
PERIODS. THE LOCATIONS FAVORED FOR FREEZING RAIN WILL SHIFT AROUND  
AS EACH STORM SYSTEM EVOLVES, HOWEVER VALLEYS OF NORTHWEST AND  
WEST CENTRAL MONTANA, AS WELL AS PORTIONS OF LEMHI COUNTY  
(INCLUSIVE OF SALMON, NORTH FORK, SHOUP), ARE THE MOST LIKELY  
AREAS TO BE IMPACTED BY FREEZING RAIN. MUCH OF THE FREEZING RAIN  
IMPACT WILL BE TO SIDEWALKS, DRIVEWAYS, AND PARKING LOTS. BLACK  
ICE ON ROADWAYS MAY ALSO BECOME AN ISSUE, PARTICULARLY FOR LESS-  
TRAVELED CORRIDORS. TEMPERATURES WILL BE GENERALLY WARMER THAN THE  
SEASONAL AVERAGE THROUGHOUT THE REGION THROUGH THE MIDDLE OF NEXT  
WEEK.  
 
AFTER NEXT WEDNESDAY, A SLIGHT CHANGE IN THE UPPER LEVEL WEATHER  
PATTERN APPEARS PLAUSIBLE, WARMING THE NORTHERN ROCKIES EVEN FURTHER  
WITH SUBTROPICAL MOISTURE SURGES. THE PACIFIC JET STREAM IS ALSO  
DEPICTED AS STRENGTHENING IN THE 7-10 DAY FORECAST PERIOD, WHICH MAY  
POINT TOWARD MORE SIGNIFICANT PRECIPITATION EVENTS ACROSS THE  
WESTERN US AROUND THE BEGINNING OF FEBRUARY.  
 

 
   
AVIATION
 
UNSTABLE CONDITIONS THIS AFTERNOON HAVE LEAD TO THE  
DEVELOPMENT OF SNOW SHOWERS ACROSS THE TERRAIN OF WESTERN MONTANA  
AND CENTRAL IDAHO. THIS HAS ALSO LED TO SOME BREEZY WESTERLY  
WINDS, PRIMARILY KBTM WITH GUSTS UP TO 20KTS. AN APPROACHING  
WEATHER SYSTEM THIS EVENING WILL LOWER CEILINGS FROM WEST TO EAST  
ACROSS CENTRAL IDAHO AND WESTERN MONTANA, CAUSING THE TERRAIN TO  
BE OBSCURED. STEADY LIGHT PRECIPITATION WILL DEVELOP, MAINLY  
ACROSS CENTRAL IDAHO AND WEST-CENTRAL/NORTHWEST MONTANA. KMSO AND  
KGPI WILL LIKELY SEE LOWERED VISIBILITY AND CEILINGS AT TIMES  
TONIGHT, STARTING AROUND 23/0300Z. PRECIPITATION IN THE VALLEYS  
WILL FALL AS A MIX OF RAIN AND SNOW, WITH A PERIODS OF LIGHT  
FREEZING RAIN POSSIBLE BETWEEN 23/0900Z AND 23/1400Z. THE BEST  
POTENTIAL FOR FREEZING RAIN WILL BE ACROSS NORTHWEST MONTANA  
VALLEYS, INCLUDING AT KGPI.  
 

 
   
MSO WATCHES/WARNINGS/ADVISORIES
 
 
MT...NONE.  
ID...NONE.  

 
 

 
 
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