494  
FXUS65 KMSO 172144  
AFDMSO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MISSOULA MT  
244 PM MST MON FEB 17 2020  
   
DISCUSSION
 
 
NORTHWEST FLOW AND COLD AIR ALOFT WILL CONTINUE TO PRODUCE BANDED  
SNOW FEATURES AT TIMES ACROSS WEST CENTRAL MONTANA THROUGH AT LEAST  
TUESDAY AFTERNOON. HIGH-RESOLUTION MODELS SUGGEST A PERIOD OF  
STRENGTHENED SNOW BANDS BOTH THIS EVENING THROUGH TONIGHT, AND AGAIN  
TUESDAY MIDDAY THROUGH TUESDAY LATE AFTERNOON. THERE IS REASONABLE  
CONFIDENCE IN THE SNOW BANDS DEVELOPING, HOWEVER THERE IS MUCH LESS  
CONFIDENCE IN THE FORECAST SNOW ACCUMULATION. BE AWARE THAT THIS  
TYPE OF SCENARIO IS CAPABLE TO PRODUCE FAST SNOW ACCUMULATIONS AND  
CAN HAVE A PROFOUND IMPACT ON CHANGING ROAD CONDITIONS FROM  
COMPLETELY DRY TO NEARLY IMPASSIBLE IN UNDER 15 MINUTES.  
TEMPERATURES WILL COOL INCREDIBLY OVERNIGHT TONIGHT FOR AREAS THAT  
CLEAR OUT, SUCH AS SOUTHERN IDAHO COUNTY (E.G., DIXIE) AND SOUTHERN  
LEMHI COUNTY (E.G., LEADORE). FOR THE REST OF THE NORTHERN ROCKIES  
TONIGHT, CLOUD COVER AND THE UNSTABLE AIR ALOFT WILL PREVENT  
TEMPERATURES FROM COOLING RAPIDLY OVER THE RECENT SNOW COVER.  
 
A RIDGE OF HIGH PRESSURE WILL BUILD OVER THE NORTHERN ROCKIES FOR  
THE LATTER PART OF THE WORK WEEK. THIS RIDGE SHOULD ALLOW FOR  
CLEAR SKIES AT NIGHT WHICH IN TURN WILL ALLOW SNOW COVERED VALLEYS  
TO COOL OFF DRAMATICALLY. HIGH ELEVATION VALLEYS HAVE A HIGH  
POTENTIAL OF EXPERIENCING TEMPERATURES TO DROP BELOW ZERO BY  
WEDNESDAY AND THURSDAY MORNING. THE DEVELOPMENT OF PATCHY FOG OR  
LOW STRATUS EACH MORNING. THE FOG COULD HINDER ON HOW COLD AN AREA  
COULD POTENTIALLY GET. THE VALLEY INVERSIONS COULD LINGER  
THROUGHOUT THE DAY KEEPING TEMPERATURES FROM WARMING DRAMATICALLY  
EACH DAY.  
 
THE MODELS ARE TRENDING TOWARDS THE NORTHERN ROCKIES MOVING BACK  
TO AN ACTIVE WEATHER PATTERN BY SUNDAY INTO NEXT WEEK.  
 

 
   
AVIATION
 
NORTHERN ROCKIES AIR SPACE WILL EXPERIENCE HIGHLY  
VARIABLE CLOUD AND VISIBILITY CONDITIONS THROUGH TUESDAY. BANDED  
SNOW FEATURES WILL EXIST AT TIMES, LOWERING CEILINGS AND  
VISIBILITY RAPIDLY. THE MAJORITY OF SNOW FEATURES WILL BE SITUATED  
NEAR KMSO, KBTM, AND ALONG THE CONTINENTAL DIVIDE NORTH OF KBTM.  
KGPI MAY ALSO EXPERIENCE BRIEF VISIBILITY AND CEILING REDUCTIONS  
THROUGH 18/0000Z DUE TO SNOW, HOWEVER ACTIVITY IS ANTICIPATED TO  
LESSEN NEARBY THEREAFTER. ALSO, ANY SNOW FEATURES OCCURRING  
THROUGH 18/0200Z WILL PRODUCE WIND GUSTS TO 25 KNOTS AT TIMES.  
MOST HIGH TERRAIN WILL BE OBSCURED, HOWEVER NOT CONTINUOUSLY,  
THROUGH TUESDAY.  
 

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

 
 

 
 
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