554  
FXUS65 KMSO 182004  
AFDMSO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MISSOULA MT  
204 PM MDT THU OCT 18 2018  
   
DISCUSSION
 
HIGH PRESSURE CONTINUES THROUGH THE WEEKEND FOR  
CENTRAL IDAHO AND WESTERN MONTANA. VALLEY FOG IN THE MORNINGS AND  
HAZE UNDER A VERY STABLE AIR MASS WILL CONTINUE THROUGH EARLY NEXT  
WEEK.  
 
MODELS AGREE ON A BREAK DOWN IN THE RIDGE AND A RETURN TO ACTIVE  
WEATHER SOMETIME NEXT WEEK. HOWEVER, THE OVERALL AGREEMENT IS POOR  
AND THE TIMING REMAINS VARIABLE FROM MODEL RUN TO MODEL RUN.  
CHANGES TO THE CURRENT PREVIOUS FORECAST INCLUDE LOWERING THE  
CHANCES OF RAIN EARLY NEXT WEEK AND PUSHING THEM BACK TO THE  
MIDDLE OR END OF NEXT WEEK. THIS IS CONSISTENT WITH MODELS HAVING  
DIFFICULTY HANDLING THE UNUSUALLY WARM WATERS IN THE GULF OF  
ALASKA, WHICH WILL HELP THE RIDGE PERSIST LONGER THAN MODELS  
INITIALLY FORECAST. ALSO, ONCE THE BREAK DOWN OF THE RIDGE STARTS  
IT LOOKS TEMPORARY AND WITH RATHER HIGH SNOW LEVELS, SO MOUNTAIN  
SNOW WILL ONLY BE AN ISSUE AROUND 7,000 FEET AND ABOVE.  
 

 
   
AVIATION
 
A RIDGE CONTINUES TO DOMINATE THE WEATHER ACROSS THE  
NORTHERN ROCKIES. STABLE CONDITIONS ARE CAUSING HAZE AND ALLOWING  
SOME PATCHY FOG IN THE MORNINGS. FOG WILL MAINLY AFFECT THE NARROW  
VALLEYS AND REMAIN ALONG THE RIVERS IN THE LARGER VALLEYS OF  
WESTERN MONTANA. AT THIS TIME IT IS NOT EXPECTED TO AFFECT ANY  
TERMINALS, HOWEVER, DEW POINTS HAVE BEEN CREEPING UP THE LAST  
SEVERAL DAYS SO THE FOGGY AREAS ARE INCREASING. TERMINAL KGPI AND  
KMSO ARE THE MOST LIKELY TO HAVE VICINITY FOG FROM 10 TO 16Z IN  
THE MORNING. HOWEVER, THE CHANCES ARE LOW ENOUGH THAT FOG WAS NOT  
PUT INTO THE TAFS.  
 

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

 
 

 
 
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