820  
FXUS65 KBOI 121009  
AFDBOI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOISE ID  
309 AM MST TUE DEC 12 2017  
   
SHORT TERM...TODAY THROUGH WEDNESDAY
 
INVERSION CONTINUES AS THE  
UPPER RIDGE SHIFTS SLIGHTLY WESTWARD THROUGH WEDNESDAY. A WEAK  
FEATURE MOVING OVER THE RIDGE WILL INCREASE MID-HIGH LEVEL  
MOISTURE TONIGHT INTO WEDNESDAY, BRINGING CLOUDS TO AREAS THAT  
HAVE REMAINED CLEAR OF THE RECENT STRATUS. EXPECT LITTLE CHANGE  
IN THE DAY-TO-DAY EVOLUTION OF LOW STRATUS AND FOG THROUGH  
WEDNESDAY, WITH DAYTIME CLEARING ACROSS THE CENTRAL SNAKE PLAIN  
AND AREAS OF BAKER AND HARNEY COUNTY. AND AREAS THAT CLEAR WILL  
SEE LOCALLY DENSE FOG REDEVELOP THIS EVENING. HAVE ADDED FLURRIES  
TO THE FORECAST FOR AREAS UNDER THE STRATUS, OTHERWISE AREA  
REMAINS DRY. FOR TEMPERATURES, KEPT CLOSE TO PERSISTENCE TODAY  
WITH VALLEY SITES SEEING BELOW NORMAL HIGH TEMPERATURES TO ABOVE  
NORMAL IN THE MOUNTAINS. IT'S SLIGHTLY COOLER IN THE MOUNTAINS  
WEDNESDAY AS THE UPPER RIDGE AXIS SLIPS EASTWARD, BUT DON'T EXPECT  
MUCH CHANGE IN THE VALLEYS.  
   
LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
 
PERSISTENT  
STRATUS/FOG IS EXPECTED TO CONTINUE THURSDAY AS THE UPPER RIDGE  
AXIS REMAINS OVER THE PACIFIC NORTHWEST. TEMPERATURES ACROSS THE  
LOWER VALLEYS EXPECTED TO REMAIN BELOW NORMAL ONCE AGAIN.  
 
CHANGES FINALLY EXPECTED LATE FRIDAY AFTERNOON AND EVENING AS THE  
UPPER RIDGE ERODES AS A WEAK FRONT PUSHES THROUGH THE REGION. THE  
INVERSION SHOULD FINALLY BREAK BUT IT WILL TAKE A MAJORITY OF THE  
DAY AS WINDS EXPECTED TO REMAIN LIGHT AND DONT INCREASE UNTIL THE  
EVENING. AS A RESULT, A WINTRY MIX IS POSSIBLE ACROSS THE LOWER  
ELEVATIONS AND SNOW IN THE MOUNTAINS. THE LOWEST ELEVATIONS  
(GENERALLY ALONG THE SNAKE RIVER AND LOWER TREASURE VALLEY), COULD  
SEE POCKETS OF FREEZING DRIZZLE FRIDAY AFTERNOON PRIOR TO THE  
INVERSION SCOURING/MIXING OUT. FOR THE REMAINDER OF THE WEEKEND,  
EXTENDED MODELS DIFFER SLIGHTLY ON THE TIMING OF THE WARM AIR  
ADVECTION AND THUS PRECIPITATION MOVING INTO THE PACIFIC  
NORTHWEST. POTENTIAL BRIEF BREAK SATURDAY BEFORE THE WARM FRONT  
MOVES THROUGH THE PACIFIC NORTHWEST AND IDAHO PANHANDLE SUNDAY AND  
MONDAY. AT THIS TIME, THE BEST CHANCE FOR PRECIPITATION SHOULD BE  
ACROSS THE NORTHERN PORTIONS OF THE FORECAST AREA. TEMPERATURES  
FINALLY REBOUND AFTER FRIDAY TO JUST ABOVE NORMAL.  
 

 
   
AVIATION
 
STRATUS/FOG IN THE LOWER VALLEYS CAUSING MVFR/IFR  
CONDITIONS. REPEAT OF STRATUS/FOG FOR WEDNESDAY MORNING. SURFACE  
WINDS LIGHT AND VARIABLE. WINDS ALOFT AT 10 KFT MSL VARIABLE 5-15  
KTS.  
 

 
   
AIR STAGNATION
 
INVERSION IS IN PLAY THROUGH THE END OF THE  
WEEK. SEE LITTLE CHANGE IN MIXING HEIGHTS OR WINDS IN THE MIXED  
LAYER THROUGH FRIDAY. A WEAK SYSTEM MOVING THROUGH THE AREA LATE  
FRIDAY WILL BE THE BEST CHANCE TO BREAK THE INVERSION, THOUGH NOT  
CONFIDENT THAT IT WILL SCOUR OUT IN THE LOWEST VALLEYS (SITES  
BELOW 3K FEET MSL).  
 

 
   
BOI WATCHES/WARNINGS/ADVISORIES
 
 
ID...DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING IDZ016.  
OR...NONE.  
 

 
 

 
 
WWW.WEATHER.GOV/BOISE  
WWW.FACEBOOK.COM/NWSBOISE  
WWW.TWITTER.COM/NWSBOISE  
 
SHORT TERM...DG  
LONG TERM....CR  
AVIATION.....CR  
AIR STAGNATION...DG  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab ID Page
The Nexlab OR Page Main Text Page