162  
FXUS65 KBOI 220338  
AFDBOI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOISE ID  
838 PM MST WED FEB 21 2024  
   
DISCUSSION
 
MARGINAL INSTABILITY AND SUPPORT FROM AN  
APPROACHING UPPER TROUGH IS MAINTAINING THE SCATTERED SHOWERS  
THIS EVENING. MOST OF THE ACTIVITY IS EXPECTED TO REMAIN  
GENERALLY NORTH OF A BURNS-BOISE-FAIRFIELD LINE OVERNIGHT. SNOW  
LEVELS NEAR 4000-5000 FEET WILL KEEP ANY LIGHT SNOW  
ACCUMULATIONS OUT OF THE LOWER VALLEYS WITH ISOLATED AMOUNTS OF  
LESS THAN AN INCH IN THE NORTHERN TIER (E.G. MCCALL). AREAS OF  
CLEAR SKIES ALONG WITH RECENT PRECIP AND LIGHT WINDS WILL  
PROMOTE PATCHY LATE NIGHT THROUGH EARLY MORNING FOG IN THE  
VALLEYS. A WEAK UPPER RIDGE ON THURSDAY WILL BRING MOSTLY DRY  
CONDITIONS, ALTHOUGH RESIDUAL MOISTURE/INSTABILITY IN THE NORTH  
RESULTS IN A 15-30 PERCENT CHANCE OF SHOWERS ACROSS THE HIGHER  
ELEVATIONS OF BAKER COUNTY INTO THE ID WEST CENTRAL MOUNTAINS.  
FORECAST WAS UPDATED TO REFLECT LATEST SHOWER TRENDS AND TO  
REMOVE MENTION OF EVENING THUNDERSTORMS.  
 

 
   
AVIATION
 
ISOLATED RAIN/SNOW SHOWERS WILL DIMINISH BY  
THU/08Z. SHOWERS WILL BRING BRIEF MVFR/IFR AND OBSCURATION IN  
THE MOUNTAINS. SNOW LEVELS 4000-5000 FT MSL. PATCHY DENSE FOG AT  
KMYL, KBKE, AND KBNO THURSDAY MORNING. FOG AND STRATUS POSSIBLE  
AT KJER AND KEUL/KONO. SURFACE WINDS: VARIABLE 5-15 KT. WINDS  
ALOFT AT 10KFT MSL: W TO SW 10-20 KT.  
 

 
   
PREV DISCUSSION
 
 
SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT...WEAKENING UPPER  
TROUGH ALONG THE COAST WILL MOVE INLAND WITH SCATTERED LIGHT  
RAIN AND SNOW SHOWERS CONTINUING TONIGHT, ALTHOUGH HI-RES MODELS  
KEEP THEM OUT OF THE SNAKE BASIN. ISOLATED THUNDERSTORMS IN  
OREGON NORTH OF BURNS UNTIL SUNSET. PATCHY FOG WILL DEVELOP IN  
THE VALLEYS LATE TONIGHT AND THURSDAY MORNING. SHOWERS WILL END  
FROM SOUTH TO NORTH OVERNIGHT AND THURSDAY AS A RIDGE OF HIGH  
PRESSURE ALOFT BUILDS IN FROM THE SOUTH. THE RIDGE WILL BRING  
GRADUAL WARMING (ABOUT 1-2 DEGREES PER DAY) AND DRYING THROUGH  
FRIDAY NIGHT. LIGHT DIURNAL WINDS.  
 
LONG TERM...SATURDAY THROUGH WEDNESDAY...DRY AND MILD WEATHER  
CONDITIONS ARE ANTICIPATED TO PERSIST THROUGHOUT THE WEEKEND AS A  
RESULT OF THE WEST-NORTHWEST FLOW ALOFT. A SURFACE HIGH ALONG THE  
WESTERN SLOPE OF THE ROCKIES WILL INDUCE EASTERLY SURFACE WINDS,  
CAUSING TEMPERATURES TO RISE 5-10 DEGREES ABOVE NORMAL ON SATURDAY  
AND SUNDAY.  
 
THE SUBSEQUENT UPPER-LEVEL TROUGH WITH A COLD FRONT WILL TRAVERSE  
THE REGION ON MONDAY. PRIOR TO THE SYSTEM'S ARRIVAL, CLOUD COVER  
WILL INCREASE ON SUNDAY NIGHT ALONG WITH UPSLOPE PRECIPITATION IN  
MOUNTAINOUS AREAS. GENERALLY, GUIDANCE IS IN CLOSE AGREEMENT WITH  
THE LATER FRONTAL PASSAGE ON MONDAY AFTERNOON. THIS SHOULD ALLOW FOR  
MONDAY TO EXPERIENCE WARMER TEMPERATURES THAN PREVIOUSLY PREDICTED.  
NEVERTHELESS, TEMPERATURES WILL DECREASE BY 10-20 DEGREES FROM  
SUNDAY TO TUESDAY. PRECIPITATION WILL BE CONCENTRATED IN HIGHER  
TERRAIN AND AHEAD OF THE FRONTAL PASSAGE FROM SUNDAY NIGHT INTO  
MONDAY, WITH CONVECTIVE SHOWERS FOLLOWING ON TUESDAY.  
 
SNOW LEVELS WILL DESCEND TO VALLEY FLOORS LATE MONDAY NIGHT,  
INCREASING THE LIKELIHOOD OF SNOW ACCUMULATION HEADING INTO  
TUESDAY. THE PROBABILITY OF MEASURABLE SNOW WILL RANGE BETWEEN  
50-70% ACROSS THE LOWER ELEVATIONS OF EASTERN OREGON AND MUCH  
OF THE SNAKE PLAIN ON MONDAY NIGHT. HOWEVER, THE LIKELIHOOD OF  
SEEING MORE THAN AN INCH OF SNOW DIMINISHES TO BETWEEN 3-8% IN  
THE WESTERN SNAKE PLAIN. THE MOUNTAINS HAVE THE POTENTIAL FOR  
MODERATE SNOWFALL ON MONDAY, WITH SNOW SHOWERS IN THE COLD  
TROUGH CONTRIBUTING TO LIGHTER ACCUMULATIONS ON TUESDAY.  
GUIDANCE INDICATES A 30% OR GREATER CHANCE OF 4 INCHES OR MORE  
OF SNOW ABOVE 5000 FEET.  
 
THE COLD AIR BEHIND THE FRONT WILL BE TRANSIENT AS THE UPPER-LEVEL  
SYSTEM MOVES EASTWARD AND THE UPPER-LEVEL FLOW SHIFTS BACK TO THE  
SOUTHWEST BEGINNING ON WEDNESDAY. MOUNTAINS WILL RETAIN A CHANCE OF  
SNOW ON WEDNESDAY, WHILE VALLEYS WILL TRANSITION BACK TO RAIN AS  
SNOW LEVELS RISE TO APPROXIMATELY 4000 FEET MSL.  
 

 
   
BOI WATCHES/WARNINGS/ADVISORIES
 
 
ID...NONE.  
OR...NONE.  
 

 
 

 
 
WWW.WEATHER.GOV/BOISE  
WWW.FACEBOOK.COM/NWSBOISE  
WWW.TWITTER.COM/NWSBOISE  
 
DISCUSSION...BW  
AVIATION.....SH  
SHORT TERM...LC  
LONG TERM....JDS  
 
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