555  
FXUS65 KBOI 091541  
AFDBOI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOISE ID  
941 AM MDT FRI MAY 9 2025  
   
DISCUSSION
 
SEEING AN INCREASE IN HIGH LEVEL MOISTURE AND  
CLOUD COVER THIS MORNING (SOME EVIDENCE SEEN IN EARLY MORNING  
KBOI WX BALLOON TRACE) AS THE UPPER RIDGE AXIS SHIFTS EASTWARD.  
OTHERWISE WARMING TREND WILL CONTINUE TODAY WITH HIGHS RUNNING  
ABOUT 10 DEGREES WARMER THAN YESTERDAY. STILL LOOKING AT  
SATURDAY BEING THE HOTTEST DAY WITH AFTERNOON THUNDERSTORMS  
POSSIBLE OVER HIGHER TERRAIN OF SW IDAHO. CURRENT FORECAST FOR  
TODAY IS ON TRACK.  
 

 
   
AVIATION
 
VFR WITH HIGH CLOUDS FILLING IN THIS EVENING.  
ELEVATED SMOKE FROM AREA BURNS IN THE VICINITY OF KMYL-KONO.  
SURFACE WINDS: E- SE 5-15 KT IN THE SNAKE PLAIN, ELSEWHERE  
VARIABLE LESS THAN 10 KT. WINDS ALOFT AT 10KFT MSL: SW 15-25 KT.  
   
KBOI
 
VFR. VARIABLE LESS THAN 5 KT THIS MORNING, BECOMING E-SE  
5-8 KT.  
   
WEEKEND OUTLOOK
 
SATURDAY WILL BE WARM AND DRY WITH INCREASING  
CLOUDS AND A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS NEAR THE  
BOISE MOUNTAINS AND ID/NV BORDER LATE AFTERNOON INTO EVENING.  
ON SUNDAY AFTERNOON, A COLD FRONT WILL MOVE FROM SE OR INTO SW  
ID, BRINGING A CHANCE OF SHOWERS AND THUNDERSTORMS (40-50%  
CHANCE) WITH GUSTY WESTERLY WINDS, LOWERING CEILINGS, AND  
MOUNTAIN OBSCURATION.  
 

 
   
PREV DISCUSSION
 
 
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...TODAY AND SATURDAY  
ARE EXPECTED TO BE THE WARMEST DAYS OF THE SEASON SO FAR, WITH  
TEMPERATURES RUNNING 10 TO 15 DEGREES ABOVE NORMAL UNDER A  
STRENGTHENING UPPER-LEVEL RIDGE TO THE EAST.  
 
ON SATURDAY, A DEEPENING UPPER-LEVEL LOW APPROACHING THE  
PACIFIC NORTHWEST COAST WILL ENHANCE SOUTHWESTERLY FLOW AND DRAW  
IN ADDITIONAL MID- AND UPPER-LEVEL MOISTURE. THIS WILL TIGHTEN  
THE PRESSURE GRADIENT, RESULTING IN BREEZY SOUTHERLY WINDS  
ACROSS THE REGION. THE COMBINATION OF DOWNSLOPE FLOW AND WARM  
AIR WILL PUSH VALLEY TEMPERATURES TO NEAR-RECORD LEVELS, WITH  
HIGHS IN THE LOW 90S. WHILE MOISTURE REMAINS LIMITED, THERE  
APPEARS TO BE ENOUGH ELEVATED MOISTURE (PRECIPITABLE WATER  
VALUES IN THE 60TH PERCENTILE) AND INSTABILITY (CAPE AROUND 250  
J/KG) TO SUPPORT ISOLATED THUNDERSTORM DEVELOPMENT, ESPECIALLY  
OVER THE HIGHER TERRAIN OF SOUTHWEST IDAHO WHERE OROGRAPHIC LIFT  
WILL AID INITIATION.  
 
BY SUNDAY, STEEPER LAPSE RATES AND INCREASED UPPER-LEVEL SUPPORT  
FROM A STRENGTHENING SOUTHWESTERLY JET WILL SPREAD ACROSS MUCH  
OF THE REGION AHEAD OF THE INCOMING LOW. ALTHOUGH MOISTURE  
CONTINUES TO BE A LIMITING FACTOR, LIFT AND SHEAR SHOULD BE  
SUFFICIENT TO SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT, AGAIN  
FAVORING THE HIGHER ELEVATIONS DURING THE AFTERNOON AND EVENING.  
INVERTED-V SOUNDINGS INDICATE THAT STRONGER STORMS COULD PRODUCE  
GUSTY OUTFLOW WINDS. TEMPERATURES ON SUNDAY WILL BE ABOUT 10  
DEGREES COOLER THAN SATURDAY, BUT STILL REMAIN ROUGHLY 10  
DEGREES ABOVE NORMAL.  
 
LONG TERM...MONDAY THROUGH FRIDAY...WETTER, COOLER, AND WINDY  
WEATHER IS IN STORE FOR MUCH OF THE LONG TERM AS A DEEP UPPER LEVEL  
LOW SLOWLY MOVES EAST. TEMPERATURES HOLD STEADY AT JUST A FEW  
DEGREES BELOW NORMAL, BUT ABOUT 15-20 DEGREES COOLER THAN THE WARMER  
DAYS IN THE SHORT TERM. THE WEATHER WILL BE MOST ACTIVE MONDAY  
THROUGH WEDNESDAY, WITH AFTERNOON GUSTS OF 20-30 MPH AND  
PRECIPITATION EACH DAY. DURING THIS PERIOD, VALLEYS HAVE A 30-40%  
CHANCE OF PRECIPITATION EACH DAY AND MOUNTAINS HAVE A 50-70% CHANCE,  
HIGHEST IN THE AFTERNOONS. CONVECTION MAY STRUGGLE WITH CLOUDS AND  
COLDER SURFACE TEMPS, BUT MODELS SHOW MARGINAL CAPE MONDAY AND  
TUESDAY AFTERNOONS SO THUNDERSTORMS AND STRONG SHOWERS CAN'T BE  
WRITTEN OFF. COLD TEMPS WILL DROP SNOW LEVELS TO 6000-7000 FT MSL,  
SO HIGH ELEVATION PASSES COULD SEE A COUPLE INCHES OF WET SNOW  
ACCUMULATION.  
 
THE UPPER LEVEL LOW WILL MOVES EAST WEDNESDAY NIGHT, AND MODEL  
SOLUTIONS DIVERGE SIGNIFICANTLY THURSDAY AND FRIDAY. WE ARE LIKELY  
TO SEE TEMPS CONSISTENT WITH THOSE EARLIER IN THE WEAK AS THE FLOW  
AMONG MODELS IS MOSTLY ZONAL. CLOUDS ARE ALSO LIKELY TO STICK  
AROUND, BUT THE MOST UNCERTAINTY LIES IN THE CHANCE OF  
PRECIPITATION. THE EC HAS ANOTHER LOW AMPLIFYING AS IT MOVES ONTO  
THE COAST BRINGING MORE PRECIP FRIDAY EVENING, WHILE THE GFS SHOWS A  
WEAK SHORTWAVE AND A MUCH LOWER CHANCE OF PRECIPITATION.  
 

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

 
 

 
 
WWW.WEATHER.GOV/BOISE  
 
INTERACT WITH US VIA SOCIAL MEDIA:  
WWW.FACEBOOK.COM/NWSBOISE  
WWW.X.COM/NWSBOISE  
 
DISCUSSION...DG  
AVIATION.....SA  
SHORT TERM...JDS  
LONG TERM....JM  
 
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