932  
FNUS75 KBOI 081854  
FWSBOI  
 
SPOT FORECAST FOR BIG GRASS   
..BLM  
UPDATED  
NATIONAL WEATHER SERVICE BOISE ID  
1254 PM MDT TUE SEP 8 2026  
 
FORECAST IS BASED ON FORECAST START TIME OF 1800 MDT ON SEPTEMBER 08.  
IF CONDITIONS BECOME UNREPRESENTATIVE...CONTACT THE NATIONAL WEATHER  
SERVICE.  
 
PLEASE CONTACT OUR OFFICE AT (208)334-9060, IF YOU HAVE QUESTIONS  
OR CONCERNS WITH THIS FORECAST.  
   
..WARMING AND DRYING THROUGH THURSDAY  
   
..BREEZY WINDS THURSDAY AFTERNOON THROUGH SATURDAY  
 
   
DISCUSSION  
 
HIGH PRESSURE OVER THE AREA WILL BRING MOSTLY CLEAR SKIES,  
WARMER THAN NORMAL TEMPERATURES, AND LIGHT DIURNAL WINDS LATER  
TODAY THROUGH WEDNESDAY. A MOSTLY DRY LOW PRESSURE SYSTEM WILL  
ARRIVE THURSDAY THROUGH THE WEEKEND, BRINGING GUSTY WEST WINDS AND  
A COOLDOWN WHILE KEEPING THE BURN AREA DRY. THURSDAY AFTERNOON  
WILL START SEEING ELEVATED WIND BREEZES WITH GUSTS OVER 20 MPH.  
   
TONIGHT  
 
SKY/WEATHER.........MOSTLY CLEAR.  
MIN TEMPERATURE.....45 TO 51.  
MAX HUMIDITY........55 TO 65 PERCENT.  
CWR.................0 PERCENT.  
WIND - 20 FOOT......NORTH-NORTHEAST 5 TO 10 MPH, BECOMING  
SOUTHEAST AND DOWNSLOPE AROUND 6 MPH AFTER  
MIDNIGHT.  
MIXING HEIGHT.......100 FT AGL.  
TRANSPORT WINDS.....SOUTHEAST AROUND 5 MPH.  
VENTILATION INDEX...5 POOR.  
   
WEDNESDAY  
 
SKY/WEATHER.........SUNNY.  
MAX TEMPERATURE.....79 TO 85.  
MIN HUMIDITY........15 TO 21 PERCENT.  
CWR.................0 PERCENT.  
WIND - 20 FOOT......SOUTHEAST UP TO 6 MPH IN THE MORNING  
SHIFTING TO THE WEST-NORTHWEST 5 TO 8 MPH IN  
THE AFTERNOON.  
MIXING HEIGHT.......6000 FT AGL.  
TRANSPORT WINDS.....WEST AROUND 10 MPH.  
VENTILATION INDEX...600 GOOD.  
   
WEDNESDAY NIGHT  
 
SKY/WEATHER.........MOSTLY CLEAR.  
MIN TEMPERATURE.....53 TO 58.  
MAX HUMIDITY........36 TO 42 PERCENT.  
CWR.................0 PERCENT.  
WIND - 20 FOOT......NORTHWEST-NORTH UP TO 6 MPH IN THE EVENING  
SHIFTING TO THE SOUTHEAST AND DOWNSLOPE 3 TO 8  
MPH OVERNIGHT.  
MIXING HEIGHT.......100 FT AGL.  
TRANSPORT WINDS.....SOUTHEAST AROUND 5 MPH.  
VENTILATION INDEX...5 POOR.  
   
THURSDAY  
 
SKY/WEATHER.........MOSTLY SUNNY.  
MAX TEMPERATURE.....83 TO 89.  
MIN HUMIDITY........15 TO 23 PERCENT.  
CWR.................0 PERCENT.  
WIND - 20 FOOT......SOUTHEAST 3 TO 8 MPH IN THE MORNING SHIFTING TO  
THE WEST 10 TO 15 MPH WITH GUSTS TO AROUND 24  
MPH IN THE AFTERNOON.  
MIXING HEIGHT.......8000 FT AGL.  
TRANSPORT WINDS.....WEST AROUND 20 MPH.  
VENTILATION INDEX...1600 EXCELLENT.  
 
 
FORECASTER...YANG  
REQUESTED BY...ALICIA SCHLARB  
TYPE OF REQUEST...WILDFIRE  
.TAG 2621344.2/BOI  
.DELDT 09/08/26  
.FORMATTERVERSION 2.0.0  
.EMAIL 2026.BIGGRASS.PLANS@FIRENET.GOV  
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab ID Page
The Nexlab OR Page
Main Text Page