233
FNUS75 KBOI 131946
FWSBOI

Spot Forecast for BIG GRASS...BLM
National Weather Service Boise ID
146 PM MDT Sun Sep 13 2026

Forecast is based on forecast start time of 1800 MDT on September 13.
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.

...WINDS THIS EVENING CALM TONIGHT...
...COOLER TMRW BEFORE WARMING TREND THRU WEDNESDAY...
...UNSETTLED LATER THIS WEEK...

.DISCUSSION...
Wind gusts up to 25 mph out of the northwest this evening begin
to weaken early tonight, remaining out of the north-northwest
through Monday. Colder temperatures tonight will allow good RH
recovery, supporting a chance for frost in the area. Temperatures
remain cool tomorrow before a warming trend brings temperatures
back up by Tuesday. Tuesday through Wednesday winds shift out of
the northeast 5 to 12 mph. Unsettled conditions later this week
will bring a 10% chance of precipitation over higher terrain.

.TONIGHT...

Sky/weather.........Mostly clear.
Min temperature.....35 to 42.
Max humidity........74 to 93 percent.
CWR.................0 percent.
Wind - 20 foot......Northwest 9 to 15 mph with gusts to around 23
                    mph.
Mixing height.......200 ft AGL.
Transport winds.....Northwest around 15 mph.
Ventilation Index...30 poor.

.MONDAY...

Sky/weather.........Mostly sunny. Areas of frost in the morning.
Max temperature.....56 to 70.
Min humidity........23 to 33 percent.
CWR.................0 percent.
Wind - 20 foot......Northwest 3 to 8 mph.
Mixing height.......4500 ft AGL.
Transport winds.....Northwest around 5 mph.
Ventilation Index...225 fair.

.MONDAY NIGHT...

Sky/weather.........Mostly clear.
Min temperature.....36 to 43.
Max humidity........55 to 76 percent.
CWR.................0 percent.
Wind - 20 foot......North 3 to 6 mph with gusts to around 14 mph in
                    the evening shifting to the northeast overnight.
Mixing height.......100 ft AGL.
Transport winds.....East around 5 mph.
Ventilation Index...5 poor.

.TUESDAY...

Sky/weather.........Sunny.
Max temperature.....64 to 79.
Min humidity........15 to 25 percent.
CWR.................0 percent.
Wind - 20 foot......Southeast 3 to 6 mph in the morning shifting to
                    the southwest with gusts to around 14 mph in
                    the afternoon.
Mixing height.......6000 ft AGL.
Transport winds.....West around 5 mph.
Ventilation Index...300 fair.

$$
Forecaster...Macfarlane
Requested by...STEPHEN HAMMOND
Type of request...WILDFIRE
.TAG 2621735.2/BOI
.DELDT 09/13/26
.FormatterVersion 2.0.0
.EMAIL stephen_hammond@firenet.gov,ROBERT_EGGERT@FIRENET.GOV,2026.biggrass.plans@firenet.gov