103
FNUS75 KBOI 122352
FWSBOI

Spot Forecast for BIG GRASS...BLM
National Weather Service Boise ID
552 PM MDT Sat Sep 12 2026

Forecast is based on forecast start time of 0600 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.

.DISCUSSION...
A dry cold front will move through around sunrise on Sunday
morning and bring a wind shift to the west-northwest, along with
breezy conditions. No precipitation is expected. Temperatures will
drop 10 to 15 degrees on Sunday, along with a slight improvement
in daytime humidity values. Cool and dry conditions continue into
Monday, with lighter winds as high pressure builds over the
region.

.SUNDAY...

Sky/weather.........Mostly cloudy in the morning, then clearing.
Max temperature.....55 to 70.
Min humidity........22 to 32 percent.
CWR.................0 percent.
Wind - 20 foot......West to northwest 10 to 16 mph with gusts to around 24 mph.
Mixing height.......6500 ft AGL.
Transport winds.....West around 15 mph.
Ventilation Index...975 excellent.

.SUNDAY NIGHT...

Sky/weather.........Mostly clear.
Min temperature.....35 to 43.
Max humidity........69 to 95 percent.
CWR.................0 percent.
Wind - 20 foot......Northwest 11 to 17 mph with gusts to around 25
                    mph through around midnight, then weakening to light and variable
        by early Monday morning.
Mixing height.......200 ft AGL.
Transport winds.....Northwest around 15 mph.
Ventilation Index...30 poor.

.MONDAY...

Sky/weather.........Sunny.
Max temperature.....56 to 71.
Min humidity........23 to 33 percent.
CWR.................0 percent.
Wind - 20 foot......Northwest 3 to 7 mph. Gusts up to 14 mph in the
                    afternoon.
Mixing height.......4500 ft AGL.
Transport winds.....Northwest around 5 mph.
Ventilation Index...225 fair.

$$
Forecaster...Rogers
Requested by...STEPHEN HAMMOND
Type of request...WILDFIRE
.TAG 2621735.1/BOI
.DELDT 09/13/26
.FormatterVersion 2.0.0
.EMAIL stephen_hammond@firenet.gov,2026.biggrass.plans@firenet.gov,ROBERT_EGGERT@FIRENET.GOV