013
FNUS75 KBOI 101909
FWSBOI

Spot Forecast for Big Grass...BLM
National Weather Service Boise ID
109 PM MDT Thu Sep 10 2026

Forecast is based on forecast start time of 1800 MDT on September 10.
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.

...FIRE WEATHER WATCH IN EFFECT FROM SATURDAY AFTERNOON THROUGH
   SATURDAY EVENING...
...BREEZY AFTERNOON WINDS AND ISOLATED THUNDERSTORMS TODAY...
...WARM, DRY, AND BREEZY FRIDAY THROUGH SATURDAY...
...ACTIVE PATTERN LATE SATURDAY WITH GUSTY WINDS AND ISOLATED
   SHOWERS/THUNDERSTORMS...

.DISCUSSION...
A cold frontal passage later today will bring elevated southwest
wind breezes with gusts over 20 mph. Isolated virga
showers/thunderstorms over the burn area this evening through late
night. Warm, dry, and moderately breezy conditions are expected
Friday. Saturday afternoon will see stronger afternoon wind gusts
and low relative humidities ahead of an approaching cold front.
There is a potential for winds of 20 to 30 mph with gusts up to 45
MPH early Saturday evening with RHs between 15 and 20 percent. As
such, a Fire Weather Watch has been issued for Saturday 12 PM through
9 PM MDT. Come late Saturday night, a strong Pacific low pressure
system moves across the area increasing the chances for
showers/thunderstorms into early Sunday.

.TONIGHT...

Sky/weather.........Mostly cloudy. Isolated showers and
                    thunderstorms in the evening. Chance of
                    precipitation 20 percent. Chance of thunder
10-15 percent.
Min temperature.....53 to 58.
Max humidity........50 to 55 percent.
CWR.................0 percent.
Wind - 20 foot......Southwest 10 to 16 mph with gusts to around 24
                    mph. Gusty and erratic winds up to 40 mph possible
from nearby thunderstorms in the evening.
Mixing height.......200 ft AGL.
Transport winds.....Northwest around 10 mph.
Ventilation Index...20 poor.

.FRIDAY...

Sky/weather.........Mostly sunny.
Max temperature.....78 to 83.
Min humidity........20 to 25 percent.
CWR.................0 percent.
Wind - 20 foot......West-northwest 5 to 11 mph. Gusts up to 14 mph in the
                    morning increasing to 22 mph in the afternoon.
Mixing height.......6500 ft AGL.
Transport winds.....West around 15 mph.
Ventilation Index...975 excellent.

.FRIDAY NIGHT...

Sky/weather.........Mostly cloudy in the evening, then clearing.
Min temperature.....52 to 57.
Max humidity........48 to 53 percent.
CWR.................0 percent.
Wind - 20 foot......Northwest-north 3 to 9 mph with gusts to around 20 mph
in the evening shifting to the southeast 4 to 8 mph
overnight.
Mixing height.......200 ft AGL.
Transport winds.....Southwest around 10 mph.
Ventilation Index...20 poor.

.SATURDAY...

Sky/weather.........Mostly sunny, then mostly cloudy in evening.
Max temperature.....79 to 84.
Min humidity........15 to 20 percent.
CWR.................0 percent.
Wind - 20 foot......South-southwest 15 to 20 mph. Gusts up to 20 mph in the
                    morning increasing up to 45 mph in the afternoon.
Mixing height.......9500 ft AGL.
Transport winds.....Southwest around 25 mph.
Ventilation Index...2375 excellent.

$$
Forecaster...Yang
Requested by...Alicia Schlarb
Type of request...WILDFIRE
.TAG 2621344.4/BOI
.DELDT 09/10/26
.FormatterVersion 2.0.0
.EMAIL 2026.biggrass.plans@firenet.gov