825
FXUS65 KBOI 052152
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
252 PM MST Fri Dec 5 2025

.SHORT TERM...Tonight through Sunday night...An atmospheric
river in the Pacific is bringing anomously high moisture to the
area this afternoon and evening, and will continue to drive the
forecast through the short term. This afternoon and tonight snow
levels have rising to 5-6 kft MSL in central Idaho and 7-8 kft
MSL in SW Idaho and SE Oregon. While this will bring 4-8 extra
inches of snow to mountains and high passes, most mountain towns
in Idaho will be within 800 ft of the snow level. Those just
above the snow level could see 1-2 inches of wet snow, compared
to 0.3-0.6 inches of rainfall below the snow level. Lower
elevations and low lands well below the snow level, especially
SE Oregon and SW Idaho will see 0.1-0.4 inches of rain through
this evening. Visibilities will be reduced within precipitation
as clouds stay low and precip rates become moderate. The rising
snow levels and wetter snow will help to improve road
conditions at the tail end of the precipitation, so the Winter
Weather Advisory will be allowed to end at the scheduled time
around midnight.

This evening through Saturday, in highlands, ridges, and open
areas gust to 25-40 mph as precipitation clears out. This is
driven by very strong winds aloft of 50-70 mph around 700 mb. A
significant 130 mph flow is expected near the tropopause. The
flow remains somewhat moist, allowing a persistent 50-70% chance
of precipitation in central Idaho mountains through the weekend.
Extra snow accumulation of 1-3 inches is possible above 4.5 kft
MSL. A few CAMs show freezing rain in these showers, though the
winds on Saturday will help mix the atmosphere reducing the risk
to less than a 10% chance. On Sunday the flow briefly sources
from the north, dropping snow levels to 4-5 kft MSL. Temps on
Sunday drop a few degrees from Saturday. This brief flow switch
also brings another pocket of moisture raising precip chances in
lower elevations to 40% and higher elevations to 80% Sunday
night.

.LONG TERM...Monday through Friday...Forecasted to be much of the
same from the short term. The upper-level ridge is still cemented in
the eastern Pacific, with moisture riding overtop. Higher PoPs (60-
90%) are mostly limited to our northern zones, with lower chances
(20-50%) for lower elevations. Beginning Thursday, the upper-level
ridge axis looks to build further north/northwest, bringing higher
heights overhead and pushing the moisture flux further north.
Current long range models disagree to what extent the moisture may
still exist along the northern higher elevation zones, thus they
retain 20-40% PoPs Thursday. There is good agreement that by
afternoon into evening Friday, our northern mountain zones will
finally receive some respite.

With the unseasonable, strong upper-level ridge in the eastern
Pacific, well above average temperatures (10-15 degrees) are
expected during the long term.  A consequence of the above average
temps will be higher snow levels. Snow levels will fluctuate with
each passing shortwave, but generally stay in the 6.5-8kft range
(highest in SE OR, lowest in central ID). This limits any additional
snow accumulations throughout the long term to be above 6.5kft, with
locations below that elevation generally just seeing rain.

&&

.AVIATION...Widespread precip and low ceilings bringing widespread
MVFR/IFR conditions with periods of LIFR. Precip continuing
throughout the day, decreasing in coverage late this evening.
Widespread concern of LLWS through Saturday morning. Snow levels: 5-
8 kft MSL (lowest in the W-cntrl ID mountains), becoming 4-5.5 kft
MSL overnight. Surface winds: under 10 kts, except near KJER/KTWF W/
NW 8-12 kt gusting to 30 kt, and SE OR with W/SW 15-20 kt gusting to
30 kt. Winds at 10kft MSL: W/NW 30-55 kt.

KBOI...MVFR/IFR in precip and low ceilings with a 30% chance of LIFR
overnight into early Saturday morning. LLWS threat persisting until
Saturday afternoon. Rain ending around Sat/05z. Surface winds: light
and variable, becoming W-NW 9-14 overnight.

Weekend Outlook...Scattered, lighter precipitation is expected
Saturday and Sunday, primarily over higher terrain. Snow levels 4-6
kft MSL. Patchy fog in mtn valleys Sat/Sun mornings. MVFR to LIFR
conditions in precipitation/fog with mountains obscured. Surface
winds: SW-NW 5-15 kt, except 15-20 kt with gusts 25-40 kt Saturday
across higher terrain and the western Magic Valley. Variable 5-15 kt
Sunday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until 11 PM MST this evening
     IDZ011-013.
OR...None.

&&

$$

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SHORT TERM...JM
LONG TERM....CH
AVIATION.....CH