852
FXUS65 KBOI 051636
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
936 AM MST Fri Dec 5 2025

.DISCUSSION...No updates to the forecast this morning. Wet and
active weather continues as a plume of relatively warm moisture
from the central Pacific remains overhead. Snow levels vary
across the area, but are generally 7-8 kft MSL to the SW and
4-5 kft MSL to the NE. Precipitation sticks around through the
day, mostly dissipating by midnight for a brief break. Snow
remains the dominant precipitation type in the Idaho mountains,
and rain elsewhere. While mountain valleys in Central Idaho are
currently forecast to have surface temps above freezing this
afternoon, lingering cold pools and overcast skies may limit
warming before periods of moderate snow arrive this afternoon.

Friday afternoon through the evening, a strong pocket of
moisture will produce periods of steady moderate snow in the
mountains and rain in the valleys/lowlands. This round of
precipitation will bring 3-7 extra inches of snow on top of what
fell yesterday, and 0.1-0.4" of rain in lower elevations. Liquid
equivalent for snow will be higher today, given more moisture
and reduced snow ratios in the warmer airmass, about 0.5-0.8" of
liquid equivalent in areas that see snow. The precipitation and
associated moisture pocket begin to move out of the area,
starting in the NW early this evening and finally out of the SE
by midnight.

Winds begin to pick up in highlands, open areas, and ridges
tongiht as gusts of 25-35 mph persist through Saturday. Light
rain/snow continues in the mountains of the weekend, heavily
driven by local terrain. Extra accumulation of a few inches is
possible. A few stray models show icy/freezing precip out of the
extra precip this weekend, but remain outliers at this time with
a chance of occurrence less than 10%.

&&

.AVIATION...Widespread precip and low ceilings bringing widespread
MVFR/IFR conditions with periods of LIFR. Precip continuing
throughout the day, decreasing in late evening. Widespread concern
of LLWS, especially beginning afternoon today. Snow levels: 3.5-
4.5kft MSL in central Idaho, 5-8kft MSL in eastern Oregon and
in/south of the Snake Plain. Will lift to 5-8 kft MSL (lowest in the
W-cntrl ID mountains) Friday afternoon/evening. Surface winds: under
10 kts except near KJER/KTWF W-NW 8-12 kt with gusts 25+ kt. Winds
at 10kft MSL: W/NW 30-55 kt.

KBOI...MVFR/IFR in precip and low ceilings with periods of LIFR
overnight. LLWS developing Friday afternoon. Rain ending around
Sat/05z. Surface winds: light and variable.

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.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Sunday night...Strengthening
northwest flow aloft will continue to funnel deep moisture over
the region resulting in periods of rain and snow through this
evening. The heaviest rain/snow rates will come later today
with the passage of a weak upper trough. With a few exceptions,
the precipitation will fall as rain at elevations below 4500
feet. Baker Valley and sheltered valleys in the w-central ID mtn
have held onto snow overnight, but warm air will eventually win
out this morning, bringing a changeover to rain. Higher
mountain valleys (4500-5000+ feet) will continue to see snow
through this morning before rising snow levels bring a change
to rain. In these valleys, expect another 1 to 3 inches this
morning before the mix/changeover. For elevations above 6000
feet precipitation type remains all snow which will result in an
additional 4 to 8 inches of accumulation through this evening.
Higher spots in the interior Boise Mtns/Sawtooth could add
close to a foot of snow on top of what has fallen through the
night. Will keep the WWA for the W-Central ID and Boise Mtns in
place. Impacts at lower elevations will drop off this afternoon,
but snowfall will continue to affect higher passes/summits
through this evening.

Precipitation scatters out late this evening with drier
conditions developing across SE Oregon overnight and into SW
Idaho early Saturday morning. Winds will be ramping up across
higher terrain as precipitation tapers off this evening. Open
terrain above 4kft MSL could see periodic gusts to 40 mph as
winds aloft reach the surface. Higher mtn peaks (7kft+) could
see gusts to 50+ mph (cue Steens and Smokey Dome among others).

Northwest flow will keep a 40-80% chance of rain/snow across
the e-central Oregon and w-central Idaho mtns Sat/Sun, while
precipitation chances drop below 20% elsewhere across SE Oregon
and SW Idaho through Sunday morning. Snow levels settle to
between 4500-5500 feet and light accumulations (up to 3") are
expected for through Sunday morning. Another surge of moisture
will push into the region late Sun/Sun night increasing
precipitation chances. The surge of Pacific air will push snow
levels back above 5000 feet. Temperatures through the weekend
are 5-10 degrees above normal.

LONG TERM...Monday through Friday...The coming week looks to
remain wet and unsettled. This is thanks to high pressure
situated off of the West Coast working to shuttle moisture
across our area via the pineapple express (more commonly known
now-a-days as an atmospheric river). Monday initially looks to
be somewhat dry, barring a 30-60% chance of precip north of the
Snake Plain, thanks to a low amplitude ridge over our area.
However, this ridge will quickly break down throughout the day,
allowing for the upper-level jet to set in overhead with ample
moisture and the opportunities for embedded shortwaves.
Resulting in periods of precipitation throughout the week. Being
on the periphery of the west coast ridge, there is some
uncertainty in temperatures throughout the long-term (if the jet
fluctuates north we would be warmer, if it fluctuates south we
would be cooler); however, this pattern would favor above normal
temperatures with winds lacking much of a northerly component.
Precipitation chances will begin tapering off to end the week as
ridging builds into the area, pushing the moisture flow and
storm track north. Areas north of the Snake Plain will maintain
a 20-40% chance of precip Thursday/Friday. The pattern of
precipitation and above normal temperatures looks like it will
extend beyond the long- term period, with the CPC highlighting
above normal temps and precip in the 8-14 day outlooks.

A consequence of the mild, above average, temps will be higher
snow levels. Snow levels will fluctuate which each passing
shortwave, but generally stay in the 5-8kft range (increasing
from the northeast to the southwest). This limits any
additional snow accumulations throughout the long term to be
above 5.5kft, with locations below that elevation generally just
seeing rain.

&&

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

&&

$$

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DISCUSSION...JM
AVIATION.....CH
SHORT TERM...DG
LONG TERM....NF