081
FXUS65 KBOI 070349
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
849 PM MST Sat Dec 6 2025

.DISCUSSION...Latest models suggest Sunday`s warm front will
not be as wet as forecast, especially in southeast OR, and PoPs
have been generally lowered 10-20 percent in southern zones
through Monday to better match QPF forecasts. Even Monday
night`s PoPs could have been lowered but model uncertainty
makes changes dubious that far out. We also generally lowered
snow levels 200-400 feet through Monday to better match latest
model consensus. The impact will be minimal, however, as the
lower snow levels will occur with less pcpn. Wind, temperature,
and weather (rain, snow, fog) forecasts still look good from
the afternoon package. No changes there.

&&

.AVIATION...Patchy fog overnight. Rain and snow coverage
increasing along/north of KBNO-KMUO-KSUN line Sunday morning,
then moving toward NV border by evening. MVFR/IFR and local
LIFR in precip and low clouds. Mtns obscured through Sunday.
Snow levels: 4k-5k feet MSL Sun AM, then 5k-7k feet Sun PM.
Surface winds: variable 10 kt or less overnight, then SE-SW
5-15 kt Sunday. Winds aloft at 10kft MSL: W to NW 20-30 kt,
increasing to 30-40 kt by Sun/15Z.

KBOI...VFR overnight. Periods of rain and MVFR conditions
Sun/15Z through Mon/05Z. Foothills obscured. Surface winds:
SE 5-10 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday night...Unseasonably warm
conditions continue through the entire forecast period.
Temperatures are already above guidance. A record high has
been set today at Ontario OR with 56 degrees as of 2pm MST.
Westerly flow continues to bring scattered snow showers over
the mountains through this evening with minimal accumulations.
A weak warm front moves over the area on Sunday, keeping
temperatures slightly cooler than today, with precipitation
during the daytime heating hours. Then temperatures continue
to warm on Monday with another warm frontal passage late.
Rain arrives Monday afternoon, generally north of a line
from Burns OR to Twin Falls ID. Temperatures on Monday
reach the low to mid 50s across the Snake Basin and eastern
OR lower elevations with unusual vertical mixing persisting.

LONG TERM...Tuesday through Saturday...The long term remains
mostly wet and active as an atmospheric river continues to
supply warm tropical moisture over a strong eastern Pacific
ridge. The flow in the moisture plume reaches a staggering
50-80 knots at 500mb in the middle of next week, and with PWs
near record levels for this time of year moisture flux will
be significant. Precipitation chances every 6 hours Tuesday
through Thursday morning are around 80-100% north of a line
from Ontario, to Boise, to Fairfield, centered primarily in
the high terrain of eastern Oregon and west central Idaho.
South of that line, precipitation chances are still elevated
at 40-60%. The very strong advection of warmer air brings
snow levels to the moon, 7-9 kft MSL. This is still low
enough for the very highest peaks to see snow, but many low
mountain ranges and mountain valleys are likely to see
predominantly rain through the event. Summits that see snow
could see 1-2 feet of snow, but below 8000 ft any snow that
falls will be wet and followed by periods of rain. North of
the Ontario, Boise, Fairfield line in the high terrain;
rainfall/liquid equivalent totals at 1.0-2.5 inches. South
of the line closer to 0.2-0.5 inches, with some portions of
far SE Oregon only seeing a few hundredths of an inch. The
strong winds aloft will mix down to the surface, bringing
gusts of 25-45 mph to open areas, ridges, and highlands.
Between Tuesday and Thursday morning the weather will be most
significant on Wednesday as a shortwave supplements the
pattern, bringing the strongest winds and highest rainfall
rates.

Late Thursday through Saturday the high pressure begins
moving inland, pushing the moisture stream north and bringing
drier weather. With the ridge overhead, valley inversions,
low stratus, and fog are all possible. The warmer airmass in
the atmospheric river and high pressure following will raise
surface temps to nearly 20 degrees above normal throughout
the long term. A possible inversion late in the week could
trap colder air near the surface, raising uncertainty in
temperature forecasts after Thursday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

www.weather.gov/Boise

Interact with us via social media:
www.facebook.com/NWSBoise
www.x.com/NWSBoise

DISCUSSION...LC
AVIATION.....SH
SHORT TERM...KA
LONG TERM....JM