705
FXUS65 KBOI 102051
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
151 PM MST Wed Dec 10 2025

.SYNOPSIS...Today through Friday night...High pressure will
continue building over the area as the warm front over the
Southern end steers Northward, continuing warmer than normal
temperatures and drier conditions Thursday and Friday. Though
not as warm as today, valley daytime temperatures are expected
to remain in the upper 50s Thursday and Friday. Small chances of
precipitation are only expected in the Northernmost mountains
of our area (near McCall and Baker City) throughout Thursday.
Patchy fog remains likely overnight tonight and Thursday
morning, especially in sheltered mountain valleys. A cooling
trend is expected Saturday, bringing daytime valley temperatures
into the lower 50s and mountain temperatures into the upper
40s. Winds will remain on the calmer side from the
Southeast/Southwest under 10 mph today through Friday for most
areas except the Magic Valley, which is still gusting 20-25 mph
this afternoon and possibly return stronger breezes up to 20 mph
Thursday and Friday. High pressure and daytime clearing with
weak winds will favor valley inversions for the remainder of the
week and over the weekend.

&&

.LONG TERM...Saturday through Wednesday...An upper-level ridge
is expected to reach peak amplification on Saturday, leading to
the greatest potential for warming aloft and the continuation of
the valley inversion throughout the Snake River Plain. This
setup will increase the chances for fog and stratus development
in the valley, and slightly colder temperatures will be observed
as cold air becomes trapped near the surface. These stagnant
conditions will remain in place through Sunday. By Monday, the
ridge is forecast to weaken, and cloud cover will increase ahead
of the next incoming cold front. Moisture appears limited with
this frontal passage, and while the ECMWF shows the highest
precipitation amounts, overall totals across guidance remain
light. Precipitation chances are similar to previous ensemble
guidance, starting Monday afternoon and increasing to a 55-70%
chance north of the Snake Plain and a 25-50% chance in and south
of the Snake Plain by Monday evening. While the front looks
strong enough to weaken the inversion, it may not be quite
strong enough to fully break it up.

Looking further ahead, another Atmospheric River (AR) event could
return to the Pacific Northwest as early as Wednesday, setting the
stage for another round of widespread precipitation. The forecast
area looks to remain on the warm side of the jet stream, with snow
levels hovering between 5,000 and 8,000 feet MSL from Monday through
Wednesday. There is high confidence in this system affecting the
region late next week, though the timing could be later (Thursday or
Friday). Temperatures throughout the extended period are expected to
remain 10-15 degrees above normal.

&&

.AVIATION...Mainly VFR with scattered to broken clouds through the
evening. Patchy dense fog and/or stratus possible (80% chance)
tonight for KBKE and KBKE. Less confident in patchy fog or stratus
development for KONO and KONO with a 30% chance Thursday morning.
Surface winds: SW-SE 5-15 kt with gusts 15-30 kt, except lighter in
the Snake Basin outside of the Magic Valley. Winds aloft at 10kft
MSL: W-NW 35-45 kt.

KBOI...VFR with Broken mid clouds through this evening. Fog/Stratus
unlikely (10% chance) Thursday morning. Surface winds: SE 4-8
kt.

&&

.AIR STAGNATION...A broad upper-level ridge over the eastern
Pacific and western US is expected to strengthen in our area for
the remainder of the week and through the weekend, causing
mixing heights to lower to 1,500 to 2,000 feet AGL Thursday and
1,200 to 1,700 feet AGL Friday through Sunday. At the same time,
winds are expected to be less than 10 mph resulting in
sustained poor ventilation. An Air Stagnation Advisory is in
effect early Friday through early Monday.


&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory from 5 AM Friday to 5 AM MST Monday
     IDZ012-014-016-033.
OR...Air Stagnation Advisory from 5 AM MST /4 AM PST/ Friday to 5
     AM MST /4 AM PST/ Monday ORZ061>064.

&&

$$

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SHORT TERM...JY
LONG TERM....JDS
AVIATION.....JDS
AIR STAGNATION...JY