771
FXUS65 KBOI 031009
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
309 AM MST Sat Jan 3 2026

.SHORT TERM...Today through Monday night...Dense fog in and near
the Treasure Valley will erode from east to west early this
morning as southeast winds increase in advance of an approaching
Pacific cold front. Current Dense Fog Advisory in the Lower
Treasure Valley is set to expire at 7 AM MST, after which fog
should no longer be dense, although lighter fog should continue
through mid-morning. Rain will begin mid-morning across our
northern zones (Baker County into the west-central Idaho
Mountains) along the old warm-frontal zone. Rain with the
approaching cold front should begin in Harney County around mid-
day and spread rapidly eastward. By sunset all Idaho zones should
be wet as the cold front gets there, while eastern Oregon begins
to dry out. Pre-cold-frontal south winds in Oregon will gust to
30 mph, then become southwest with gusts 35 to 45 mph along and
after the front passes. All this wind will mix out any remaining
cold air in the valleys. Instability looks strong enough for a
slight chance of thunderstorms this evening in/near eastern
Valley County/ID as the cold front passes. There`s not much
"cold" air behind the front, coming from the west rather than
the north, so Sunday, and Monday as well, will still be mild.
Higher elevations will notice the greatest cooling as the upper
trough replaces the current upper ridge over our CWA. The next
cold front and more pcpn will come in mainly Sunday night, cold
enough for several inches of snow above 4500 feet north to 6000
feet south. The upper trough itself will come through on Monday
with further slight cooling and more rain and snow showers,
then clearing and colder Monday night as the trough exits east.

.LONG TERM...Tuesday through Saturday...Tuesday will see a
shortwave trough steer southeast out of the area, bringing a
brief break in pcpn and limiting scattered showers to the west-
central mountains. A reinforcing shortwave from the northwest
will increase precipitation chances again come late Tuesday/
early Wednesday, and north-northwesterly flow behind a cold
front will support cooling temperatures. Peak valley temperatures
will be in the upper 40s Tuesday, before dropping into the
upper 30s by Saturday. Mountain temperatures are looking to stay
in the 20s Tuesday through Saturday. Cooling temperature and
lowering snow levels behind the cold front will support a wintry
mix throughout the Snake Plain by Wednesday afternoon. By
Thursday morning, snow levels will drop to valley floors.
However, as the snow level drops, precipitation chances will be
on the decline as the trough departs to the east. Little to no
snow accumulation is expected throughout the Snake Plain.
Friday and Saturday will see a cold but dry pattern.

&&

.AVIATION...IFR to VLIFR due to fog in low elevations and sheltered
valleys, especially Lower Treasure Valley (KONO to KEUL/KMAN).
Gradual improvement this morning. Scattered showers from W to E
after 12Z. Isolated lightning over central Idaho mtns late
afternoon/early evening. Snow levels around 6-7kft MSL. IFR/LIFR
in snow, MVFR/IFR in heavier rain. Mtns obscured in low ceilings
and precip. Surface winds: E-S 5-15 kt, with Sat PM gusts 20-35
kt, In SE Oregon and near the NV border, S-SW 15-25 kt with
35-45 kt Sat PM. Wind aloft at 10kft MSL: SW 15-30 kt in SW
Idaho, SW 30-50 kt in E Oregon.

KBOI...Mainly VFR. LIFR fog dissipating before sunrise due to
increasing SE winds. VCFG lingering through sunrise. Intermittent
rain showers between Sat/17Z-Sun/03Z. Surface winds: SE 7-15 kt
through this morning/early afternoon. Late afternoon gusts peaking
at 25-35 kt.

Sunday Outlook...Showers mainly over central ID mountains with
snow level 5-6kft MSL. IFR/LIFR in snow. Mtns obscured. Patchy
morning fog in sheltered valleys. Surface winds: SW- SE 5-15 kt
with gusts 15-30 kt.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Dense Fog Advisory until 7 AM MST this morning IDZ012.
OR...Dense Fog Advisory until 7 AM MST /6 AM PST/ this morning
     ORZ064.

&&

$$

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SHORT TERM...LC
LONG TERM....JY
AVIATION.....JY