182
FXUS65 KBOI 221003
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
303 AM MST Sat Nov 22 2025

.SHORT TERM...Today through Monday night...An upper level ridge
over the region today into Sunday will bring dry and stable
conditions. Fog and stratus have been limited by high clouds and
light southerly winds so far this morning. We could see an
increase in Fog/Stratus coverage for the Snake River Plain later
this morning between 7 AM and 10 AM, with the best chance
across south central Idaho, including the Magic Valley. Valleys
and basins in eastern Oregon and west central Idaho will also
see periods of fog through the early afternoon. However,
widespread dense fog advisory appears unlikely at this time. We
will end the Dense Fog Advisory for all zones except the Western
Magic Valley.

Drying south to east winds are expected to increase this
afternoon, which will help lift and dissipate fog and stratus,
yielding mostly sunny conditions for most. Stratus could remain
longer across the sheltered valleys of eastern Oregon. The
increased winds today along with mostly clear skies should allow
temperatures to warm about 4 to 7 degrees above normal.

High res models indicate stratus redeveloping tonight mainly
across the Lower Treasure Valley and Upper Weiser Basin along
with Baker Valley. This is pretty typical for this type of event
as what remains of the boundary layer moisture pools at the
lowest part of the valley. Given the drier near surface air,
widespread fog appears unlikely.

Warm and dry on Sunday with increasing southeasterly surface
winds ahead of the next cold frontal passage. This system will
move across the region late Sunday into early Monday, bringing
precipitation mainly to the Central Idaho mountains Monday
morning. There is about a 20 percent chance of rain showers in
the valley Monday morning. Snow levels start out around 6000
feet Sunday night and fall to between 2500 to 3500 feet late
Monday morning with passage of the front. Thus, light snow is
possible above 5000 feet, with between 1 to 2 inches expected.
Breezy northwesterly winds will bring near normal temperatures,
which should mix out the valley inversion.

.LONG TERM...Tuesday through Saturday...The front end of a
large amplifying ridge is expected to build into the region
Tuesday through Thursday. This ridging will bring drier
conditions through most of Tuesday, but peak lower elevation
temperatures are expected to remain in the lower 40s. Valley
temperatures are expected to take on a slight warming trend from
the mid/upper 40s into the lower 50s Wednesday through Friday.
The aforementioned ridging pattern is expected to steer a plume
of moisture off the Pacific NW coast into the area late Tuesday
to the end of the week, favoring a 20-30% chance of
precipitation in lower elevations and a 50-60% chance in higher
elevations everyday of the extended forecast period. Snow levels
are expected to take on an upward trend from the 3000-4000 ft
range Tuesday and early Wednesday into the 5000-6000 ft range
late Wednesday to the end of the week. Mountain locations may
get some wintry mix in precipitation throughout the week. A
longwave trough, with some guidance uncertainty on the arrival
pattern, is generally expected to dig into the area Friday
through Saturday, favoring widespread precipitation and a
cooling trend throughout the area towards the end of the
extended.

&&

.AVIATION...Patches of MVFR stratus/fog in the mountains and
near the Nevada border overnight. Areas of LIFR-IFR fog/stratus
will redevelop in the valleys early Saturday morning, improving
late morning/early afternoon. Surface winds: light and variable,
becoming E-SE 5-10 kt Saturday morning/afternoon. Winds aloft
at 10kft MSL: W- SW 5-10 kt.

KBOI...VFR conditions expected overnight. A less than 30%
chance of LIFR-IFR fog/low stratus will develop at the terminal
Saturday morning 12-17Z, with higher chances west-southwest of
the terminal. Surface winds SE 5-10 kt.

Sunday Outlook...Areas of valley fog/stratus Sunday morning
with improvement in the afternoon. A cold front late Sunday will
bring light precipitation mainly to northern areas and mountain
obscuration. Snow levels 5500-6500 ft MSL Sunday evening,
falling to 3000-4500 ft MSL by Monday morning. Surface winds:
SE-SW less than 10 kt early Sunday, then W-NW 5-15 kt in the
afternoon/evening.

&&

.AIR STAGNATION...High pressure aloft will continue through
Sunday night, with daytime mixing heights peaking between 1500
and 2500 feet AGL in the valleys. Relatively light winds and a
low-level inversion will continue to limit ventilation in most
valleys. A cold front late Sunday into early Monday morning
will bring increased west to northwest winds, improving mixing
and ventilation.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Dense Fog Advisory until 10 AM MST this morning IDZ016.
OR...None.

&&

$$

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