117
FXUS65 KBOI 271620
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
920 AM MST Thu Nov 27 2025

.DISCUSSION...Dense fog in the Treasure Valley is expected to
clear before noon, most likely around 10 am local time. Lifting
of the fog deck near Ontario and Caldwell raise confidence in
the dissipation timing. In the warm sector of an upper level
system today`s temperatures are still forecast to reach 5-10
degrees above normal, though potentially inhibited by high
clouds moving in. Otherwise, winds will increase to 15-25 mph in
parts of SE Oregon and ridgetops in Idaho ahead of a cold front
coming tonight. The warm front will drop temps slightly to 5
degrees above normal with a 40-60% chance of precipitation
Friday. Precip is most likely over high terrain with about a 10%
chance of measurable precip in lower elevations. Friday morning
some clearing, light winds, and high RH may lead to more fog in
mtn valleys and the Treasure Valley. The forecast seems on
track, no updates this morning aside from continued fog
monitoring.

&&

.AVIATION...Areas of IFR/LIFR due to fog will continue in the
Treasure Valley impacting KBOI, KEUL and in the Long Valley
impacting KMYL until around 18Z. Expect VFR conditions this
afternoon in all areas of southwestern Idaho and southeastern Oregon
after the fog dissipates. High clouds will spread back over the
areas this afternoon.  Surface winds: light and variable at less
than 10 kts, this morning in most areas, becoming E-SE 10-15 kt
across the Snake River plain this afternoon. Winds aloft at 10kft
MSL: W 20-30 kt.

KBOI...IFR/LIFR visibilities in dense fog expected to continue until
around 18Z. Fog will diminish 18Z with VFR conditions expected this
afternoon. Calm winds this morning will become southeasterly at 5 to
10 kts this afternoon.

Weekend Outlook...A cold front will return precipitation late
Saturday through early Sunday, with snowfall likely in the mountains
and light rain and/or snow in the lower elevations. Snow levels
around 3000 ft on Sunday. Patchy fog expected during overnight/early
morning hours on both days. Winds E-SE 5-10 kt Saturday becoming W-
NW 5-10 kt Sunday, with afternoon gusts 15-20 kt near KMUO.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Saturday night...Light warm-frontal
pcpn has shifted east of our CWA. leaving areas of fog, locally
dense, in the valleys this morning. At the time of this writing
we are on the verge of issuing a Dense Fog Advisory for the
Lower Treasure Valley east to Boise through the morning hours.
Otherwise, our CWA will be in the warm-sector between the
exiting warm front and the next cold front due to arrive Friday.
Early this morning the cold front was just off the northwest
coast with a supporting upper level trough near 140W. These will
move inland tonight, and through our CWA Friday. Until then our
area will be partly cloudy, dry, and mild. The cold front will
bring a brief period of rain and snow to Baker County Friday
morning, then hit our Idaho zones a little harder later Friday,
generally north of the Snake Basin. Gusty northwest winds 20-30
mph will follow the front Friday afternoon, strongest in the
Western Magic Valley. Clearing, calming, and colder Friday
night, especially at higher elevations. Northwest flow aloft
Saturday will bring another short wave trough from BC into our
CWA Saturday night, and it is that trough that may bring the
first light snowfall of the season to the lower southern valleys
including the Treasure Valley and western Magic Valley. GFS, in
particular, looks cold and moist enough for snow, while other
models also have that signal, but weaker for now.

LONG TERM...Sunday through Thursday...Early Sunday will
see the back end of a shortwave trough exit the area as a
large ridge builds into the Northwest region through most of
Monday, bringing dry conditions. Valley daytime temperatures
are expected to remain in the lower to mid 40s Sunday through
Monday, and snow levels in the 2000-3000 ft range. Late Monday
through Wednesday will see a longwave trough digging into the
region, though with uncertainty over the arrival and depth of
this trough. For now, precipitation is generally expected
Tuesday through early Wednesday. Lower elevation daytime
temperatures are expected to remain in the lower to mid 40s
throughout the extended period, and snow levels in the
3000-4000 ft range. Late Wednesday and early Thursday will
tentatively see a brief elongated ridge pattern extend into
the area, returning drier conditions.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Dense Fog Advisory until 10 AM MST this morning IDZ012-014.
OR...Dense Fog Advisory until 10 AM MST /9 AM PST/ this morning
     ORZ064.

&&

$$

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DISCUSSION...JM
AVIATION.....JB
SHORT TERM...LC
LONG TERM....JY