736
FXUS65 KBOI 202101
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
201 PM MST Thu Nov 20 2025

.SHORT TERM...Tonight through Saturday night...At 1 PM MST radar
still showed light rain echoes from Baker County through Malheur
County into Owyhee County but slowly decreasing. Expect most of
it to end by sunset. A few more weak echoes in the Boise Mountains
and Upper Weiser River Valley should also end by sunset. Today`s
rain has added moisture to the lowest atmospheric levels which
should lead to more fog than previously forecast. Difficult to
determine where fog may become dense so no advisory will be
issued with this package. Expect little day-to-day wx change
through the short term, with a weak upper high creating an
inversion in the valleys below, with the usual fog and low
clouds. Except for a slight chance (15-20%) of rain near the
ID/NV border tonight there should be no pcpn through Saturday
night. Light winds through the period.

.LONG TERM...Sunday through Thursday...High pressure and weak
flow aloft will keep Sunday mostly dry with temps remaining
above normal. However, that evening and early Monday a broad
Alaskan low will swing mostly north of the area. High terrain
in SW Idaho and SE Oregon will see a 20-40% chance of
precipitation. The strong northwesterly flow behind the low
will lower snow levels to 3.5 to 5 kft MSL, lower to the north.
This means most mountain towns could see snow with minimal
accumulation Monday morning. Temps also drop behind the low
on Tuesday, down to normal for this time of year. Weak high
pressure will again build into the area, but flow will remain
strong and moist enough for another shot at precipitation
Wednesday. Precipitation is likely to be very orographic as
only a few model members show a shortwave providing dynamics.
Precipitation will last through much of Thanksgiving day, but
that night another brief dry spell will set in before what is
shaping up to be a much colder weekend.

&&

.AVIATION...Low clouds continue to bring localized IFR-MVFR
reductions across the area, with isolated light precipitation
and snow levels at 5-7 kft MSL. Patchy fog will lift later this
afternoon and early evening before returning tonight with a 40%
chance of fog near the foothills in the Snake Plain and in mtn
valleys. Fog less likely elsewhere or will lift to stratus.
Surface winds: light and variable. Winds aloft at 10kft MSL:
S-W 5-15 kt.

KBOI...VFR and low-mid level clouds. While clouds will slightly
improve to broken, a ceiling is expected to persist through the
day. Fog/low stratus may return tonight with a 35% chance of
LIFR and fog being the more likely of the two. Surface winds
light and variable.

Weekend Outlook...Mountain valley and valley floor low stratus/
fog in the mornings Friday into Saturday, and again Saturday
into Sunday. On Sunday evening a cold front will be moving into
SE Oregon. Precipitation will hold off until early Monday
morning. Snow levels 5500-7000 ft MSL. Surface winds: variable
under 10 kt.

&&

.AIR STAGNATION...High pressure will create stable conditions
through early Monday, with mixing heights near or slightly
above 2000 feet AGL. A weak surface-based inversion, together
with light winds, will result in relatively poor ventilation
in the valleys.

&&

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

&&

$$

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SHORT TERM...LC
LONG TERM....JM
AVIATION.....JM
AIR STAGNATION...LC