126
FXUS65 KBOI 031526
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
926 AM MDT Wed Sep 3 2025

.DISCUSSION...Still hot today, but not 100 degrees anymore this
year, as we will be steadily cooling through at least next week.
Isolated PM showers and thunderstorms again in eastern OR today
through Friday, then better chances over all our CWA this
weekend when a Pacific short wave trough comes inland with
monsoon moisture still present. By late Sunday the trough and
moisture should exit east. The parent north Pacific upper low
will come fully inland Tuesday and into our CWA Wednesday,
bringing even better chances of showers along with fall-like
temperatures: highs in the 50s and 60s in the mountains and
70s in the valleys. Current forecast is on track.

&&

.AVIATION...VFR. Isolated showers/thunderstorms in SE Oregon,
capable of 30-40 kt gusts from downdrafts. Smoke layers.
Surface winds: variable 5-10kt becoming W-NW 5-15kt during the
afternoon, gusts to 25 kt in eastern OR. Winds aloft at 10kft
MSL: variable 5-15kt.

KBOI...VFR. Smoke layers aloft. Surface winds: SE 5-10kt,
becoming NW 5-10kt during the afternoon.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Friday night...An upper level ridge
axis will remain oriented over eastern WA and Idaho today, with
a weak elongated system over northern CA and southern OR
extending into Arizona. This system will bring mostly cloudy
skies to southeast OR and isolated showers and thunderstorms
each afternoon into Friday. Gusty erratic outflow winds up to
45 mph possible this afternoon and Thursday afternoon. The
upper level ridge will slowly weaken into Friday, and temps
will cool a few degrees each day. The system will remain
stationary through the short term before lifting northward late
Friday. Temperatures will remain 8-13 degrees above normal
Today, before cooling 2-3 degrees on Thursday and Friday.

LONG TERM...Saturday through Wednesday...The aforementioned
system will lift northward over the area on Saturday as a
shortwave moves inland off the Northern CA coast. Precipitable
water values reach the 80th percentile on Saturday, not nearly
as impressive as the last event on August 27th. The dynamics of
this trough will interact with the mid level moisture already
in place, with a 20-30 percent chance of thunderstorms across
eastern OR and far southwest ID, and a 10-20 percent chance of
thunderstorms north and east of the Snake Plain. Temperatures
will cool to near normal on Saturday. Showers and thunderstorms
will linger into Sunday and Monday as the trough remains just
offshore, with moisture lingering over the Rocky Mountains. The
trough is forecast to slowly move inland during the Tuesday-
Thursday timeframe with much cooler and unsettled conditions
possible. High temperatures have the potential to lower to 5-10
degrees below normal depending on where the center of the upper
level trough moves. If the center of the trough moves overhead,
high temperatures would be in the 50s and 60s with the first
taste of fall this season.

&&

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

&&

$$

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DISCUSSION...LC
AVIATION.....LC
SHORT TERM...KA
LONG TERM....KA