761
FXUS65 KBOI 291559
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
959 AM MDT Sun Jun 29 2025

.DISCUSSION...Westerly flow continues today before weakening as a
ridge builds over the area in response to a trough digging along
the CA coast. This will bring warmer temperatures and a 10-20
percent chance of thunderstorms beginning on Monday afternoon
lasting through the week. Forecast was updated to add mention
of thunderstorms on Wednesday.

&&

.AVIATION...VFR. Clear skies. Surface winds: W-NW 5-15 kt. Afternoon
gusts to 20 kt in the Snake Basin east of KBOI. Winds aloft at 10kft
MSL: W-NW 10-15 kt.

KBOI...VFR. Clear skies. Surface winds: W-NW 5-10 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...Zonal flow today
will bring warm temperatures and light breezes each afternoon.
Lingering surface smoke may be visible, but is expected to
mostly clear by sunrise. An amplifying ridge to our south will
increase temperatures sharply on Monday and especially Tuesday.
Temperatures 10 degrees above normal on Monday rise to almost
15 degrees above normal on Tuesday, resulting in lower
elevations having forecast high temperatures a few degrees above
100. This has prompted the issuance of a heat advisory for
parts of the Snake Plain, Treasure Valley, and Weiser Basin.

The amplifying ridge will be supplemented by a closed low off
the California coast, allowing some monsoonal moisture to reach
our area. Precipitation chances are low Monday night, with only
isolated showers and thunderstorms expected over the Owyhees,
ID/NV border, and south-central Oregon. Precipitation chances
increase Tuesday night as the low moves inland, to 20% across
much of southeast Oregon and far southwest Idaho. The potential
for thunderstorms alongside the heat on Tuesday presents a
critical fire weather setup, with a limiting factor being storm
coverage. Thunderstorms may only be isolated with limited
moisture and increased cloud cover. As the low continues inland,
the high pressure ridge centered over the four corners begins to
breakdown.

LONG TERM...Wednesday through Sunday...Thunderstorms should be most
active in our Idaho zones Wednesday as the upper ridge continues to
break down and shift east.  At that time an upper low in southern
California will be far enough inland to direct the monsoon moisture
across southern Idaho rather than southeast  Oregon.   At the same
time, a larger scale upper trough will move onto the northwest coast,
with a surface cold front setting up in eastern Oregon, and greatest
instability for thunderstorms just east of the front, while Oregon
becomes cooler and more stable.  The front will shift into ID Wednesday
night and should be east of our CWA Thursday morning.  The upper trough
will also move inland across BC.  So Thursday should be relatively
quiet thunderstorm-wise.  Then, both ECMWF and GFS show another Pacific
upper trough approaching the Oregon coast.  As it moves onshore,
thunderstorms should become more active again -- Friday, July 4 in our
Oregon zones and Saturday in our Idaho zones.  By Sunday nearly all
thunderstorms should be in eastern ID while our CWA dries out and cools
to normal under the upper trough.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory from 11 AM to 8 PM MDT Tuesday IDZ012-014-033.
OR...Heat Advisory from 11 AM MDT /10 AM PDT/ to 8 PM MDT /7 PM
     PDT/ Tuesday ORZ064.

&&

$$

www.weather.gov/Boise

Interact with us via social media:
www.facebook.com/NWSBoise
www.x.com/NWSBoise

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