542
FXUS65 KBOI 091542
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
942 AM MDT Wed Jul 9 2025

.DISCUSSION...The main concern later today continues to be the
potential for strong outflow winds from thunderstorms. Water
vapor imagery this morning shows an upper-level low centered
over northern California, which is expected to track northeast
across southeast Oregon and southwest Idaho this afternoon and
evening. Increasing mid-level moisture and strengthening
southwesterly flow, combined with steep low-level lapse rates
from daytime heating, will set the stage for scattered
thunderstorm development.

The most favorable area for storms looks to stretch from
central Harney and Malheur Counties into southwest Idaho,
including the Boise Mountains and areas along the Idaho-Nevada
border. The strongest storms could produce isolated severe wind
gusts up to 60 mph, especially from Malheur County eastward
through the Snake River Plain and into the Boise Mountains.
While not everyone will see winds this strong, a broad area of
35 to 50 mph gusts looks increasingly likely across northern
Malheur County, the Weiser Basin, the Treasure Valley, and into
the West Central and Boise Mountains. Blowing dust will likely
accompany these winds, especially at lower elevations and in
more open terrain, lowering visibilities. The greatest threat
for winds/blowing dust in the Boise Metro area looks to be
between 4 PM and 7 PM MDT.

This system isnt particularly wet, with precipitable water
values in the 5060th percentile and most high-res models
showing localized rainfall rates of around 0.25 to 0.50 inches
per hour. While this typically wouldn`t raise flooding concerns,
we`ll be keeping an eye on burn scar areas, particularly the
Wapiti Burn Scar, where thresholds for debris flows and flooding
are lower.

Storm chances will continue through sunset across most areas,
lingering through midnight in the Boise Mountains.

&&

.AVIATION...Isolated to scattered showers and thunderstorms will
develop across the area Wednesday afternoon/early evening. Gusts up
to 50 kt and blowing dust reducing visibility will be possible.
Surface winds: W-NW 5-15 kt through morning and early afternoon,
with locally stronger winds of 30-50 kt with outflows. Winds aloft
at 10kft MSL: S-SW 5-15 kt.

KBOI... Isolated thunderstorms developing after 22Z with a 30%
chance of terminal being impacted. Strong outflow winds are more
likely. Otherwise, VFR conditions. Surface winds: Winds NW 5-15 kt
with gusts to 20 kt Wednesday afternoon. Outflow winds of 30-40 kt
possible (30% chance) between 23Z and 02Z. WNW winds at 8-10 kt
overnight.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Friday night...Water vapor satellite
imagery showing an upper low centered over northern CA tonight.
Showers and thunderstorms will develop out ahead of the low
as it tracks through SE Oregon and SW Idaho this afternoon. The
higher thunderstorm probability will stretch from central
Harney and Malheur counties in Oregon into southwest Idaho from
the Boise mtns to the NV border. Outflow winds will be the main
threat from storms with gusts up to 60 mph possible from
Malheur County eastward through the Snake Plain and Boise mtns.
While not all locations will see winds this strong, a broad area
of 35 to 50 mph winds is looking more likely across northern
Malheur County, the Weiser Basin, Treasure Valley and
W-Central/Boise mtns. Blowing dust will accompany the winds as
well, especially at lower elevations. This system isn`t
particularly wet (PW values in the 50-60 %tile) with majority of
high res models showing 0.25-0.50"/hr rainfall. While these
amounts aren`t generally a flood concern, will need to keep an
eye on burn scars, especially the Wapiti, which carry lower
thresholds for flood/debris potential. The chance for
thunderstorms carries through sunset for most locations,
lingering through midnight in the Boise mtns. Biggest changes to
the forecast tonight were to increase thunderstorm chances to
30-40% in area where strong outflow winds are more likely (which
also matches up with SPC`s area of Marginal Risk).

Thursday and Friday will see a return to dry weather under
weak troughing in NW flow. Temperatures both days will be at or
slightly below normal. Daytime mixing will bring breezy
conditions on Thursday with gusts of 25-35 mph in Snake Plain
east of Boise.

LONG TERM...Saturday through Wednesday...A strong ridge of high
pressure is expected to slowly build into the area off the
California coast over the weekend, returning a warming and
drying trend from Saturday to early next week. Valley daytime
temperatures are expected to reach the mid to upper 90s Saturday
and Sunday, and close to 100 on Monday. Long-term guidances
generally project an upper trough sweeping across the northwest
region, but precipitation is not hinted by this system.
Wednesday will see a ridge build into the area on top of the
large high pressure system over the desert southwest, continuing
very warm and dry conditions.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning from 3 PM this afternoon to midnight MDT
     tonight IDZ400-420-423-424-426.
OR...Red Flag Warning from 3 PM MDT /2 PM PDT/ this afternoon to
     midnight MDT /11 PM PDT/ tonight ORZ670-672>674.

&&

$$

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DISCUSSION...JDS
AVIATION.....JR
SHORT TERM...DG
LONG TERM....JY