365
FXUS65 KBOI 010001
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
601 PM MDT Mon Aug 31 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Warm today and Tuesday.

- Isolated thunderstorms in S-central ID this evening,
  increasing across Central ID Tuesday afternoon/evening.

- A strong low pressure system later this week will bring
  cooler and windier conditions with periods of showers and
  thunderstorms, especially to Oregon and west-central Idaho.

&&

.SHORT TERM /Through Wednesday Night/...
Issued 236 PM MDT MON AUG 31 2026
A fall-like pattern will bring active conditions to our area
through the period. Isolated thunderstorms will develop this
evening across south-central Idaho. Then, a longwave trough
will approach the Pacific Northwest tonight into Tuesday. The
system will place our area in southerly flow aloft, keeping
temperatures warm with highs near normal. Monsoonal moisture
will increase in the southerly flow with isolated showers moving
across the area in the morning, then deepening across central
Idaho in the afternoon with showers and thunderstorms in the
eastern mountains. Thunderstorms may produce brief heavy
rainfall, small hail, and gusty winds to 50 mph. Conditions will
be drier to the west with little to no storm development across
far western Idaho and southeast Oregon. Winds Tuesday will be
breezy with gusts 15-30 mph, which combined with low afternoon
humidity will produce elevated fire weather concerns across
southeast Oregon and southern Idaho.

A shortwave trough will rotate across our area on Wednesday.
This will interact with weak instability across central Idaho to
produce another round of showers and a 20% chance of
thunderstorms in the morning across the central Idaho mountains
and northeast Oregon with mostly dry conditions elsewhere.
Cooler air accompanying the shortwave will drop temperatures to
around 10 degrees below normal. Winds will remain elevated on
Wednesday with gusts 20-35 mph. Another shortwave trough will
approach from the west Wednesday night bringing another round of
showers to southeast Oregon and west-central Idaho.

&&

.LONG TERM /Thursday through Monday/...
Issued 236 PM MDT MON AUG 31 2026
The pattern will remain active through the weekend as an upper
low spins over the Pacific Northwest. Moisture will continue to
move east through the area Thursday morning, with a 40-70%
chance of showers in the Treasure Valley. Higher precipitation
chances will prevail across southeast Oregon and the central
Idaho mountains. A 10-30% chance of thunderstorms will develop
in the afternoon and evening with daytime heating. Moderate
precipitation totals Wednesday night into Thursday are forecast
in the mountains, with locally heavy amounts possible from
thunderstorms. Precipitation chances will be minimal in the
Magic Valley as the low stalls. Temperatures will cool another
few degrees to end up 10-15 degrees below normal. Winds will
remain gusty across the area, especially higher terrain and near
the Nevada border.

Additional impulses will rotate around the main upper low
stalled across the Pacific Northwest through the end of the
period, bringing rounds of showers to the area, with
thunderstorm potential each afternoon and evening. Temperatures
are expected to remain below normal through the end of the
period, although a gradual warming trend is forecast by the
weekend into early next week. However, forecast confidence late
in the period is low due to interaction between tropical
activity off the coast of Baja California and the upper low
over the Pacific Northwest. There is potential for entrainment
of tropical moisture across the West under southerly flow aloft,
but models vary considerably, so this potential will continue
to be monitored.

&&

.AVIATION /00Z Tuesday through Wednesday/...
Issued 554 PM MDT MON AUG 31 2026
VFR in most areas of southwestern Idaho and southeastern Oregon
through Wednesday. Expect some reduction in visibility from a
wildfire located southwest of KBKE and from another wildfire
in the Boise National Forest well to the NE of KBOI. There is
about a 30 percent for showers and thunderstorms with gusty
winds for Tuesday afternoon...mainly in southwestern Idaho.
Surface winds favoring an ESE direction, except SW in eastern
Oregon, with speeds peaking at 10-15 kt this afternoon.

KBOI...VFR with diurnal winds less than 10 kt. Potential for
showers and thunderstorms near the terminal on Tuesday
afternoon.

&&

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

&&

$$

www.weather.gov/Boise

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AVIATION.....JB
SHORT TERM...ST
LONG TERM....ST