063
FXUS65 KBOI 221218
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
618 AM MDT Wed Jul 22 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Numerous showers and thunderstorms today across the central
  Idaho mountains. Thunderstorms may produce heavy rain,
  creating a risk of flash flooding and debris flows,
  especially over burn scars and steep terrain.

- Isolated to scattered showers and thunderstorms elsewhere
  today and Thursday, with brief heavy rain and gusty winds
  possible.

- Areas of smoke will continue through the week.

- Very hot, dry, and breezy to end the week.

&&

.SHORT TERM /Through Friday Night/...
Issued 340 AM MDT WED JUL 22 2026
An upper level ridge centered across the south-central U.S. and
extending into the Pacific Northwest, combined with a trough
off the coast, will continue to transport monsoonal moisture
across the area under southerly flow. A shortwave impulse will
lift north out of Nevada bringing scattered showers to southwest
Idaho this morning. This afternoon, the wave will move into
central Idaho, producing numerous showers and thunderstorms over
the mountains. Thunderstorms will be capable of producing heavy
rain, creating a risk of flash flooding and debris flows,
especially over burn scars and steep terrain. A Flash Flood
Watch remains in effect for the Wapiti burn area this afternoon
and early evening. Additionally, there will be enough
instability for isolated to scattered showers and thunderstorms
across most of southeast Oregon and the higher terrain south of
the Snake River in southwest Idaho. Heavy rain will be possible
in stronger storms with gusts to 45 mph. Most lower elevations
will see a less than 20% chance of showers and thunderstorms
today. Temperatures will be slightly lower today due to
increased cloud cover and precipitation. Areas of smoke from
regional wildfires will persist today, especially across east-
central Oregon and west-central Idaho into the Treasure Valley.

On Thursday, the flow aloft will turn southwesterly as the ridge
axis starts to move east, pushing deeper monsoonal moisture out
of the area. However, a weak impulse ahead of the trough off
the coast will bring a 10-30% chance of showers and
thunderstorms to eastern Oregon and western Idaho in the
afternoon and evening. Instability will extend into the lower
elevations, bringing a better chance for thunderstorms to reach
the Treasure Valley than previous days. Storms will be capable
of gusty winds. Otherwise, southwest flow will bring hotter
temperatures with lower valleys forecast to reach just over 100
degrees. Winds will become breezy in southeast Oregon. This
trend will continue into Friday as gusts 20-35 mph overspread
the higher elevations. Temperatures will be very hot with lower
valleys approaching 105 degrees. Much drier air will arrive from
the west, limiting thunderstorm potential to south-central
Idaho and increasing fire weather concerns. Southwest flow
aloft will transport some of the smoke away from the area, but
drainage winds each night will continue to bring smoke impacts
to some areas.

&&

.LONG TERM /Saturday through Wednesday/...
Issued 340 AM MDT WED JUL 22 2026
A hot, dry, and breezy pattern will continue through the
extended as southwest flow aloft persists between upper
troughing along/off the coast and an upper ridge over the south-
central U.S. Highs Saturday will remain very hot, forecast to
exceed 100 degrees once again in the lower valleys. Winds will
increase further ahead of a trough moving into western
Washington, with widespread gusts 20-35 mph, strongest over
higher terrain. Additionally, relative humidity will be very low
resulting in elevated fire weather concerns. The trough will
bring a slight cooldown Sunday into early next week, but it will
still be hot and dry with lower valleys reaching the mid 90s.
Winds will subside after Saturday, but it will still be breezy
each afternoon. Dry air will keep shower and thunderstorm
chances less than 10%.

&&

.AVIATION /12Z Wednesday through Thursday/...
Issued 604 AM MDT WED JUL 22 2026
Generally VFR, localized MVFR/IFR due to wildfire smoke across
mainly SE Oregon with improvement during the day. Scattered
showers lifting north this morning, increasing with
thunderstorms developing over the higher terrain this
afternoon. Thunderstorms could bring torrential rain, wind gusts
to 40 kt, and MVFR/IFR conditions with terrain obscuration,
most likely across central Idaho. High density altitude due to
continued hot temperatures. Surface winds: variable less than 10
kt this morning, becoming W-NW 5-15 kt in the afternoon. Winds
aloft at 10kft MSL: variable 5-10 kt.

KBOI...Generally VFR, a low chance of MVFR visibility due to
wildfire smoke. Mid/high clouds today with isolated showers.
Variable outflow gusts from distant thunderstorms possible late
this afternoon and evening, but low confidence. High density
altitude this afternoon due to heat. Surface winds: variable
less than 8 kt becoming WNW 5-10 kt late morning and afternoon.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Quality Alert until 3 PM MDT this afternoon for IDZ011-012-
     014-033.
     Flash Flood Watch from noon MDT today through this evening for
     IDZ013.
OR...Air Quality Alert until 1 PM MDT /noon PDT/ this afternoon for
     ORZ061>064.
&&

$$

www.weather.gov/Boise

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

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