273
FXUS65 KBOI 191231
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
631 AM MDT Sun Jul 19 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Isolated showers and thunderstorms along the Idaho/Nevada
  border today.

- Areas of smoke in southeast Oregon, drifting into southwest
  Idaho through the week.

- Hot temperatures this week, hottest on Monday.

- Showers/thunderstorms increase through midweek with heavy
  rainfall possible especially on Wednesday.

&&

.SHORT TERM /Through Tuesday Night/...
Issued 338 AM MDT SUN JUL 19 2026
Hot and mostly dry conditions are expected today as an upper
level ridge remains centered over the central U.S. An upper
level trough moving across southern Canada will keep the flow
aloft southwesterly and will transport drier air into the
region. However, a 20% chance of showers and thunderstorms will
persist along the Idaho/Nevada border this afternoon with lower
chances elsewhere. Highs today will be similar to yesterday, in
the upper 90s to around 100 degrees in the lower valleys. Smoke
from wildfires mainly in Oregon will persist across southeast
Oregon and increase across southwest Idaho today. Winds will
mostly be light from the northwest, locally breezy in the
afternoon and evening.

On Monday, the ridge will begin to build north along the West
Coast, allowing for a return of southerly flow aloft. Monsoonal
moisture will reenter the area, and a weak impulse early Monday
will generate a 10-20% chance of showers across southeast Oregon
and the west-central Idaho mountains. Temperatures will reach
their peak on Monday before deeper moisture returns, with highs
up to 103 degrees in the Treasure Valley. A Heat Advisory has
been issued for portions of southwest Idaho and southeast
Oregon. Warm overnight lows in the upper 60s to lower 70s at
lower elevations will limit overnight relief. Shower and
thunderstorm chances will rise to 20-40% near the Idaho/Nevada
border in the afternoon/evening. Northwest winds will become
breezy late in the day with wind gusts 15-30 mph. On Tuesday,
increasing moisture will cool temperatures a couple degrees, but
it will still be hot. Shower and thunderstorm chances will
increase across the higher terrain but remain limited over the
lower elevations. Storms will be capable of gusty winds and
brief heavy rain. Smoke will persist across the area Monday and
Tuesday.

&&

.LONG TERM /Wednesday through Sunday/...
Issued 338 AM MDT SUN JUL 19 2026
Shower and thunderstorm potential will increase on Wednesday as
an embedded shortwave trough lifts north through the Great
Basin. This feature should provide additional lift for more
widespread convection with a 20-60% chance of showers/storms
across all areas. Deep monsoonal moisture in place (PW around
1.25 inches / above the 95th percentile) will create a risk of
heavy rain and flash flooding, especially over burn scars and
steep terrain. Starting Thursday, the flow aloft will turn
southwesterly as an upper trough deepens off the Pacific
Northwest coast. This will gradually push deeper moisture to the
east with a drying trend from the west through the end of the
week. By the weekend, only minimal chances for precipitation
will persist across eastern areas. Southwest flow will bring
hot, dry, and breezy conditions late week into the weekend.
Smoke will likely continue to impact much of the area through
the end of the week, especially across southeast Oregon.

&&

.AVIATION /12Z Sunday through Monday/...
Issued 622 AM MDT SUN JUL 19 2026
Mainly VFR. Wildfire smoke across the area will locally reduce
visibility to MVFR/IFR, especially near KBNO. Some improvement
expected in the afternoon. High density altitude this
afternoon due to heat. Isolated thunderstorms along the
ID/NV border this afternoon. Isolated showers/virga lifting
north through SE Oregon overnight. Surface winds: SW-NW 5-15
kt. Winds aloft at 10kft MSL: SW 5-15 kt.

KBOI...VFR. Visibility reduced due to wildfire smoke, although
VFR expected to prevail. High density altitude this afternoon
due to heat. Surface winds: light and variable this morning.
Then NW 7-12 kt with occasional gusts to 20 kt this afternoon.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory from noon to 9 PM MDT Monday for IDZ012-014>016-
     030-033.
OR...Heat Advisory from noon MDT /11 AM PDT/ to 9 PM MDT /8 PM PDT/
     Monday for ORZ063-064.
     Air Quality Alert until noon PDT Monday for ORZ061-062.
&&

$$

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