412
FXUS65 KBOI 181211
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
611 AM MDT Sat Jul 18 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Showers/thunderstorms across south-central Idaho and the
  central Idaho mountains this afternoon. Storms will be capable
  of brief heavy rainfall, gusty outflow winds and small hail.

- Areas of smoke in southeast Oregon, increasing across
  southwest Idaho through the weekend and into next week.

- Hot temperatures through next week, with valley highs in the
  upper 90s to around 100 degrees, hottest Monday.

- Showers/thunderstorms increase next week with heavy rainfall
  possible.

&&

.SHORT TERM /Through Monday Night/...
Issued 330 AM MDT SAT JUL 18 2026
An upper level low moving into southern British Columbia today
will help flatten a ridge centered over the central/western U.S.
As a result, the flow aloft will veer from southerly to
southwesterly. This will push deep monsoonal moisture to the
east, decreasing shower and thunderstorm coverage compared to
previous days. Isolated to scattered storms will develop this
afternoon along the higher terrain near the Idaho/Nevada border
and over the central Idaho mountains. Showers/storms may drift
north into the Magic Valley before dissipating. Thunderstorms
will be capable of brief heavy rain, small hail, and gusts 30-50
mph. Moisture will continue to decrease on Sunday with only
isolated activity along the Nevada border. Temperatures today
and Sunday will remain hot with lower valley highs in the upper
90s to around 100 degrees.

The pattern will begin to shift Monday as the ridge extends north
along the West Coast. The flow aloft will once again become
southerly, transporting monsoonal moisture back into the area.
A resulting 20-40% chance of showers and thunderstorms will
develop near the Idaho/Nevada border in the afternoon/evening.
Highs will rise a few more degrees, with lower valleys reaching
100-105 degrees.

Outside of storms, winds will be typical, except breezy late
Monday with gusts 15-30 mph. Westerly to northwesterly surface
winds will transport wildfire smoke into southeast Oregon, with
smoke also likely to increase across southwest Idaho through the
weekend and into early next week.

&&

.LONG TERM /Tuesday through Saturday/...
Issued 330 AM MDT SAT JUL 18 2026
Deep monsoonal moisture will increase through the middle of the
week under southerly flow aloft. Ensemble-mean precipitable
water values increase to around 1.25 inches by Tuesday and
Wednesday, or above the 95th percentile. Shower/storm chances
increase to 20-50% across the higher terrain on Tuesday, then
across all areas Wednesday and Thursday as deterministic models
hint at shortwave impulses aiding development. The deep
moisture and potential for slower storm motion will result in
heavy rain and flooding concerns through much of the week. On
Friday and Saturday, an upper trough entering the Pacific
Northwest should begin to push the moisture to the east, with
precipitation chances gradually decreasing from the west. The
ridge will keep temperatures hot through the period, averaging a
few degrees above normal. Smoke will likely continue to impact
much of the area through the week, especially across southeast
Oregon.

&&

.AVIATION /12Z Saturday through Sunday/...
Issued 605 AM MDT SAT JUL 18 2026
Mainly VFR. Wildfire smoke will reduce visibility at times in
SE Oregon today, possibly extending into SW Idaho tonight.
Isolated shower and storm development over Central and S-Central
Idaho this afternoon with gusty winds and locally heavy
rainfall. High density altitude due to heat in the afternoon.
Surface winds: NW or variable 5-12 kt. Localized gusts 15-25 kt
late this afternoon and evening. Winds aloft at 10kft MSL: S-SW
5-15 kt.

KBOI...VFR with some haze due to wildfire smoke. High density
altitude due to heat in the afternoon. Surface winds variable
less than 8 kt this morning, becoming NW 7-12 kt with gusts up
to 20 kt this afternoon, then light and variable overnight.

Sunday Outlook...High density altitude due to heat. Areas of
smoke reducing visibility mostly across SE Oregon and near the
OR/ID border in SW Idaho. Surface winds: SW-NW 5-15 kt,
afternoon gusts 15- 25 kt.

&&

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

OR...Air Quality Alert until noon PDT Monday for ORZ061-062.
&&

$$

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