525
FXUS65 KBOI 191018
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
418 AM MDT Wed Aug 19 2026

.KEY MESSAGES...
- Heat Advisory Thursday and Friday for lower elevations as
  temperatures push above 100 degrees.

- Increased chance of showers and thunderstorms over higher
  terrain Friday and Saturday.

- Above normal temperatures next week with a chance of
  thunderstorms over the mountains of southwest Idaho.


&&

.SHORT TERM /Through Friday Night/...
Next few days will see heat build over the region as the Desert
SW ridge expands northward. Guidance has edged higher over the
past 24h, pushing more lower elevation sites in the 98-104 range
for Thur/Fri. Certainly 850-700 thickness values would support
hotter temperatures than NBM has for these days so have trended
the forecast highs warmer, especially on Friday which will be
the hottest day. Resulting highs and overnight lows (Thursday
night) supported issuance of a Heat Advisory Thur/Fri across
the Snake Plain and Weiser Basin. Otherwise looking at dry
conditions across the area today. The building upper ridge will
push monsoon moisture back to the ID/NV border on Thursday,
then northward through into w-central Idaho on Friday, resulting
in a chance of thunderstorms each afternoon. Precipitation
chances have increased to 30-50% for Friday/Friday night across
the western Magic Valley and eastern Boise mtns. The initial
push of thunderstorms will likely produce more wind than rain on
Friday as the near surface layer is fairly dry.

&&

.LONG TERM /Saturday through Wednesday/...
An upper trough will enter the Pac NW on Saturday, tracking
northeastward into Canada by Sunday. Gusty southwest winds
develop across open terrain in SE Oregon and SW Idaho south of
the Snake Plain on Saturday bringing elevated fire weather
conditions. Forecast temperatures have continued to edge warmer
for Saturday as guidance is delaying a frontal passage until
the late afternoon/evening. Seeing a growing number solutions
keep lower elevations in the upper 90s, which is warmer than
the current NBM. Increased moisture aloft (precipitable water
values reaching the 80th percentile) will support a 20-50%
chance of afternoon/evening thunderstorms over w-central and
s-central ID and the mtns of Baker County. Gusty winds and brief
heavy rain could accompany storms.

The remainder of the extended period will be defined by the
persistent Four Corners ridge which will place our region under
southwest flow. Near normal temperatures Sunday, will be on the
rise next week as the ridge rebounds. Moisture circling the
ridge will keep a chance of afternoon thunderstorms mostly
across SW Idaho zones.

&&

.AVIATION /06Z Wednesday through Thursday/...
Issued 1216 AM MDT WED AUG 19 2026
VFR under mostly clear skies. Patchy smoke in e-central Oregon
valleys through mid-morning Wed. Surface winds: less than 10kt
through Wed. Winds aloft at 10kft MSL: SW-W 5-15 kt.

KBOI...VFR under mostly clear skies. Light surface winds
through Wednesday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Heat Advisory from noon Thursday to 9 PM MDT Friday for IDZ012-
     014-016-033.
OR...Heat Advisory from noon MDT /11 AM PDT/ Thursday to 9 PM MDT
     /8 PM PDT/ Friday for ORZ064.
&&

$$

www.weather.gov/Boise

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

SHORT TERM...DG
LONG TERM....DG
AVIATION.....DG