300
FXUS65 KBOI 182326
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
526 PM MDT Tue Aug 18 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Temperatures warming through the end of the week with lower
  elevations around 100 degrees Thursday and Friday.

- Increased chance of showers and thunderstorms over higher
  terrain this weekend and into next week.

&&

.SHORT TERM /Through Thursday Night/...
Issued 232 PM MDT TUE AUG 18 2026
A ridge of high pressure will continue to build into the region
through the work week, bringing a steady warming and drying
trend. Clouds have decreased across most of the region today,
with a scattered cumulus build ups over high terrain in Central
Idaho and near the ID-NV border. A few virga showers will
continue near the ID-NV border through the evening, otherwise
mostly clear and warm conditions will continue. Temperatures
will increase to about 8-12 degrees above normal by Thursday,
with lower elevations reaching near or slightly above 100F. A
push of monsoon moisture will primarily stay to our south on
Thursday afternoon, although there is a low chance (10-20%) of
showers and thunderstorms over the Magic Valley late Thursday.
Rainfall accumulations will be minimal with any thunderstorms
that form, so gusty outflow winds and lightning are the primary
concerns.

&&

.LONG TERM /Friday through Tuesday/...
Issued 232 PM MDT TUE AUG 18 2026
Southerly flow aloft brought about by the offshore Pacific low
pressure system and the Four Corners upper-level ridge will keep
temperatures hot on Friday. Another day of 100 degree heat to lower
elevations is expected. The upper-level trough will move inland late
Friday into Saturday, moving through the Interior NW on Saturday.
Cooling aloft and increased moisture will support a 20-30% chance of
showers and thunderstorms across higher terrain of e-central Oregon
and SW Idaho Friday, shifting to mostly SW Idaho for Saturday and
Sunday. Temperatures will be cooler behind this disturbance,
lowering to near-normal Saturday and Sunday. Long-range models hint
at the Four Corners ridge rebuilding over the area early next week
with temperatures warming again. The real question will be moisture
early next week; some models show a strong surge with high
precipitation chances and QPF totals, while others show a more
limited scenario. The current forecast shows somewhere in the
middle, with a 10-30% chance of showers/storms over SW Idaho.

&&

.AVIATION /00Z Wednesday through Thursday/...
Issued 520 PM MDT TUE AUG 18 2026
VFR with scattered cumulus over most areas. Isolated
showers/thunderstorms continuing north and east of KMYL and
higher terrain south of KTWF through around Wed/03Z. High
density altitude in hot afternoon temperatures through sunset.
Patchy smoke near KBKE and KMYL late tonight through Wednesday
morning. Surface winds: W-NW 5-15 kt, becoming NW or variable
under 8 kt tonight. Winds aloft at 10kft MSL: W 5-20 kt.

KBOI...VFR with mostly clear skies. Surface winds: NW 6-10 kt
this evening, becoming variable under 7 kt after sunset.

&&

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

OR...None.

&&

$$

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AVIATION.....JY
SHORT TERM...SA
LONG TERM....CH