FXUS65 KBOI 200606
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1206 AM MDT Wed May 20 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Mostly dry with temperatures warming through Friday. 

- Well above normal temperatures over Memorial Day Weekend.
  Gusty winds and a few mountain showers on Memorial Day.

- Turning cooler with gusty winds and increasing chance of 
  precipitation starting Tuesday.

&&

.SHORT TERM /Through Thursday Night/...
Issued 157 PM MDT TUE MAY 19 2026
Our region will remain positioned on the western edge of upper 
level troughing through Thursday. While the focus of organized 
precipitation will remain to our east, daytime instability will 
support widespread cumulus buildups over the mountains as seen 
this afternoon. There's a slight chance that showers could 
develop from the cumulus field across e-central Oregon and 
w-central Idaho mtns each afternoon. Localized gusty winds will
be possible from showers or more robust cumulus (with or w/o 
precipitation). Shower chances briefly increase to 15-25% in the
w-central Idaho mtns and s-central Idaho zones Wednesday night 
in response to a passing shortwave trough. Otherwise it's dry 
and temperatures are on the way up, leaving behind any 
frost/freeze concerns for the Snake Plain. By Thursday high 
temperatures will be several degrees above normal.

&&

.LONG TERM /Friday through Tuesday/...
Issued 157 PM MDT TUE MAY 19 2026
A ridge of high pressure will build over the Western US by the
end of this week, bringing generally clear, warm and dry 
conditions to the region through Monday. Temperatures will be 
about 10-15 degrees above normal. The ridge will reach peak 
strength on Sunday, with high temperatures near 90F in the 
Treasure Valley. By Monday, models indicate that an upper level 
low moving into the Pacific Northwest will begin to increase 
chances for precipitation. The upper level trough will move 
inland on Tuesday, with about half of the models showing that 
the trough will evolve into a closed low over the Pacific NW by 
Tuesday or Wednesday. In either scenario, temperatures will cool
down 10-20 degrees by Tuesday increasing winds and chance of 
showers and thunderstorms (20-30% chance).

&&

.AVIATION /06Z Wednesday through Thursday/...
Issued 1159 PM MDT TUE MAY 19 2026
VFR. Scattered to broken middle and high clouds. Isolated rain
showers in the central Idaho mountains and in southern Twin
Falls County after 20Z. Surface winds variable less than 10 kt,
becoming WNW 10-20 kt after 20Z. Gusts to 25 kt in the Snake 
Basin east of KBOI after 20Z. Winds aloft at 10kft NW 15-20 kt.

KBOI...VFR. Scattered to broken clouds AOA 15kft. Surface winds
SE 5-10 kt, becoming WNW 10-20 kt after 20Z.

&&

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

OR...None.

&&

$$

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AVIATION.....LC
SHORT TERM...DG
LONG TERM....JB