557
FXUS65 KBOI 122317
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
517 PM MDT Tue May 12 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Record high temperatures this afternoon, where low lying areas
  will see highs in the 90s.

- A cold frontal passage brings very gusty winds, a slight
  chance of thunderstorms, and cooling conditions Wednesday.

- Just above normal temps through Friday before another
  cooldown this weekend, conditions stay dry and breezy.

&&

.SHORT TERM /Through Thursday Night/...
Issued 230 PM MDT TUE MAY 12 2026
High pressure over the area, and mostly clear skies today will
allow temps to climb through late this afternoon. Low-lying
areas including the Snake Plain and valleys in the Boise
Mountains, Weiser Basin, and Malheur County will see temps in
the 90s for their afternoon highs. This threatens daily high
temp records for many locations in Southwest Idaho and Southeast
Oregon. Alongside the hot temps is exceptional dryness. The 18Z
sounding revealed a nearly dry adiabatic atmosphere up to 500
mb. There is just enough moisture at this level to produce some
altocumulus, and with visible virga there is a slim chance for
strong winds near the clouds. Right now, this seems very
unlikely given the depth of the dry layer and limited moisture
available to convection.

Temperatures cool quickly after sunset as the focus shifts to a
quickly encroaching upper level low moving inland. This low will
carry a strong cold front through most of the intermountain
west. The primary hazard for our area as this front moves
through is the winds. Late in the morning through the early
evening, wind gusts increase to 40-55 mph across open areas and
ridges. A Wind Advisory has been issued in the areas expected
to see the strongest winds. Outside of the advisory, winds will
still gust 30-40 mph throughout the day save for a few very
sheltered mountain valleys. Winds will kick up dust, especially
along the front, leading to reduced visibilities. In the
morning and early afternoon, as the front itself passes,
thunderstorms will be possible. Gusts out of thunderstorms could
locally enhance the already gusty conditions in parts of the
upper Snake Plain. The enhancement could briefly take winds up
to 60 mph. Forecasts, however, continue to favor thunderstorm
development over the West Central and Central Idaho mountains.
Moderate rain and small hail will also be possible in storms.

Winds finally begin to weaken after sunset, but remain elevated
overnight. Behind the front, temps on Thursday will be seasonal
across the area. Winds stay elevated through the day, especially
in Central and South-Central Idaho and Central Oregon. While
Tuesday is the driest day, afternoon minimum relative humidities
remain in the teens for southern areas each day. The coincidence
of dry air and gusty winds highlights elevated fire weather
conditions, especially Wednesday.

&&

.LONG TERM /Friday through Tuesday/...
Issued 230 PM MDT TUE MAY 12 2026
Good model agreement in the overall large scale pattern Friday
through Sunday. Dry westerly flow Friday with temperatures around
normal. A substantial cool down for the weekend (temperatures 10
degrees below normal) as a shortwave trough moves across the area.
Not a lot of moisture expected with this system so there`s only a
low end chance (20-30 percent) of precipitation for northern Baker
County and portions of the West Central and Boise Mountains. Expect
breezy NW winds Saturday and Sunday afternoon, especially across
Baker County and the Snake River Plain. Temperatures expected to
trend up with dry conditions on Monday. Forecast uncertainty grows
Tuesday with some model guidance suggesting another shortwave trough
with limited moisture may move across the region.

&&

.AVIATION /00Z Wednesday through Thursday/...
Issued 509 PM MDT TUE MAY 12 2026
VFR with some shallow convection near terrain this evening.
Isolated storms could produce localized gusty winds. Significant
cold front to pass through the area Wednesday morning, with a
dramatic shift in wind direction and increase in wind speed.
Frontal passage 15-17Z for Oregon sites and 17-20Z for Idaho
locations. Surface winds SSE 10-20 kt with higher gusts this
evening, becoming SSW 10-20 kt overnight, then WNW 20-30 kt with
higher gusts after frontal passage. Periods of LLWS possible
near the front. Winds aloft at 10kft MSL: SSW 20-25 kt.

KBOI...VFR. Significant cold frontal passage 17-19Z Wednesday,
with strong winds expected. Surface winds ESE 10-12 kt with
gusts in the evening, becoming WNW 20-25 kt with gusts to 35 kt
after 17Z.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from noon Wednesday to midnight MDT Wednesday
     night for IDZ012-014>016-028>030.
OR...Wind Advisory from noon MDT /11 AM PDT/ Wednesday to midnight
     MDT /11 PM PDT/ Wednesday night for ORZ063-064.
&&

$$

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AVIATION.....MC
SHORT TERM...JM
LONG TERM....TL