440
FXUS65 KBOI 230857
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
257 AM MDT Sun Jun 23 2024

.SHORT TERM...Today through Tuesday night...Temperatures in the
Treasure Valley could reach 100 degrees again today. However,
the arrival of the next Pacific system moving inland across
British Columbia will increase westerly flow aloft, leading to
breezy northerly surface winds in the valley and westerly winds
elsewhere. Expect wind gusts of 25-35 mph in higher elevations,
while winds will be lighter in lower elevations. This setup is
likely to result in slightly cooler temperatures today. Ensemble
probabilities for temperatures reaching 100 degrees or higher
are between 30-70%, with Ontario having the highest probability
at 70% due to warmer surface temperatures from northerly
downslope winds. Hot, dry, and breezy conditions will promote
active fire behavior this afternoon, potentially causing smoke
plumes and hazy conditions, especially east-northeast of the
fire in southwest Owyhee County.

As the Pacific system continues east across West-Central Canada
on Monday, a surface cold front will pass through, bringing
cooler temperatures with valley highs around the mid-90s.
However, the air mass will remain too dry for any precipitation
with the frontal passage.

A stronger Gulf of Alaska trough will approach the Pacific
Northwest coast on Tuesday, causing the upper-level flow to
shift to south-southwest, bringing hot temperatures back to the
forecast area. Ensemble guidance indicates a 25% chance of high-
based moisture from the southwestern U.S. reaching the
Idaho/Nevada border Tuesday night, potentially leading to
thunderstorms. Temperatures in the Treasure Valley will again
approach 100 degrees on Tuesday, with a 20-30% chance of
reaching or exceeding 100 degrees.

.LONG TERM...Wednesday through Sunday...The Gulf of Alaska
trough will move inland across western Canada and the Pacific
Northwest on Wednesday, keeping the forecast area in the warm
sector for another hot and mostly dry day. The southerly flow
might bring enough high-based moisture for afternoon
thunderstorms in south-central Idaho. The associated cold front
is expected to reach the forecast area on Thursday, bringing
significantly cooler temperatures and breezy westerly winds. A
temperature drop of about 20-25 degrees is possible, which could
result in below-normal temperatures on Thursday and Friday.
There is around a 90% chance that temperatures will remain below
90 degrees on both days. While the air mass will remain mostly
dry, there could be enough moisture in the West Central
Mountains of Idaho for showers and thunderstorms on Thursday and
Friday. The strongest winds are expected on Thursday with the
passage of the upper-level trough and jet. Temperatures will
rebound into the low 90s next weekend as another ridge develops
in response to another Pacific trough.

&&

.AVIATION...VFR. Mostly clear skies. Hot temperatures will
bring high density altitudes. Reduced visibilities from smoke
near a prescribed fire in SW Idaho. Surface winds: variable 10
kt or less becoming W-SW 10-20 kt with gusts to 30 kt after
Sun/18Z, strongest in the higher terrain. Winds aloft at 10kft
MSL: W-SW 15- 25 kt.

KBOI...VFR. Mostly clear skies. Hot temperatures will bring high
density altitudes. Surface winds: variable 10 kt or less then
N-NW 5-10 kt after Sun/15Z.

&&

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

&&

$$

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SHORT TERM...JDS
LONG TERM....JDS
AVIATION.....JDS