812
FXUS65 KBOI 050232
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
832 PM MDT Thu Jul 4 2024

.DISCUSSION...This evening will continue to be warm with light
winds and clear skies. Winds will continue to diminish as the
sun sets, generally blowing from the west-northwest at 5-10 mph
in the Western Snake River Plain.

On Friday, an upper-level ridge will build along the coast,
tightening the pressure gradient across the forecast area as low
pressure remains over the northern plains. This will increase
surface winds Friday afternoon, especially from Mountain Home
through the Western Magic Valley. Temperatures will rise by
another 5 degrees, reaching the mid-90s in the valley. Surface
winds will further increase on Saturday as a shortwave and jet
max move through the northwesterly flow. Expect dry conditions
with wind gusts up to 35 mph and temperatures close to 100
degrees in the lower valleys.

A heat wave is expected to begin on Sunday across the
Intermountain West, with temperatures likely to exceed 100
degrees and continue through at least next Thursday. The NBM
and GFS models remain on the higher end of all temperature
guidance, with the deterministic GFS being the highest,
sometimes by over 5 degrees. There is about a 25% chance that
temperatures could exceed 109 degrees on Wednesday and
Thursday.Most guidance shows monsoonal moisture from the
southwestern U.S. reaching the region by Wednesday, which is
typical with this synoptic pattern. The increased cloud cover
could keep temperatures from reaching their full potential.

The Excessive Heat Watch has been updated to include the West
Central and Boise Mountain valleys and Camas Prairie from
Tuesday through Thursday. Winds for Friday and Saturday have
also been updated as the latest guidance indicates higher winds.
Sent the forecast update out 8 PM MDT.

&&

.AVIATION...VFR. Haze from fireworks is likely near populated areas.
Surface winds: W to NW 5-15 kt becoming variable 10 kt or less
overnight. Winds aloft at 10kft MSL: NW 10-20 kt.

KBOI...VFR. Haze from fireworks is likely. W to NW 5-15 kt, becoming
variable or southeast 3-6 kt after 05/05Z. Then W to NW 5-15 kt
Friday afternoon.

Weekend Outlook...VFR and mostly clear. High density altitude due to
hot temperatures. Variable winds less than 10 kt during the late
evenings through mornings, and generally NW 5-15 kt with gusts of 15-
25 kt during the afternoons and early evenings.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday night...Dry and getting
hot. The Excessive Heat Watch will be maintained this afternoon
with no changes. The models are consistent with their depiction
of an extreme heat event beginning Saturday and extending deep
into next week. Temps Friday will be around 5 degrees above
normal, but will be closer to 10 above normal Saturday. There`s
roughly a 60% chance of getting to 100 in Ontario Saturday, and
around a 30% chance in Caldwell/Nampa/Meridian/Boise/Mountain
Home.

Breezy conditions will develop mainly south and east of
Mountain Home tomorrow afternoon/evening, and again and even
stronger Saturday afternoon. This, along with low RH values, has
resulted in the issuance of a Fire Weather Watch (see the fire
weather watch for details). So please be careful with fireworks
- any fires that get started tonight will have an above-normal
chance to really get going tomorrow and into the weekend.

LONG TERM...Sunday through Thursday...Temps will remain hot and
get hotter through the long term period. The latest forecast
calls for readings above 100 in lower elevations Monday through
Thursday, with Wed and Thu expected top be the hottest days.
Records will be set through this period in many locations, and
all-time records may be reached. The all-time record for Boise,
for example, is 111. The latest forecast for Wed is 108, but
there`s a 40% chance of above 110 according to the NBM. Moisture
will eventually work its way around the west side of the ridge
and into our area next week, but uncertainty in timing is high.
Cloud cover associated with this moisture is the main factor
bringing uncertainty to the temperature forecast, as the models
are very consistent with the overall pattern.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Watch from Tuesday morning through Thursday
     evening IDZ011-013-028.
     Excessive Heat Watch from Saturday afternoon through Thursday
     evening IDZ012-029.
     Fire Weather Watch Friday evening IDZ424-426.
     Excessive Heat Watch from Monday afternoon through Thursday
     evening IDZ014>016-030-033.
OR...Excessive Heat Watch from Saturday afternoon through Thursday
     evening ORZ061>064.

&&

$$

www.weather.gov/Boise

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

DISCUSSION...JDS
AVIATION.....SH
SHORT TERM...SP
LONG TERM....SP