269
FXUS65 KBOI 071557
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
957 AM MDT Sun Jul 7 2024

.DISCUSSION...A high pressure system remains just off the West
Coast this morning with northwesterly flow aloft. As the ridge
begins to move inland over the next several days, the
temperatures will warm to near record values Tuesday through
Thursday. No updates.

&&

.AVIATION...VFR and clear. High density altitude due to hot daytime
temperatures. Surface winds: variable less than 10 kt, then N-NW 10-
15 kt with gusts to 20 kt after Sun/18Z. Winds aloft at 10kft MSL:
NW 10-20 kt.

KBOI...VFR and clear. High density altitude due to hot daytime
temperatures. Winds generally variable and less than 5 kt through
07/18Z, then NW 08-12 kt with gusts to 18 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...An upper level
trough will move into the Great Plains, increasing the pressure
gradient with northerly flow as the deep high pressure system
moves onto the California Coast from the Pacific. This
northwesterly flow will bring breezy winds, especially near the
Nevada border on Sunday afternoon. Daytime heating will lead to
mainly diurnal wind shifts after Sunday, with light overnight
winds and breezy afternoon winds in the Snake River Valley on
Monday and Tuesday.

Northwesterly flow will allow for slight cooling on Sunday
before the massive warming trend beginning Monday. There is
increasing confidence of dangerous heat beginning in valleys as
early as Monday evening, although the most extreme heat still
looks to occur later in the week. Overnight lows will dip into
the 60s-70s for most valley locations and the 50s for higher
elevations, which will bring needed relief from triple digit
highs. Very low relative humidities across the region will
exacerbate extremely hot conditions, leading to rapid
dehydration and onset of heat illness if there is prolonged
exposure.


LONG TERM...Wednesday through Sunday...The most extreme heat of
the week will occur as the ridge axis passes over the region on
Wednesday, with about a 20% chance of the Treasure Valley
exceeding 110F. This would bring us very close to the all time
record high temperature of 111F at the Boise airport. The
extreme heat will continue through Friday as the high pressure
system slowly moves East. HeatRisk shows widespread major with
pockets of extreme impacts by Wednesday in many areas of the
Snake River Valley.

By Saturday night, deterministic models show good agreement in
a weak monsoon push, with warm southerly upper level flow
allowing for some pulses of moisture into the region. High
uncertainty remains in the extent and amount of moisture that
will move into the region next weekend, but there is at least a
10% chance of showers and thunderstorms, a welcome relief to the
extreme heat wave.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Watch from Tuesday afternoon through Friday
     evening IDZ011-013-028.
     Excessive Heat Watch from Monday afternoon through Friday
     evening IDZ012-014>016-029-030-033.
OR...Excessive Heat Watch from Monday afternoon through Friday
     evening ORZ061>064.

&&

$$

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DISCUSSION...KA
AVIATION.....JM
SHORT TERM...SA
LONG TERM....SA