793
FXUS65 KBOI 210229
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
829 PM MDT Sat Jul 20 2024

.DISCUSSION...Forecast is on track for tonight so no updates. We
saw a few showers and thunderstorms over the eastern Boise
mountains and along the northern NV border this afternoon that
are on their way down with sunset. The rest of tonight will be
dry and mild across the region. Evening satellite imagery
showing thick smoke coming from the Falls Fire and especially
the Durkee Fire. Current winds aloft are transporting it to the
east and southeast and this movement will continue overnight. In
the Snake Plain an increase in easterly low-level winds could
bring some improvement in smoky conditions near the surface (the
easterly winds only extend up to ~10kft MSL) while smoke
thickens aloft. Any improvement would likely be short-lived due
to daytime mixing. Otherwise see little change in thunderstorm
potential tomorrow afternoon across SE Oregon and SW Idaho south
of the Snake Plain. Gusty outflow winds up to 55 mph will
accompany cells that develop with the potential for outflow to
impact sites well away from showers/storms, though likely at
lower speeds.

&&

.AVIATION...Low VFR/MVFR visibility due to smoke. Local IFR near
KBNO-KBKE-KONO. High density altitude due to heat. Numerous showers
and thunderstorms after Sun/18Z in E Oregon and far SW Idaho,
capable of 30-45 kt outflow winds and brief rain. Surface winds:
easterly or variable 5-15 kt overnight into Sunday. After Sun/14Z, E
10-20 kt with gusts 25-30 kt for KJER-KTWF-KMUO. Winds aloft at
10kft MSL: variable 5-15 kt.

KBOI...Low VFR/MVFR visibility due to smoke. High density altitude
due to heat. Surface winds: generally SE 5-12 kt overnight through
Sunday afternoon. Sunday P.M. showers/thunderstorms along the OR/ID
border could bring 25-35 kt outflow wind gusts toward the terminal
after Mon/00Z.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday night...Continued hot and
smoky, but smoke from Oregon wildfires has become thick enough
to slightly lower afternoon temps in eastern Oregon and western
Idaho. Still hot enough to maintain Excessive Heat Warning and
Heat Advisory through at least Wednesday evening in the zones
listed below. An upper ridge has become well- established over
the interior west from the southern Great Basin northward
through the Intermountain region and into Alberta. Latest models
move a Pacific short wave trough northeastward along the OR and
WA coasts Sunday and Sunday night, similar to a week ago. The
trough will develop scattered thunderstorms in eastern Oregon
Sunday afternoon and especially Sunday evening, with Harney and
southern Malheur Counties affected most. Storms will mainly
feature lightning and gusty outflow winds, but also a 30-60
percent chance of measurable rain reaching the ground Sunday
evening. On Monday the trough and thunderstorms will be in WA,
but models show more thunderstorms developing Monday afternoon
and evening along the Nevada border and in eastern parts of
Valley and Elmore Counties.

LONG TERM...Tuesday through Saturday...Initially, an upper level
ridge will be centered over NV, with an axis extending north
through our area, then northeast into MT. A deep upper-level low
will be centered off the coast of western Canada. The low is
forecast to move slowly east through western Canada, while the
ridge is forecast to drift south toward the US/Mexico border.
As a result, southwest flow aloft will move into and remain
over our area. Heights will fall and temperatures will cool
after Wednesday. This southwest flow will push most of the
moisture out of the area to the east. However, there should be
enough moisture remaining over south-central and far southwest
Idaho for isolated to scattered showers and thunderstorms most
afternoon and evenings all the way through Saturday. Temps will
still be around 10 degrees above normal Tue/Wed, but cooling to
near normal Fri/Sat.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Warning until 9 PM MDT Wednesday IDZ012-014-033.
     Heat Advisory until 9 PM MDT Wednesday IDZ015-016-029-030.
OR...Excessive Heat Warning until 9 PM MDT /8 PM PDT/ Wednesday
     ORZ063-064.
     Heat Advisory until 8 PM PDT Wednesday ORZ061-062.
     Red Flag Warning from noon MDT /11 AM PDT/ Sunday to midnight
     MDT /11 PM PDT/ Sunday night ORZ636-637.

&&

$$

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DISCUSSION...DG
AVIATION.....SH
SHORT TERM...LC
LONG TERM....SP