330
FXUS65 KBOI 141501
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
900 AM MDT Sun Jul 14 2024

.DISCUSSION...At 8 AM MDT sprinkles seen on radar in northern
Malheur County/OR and Washington County/ID, not well depicted
by hi-res models. The peak of mid/high level monsoon moisture
should occur today with 25-40 percent areal coverage of
thunderstorms this afternoon in southern Harney and Malheur
Counties in Oregon, and in southern Owyhee and Twin Falls
Counties in Idaho, then into eastern Valley, Boise, and Elmore
Counties in Idaho this evening, then exiting east of our CWA
Monday. This is not a major monsoon surge, but any thunderstorms
could start new fires and Red Flag Warnings for lightning will
continue through midnight MDT tonight in all of Harney and
Malheur Counties in Oregon, and in Idaho south of the Snake
River. Clouds and smoke today will lower max temps 3-6 degrees
from yesterday, with several degrees further cooling Monday as
the hot upper high in the Great Basin shifts eastward to the
southern Rockies. The streak of 100F days at Boise should end
Monday but just barely. On Tuesday the upper high will edge
westward again, and later this week also build northward into
our area, resulting in another very hot period Wednesday through
at least Sunday. The current Excessive Heat Warning in the
Lower Treasure valley, and Heat Advisory in Malheur and Baker
Counties and the Upper Weiser Valley, will continue until
midnight MDT tonight, then no heat products Monday or Tuesday.
A new Excessive Heat Watch is being planned starting Wednesday.
No updates for now.

&&

.AVIATION...Generally VFR, with areas MVFR and IFR visibility
due to smoke, especially from e-central Oregon into the
w-central Idaho mountains. Isolated showers this morning.
Scattered thunderstorms this afternoon, especially in SE OR
and SW ID south of the Snake River. Isolated thunderstorms
elsewhere. Outflow gusts 45 to 55 kt near showers/storms.
Surface winds: NW-SW 5-15kt. Winds aloft at 10kft MSL: S-W
10-15 kt this morning becoming W to NW 10-20 kt this afternoon.

KBOI...VFR but smoky. Visibility near 6 miles after 14/00Z at
times. High density altitude due to hot daytime temperatures.
Light winds.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...The area is well
encompassed in monsoon moisture this morning which has
translated to widespread cloud clover and high-based showers
(mostly virga). Southerly flow on the back side of an upper
high will keep the moisture in place through Monday while
daytime heating and a trough along the coast will provide the
instability and lift to support shower and thunderstorm
development. Today will be the most active day across the region
with most sites seeing a low chance of showers/storms (15-20%),
while areas of SE Oregon and higher terrain south of the Snake
River will see greater coverage. Showers and storms will drop
gusty outflow winds up to 50 mph, though stronger gusts are
possible. Cloud cover will bring a mild start, but also lead to
a slower warmup and lower high temperatures than recent days.
Have kept the heat products in place for today across lower
elevations. The Falls fire and Cow Valley fire, along with new
starts from yesterday`s lightning, will keep smoke in the
region with the flow aloft pushing smoke to the east. Monday
sees another round of showers and thunderstorms over the higher
terrain of SE Oregon and SW Idaho south of the Snake River.
Otherwise clouds and minimal cooling aloft will take several
more degrees off high temperatures, bringing most valley sites
below 100F. Tuesday is dry across the region as the upper high
rebuilds westward into Utah. Temperatures will respond
accordingly, warming a few degrees from Monday and likely
starting a new streak of 100 degree days at lower valley sites.

LONG TERM...Wednesday through Sunday...The latest guidance is
in better agreement than yesterday on the evolution of the
upper level ridge. It appears the ridge will indeed build back
into our area and bring another period of extreme heat to the
region. The latest forecast calls for temperatures over 100 in
the lower elevations each day, with Boise forecast to see
another string of at least 5 consecutive days of 105 or higher.
Deterministic model agreement breaks down next weekend, when the
GFS shows a trough moving into the area Sunday while the ECMWF
and Canadian hold it off for several more days. Unless we get
lucky and the latest operational GFS happens to verify well,
our extreme heat will last beyond Sunday, and perhaps well into
the following week. There are slight chances of thunderstorms
throughout the long term, but models disagree significantly on
both timing and location.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Excessive Heat Warning until midnight MDT tonight IDZ012.
     Red Flag Warning until midnight MDT tonight IDZ423-426.
     Heat Advisory until midnight MDT tonight IDZ033.
OR...Excessive Heat Warning until midnight MDT tonight ORZ064.
     Red Flag Warning until midnight MDT /11 PM PDT/ tonight
     ORZ636-637.
     Heat Advisory until midnight MDT /11 PM PDT/ tonight
     ORZ062-063.

&&

$$

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