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000
FXUS65 KBOI 110914
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
314 AM MDT Thu Apr 11 2024

.SHORT TERM...Today through Saturday night...Today, a ridge
axis traverses the forecast area in response to a low-pressure
system descending southward from the Gulf of Alaska along the
Western Canadian coast. As a result, temperatures are expected
to soar 10-13 degrees above normal.

During the afternoon, the upper-level flow shifts to the
southwest, ushering in mid to high-level moisture across the
forecast area. While moisture and instability are somewhat
limited, high-res models suggest the possibility of showers
developing off the higher terrain by evening. However, due to
the persistently dry boundary layer, precipitation amounts are
anticipated to be minimal.

Friday presents more favorable conditions for organized
thunderstorm activity. As the low center approaches the central
California coast, upper-level diffluence and 50 knots of shear
are forecasted across the area. Additionally, precipitable water
levels approach the 90th percentile, accompanied by surface-
based CAPE ranging from 500-700 J/kg. Despite the surface
temperatures peaking around 15 degrees above normal, further
buoyancy may be constrained by the proximity of the low center
and cold air aloft, which are expected to remain west of the
area. These conditions could support the development of a few
stronger, potentially rotating thunderstorms Friday afternoon
and evening, elevating the risk of wind and hail. The Storm
Prediction Center (SPC) has already outlined much of the area in
a marginal risk for severe thunderstorms, with a 5% chance of
severe wind and hail on Friday. Surface temperatures in the
valley are projected to reach the upper 70s, with a 75% chance
of the Treasure Valley exceeding 80 degrees.

On Saturday, the upper-level low progresses inland across
central California and into west-central Nevada. This will
sustain warm southeasterly flow across most of the forecast
area, keeping temperatures approximately 15 degrees above
normal. Parts of the western Snake River Plain have a 50-75%
chance of reaching or exceeding 80 degrees. Southeast Oregon may
experience slightly cooler conditions and a slight chance of
precipitation as it lies closest to the northeast flank of the
upper low.

.LONG TERM...Sunday through Thursday...The upper low to our
southwest moves east of our area through Sunday, continuing to
bring a chance of precipitation and kicking off a period of
cooler temps through the long term period. Sunday, a 15-20%
chance of thunderstorms exists in SE Oregon and in Central ID,
while the chance for rain showers is roughly 30-40% for our
entire area. Sunday will be our last warmer than normal day,
before another upper low moves from the north into our area.
This low brings temps down to 5-10 degrees below normal through
Thursday, and keeps precipitation chances around 30-50% each day
for the higher terrain. Snow levels will be right around
4000-5000 ft during the day, but down to 3000 ft overnight on
Tuesday and Wednesday. Minimal snow accumulation over the
mountains given the weaker precip. The core of the low is east
of our area on Wednesday, but moisture embedded in the flow will
continue to support isolated precipitation. Winds will be
breezy each afternoon.

&&

.AVIATION....VFR and mostly clear skies through Thu/22z. Late
Thursday afternoon isolated light showers and virga develop.
Confidence of accumulating precip is low, but erratic winds are
possible around showers. Surface winds: variable less than 10 kt,
becoming SW-SE 5-15 kt Thursday afternoon. Winds aloft at 10kft MSL:
W-SW 15-25 kt.

KBOI...VFR and mostly clear. Confidence in showers near BOI is low
(<15%), but virga in the area may cause light erratic winds Thursday
evening. Surface winds: SE 5-10 kt.

Weekend Outlook...Mostly VFR, but scattered MVFR and local IFR are
possible each afternoon as thunderstorms and showers develop. Friday
afternoon/evening will be the best chance for thunderstorms over the
entire area, with stronger storms producing small hail and gusty
winds. Saturday the afternoon thunderstorm threat continues, but
mainly in SE OR and the W-Central Mtns and lower chances for hail
and gusty winds. Sunday most of the area sees rain showers with only
an isolated thunderstorm threat. Surface winds on Friday/Saturday E-
SE 10-20 kt in the afternoon, becoming SW-NW 10-20 kt on Sunday
afternoon.

&&

.HYDROLOGY...The Owyhee River below Owyhee Dam is expected
to remain above flood stage through Friday afternoon, then
decrease below flood stage late Friday evening. This could be
delayed further depending on how much rainfalls on Friday.

&&

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

&&

$$

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SHORT TERM...JDS
LONG TERM....JM
AVIATION.....JM
HYDROLOGY....JDS