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000
FXUS65 KBOI 091547
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
947 AM MDT Tue Apr 9 2024

.DISCUSSION...A weak system passing by mainly to our north will
bring a 30-50 percent chance of light rain/snow to the higher
elevations of Baker County into the West Central ID mountains
(McCall) today. Elsewhere, expected some clouds but dry
conditions. The precip and clouds diminish late this afternoon
as the system exits to our east. Breezy west-northwest winds
develop by this afternoon, especially in s-central Idaho.
Temperatures will be a few degrees above normal. No updates.

&&

.AVIATION...VFR with increasing mid/high clouds. Showers
developing through Tue/22Z around KMYL and KBKE, bringing local
MVFR/IFR conditions and mountain obscuration. Snow levels
4500-6000 ft MSL. Surface winds: variable 10 kt or less,
becoming NW 5-15 kt Tuesday afternoon, except W-NW 10-20 kt with
gusts to 25-30 kt for KJER/KTWF. Winds aloft at 10kft MSL: W-NW
15-25 kt.

KBOI...VFR with increasing mid and high clouds. Virga and
showers expected to remain north of KBOI terminal Tues
afternoon, but will watch for outflow wind gusts that may reach
KBOI. Surface winds: E- SE less than 10 kt overnight,
transitioning to NW 5-10 kt around Tues/16Z, increasing to 10-15
kt Tuesday afternoon.

&&

.HYDROLOGY...The Owyhee River below Owyhee Dam is expected
to remain in moderate flood stage through Friday morning due
to flood control release measures, then decrease below flood
stage late Friday evening.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Thursday night...This morning, high
clouds precede the approach of the next upper-level trough.
Satellite imagery indicates a weak trough lingering over
northwest Washington, expected to progress eastward, reaching
Northern Idaho by this afternoon. There`s a 30 percent chance of
showers forecasted ahead of a weak cold front across the
elevated terrain of Baker County and the West Central Mountains
by early afternoon. While a few high-resolution models,
particularly the NAMNest, suggest showers developing further
south around Ontario, most anticipate precipitation confined to
the mountainous areas. Nevertheless, the front will usher in
breezy northwesterly winds today, notably affecting regions from
Mountain Home through the Western Magic Valley.

From Tuesday night through Thursday, a broad upper-level ridge
will dominate the region, coinciding with the emergence of
another low pressure system over the Gulf of Alaska.
Temperatures are expected to stay a few degrees above normal
during Tuesday and Wednesday. However, by Thursday, temperatures
are forecasted to soar about 15 degrees above normal as
southeasterly winds intensify in response to the distant low
pressure system well off the Pacific Northwest Coast. Moisture
levels are set to increase across the area Thursday night as the
upper-level flow shifts southwestward, leading to the potential
for showers once again in the mountainous regions.

LONG TERM...Friday through Tuesday...An upper level closed low
moves southward along the Pacific Coast at the beginning of the
long term period. The position of the low has varied greatly
between forecasts despite model agreement on it`s track, so
there is plenty of uncertainty on the weather for the first half
of the long term period. Friday afternoon/evening, models still
favor thunderstorms and precipitation, but latest runs have the
closed low further off the coast, limiting moisture flow and
decreasing storm chances in eastern portions of our forecast
area. Over the weekend, the low dives southward, finally moving
inland when it reaches the far southern coast of California.
Despite still being in the deformation zone north of the low,
the limited moisture is only supporting a 20-30% chance of rain
showers Saturday/Sunday. While the closed low contains a much
colder airmass, if it stays too far south of our area then temps
won`t change too much for the area. This, combined with the
model uncertainty in the position of the low, means there is a
significant spread in forecast temperatures on Saturday and
Sunday. The closed low moves east Monday and Tuesday, but
models have been consistent with a trough beginning to move in
from the north following the exit of the closed low. Temps drop
Monday and Tuesday from 10-15 degrees above normal over the
weekend down to about normal.

&&

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

&&

$$

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DISCUSSION...BW
AVIATION.....JR
HYDROLOGY....JDS
SHORT TERM...JDS
LONG TERM....JM