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000
FXUS65 KBOI 130234
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
834 PM MDT Fri Apr 12 2024

.DISCUSSION...Showers and thunderstorms have weakened this
evening with the loss of daytime heating. Isolated to scattered
development will follow a minor shortwave trough as it tracks
northeastward overnight. By midnight MDT expect any lingering
showers and thunderstorms to be focused over the w-central Idaho
mtns with drying and clearing conditions to the south and west.
The hail threat is past for this evening while the chance for
gusty outflow winds to 45 mph will linger across SE Oregon and
far SW Idaho through about 10MDT/9PDT. Have made minor updates
for the rest of this evening.

&&

.AVIATION...Mainly VFR. Scattered showers and isolated
thunderstorms through the evening. Storms will produce brief
heavy rain, along with the potential for outflow wind gusts to
40 kt and small hail. MVFR and brief IFR in storms, along with
mountain obscuration at times. Surface winds outside of storms:
becoming variable less than 10 kt overnight. Winds aloft at 10k
ft MSL: southerly 20-35 kt this evening, becoming variable 5-15
kt by 12Z Saturday.

KBOI...Mainly VFR. Scattered showers through 06Z. Currently,
there is a 40% chance of showers reaching KBOI terminal.
Outside of any outflow from relatively nearby storms, surface
winds SE 5-15 kt through 06Z, decreasing overnight.

Sunday Outlook...Mountain obscuration with MVFR to IFR in
scattered showers and thunderstorms, mainly on the Oregon side.
Surface winds SW-SE 10-20 kt Sunday with gusts 20-30 kt during
afternoon. Snow lowering to 6000-7000 ft MSL Sunday.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday night...A marginal threat
of severe thunderstorms exists over our area through this
evening. The main concerns with the storms will be the potential
for strong outflow winds in excess of 50 mph and hail. Latest
radar loops show scattered showers in far southern Idaho and in
Harney County, Oregon. Coverage is expected to expand and cells
become stronger as it becomes more unstable with the afternoon
heating. Initially, it appears that the stronger storms will
develop over SE Oregon before extending into SW Idaho later
this afternoon into this evening per latest hi-res models.

The upper low responsible for the convective activity is
expected to drift eastward and reach the west coast on Saturday.
A wedge of warm but drier/stable air moves into most of our
area ahead of it on Saturday. Only the western/northern fringes
(Harney County, Baker County, West Central ID Mountains) will
have a 15-30 percent chance of showers and afternoon
thunderstorms. Temperatures remain unseasonably warm once again
as highs will be well into the 70s and lower 80s in the valleys.

Models have been consistent in showing the upper low
transitioning to two distinct low centers on Sunday. The
northern low is expected to move northeastward through Nevada
and approach our southern border areas. Showers will accompany
the low, especially near the center of the low, with the highest
coverage (greater than 60 percent) near the OR/NV border.
Instability is marginal on Sunday, but enough for a slight
chance of thunderstorms. Temperatures will be 10 to 20 degrees
cooler. A cold front moving up from the south (which is unusual)
will support breezy southerly winds during the afternoon.

LONG TERM...Monday through Friday...The center of an upper
level low to our south will move east through Utah on Monday as
a shortwave ridge moves overhead. Meanwhile, a strong surface
pressure gradient will set up over the area. Conditions will be
mostly dry on Monday with gusty northwest winds, strongest
across south-central Idaho where a 90% chance of maximum gusts
45 mph or greater will develop. Forecast confidence decreases on
Tuesday, which carries through the remainder of the forecast
period. The uncertainty is associated with a deep upper level
trough dropping south out of Canada. Ensembles are split into
two main clusters, each equally likely at this point. The first
cluster depicts the trough moving into the Pacific Northwest,
bringing much cooler temperatures to all areas and snow to the
mountains, then keeps a weak trough overhead through Friday. The
second cluster is milder and drier, developing a ridge along
the West Coast with the trough dropping south into the Plains.
The current forecast reflects the uncertainty, bringing a 20-50%
chance of precipitation to the mountains on Tuesday, gradually
decreasing through Friday. Temperatures are also forecast to
cool to several degrees below normal on Tuesday and moderate
through Friday. Winds will remain breezy on Tuesday.

&&

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

&&

$$

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DISCUSSION...DG
AVIATION.....SP
SHORT TERM...BW
LONG TERM....ST