589
FXUS65 KBOI 020944
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
344 AM MDT Thu Oct 2 2025

.SHORT TERM...Today through Saturday night...Overnight water
vapor satellite imagery showing an elongating trough along the
West Coast, defined by a closed low off the BC coast and
secondary wave digging toward the central CA coast. We`ll remain
positioned along the eastern edge of the trough with a weak
frontal boundary as the focus of shower development today.
Lining up over s-central Idaho this morning, the front will
shift westward through the day. By this evening it will roughly
extend from southern Malheur County through the Treasure Valley
into the Boise and W-Central Idaho mtns. The front will briefly
stall in this position tonight into Friday allowing for a narrow
band of moderate to locally heavy rain to form. Mountain sites
in the Owhyee`s up through Idaho City, Lowman, Warm Lake and
Yellow Pine are inline for 0.75-1.25 inches of rain through
midday Friday. Banner Summit and the Wapiti burn scar are now on
the eastern fringe of the forecast heavier rainfall with
0.75-1" expected. In the Snake Plain the rainfall maximum covers
Caldwell to Mtn Home with rain totals of 0.4-0.6". The Flash
Flood Watch will remain in place with the concern being areas
in and around burn scars.

The trough/front will slowly shift eastward through Saturday.
This will keep a 60+% chance of rain across southern Harney and
Malhuer counties and higher terrain of SW Idaho through Friday
night. It will also act to fill in precipitation over the
western Magic Valley which is going to miss out on most of
tonight`s rainfall. A 20-25% chance of showers linger in the SW
Idaho mtns and central Snake Plain on Saturday, dropping to
less than 20% Saturday night. Snow levels will drop to around
7kft MSL Saturday night so any lingering showers could bring
light snow to the mtn tops. Gusty winds will follow the front
Friday night into Saturday. In typical fashion the strongest
winds will blow through the Snake Plain east of Boise where 30
mph winds and gusts to 45 mph are possible. Today will bring
little change in temperatures from yesterday, with 5-15 degrees
of cooling behind the front on Friday.

.LONG TERM...Sunday through Thursday...A shortwave trough
amplifies Sunday evening, extending from Montana to Northern
California. The amplification will bring a slight chance of
showers and storms to Central Idaho Sunday, with a wintry mix
possible for mountains with snow levels around 7 kft MSL. As the
now longwave trough becomes closed over Northern California,
and a closed high develops off the Canadian West Coast,
deterministic model agreement lessens Monday through Thursday.
This blocked pattern will at least keep us dry through the early
parts of next week. Whether it`s an Omega or Rex block... I`ll
concede to the Rex block designation that day shift prescribed,
but only due to the brief nature of the block. An Omega would
normally be fairly persistent, but a strengthening Alaskan low
will move southeastward into the closed high, disrupting the
balance of the block. Most ensemble members show the disruption,
but a healthy chunk of others, including the GFS deterministic,
show the Alaskan low moving south into the Pacific before
heading eastward and onto the coast. These two differing
solutions lead to widely different scenarios Wednesday onward.
Both hint at unsettled patterns, but the coastal track is far
more dynamic than the Pacific southward track.

&&

.AVIATION...Isolated showers will become widespread with embedded
thunderstorms across E Oregon and SW Idaho by Thursday late
afternoon. MVFR/IFR and localized LIFR in moderate/heavy precip and
low clouds. Mountains become increasingly obscured. Surface winds:
variable 5-10 kt. Winds aloft at 10kft MSL: SW 15-30 kt.

KBOI...VFR this morning. Showers returning Thu/23Z, and will become
continuous Thu night. Periods of MVFR/IFR in moderate/heavy rain Thu
night. Surface winds: variable 3-6 kt with some brief period of SE
this morning and NW this afternoon.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flash Flood Watch from this evening through Friday afternoon
     IDZ011-013.
OR...None.

&&

$$

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SHORT TERM...DG
LONG TERM....JM
AVIATION.....JM