Placerville, Idaho Weather Forecast Discussion

326
FXUS65 KBOI 011537
AFDBOI
Area Forecast Discussion
National Weather Service Boise ID
937 AM MDT Wed Oct 1 2025
.DISCUSSION...Scattered stratus clouds across the region will
continue to mix out throughout the morning with a brief period
of clearing skies by early afternoon. Isolated rain showers
will move in by mid afternoon, bringing light rainfall to the
region, primarily north and west of the Treasure Valley.
Instability remains limited, but a 10-20% chance of a stray
thunderstorm will accompany afternoon showers. Much cooler
temperatures with breezy afternoon westerly winds are
anticipated across the region with gusts up to 30 mph over high
terrain. No updates necessary to the forecast.
&&
.AVIATION...Low to mid clouds persisting all day.
Isolated showers throughout the day. MVFR/IFR conditions
possible in low clouds/precipitation, resulting in mountain
obscuration. Ceiling heights increasing to VFR throughout the
morning. Showers increasing in coverage after Thu/06z in a line
from KEUL to KREO. Surface winds: SW-SE 5-15 kt with gusts to 25
kt in SE Oregon. Winds aloft at 10kft MSL: SW 15-30 kt.
KBOI...VFR. Mostly cloudy through the day. A 30% chance of showers
after Thu/07z. Surface winds: S-SE 8-12 kt.
&&
.PREV DISCUSSION...
SHORT TERM...Today through Friday night...Today is mostly dry
across the region as a large low pressure system remains locked
up offshore. Mountains will keep a 20% chance of showers
through the day while more stable conditions drop the
thunderstorm threat to 10-15%. Southwest flow aloft will
continue to feed breezy surface winds, especially across SE
Oregon and higher terrain outside of the Snake Plain in SW
Idaho where gusts of 25 to 35 mph are expected. The upper low
will edge eastward tonight, pushing a front into the region
which ups the precipitation chances into Thursday.
The upper low will elongate along the West Coast late Thursday
into Friday, stalling it`s eastward movement and thus stalling
the cold front over the region. Over the last 24 hours model
guidance has shifted slightly westward with the position of the
stalled front and accompanying precipitation band. The area of
heaviest rainfall is fairly narrow with the 00Z guidance placing
the axis along a line running from the ID/OR/NV triple point,
through Mountain Home into the Boise Mtns. Over a 30h period,
forecast guidance is showing 0.75-1.5" of rain in this area with
amounts trailing off over the western Magic Valley and lower
Treasure Valley into SE Oregon. Models continue to be in good
agreement with the development, timing and magnitude of this
event with uncertainty remaining in the placement. Given the
small/narrow scale of the precipitation band, even a minor
change in the position of the front will make a significant
change in rain chances/amounts. For example the NBM 25-75 %tile
box for Banner Summit, has a range of 0.04"-1.05" for the 24h
precipitation total through Friday.
The upper low kicks eastward on Friday, bringing drier
conditions to SE Oregon. Rain tapers off from east to west
across Idaho zones late Friday- Friday night. Northwest winds
will pick up behind the front on Friday and remain gusty across
open/elevated terrain Friday night. Windier spots along the I-84
corridor will see gusts of 25 to 35 mph. Temperatures will
continue to gradually cool with highs on Friday 5-10 degrees
below normal (valleys mid-60s, mtns mid-50s).
LONG TERM...Saturday through Wednesday...Behind the trough in
the short term, strong northwesterly winds continue through
Saturday. The northwesterly component will favor especially
strong winds in the lower Snake Plain, with gusts 25-35 mph.
Isolated light showers continue in Central Idaho on Saturday,
right on the border of our forecast area. A new trough quickly
amplifies into a closed low over California on Sunday and
Monday, while high pressure builds off the Canadian west coast.
Another low in the mid-Pacific supports development of an Omega
block, and while we will be close to the CA low, the flow is dry
enough in the current model runs to support drier conditions
and a slight warming trend Sunday through Wednesday. Temps warm
from about 5 degrees below normal to about normal.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...SA
AVIATION.....NF
SHORT TERM...DG
LONG TERM....JM

NWS BOI Office Area Forecast Discussion