652
FXUS65 KBOI 040306
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
906 PM MDT Fri Oct 3 2025

.DISCUSSION...Isolated showers remain over southwest Idaho this
evening within the deformation zone of an upper low. Showers are
expected to persist and re-intensify across south-central
Idaho overnight, resulting in periods of reduced visibility
from rain and fog/mist in the Magic Valley. Temperatures are
currently running 5 to 15 degrees cooler than this time
yesterday, with more cold air advection expected Saturday. The
surface pressure gradient will tighten further tonight as the
upper low continues east. Increased northwesterly winds will
become prominent in east-central Oregon tonight and southwest
Idaho by the early morning hours. Wind gusts will become common
across the Snake Plain and neighboring areas on Saturday,
especially across SW Idaho during the late morning and
afternoon. Gusts of 25-35 mph can be expected in these areas,
except gusts up to 35-45 mph around Mountain Home and the Magic
Valley.

&&

.AVIATION...Mostly VFR. Low cloud ceilings with brief MVFR
conditions will continue across Magic Valley. Few light showers
continuing across SW Idaho tonight/Sat, with heavier rounds
expected for KTWF and KJER early morning Saturday after 12z.
Mtns obscured in low ceilings and precip. Snow levels 7k-8k ft
MSL. Surface winds: N-NW 5-15 kt this evening, with gusts to
20-25 kt overnight. Then, N-NW 10-20 kt gusting up to 30 kt
Saturday, with localized gusts up to 40 kt in the Snake Plain.
Winds aloft at 10 kft MSL: N-NW 10-20 kt.

KBOI...VFR. Mostly cloudy with few low clouds. Foothills obscured.
Scattered light showers through tonight. Surface winds: NW 8-12
kt with gusts up to 20 kt tonight after 04z.

Sunday Outlook...Patchy AM fog for sheltered mountain valleys
and basins. Isolated showers continuing over central Idaho
mountains through the weekend. MVFR/IFR in heavier rain
showers, IFR/LIFR in snow. Snow levels 6k-7k ft MSL. Mountains
obscured in precip. Surface winds: NW-NE 5-10 kt Sunday.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday night...At 2 PM MDT the main
rain band still extended through Owyhee, NV - Mountain Home -
Missoula,MT, held there by an upper low approaching from western
NV. The band has greatly weakened since this morning, but it
will remain in our eastern CWA until the upper low moves to
western UT around sunrise Saturday. Showers will continue in
our eastern zones in Idaho through the night, and there is
enough instability for a 10-20 percent chance of thunderstorms
through about 8 PM MDT this evening. Meanwhile, to our northwest,
there is another cold front across southern BC out into the
north Pacific along 50N. The front should weaken when it reaches
our CWA Saturday morning, producing a 20-30 percent chance of
showers in the central ID mountains but only clouds elsewhere
in our CWA. Saturday night through Sunday night should be drier
but residual low-level moisture will produce patchy fog in the
valleys early Sunday morning. Temperatures will stay cool through
the period, but lows tonight will stay up due to cloud cover and
moderate northwest winds. Models increase the NW winds to 15 to
25 mph in most areas Saturday morning, but 20 to 30 mph in the
Snake Basin and gusts 30 to 40 mph between Mountain Home and
Twin Falls. Winds and clouds will decrease Saturday evening,
and Sunday morning will be colder, generally near 40 degrees
in the southern valleys and mid 20s to mid 30s in the higher
valleys and mountains. Lows Sunday night will be cooler still:
20s in the mountains and 30s to near 40 in the valleys. Low
temps in the Lower Treasure Valley Sunday morning will be in the
mid 30s, cold enough for patches of frost (which can form at 36
degrees under calm conditions).

LONG TERM...Monday through Friday...Dry conditions can be
expected area-wide through mid-week. This will be thanks to a
brief blocking pattern provided by a closed-low over California
and ridging building in north of it over our area. As the ridge
builds in, temperatures will take on a warming trend, starting
5-10 degrees below normal Monday before increasing to near
normal on Tuesday. Beyond Tuesday, slight warming is expected
each day with daily highs leaning above normal. Overnight lows
will be near normal throughout the period. More unsettled
weather will make its way into the forecast Late Wednesday
through Friday. This is thanks to a deepening low over the Gulf
of Alaska breaking up the blocking pattern that kept us dry.
Model ensembles are falling into more agreement on this low
setting up off the west coast and remaining semi-stationary
through Friday. While our area won`t be feeling the full effects
of this low, southwesterly flow aloft and increasing moisture
will allow for a chance of showers across higher terrain
Wednesday/Thursday, and then area-wide come Friday as it slowly
creeps closer to the coast. Ensemble guidance (GFS, EURO, and
EURO AI ensembles) have been consistent across multiple run
times in bringing measurable precipitation to the valley on
Friday. Unsettled conditions are looking to persist past Friday,
so stay tuned!

&&

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

&&

$$

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DISCUSSION...SH
AVIATION.....JY
SHORT TERM...LC
LONG TERM....NF