188
FXUS65 KBOI 091556
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
956 AM MDT Thu Oct 9 2025

.DISCUSSION...Unseasonably warm and dry weather will continue
through Friday, with high temperatures running 10 to 15 degrees
above normal and reaching the low to mid-80s in the valleys
today and Friday. This warming trend is driven by strengthening
southwest flow aloft ahead of an upper-level trough moving south
along the Pacific Northwest coast. This flow will also bring
increased southerly surface winds, producing gusts of up to 40
MPH.

The cold front remains the main focus, with its passage expected
Friday evening into early Saturday morning across eastern Oregon
and southwest Idaho. Ahead of the front, a dry slot associated
with the deepening low off the Oregon coast will maintain warm,
dry conditions through the day. The leading edge of the frontal
system, combined with increased moisture from the southwestern
U.S. and increased instability over southwest Idaho, will be the
catalyst for isolated evening thunderstorms across southern
Idaho. No updates needed at this time.

&&

.AVIATION...VFR. LLWS redeveloping late Thu night/early Fri
morning. Showers developing over the ID W-central mountains
overnight tonight. Surface winds: S-E 10-20 kt with gusts up to
25kt. Winds aloft at 10kft MSL: S-SE 20-30 kt.

KBOI...VFR. LLWS developing late Thu night/early Fri morning.
Surface winds: SE 10-15 kt with gusts up to 25 kt.

Weekend Outlook...Areas of mountain obscuration Sat morning with
showers and isolated thunderstorms. Showers continue into Sunday
with snow levels 5-7kft MSL and mountains obscured. Breezy
conditions Saturday and Sunday afternoon with W-NW gusts of
20-30kt.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Saturday night...Unseasonably warm
and dry weather will continue through Friday, with highs 10-15
degrees above normal, and in the low to mid 80s in the valleys
Thursday and Friday. This warming trend is driven by a
strengthening southwest flow aloft ahead of a upper level trough
moving south along the Pacific NW coast. By Friday, the trough
deepens into a closed low near the OR coast, drawing a dry slot
over southeast OR and southwest ID, with warm and dry conditions
for much of the day. Increasing instability over southwest ID
ahead of a cold front will spark isolated evening thunderstorms
across southern ID Friday evening into early Saturday morning as
the cold front sweeps across eastern OR and southwest ID. The
front brings cooler air and increasing precipitation chances of
15-30 percent in the valleys and 50-70 percent over the west
central ID and Boise Mountains due to upslope enhancement. The
forecast continues to trend drier from previous forecasts. The
trough moves inland by Saturday, with showers increasing to 20-40
percent in the valleys and continued 50-80 percent in the
mountains. Winds become west-northwest behind the front on
Saturday afternoon with gusts to 20 to 30 mph.

LONG TERM...Sunday through Thursday...Cool and unsettled in the
long term period with low confidence on the timing of the
precipitation as a general trough remains over the Pacific NW.
The center of the trough moves overhead on Sunday and weakens
considerably. Snow levels fall to 5,000-7,000` MSL Sunday with
precipitation likely over the mountains. Temperatures drop to
around 10 degrees below normal Sunday. A reinforcement of cold
air from the north retrogrades into another low pressure system
off the Pacific NW coast on Monday, shifting the flow to
southwest again, with moderating temperatures Monday and
Tuesday. This trough digs into southern NV/CA by Wednesday with
wrap around subtropical moisture impacting the area. While both
the deterministic and ensemble guidance show good agreement on
the overall pattern, forecast confidence decreases beyond Sunday
due to the interaction between the mid-latitude trough and the
remnants of Hurricane Priscilla and Tropical Storm Octave.
Models struggle with the handling of these tropical systems and
their interactions with the mid-latitude jet stream.

&&

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

&&

$$

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DISCUSSION...JDS
AVIATION.....NF
SHORT TERM...KA
LONG TERM....KA