952
FXUS65 KBOI 172019
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
219 PM MDT Fri Oct 17 2025

.SHORT TERM...Tonight through Sunday night...A shortwave ridge
will transit across the region keeping mostly clear and dry
conditions in place through Saturday. This will provide
efficient radiational cooling overnight and the lower Snake
Plain will see low temperatures in the 33-37 degree range. Thus
the Frost Advisory will remain in place through Saturday
morning. As we enter inversion season, mountains will tap into
warming aloft as high temperatures rise 2 to 5 degrees from
today to Saturday, while sheltered mtn valleys and lower
elevations will see high temperatures remain unchanged or even
a couple of degrees cooler than today.

Next up is a cold frontal passage on Sunday. Little change in
newest guidance with the higher precipitation chances (60-90%)
across the mtns of e-central Oregon and w-central Idaho during
the day Sunday. The southern extent of shower development along
the front will stretch from central Malheur and Harney counties
into the lower Snake Plain where a 15-20% chance for measurable
precipitation is forecast. This leaves areas along the NV border
and in the western Magic Valley dry through the weekend. Snow
levels will drop behind the front on Sunday allowing for minor
accumulations (<2") above 6500-7000 feet. Southerly winds will
pick up ahead of the front on Sunday, mostly across higher
terrain where gusts of 20 to 30 mph are expected. The frontal
passage Sunday afternoon brings a wind shift to the W-NW and
increases the gust potential to 25-40 mph across the entire
area. Lower elevations escape the frost threat Saturday night,
but sheltered spots will see frosty temperatures return early
Monday morning.

.LONG TERM...Monday through Friday...Behind the trough in the
short term, Monday will be around 5 degrees colder than Sunday.
Progressive model runs have slightly flattened the trough,
reducing the potential for temperatures to drop too much. This
will still be a few degrees below normal. Under generally zonal
flow, temps slightly warm each day. An isolated closed low
Tuesday evening passes over the southwestern US, pulling
slightly lower heights north of the low further south,
generating a shortwave that will pass through the area. For the
most part, this will just mean an increase in cloud cover, but a
slight chance of precipitation in north and central Idaho.
Showers could just stray into the W-Central Mountains.
Additionally, closed low tracks are inherently uncertain, so the
potential for precip could change in the next few model runs.
Snow levels with this system will be around 7-8 kft MSL.

The next major weather event begins to set up late Thursday into
Friday, as an atmospheric river impacts the PacNW coast and
Cascades. Uncertainty in the synoptic set up of the low driving
the event allows for a few ensemble members to show the trough
amplifying far enough inland for tropical moisture to reach our
CWA. At the earliest, SE Oregon could see precipitation Friday
night. Although, most models don`t bring the moisture in until
after the long term. The winds are likely to precede the
moisture though, so Friday afternoon could be pretty gusty.
Notably, this atmospheric river is very wet (even for ARs), and
extended outlooks show a significant amount of rain and snowfall
potential, especially for coastal states.

&&

.AVIATION...VFR. Skies have become mostly scattered, with some
local ceilings especially in the mountains. Tonight clouds
should continue to clear, and a few TAF sites have enough
lingering surface moisture for a chance of fog or low stratus.
Surface winds: variable less than 10 kt quickly becoming W-NW
5-15 kt this afternoon. Winds aloft at 10kft MSL: W-NW 20-40 kt.

KBOI...VFR with mostly clear skies. Possible low clouds Saturday
morning, though the chance is slim given slightly drier air than
would normally be favorable. Surface winds: variable becoming NW
6- 10 kt this afternoon, variable but generally westerly 3-7 kt
tonight.

Weekend Outlook...Mostly clear conditions on Saturday. Sunday
clouds increase with scattered showers north of a KBNO-KMUO
line after Sun/12Z. Snow levels during precip drop from 9000 ft
MSL Sun morning to 5000 ft MSL Sun evening. Surface winds: S-SE
5-15 kt Sat, and SW- SE 5-15 kt with gusts up to 25-35 kt Sun.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Frost Advisory until 9 AM MDT Saturday IDZ012-014-016.
OR...Frost Advisory until 9 AM MDT /8 AM PDT/ Saturday ORZ064.

&&

$$

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