193
FXUS65 KBOI 132000
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
200 PM MDT Sun Sep 13 2026

.KEY MESSAGES...
- Breezy and much cooler today, with lingering showers in
  northeast OR and the central ID mountains.

- Warming and drying this week.

- Unsettled conditions later this week bring precipitation to
  higher terrain.

&&

.SHORT TERM /Through Tuesday Night/...
Behind a cold front that passed through this morning, much of
the region is remaining cool even in areas with clear skies.
Forecast highs for this afternoon are on track to verify. Post-
frontal winds continue to gust across the area, with sustained
winds 10 to 15 mph and gusts up to 25 mph. Gusts this afternoon
could be as high as 35 mph in the Snake Plain between Mountain
Home and Twin falls. As the core of the low moves in behind the
front, showers will continue across eastern and northeastern
Oregon as well as Central Idaho. Light to moderate rainfall is
expected out of showers, and a few may develop into
thunderstorms during peak afternoon/evening instability.
Precipitation dissipates overnight, and morning low temperatures
on Monday will be about 10 degrees cooler than Sunday morning
especially in Idaho. Cold enough for RHs to approach saturation
and support fog development in higher and colder valleys, and
frost in highlands. Cooler temperatures begin to warm Monday and
especially Tuesday as heights rise in the region.

&&

.LONG TERM /Wednesday through Sunday/...
A weak cut-off low looks to remain centered over the region through
Saturday. This feature will keep temperatures slightly below
seasonal normals, along with periodic chances (15-30 percent) for
rain showers and isolated afternoon thunderstorms, primarily over
the higher terrain of eastern Oregon and southwest Idaho. While
widespread heavy precipitation is not expected due to limited
moisture transport initially, moisture does look to increase later
in the week as more monsoonal moisture is pulled into the low. Thus,
greater potential for heavier rainfall exists, especially across the
central Idaho mountains. By Sunday, ensemble clusters show
increasing divergence regarding the evolution of the pattern. A
subset of cluster guidance maintains a secondary longwave trough
dropping out of the Gulf of Alaska, which would prolong cool
temperatures and unsettled shower activity. Conversely, other
deterministic solutions favor the advancement of a flat high-
pressure ridge from the Great Basin, leading to a warmer and drier
pattern heading into early next week. Given the high uncertainty
inherent to cut-off systems, forecast confidence remains low for the
Sunday period.

&&

.AVIATION /18Z Sunday through Monday/...
Issued 1133 AM MDT SUN SEP 13 2026
Mainly VFR. Scattered to broken clouds today. Isolated showers
and thunderstorms this afternoon and evening across Baker County
into the West Central Idaho Mountains. Outflow winds to 30 kts
and brief heavy rain possible. Patchy valley fog Monday morning
near KBKE, KMYL, and KBNO. Surface winds: W to NW 5-15 kt, with
gusts to 20-30 kt in the Magic Valley and on ridgetops. Winds
aloft at 10kft MSL: SW-W 25-45 kt.

KBOI...VFR with mid level clouds. Surface winds: WNW 10-15 kt
with gusts to 25 kt, decreasing to variable less than 10 kt
overnight.

&&

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

OR...None.

&&

$$

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SHORT TERM...JM
LONG TERM....JDS
AVIATION.....JDS