Area Forecast Discussion
Issued by NWS Boise, ID

Home |  Current Version |  Previous Version |  Text Only |  Print | Product List |  Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
318
FXUS65 KBOI 120918
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
318 AM MDT Mon May 12 2025

.SHORT TERM...Today through Wednesday night...The upper-level
low will move inland across Oregon today, continuing the threat
for showers and isolated thunderstorms. Showers are expected to
begin across southeast Oregon later this morning behind a cold
front pushing west to east. Precipitation coverage will expand
eastward with the front into southwest Idaho this afternoon. The
highest PoPs (6080%) will be focused across Baker, northern
Malheur and Harney Counties, while lower chances extend into
southwest Idaho due to elongation of the upper trough.

The best dynamics and instability will remain centered over
southeast Oregon this afternoon and evening, supporting
thunderstorm development. A few storms may be capable of
producing gusts up to 50 mph. Farther east, southwest Idaho will
stay mostly dry for much of the day, though showers could
develop late this evening over south-central Idaho as the front
progresses. Winds will remain breezy area-wide, with gusts in
the 2030 mph range. Highs today will trend slightly below
normal.

On Tuesday, the upper low moves directly overhead, bringing a
3050% chance of showers along with isolated afternoon
thunderstorms. Tuesday will be the coolest day of the week, with
valley temperatures running about 10 degrees below normal. By
Wednesday, the upper low exits east of the region, with cold
northwesterly flow setting in behind it. Moisture and
instability look sufficient for scattered showers and a slight
chance of thunderstorms over the higher terrain of southwest
Idaho. Temperatures will stay on the cool side, roughly 69
degrees below normal.

.LONG TERM...Thursday through Monday...Thursday a weak upper
ridge will bring slightly warmer temperatures, bringing much of
the area to just a few degrees below normal. Temperatures hold
steady as a weak trough moves through on Friday, bringing a
20-30% chance of showers and kicking off an active pattern
through Monday. A deeper trough from the Gulf of Alaska will
move overhead this weekend, bringing additional precipitation.
Cold air aloft and instability will also support a slight chance
of thunderstorms, with the best chance on Saturday as the low
moves overhead. Breezy winds are expected this weekend with
enhanced gradient forcing.

&&

.AVIATION...VFR. Precipitation returns this afternoon, with most
thunderstorm activity occurring in SE OR after Mon/17Z through
Tue/05Z. Thunderstorms may produce outflow gusts up to 40 kt and
small hail. During this time, light showers and virga will develop
in SW ID. MVFR/IFR in precipitation and mountains may be obscured.
Surface winds: SW-NW 5-15 kt, becoming W-SW 10-20 kt this afternoon.
Winds aloft at 10kft MSL: SW 20-35 kt.

KBOI...VFR. Light showers and virga developing this afternoon. Winds
becoming variable 5-10 kt this morning, increasing to 10-15 kt
westerlies with gusts 25 kt Monday afternoon.

&&

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

&&

$$

www.weather.gov/Boise

Interact with us via social media:
www.facebook.com/NWSBoise
www.x.com/NWSBoise

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