946 
FXUS65 KBOI 282023
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
223 PM MDT Sun Sep 28 2025

.SHORT TERM...Tonight through Tuesday night...Showers and 
thunderstorms already underway along the ID/NV border east
of Owyhee and will continue through sunset. The main Pacific 
frontal band is now forecast to reach eastern Oregon Monday 
afternoon and western Idaho Monday evening through Tuesday 
morning. This later timing will allow our CWA to be several 
degrees warmer Monday than previously forecast, especially 
in Idaho. Latest models continue to slowly decrease total 
rainfall Monday through Wednesday, now only .50 to .80 inch
in the Idaho mountains north of the Snake Basin, .30 to .50 
inch in the Idaho valleys, and .20 to.40 inch in eastern
Oregon, much less than forecast several days ago. A 20-30 
percent chance of thunderstorms with local heavy rain is 
still forecast as the front is passing, with the greater 
chances in southern areas, and more likely in Idaho than in 
Oregon. Temperatures will lower about 10 degrees Tuesday from 
Monday, with similar temps on Wednesday. Winds should only
be 10 to 20 mph as the front passes. Strongest gusts (near
40 mph) are expected in southern Harney County Tuesday 
afternoon. 

.LONG TERM...Wednesday through Sunday...Largely unsettled
pattern is expected to continue through the end of the week 
from Wednesday to Friday, as a large upper low mostly lingers 
over the coast of British Columbia. Strong southwesterly flow 
from this low will steer Pacific moisture into the northwest 
region, sustaining isolated showers across most of the area 
until Friday. Toward the end of the week, the upper low is 
projected to break off and dig into the region as a longwave 
trough. Precipitation intensity is expected to gradually 
decrease through the week, with higher elevations generally 
seeing the greater amounts Thursday through Friday. The pattern 
is expected to bring a steady cooling trend through the week, 
dropping peak valley temperatures down from the lower 70s 
Wednesday into the mid to lower 60s Friday to Sunday. There is 
considerable guidance uncertainty on a second longwave trough 
expected to dig into the region Saturday and Sunday; the pattern
can either slowly form a closed upper low off California or dig
across the region as a longwave pattern. For now, next weekend 
will mainly see little or no precipitation and a strong cooling
trend into the 50s/60s. 

&&

.AVIATION...VFR. Isolated showers/thunderstorms in south-central
ID (Magic Valley) and eastern Oregon this afternoon/early 
evening. Thunderstorms capable of 30kt outflows. Surface winds: 
variable or SW-NW 5-10 kt through early afternoon. Winds aloft
at 10kft MSL: S-SW 10-20 kt.

KBOI...VFR with clear skies. Surface winds: N-NW up 5-10 kt this 
afternoon/early evening.

&&

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

&&

$$

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SHORT TERM...LC
LONG TERM....JY
AVIATION.....JY