021
FXUS65 KBOI 170924
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
324 AM MDT Sun Aug 17 2025

.SHORT TERM...Today through Tuesday night... A Flash Flood
Watch has been issued for this afternoon and evening over
burn scars in eastern OR and adjacent parts of western ID.
The area corresponds closely to WPC`s excessive rainfall
outlook area. Contributing factors include: a short wave
trough rounding the base of a larger scale upper trough over
the northwestern US, thunderstorms depicted in hi-res forecast
models this afternoon, abnormally high precipitable water
(0.75 to 0.90 inch), significant instability (NAM LI -2 to
-4 and CAPE 600 to 1000 J/KG), greater sunshine than yesterday
leading  to steeper lapse rate, and yesterday`s rainfall to
help moisten lower atmospheric layers today. These factors will
continue through this evening, then end overnight. No further
threat is expected Monday as the main upper trough fills and a
hotter and drier upper high builds westward toward our CWA
from the Rockies and Great Basin. However, as early as Tuesday
aafternoon circulation around the high will draw monsoon
moisture into southern Idaho from the south. Models are
inconsistent on this so we are keeping Tuesday dry for now
in our forecast.

.LONG TERM...Wednesday through Sunday...By Wednesday enough
monsoon moisture should arrive in southern Idaho for at least
a 15 percent chance of thunderstorms near the ID/NV border,
and through the rest of the week as well. The whole period
will be hot with high temps 5 to 10 degrees above normal,
with the upper high centered directly over the Great Basin.

&&

.AVIATION...Mostly VFR. Isolated thunderstorms again this
afternoon and evening. Storms will produce heavy rainfall,
small hail, and gusty outflows. Local visibility restrictions
due to wildfire smoke in the W-Central ID Mtns. Surface winds:
Light and variable this morning, becoming mostly NW 5-15 kt
this afternoon.Winds aloft at 10kft MSL: SW 10-20 kt.

KBOI...VFR. Thunderstorms in the area again late this afternoon
and evening. Storms could produce heavy rainfall, hail, and 35
kt outflows. Surface winds outside outflows: NW 5-15 kt.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flash Flood Watch from this afternoon through this evening
     IDZ011-012-015-029-033.
OR...Flash Flood Watch from this afternoon through this evening
     ORZ061>064.

&&

$$

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SHORT TERM...LC
LONG TERM....LC
AVIATION.....JM