Harper, Oregon Weather Forecast Discussion

898
FXUS65 KBOI 121610
AFDBOI
Area Forecast Discussion
National Weather Service Boise ID
1010 AM MDT Fri Sep 12 2025
.DISCUSSION...An upper level trough is weakening over the area
today as it moves eastward. Isolated showers and thunderstorms
are forecast to develop over the mountains this afternoon and
last through the evening before tapering off. Saturday will be
dry with mostly clear skies and patchy fog in the morning. Next
system arrives Sunday with showers and thunderstorms developing
during the afternoon areawide. Current forecast reflects this
well with no updates.
&&
.AVIATION...Areas of low clouds and fog this morning with
mountain obscuration. Isolated showers and thunderstorms this
afternoon, tapering off after sunset. Winds aloft at 10kft MSL:
NW 5-15kt. Surface winds: NW 5-15kt this afternoon.
KBOI...VFR. Light surface winds becoming NW 5-15kt this
afternoon.
Weekend Outlook...Generally VFR. Patchy fog Saturday morning,
otherwise mostly clear. Increasing high clouds Sunday, with
showers and thunderstorms developing in eastern OR and southwest
ID late afternoon and evening. Gusty outflow winds up to 45kt
possible Sun afternoon and evening.
&&
.PREV DISCUSSION...
SHORT TERM...Today through Sunday night...The upper-level low
has elongated over the northern Rockies this morning, extending
from southeast Oregon into north-central Montana. This feature
is maintaining isolated showers and thunderstorms, mainly across
Baker County and the west-central Idaho mountains this morning.
The low will remain over the region today with sufficient
moisture to support additional showers and thunderstorms this
afternoon. Convection will initiate over higher terrain, with a
few storms drifting into the lower valleys by evening. Storms
may produce heavy rain and small hail. Precipitation chances
will diminish tonight with the loss of daytime heating.
An upper-level ridge will briefly build over the area Saturday,
bringing a break from precipitation and allowing temperatures
to rebound to near normal.
Latest guidance trends faster and stronger with the next low
pressure system expected to move through on Sunday. While some
timing differences remain, conditions appear favorable for
thunderstorm development (3050 percent chance) as the trough
passes during peak heating. Precipitable water values
approaching the 85th percentile, along with modest shear and
instability, will support a risk for heavy rain, small hail, and
gusty outflow winds.
LONG TERM...Monday through Friday...Shower chances diminish
Monday as an upper level trough moves east of the area.
Temperatures are expected to be 5-10 degrees below normal Monday
and Tuesday behind the front. By Wednesday, upper level ridging
should bring warmer temperatures within a few degrees of
normal. However, forecast confidence decreases by Thursday and
Friday with models split between another trough moving into the
Pacific Northwest, resulting in slightly cooler temperatures, or
the upper level ridge hanging on and bringing continued warmer
and dry conditions.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...KA
AVIATION.....KA
SHORT TERM...JDS
LONG TERM....JB

NWS BOI Office Area Forecast Discussion