Jamieson, Oregon Weather Forecast Discussion

446
FXUS65 KBOI 102001
AFDBOI
Area Forecast Discussion
National Weather Service Boise ID
201 PM MDT Wed Sep 10 2025
.SHORT TERM...Tonight through Friday night...A closed low over
northern California is moving up to the OR/NV border this
evening, bringing widespread showers and scatter thunderstorms.
Thunderstorms could produce gusts up to 50 mph, heavy rain, and
small hail. Heavy rain over burn scars in Eastern Oregon have
prompted the issuance of a Flash Flood Watch through the night.
The low has been visible on satellite throughout the day
following the track described all models. An area of
thunderstorms has already formed close to and in the moisture
band of the low. The environment over our forecast area has 0.8
inches of PW (about 80th percentile) and about 400 J/kg of
SBCAPE. Though, with the cloud cover and moisture, CAPE values
vary widely among HREF members, from 100 up to 1000 J/kg. That
said, we will have the broad forcing on the left exit of an
upper jet core and surface low moving in. All CAMs show a broad
area of showers and thunderstorms directly associated with the
center of the low being the primary threat tonight. SPC has
added a marginal risk of severe weather and WPC maintains their
marginal risk for excessive rainfall resulting in flash
flooding.
Consensus among the CAMs shows a broad 40-50 mph gust front
moving through the Snake Plain tonight, including the Treasure
Valley and Magic Valley. While uncertainty is high in the exact
track due to the cause being thunderstorms, consensus among CAMs
for an outflow is a significant indicator of occurrence. The
moisture is also projected to fuel heavy rain rates in stronger
showers and storms. Models project 0.5" in one hour locally,
but the environment could be conducive to much more if storms
can become organized in our marginally sheared environment (EBWD
of 29 kts). Reports of small hail in storms this morning support
the inclusion of hail as a possibility in storms tonight. Wrap
around moisture supports a 15-30% chance of precipitation Friday
evening before a shortwave ridge begins to move in behind the
low.
.LONG TERM...Saturday through Wednesday...Warmer and drier weather
Saturday and Sunday with models in close agreement moving a
weakening short wave ridge eastward across our CWA.  Models then
bring a north Pacific upper low inland across WA Sunday night and
a lobe ahead of it carrying showers and a chance of thunderstorms
into southeast OR.  GFS forecasts the low center to deepen over WA
Monday, then move to southern OR Tuesday, and across southern ID
Wednesday.  This track is favorable for significant rainfall in our
CWA as well as below normal daytime temperatures. Latest NBM
forecast, however,  keeps total pcpn less than .20 inch even during
the wettest period (Sunday night through Monday), while NBM MOS
statistical guidance keeps the chance of any measurable amount at
only 30 to 50 percent.  These values may look conservative but
not unrealistic, as forecasting the track of inland closed lows
is difficult, and by Sunday night the models have fallen out of
agreement.
&&
.AVIATION...VFR. Scattered showers and isolated thunderstorms
in se OR, and also after 11/00Z in sw ID.  Mountains locally
obscured in clouds and pcpn.  Thunderstorms will have local
heavy rain, small hail, and gusts to 45 kt.  After 11/06Z
numerous showers north of KBNO-KMYL with frequent mountain
obscuration. Showers ending elsewhere from south to north by
11/12Z. Scattered showers and local mountain obscuration
continuing west of KBNO-KBKE through 11/18Z. Surface winds:
variable 5-15 kt. Winds aloft at 10kft MSL: E-S 15-20 kt.
KBOI...VFR. Scattered-broken clouds at or above 10 kft AGL
until 11/01Z. Showers and thunderstorms from 11/01Z until
11/06Z. Gusts to 40 kt and local MVFR in heavy rain with
thunderstorms. After 11/06Z scattered clouds 5 kft AGL and
broken aoa 10 kft AGL. Surface winds: NW 10kt until 11/01Z, then
variable through 11/10Z, then light SE.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...Flash Flood Watch through late tonight ORZ061>064.
&&
$$
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SHORT TERM...JM
LONG TERM....LC
AVIATION.....LC

NWS BOI Office Area Forecast Discussion