Sunnyslope, Idaho Weather Forecast Discussion

743
FXUS65 KBOI 211603
AFDBOI
Area Forecast Discussion
National Weather Service Boise ID
1003 AM MDT Sun Sep 21 2025
.DISCUSSION...A cold front will move through the region today
with scattered showers and isolated thunderstorms. The cold
front will bring breezy conditions this afternoon with wind
gusts of 20-30 mph from the west-northwest. Temperatures cool to
around 5 degrees below normal on Monday. Breezy conditions
continue on the Idaho side on Monday with gusts of 20-30 mph
during the afternoon in the Treasure Valley and Magic Valley. A
ridge rebuilds over the area on Monday with warm and dry
conditions for the remainder of the week. No updates.
&&
.AVIATION...Generally VFR. Isolated showers and thunderstorms this
morning, becoming scattered this afternoon ahead/along a cold front
moving W to E. Stronger cells will be capable of brief rain, small
hail, and gust outflows to 30-40 kt. Mtns obscured in precip.
Surface winds: variable up to 10 kt, then SW-NW 5-15 kt with 15-25
kt gusts this afternoon. Winds aloft at 10kft MSL: SW to W 10-25 kt.
KBOI...VFR. A 20% chance of light rain this morning. Scattered
showers will move through Treasure Valley between 21/17Z and 22/03Z,
with 40% chance of impacting KBOI. Activity capable of brief rain,
lightning, and outflow gusts around 30 kt. SE surface winds will
transition to NW between 16Z-18Z.
&&
.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...Latest satellite
imagery shows mid-level clouds over our CWA and a cold front
approaching from the northwest.  The front will pass through
eastern OR this morning and western Idaho late morning through
afternoon, with showers and scattered afternoon thunderstorms.
In Oregon most of the showers will occur in Baker County (20
to 50 percent coverage), with less than 20 percent coverage to
the south. The most numerous showers and thunderstorms will be
on the Idaho side north of the Snake Basin this afternoon: 60
to 90 percent coverage of showers and 30 to 40 percent chance
of thunderstorms in the West-Central Idaho Mountains and Boise
Mountains. We also have 50 to 70 percent coverage of showers
and 20 to 30 percent chance of thunderstorms in the southern
Sawtooths and Owyhee Mountains this afternoon. The front should
exit our CWA to the east by late afternoon, with decreasing
clouds this evening. The front will also introduce west/
northwest winds 15 to 25 mph this afternoon and 10 to 20
degrees cooling compared to yesterday. Winds will decrease this
evening and tonight will be at least 10 degrees cooler than the
current night. Patchy fog will form in northern valleys toward
morning. Monday looks sunny, breezy, and cool under northwest
flow aloft behind the exiting upper trough. However, HRRR model
shows patchy smoke getting into northern-most areas from the
north on Monday. Tuesday morning should be the coldest period,
with lows in the upper 20s through 30s in the mountains and
higher basins, and 40s in the lower southern valleys. High
pressure aloft will build rapidly over our area Tuesday night
and Wednesday, with clear skies and warmer temps promised for
Wednesday, but Wednesday morning low will still be cool.
LONG TERM...Wednesday through Sunday...A prominent upper-level
ridge will center over the northwestern U.S. on Wednesday,
reinforcing dry conditions and boosting max temperatures to
5-10 degrees above normal. This ridge will quickly flatten and
shift eastward on Thursday as a series of progressive shortwave
troughs pass through SW Canada. Despite the shift, warm and dry
conditions are expected to prevail for E Oregon and SW Idaho
through the week. Thereafter, a considerably broader, Gulf of
Alaska trough is forecast to expand southward over the E Pacific
by the weekend, re-amplifying the warm and dry ridge over the
Northwest. Long range models suggest this trough will reach the
West Coast by late weekend or early next week, promoting cooler
temperatures and a slight increase in precipitation
probabilities. Ensembles continue to struggle with the evolution
of this trough, however, which would drastically determine how
cool and wet conditions will become once it moves onshore.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...KA
AVIATION.....CH
SHORT TERM...LC
LONG TERM....SH

NWS BOI Office Area Forecast Discussion