Crystal, Idaho Weather Forecast Discussion

497
FXUS65 KBOI 111554
AFDBOI
Area Forecast Discussion
National Weather Service Boise ID
954 AM MDT Thu Sep 11 2025
.DISCUSSION...
As an upper low moves overhead, wrap around moisture will bring
numerous showers and thunderstorms to central ID, NE OR, and
S-central OR. Across the rest of the area, shower and storm
coverage will be more scattered. Stronger storms will bring
heavy rain that continues to pose a flash flooding threat to
burn scars in the area. Isolated coverage of showers this
morning will steadily increase through the day. By this
afternoon, outflows up to 40 mph and small hail become possible.
There`s no update to the previous forecast, the Flash Flood
Watch for E Oregon remains in place, especially for burn scars.
Slow moving storms near the center of the low may allow rainfall
to accumulate in the same spot for a prolonged period of time.
While in the central mountains of Idaho decent instability could
allow storms to organize over burn scars in this region, though
chances are less than in Oregon.
&&
.AVIATION...Numerous showers and isolated thunderstorms in
S-central and E OR, and central ID. Scattered showers possible
across the rest of the area this evening, Mountains locally
obscured in clouds and showers. Thunderstorms may result in
brief MVFR/IFR conditions and contain locally heavy rain, small
hail, and gusts to 35 kt. Surface winds: mainly SW-NW 5-15 kt.
Winds aloft at 10kft MSL: SE-SW 5-15 kt.
KBOI...VFR. Scattered-broken mid level clouds today with isolated
showers in the vicinity. Surface winds: NW 5-10 kt.
Weekend Outlook...Scattered showers and thunderstorms will develop
Friday afternoon, mainly over the higher terrain, resulting in
localized MVFR/IFR conditions and mountain obscuration. Drier
conditions will return Saturday before shower and thunderstorm
chances return on Sunday. Surface winds mainly SW-NW 5-15 kt.
&&
.PREV DISCUSSION...
SHORT TERM...Today through Saturday night...The upper-level
low will continue to move slowly northeast across the forecast
area today, maintaining the threat for showers and
thunderstorms. Stronger embedded storms will bring the potential
for heavy rainfall, especially across southeast Oregon, where
flash flooding and debris flows remain a concern on burn scars.
Isolated showers and thunderstorms will persist this morning
before expanding in coverage this afternoon, mainly along the
northern and eastern flank of the low. This will again place
northern Harney and Malheur Counties, along with Baker County,
in the most favorable zone for convective development and an
increased risk of flash flooding. Rainfall reports of 0.75 to
1.25 inches have already come in from southeast Oregon
yesterday, so it will not take much additional rainfall to cause
flooding. WPC continues to highlight this threat in a Marginal
Risk for Excessive Rainfall, and the Flash Flood Watch has been
extended through late tonight.
Farther east, slightly stronger dynamics and instability will
support thunderstorm development across south-central Idaho from
the western Magic Valley north into Valley County. CAMs differ
on where initiation will occur, with some showing development in
Valley County and others farther south into Boise and Elmore
Counties. Confidence in exact placement is therefore lower, but
these areas will need to be monitored for flash flood potential
should storms track farther south.
Precipitation chances will decrease tonight with the loss of
daytime heating. By Friday, scattered showers will linger over
higher terrain, mainly Baker County and the west-central Idaho
mountains, as the low exits the area. An upper-level ridge will
briefly build in on Saturday, bringing a break from
precipitation and allowing temperatures to rebound to near
normal by Sunday. Temperatures will remain below normal today
and Friday.
LONG TERM...Sunday through Thursday...An upper level trough
and cold front will move into the Pacific Northwest on Sunday.
This will bring a 20-50% chance of showers to our area with the
highest chance across the northern mountains. There will also be
enough instability for a slight chance of thunderstorms. High
temperatures are forecast to be near to slightly above normal
across SW Idaho and below normal across SE Oregon, although this
will be dependent on the timing of the front. Winds will become
breezy as well as the front pushes through the area. Shower
chances diminish Monday as the trough closes off and shifts east
across our 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 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...Flash Flood Watch until 9 PM MDT /8 PM PDT/ this evening
     ORZ061>064.
&&
$$
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DISCUSSION...JM
AVIATION.....JM
SHORT TERM...JDS
LONG TERM....ST

NWS BOI Office Area Forecast Discussion