604
FXUS65 KBOI 221722 CCA
AFDBOI

Area Forecast Discussion...CORRECTED
National Weather Service Boise ID
944 AM MST Fri Nov 22 2024

...corrected "Total QPF..."...

.DISCUSSION...Light rain and snow continues this morning over
the northern half of our CWA, associated with a northward-
moving warm front. To the south our southern zones will become
quite warm this afternoon with valley highs 55 to 62, near
record highs. Cold front in eastern Oregon will not reach
western Idaho through tonight due to a vort center near
40N/132W moving rapidly eastward. The vort will induce a wave
on the cold front. This will create another warm front in
eastern Oregon that will pass northeastward through our CWA
tonight, followed by the cold front Saturday. High PoPs will
continue through Saturday morning, turning showery Saturday
afternoon. Total QPF is 1-2 inches in the northern half of
our CWA through Saturday night. This will cause rivers to
rise but not enough to flood. Instability under the upper
trough will develop a slight chance of thunderstorms Saturday
afternoon. SPC also depicts an area for general (non-severe)
thunderstorms in central Idaho. Southwest winds will increase
in eastern Oregon today and we may issue a Wind Advisory in
southern Harney County for this afternoon. Otherwise current
forecast is on track.

&&

.AVIATION...Mostly VFR. Widespread rain/snow creating MVFR/IFR
at times, especially in the mountains. Mountain obscuration.
Snow levels 6500-8000 feet. Surface winds: SW to SE 5-15 kt,
with gusts to 30 kt south of KBNO. Winds aloft at 10kft MSL:
SW 45-65 kt, weakening to 30-50 kt by 23/00Z.

KBOI...Mainly VFR with periods of rain. MVFR ceilings possible
in heavier rain. Surface winds: SE 11-17 kt with gusts to 25
kt, decreasing this evening to ESE 8-12 kt.

Weekend Outlook...Mountains obscured. Cold front Fri night
thru Sat, bringing widespread rain/snow and MVFR to LIFR
conditions at times. Snow levels falling to 4500-5500 ft MSL
Saturday and 3000-4000 Sunday. Surface winds becoming SW-NW
5-15 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Sunday night...Widespread
precipitation associated with an atmospheric river will persist
across our northern areas this morning, generally north of a
Burns-Boise-Fairfield line. Snow levels have risen to 7500-8500
feet, limiting any snow accumulations to the highest peaks.
Models continue to support decreasing precip from south to north
this afternoon, although light precip will continue across
central Idaho. The drier south-southwest flow aloft brings
warmer air to the region allowing for temperatures to climb into
the 50s and possibly the lower 60s in a few spots this
afternoon. The somewhat drier conditions look to be short-lived,
however, as a very moist frontal system brings a round of
widespread precipitation tonight through Saturday morning.
Liquid precipitation totals of 1 to 2 inches are expected in the
higher elevations while the valleys average a quarter to half
inch. Snow levels lower to around 5500 feet overnight, but still
the bulk of heavier snow totals will be limited to the
mountains above 6500 feet. Post-frontal instability will bring
showers in the afternoon, along with a slight chance (less than
25 percent) of thunderstorms. Convection diminishes Friday
night, followed by drier conditions associated with a weak upper
ridge on Sunday. Temperatures trend cooler over the weekend,
from around 5 degrees above normal on Saturday to near normal on
Sunday.

LONG TERM...Monday through Friday...The slow moving cut off
upper level low off the Washington State coast will continue to
push moisture and cool air into the region on Monday. There is
fairly good agreement amongst deterministic models that light
precipitation will begin in SE OR on Monday morning, expanding
into SW ID as the low moves inland on Tuesday morning. Ensemble
forecasts keep light precipitation in the forecast through
Tuesday, with below normal temperatures and snow levels around
4000-5000 feet on Monday-Tuesday. Accumulations look to be
minimal with the systems, with a 10% chance of 4" of snow by
Tuesday morning in McCall, ID and low rainfall totals of less
than 0.10" inch in valleys.

A ridge of high pressure will then develop over the
northeastern Pacific, pushing the remnants of the cut off low
east and setting us up for a mostly dry and clear northwestern
flow pattern from Wednesday-Friday. Thanksgiving Day looks to be
mostly clear with slightly below normal temperatures thanks to
the chillier northerly flow. The ridge looks to push steadily
inland and weaken by Friday evening, with the ECMWF
deterministic model showing a weak shortwave moving through the
region on Friday afternoon, introducing a low chance of
precipitation to the region then.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...LC
AVIATION.....SP
SHORT TERM...BW
LONG TERM....SA