Area Forecast Discussion
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FXUS66 KSTO 310842

Area Forecast Discussion
National Weather Service Sacramento CA
142 AM PDT Sat Jul 31 2021

Late day mountain thunderstorm chances expected through the
weekend. Temperatures will gradually moderate through the weekend,
returning to near-normal by Sunday.


Plenty of mid- and high-level clouds passing overhead tonight as
leftover remnants from the afternoon and evening convection.
Composite radar still shows some showers to the east of the Sierra
crest this early Saturday morning, as well as a few echos from
showers in Shasta County. Onshore gradient from San Francisco to
Sacramento is stronger compared to this time 24 hours ago, and is
reflected in the winds at Travis Air Force Base with gusts around
25 kt. Should see overnight lows in/around the Delta a tad cooler
than Friday with temperatures around sunrise in the 50s to 60s
from Solano to Sacramento Counties, and middle 60s to low 70s for
other Valley communities.

Broad and high-amplitude upper level ridge over the Great Plains
will begin to weaken over the next 24 hours. Decreasing
geopotential heights aloft should bring minor synoptic-scale
cooling to the region this afternoon as well as on Sunday. Highs
today will range from the upper 80s in the Delta, middle 90s to
near 100 in Sacramento County and northern San Joaquin Valley, and
100 to 105 deg F for the central and northern Sacramento Valley.
Afternoon and evening shower/thunderstorm chances will be renewed
again this afternoon, generally impacting the Sierra and southern
Cascades. Best chances will likely be along and to the east of
the crest, but can`t rule out a slight chance on the west side. If
you have outdoor plans this weekend in the mountains, keep and
eye on the skies, and when thunder roars go indoors!

Upper level ridge will retrograde west toward the Desert Southwest
and Rockies through the weekend. Combined with an upper level
trough west of California, southwesterly flow aloft will prevail
for the region into the first half of next week. Minimal day-to-
day changes in temperatures are forecast as most locations will
land near or just above early August climatological normals.
// Rowe


Clusters and ensemble guidance continue to favor dry, southwest
flow aloft through the end of next week with an upper level ridge
parked over the Desert Southwest / southern California and a
trough off the West Coast. National Blend of Models has a moderate
spread in the 25th to 75th percentile temperatures by Thursday --
96 to 103 deg F for KRDD and 93 to 100 deg F for KSAC. A few
clusters hint at the shortwave trough clipping far northwest
California late next week, though still plenty of uncertainty this
far out. Overall generalization for mid/late next week has
temperatures within about 5 deg F of normal with occasional breezy
conditions around the Delta. // Rowe

Mainly VFR conditions for the next 24 hours. Local MVFR/IFR
conditions over Plumas and Butte Counties due to wildfire smoke.
HZ may impact RDD/RBL after 22Z due to an additional wildfire.
Onshore flow with surface gusts up to 20 knots this afternoon in
the Central Valley, and up to 30 knots in the vicinity of the
Delta. Isolated- scattered showers and thunderstorms over the




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