Wildfire and Astronomical Low Tide in California, August 1 to 31, 2021

Area Forecast Discussion
National Weather Service Sacramento CA
1042 PM PDT Sat Jul 31 2021

.SYNOPSIS...
Late day mountain thunderstorm chances expected through the
weekend. Near normal temperatures will continue through the rest
of the weekend into next week.

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.DISCUSSION...
The Evening Update: Cloud cover from the Desert SW has been shifting
Ewd this evening as the Ern Pac trof moves inside 130W. This will be
the trend into Sun as the Sierra convection will be farther E, near
the Sierra Crest and mostly to the east, as SWly flow will prevail
over Norcal. This will push smoke from the Dixie Complex generally
off to the NE as well.

Weakening of the ridge has allowed virtually the entire CWA to enjoy
some cooling. Save for KSMF at 05z, the other sites were running
from 1 to 11 degrees cooler, albeit the Delta Breeze is weaker and
the marine layer just slightly deeper. Temps on Sun expected to be
similar to today in the Delta influenced areas and near their
respective normals while again reaching into the triple digits in
the Nrn Sac Vly. Forecasts suggest energy within the Ern Pac trof W
of 130W will be dropping Swd on Sun which should slow the Ewd
progression of the trof allowing for warmer temps away from the
Delta influence.  JHM

.Previous Discussion...
Upper level ridging is weakening, with a little cooler onshore flow
spreading in. South to west winds are generally gusting up to 15 to
20 mph, locally up to 30 mph in the Delta. Temperatures are less hot
this afternoon by 5 to 10 degrees compared to 2 pm yesterday. For
the northern Sacramento Valley it was seasonably hot at 100 for
Redding, 97 for Red Bluff.

Monsoonal moisture continue to bring afternoon and evening shower
and thunderstorm chances. The main areas of development are around
Lassen National Park/Burney Basin and the Sierra south of Highway
50. Shear is limited and storms are tending to pop up and collapse
fairly quickly. Some brief heavy rain and small hail are possible
into this evening, though, so be prepared if outdoors or driving
in the area. Strongest storms so far have been further to the
south in Yosemite or east of the crest. One last afternoon of
thunderstorms is possible on Sunday, followed by drier weather for
the rest of the week as monsoonal moisture shifts to the east.

Southwesterly flow continues next week with near normal
temperatures.

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.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

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

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.AVIATION...

VFR conditions expected at the TAF sites the next 24 hours. Areas
of smoke near the Dixie and McFarland fires will bring localized
MVFR conditions. Southerly winds 7-15 knots, locally stronger in
the Delta region. Isolated-scattered showers and thunderstorms
over the mountains.
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.STO WATCHES/WARNINGS/ADVISORIES...
None.
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