Wildfire in California, October 1 to 20, 2021

Area Forecast Discussion
National Weather Service Sacramento CA
108 PM PDT Thu Sep 30 2021

.SYNOPSIS...
Warming temperatures with light winds and dry conditions into the
weekend. Cooler temperatures return next week.

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.DISCUSSION...
Clear skies prevailing overhead mostly of northern California on
this final afternoon of September. Today also marks the final day
of the 2021 Water Year, which will conclude with nearly the
entire Central Valley from Redding to Bakersfield under D4
Exceptional Drought. Downtown Sacramento has gone 194 consecutive
days without measurable rainfall (>= 0.01"), matching the previous
all-time record of 194 days set way back in 1880. With the
probability of precipitation at 0% for Downtown Sacramento through
midnight, there is exceptionally high confidence that a new
record will be established, and will only continue to grow.

Upper level, positively-tilted ridge axis is directly overhead
northern California today, which will promote above normal
temperatures for the region. Forecast highs this afternoon will
peak in the upper 80s to low 90s, or about 4 to 8 deg F above late
September normals. Ridge axis will shift southeast tomorrow as a
shortwave approaches the Pacific Northwest. As a result, we should
see a few or several degrees of cooling from today to Friday.
Temperatures will gradually warm again this weekend with dry
conditions. // Rowe

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.EXTENDED DISCUSSION (Monday THROUGH Thursday)...
A cooling trend will commence early next week as a longwave
trough begins to approach the Pacific Northwest. As this trough
approaches the PacNW, a weak closed low off the southern
California coast will lift inland sometime around the middle of
next week. Cluster analysis of the ensembles shows some degree of
uncertainty with respect to timing and placement of these
features, which is entirely expected this far out. Nonetheless,
the arrival of the PacNW trough will bring some precipitation
prospects for far northern California. For now have populated the
extended days 6-8 probability of precipitation with the National
Blend of Models to account for these unknowns. While there is
still low confidence with respect to the timing and location of
the precipitation, there is much greater confidence that the
extended forecast will be cooler with some Valley communities
struggling to hit 80 deg F by Wednesday or Thursday. // Rowe

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.AVIATION...

VFR conditions continue over interior Northern California with
mostly clear skies this evening followed by some high clouds
overnight. Surface winds generally below 12kt, except local gusts
to 16 kt near the Delta.

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.STO WATCHES/WARNINGS/ADVISORIES...
None.

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