Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 222036
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
136 PM PDT Mon Sep 22 2014

.Synopsis...
Dry and warmer temperatures early this week. Cooler and wetter
weather expected for the middle to end of the week.

&&

.Discussion...
Short-wave ridging developing in the wake of an upper low that
brought cooler temperatures and thunderstorms over the weekend.
The upper low began reintegrating with the mean westerly flow
aloft and quickly ejected out of the area over the last 24 hours.
Fall begins this evening, and a fall-like cool, wet upper trough
will arrive later this weekend to welcome in some seasonal
weather. Increased southwest winds and a period of dry weather
just ahead of the troughs arrival could make containment efforts
at the King fire more difficult.

Near normal temperatures are expected in the benign flow from
today through Wednesday, but temperatures will drop to several
degrees below normal from Thursday into the weekend. This aligns
with the arrival of the main band of precipitation arriving on
Thursday. Have added slight thunderstorm chances over the Sierra
during the afternoon...where the best instability is progged. Main
forecast challenge is timing/coverage/intensity of precipitation
as models tend to struggle significantly with seasonal transition
systems. DRP

&&

.Extended Discussion (Friday through Monday)

Upper level trough will remain over Northern California Friday
into the weekend bringing cooler temperatures and a chance of
precipitation. Temperatures will be in the 70s to near 80 in the
Valley and 50s and 60s in the mountains on Friday. These
temperatures are around 6 to 12 degrees below normal for this time
of year. Temperatures may warm up over the weekend but how much
depends on how quickly the trough moves to the east.

Scattered showers will be possible over interior Northern
California on with the best chance north of Interstate 80. The
models continue to vary with the strength, track and timing of the
trough for low confidence in when the precipitation will end and
coverage of precipitation. The GFS is the fastest and weaker with
the trough and the ECMWF the slowest and forming a closed low over
Northern California. The forecast leans towards the ECMWF with
precipitation possibly lingering into next weekend especially over
the mountains.


&&

.Aviation...

Generally VFR conditions next 24 hrs except local MVFR/IFR conditions due to
smoke around King Fire including nearby foothill locations.

&&

.STO Watches/Warnings/Advisories...
None.
&&

$$







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