Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 281618
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
918 AM PDT Mon Jul 28 2014
Moisture surge will bring a few sprinkles and thunderstorms to
portions of interior NorCal into mid-week. The increase in clouds
and return of the Delta Breeze will result in a little cooler
temps for portions of the Central Valley today.
Water vapor imagery shows a dry slot over northwestern California in
the southwesterly flow between the Four Corners monsoon ridge and
a trough in the Gulf of Alaska. Visible satellite imagery shows
mid to high level clouds advancing back into interior northern
California this morning as this dry slot retreats to the north.
Expect an increase in cloudiness today through the mid to high
levels as monsoon moisture surges in from the south. Energy
rotating clockwise through the Four Corners monsoon ridge will
cycle through the region today and into midweek producing an
increased likelihood of isolated showers and thunderstorms
primarily over the Northern Coastal range, Lassen Park, and the Sierra
Nevada crest. The moisture and instability associated with this
system is less impressive than the monsoonal surge we experienced
two weeks ago.
Temperatures will remain hot through the upcoming week as the Four
Corner monsoon ridge persists over the western US. There will be
minor day to day fluctuations based on the depth of the marine
layer and strength of onshore flow and cloud cover, but the main
theme will remain hot.
Smoke from the Sand Fire south of Placerville along highway 49
will remain concentrated in the Sierra Nevada Foothills again this
evening and into early morning Tuesday.
.Extended Discussion (Friday through Monday)
Models show the western CONUS ridge maintaining it`s position
over the Intermountain Rockies through the extended, Thursday to
Sunday, with fairly weak S to SSW flow aloft. The resultant flow
aloft will bring some monsoonal moisture northward into the
Sierra. Therefore, we have left a minimal thunderstorm threat over
the Sierra crest south of Highway 50 and around the periphery of
Shasta county. Temperatures remain around normal, with the mid to
upper 90s in the valley and 70s to 90s in the mountains/foothills.
Of course, temperatures will depend on the resultant cloud cover.
The ECMWF and GEM models show an embedded weak low feature aloft
moving northward into NV by Saturday/Sunday, and could add some
instability over northern CA. However, we didn`t bit on any
additional convective coverage this feature this far out as it is
very subtle at this point. JClapp
Mainly VFR next 24 hours. Winds generally 10kts with local gusts
15-20 kts across valley, and sustained 15 to 25 kts poss through
delta. Isolated showers/thunderstorms over Sierra this afternoon,
with slight chance moving into foothills and southern Sac/northern
San Joaquin valley after 00Z Tue.