Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 282129
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
229 PM 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 ridge and a
Gulf of Alaska trough. Mid to high level monsoonal moisture has
advanced back into interior northern California today as the dry
slot retreats further to the north. 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.
Precipitation will most likely fall as virga over the valley, but
some isolated sprinkles could reach the valley floor. Mosaic radar
already shows moderate convective activity pushing northward from
central California this afternoon. Cells have managed to produce light
precipitation (a few hundreths of an inch) according to mesonet
stations in central California.
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.
.Extended Discussion (Friday through Monday)
Models show the western CONUS ridge maintaining it`s position
over the Intermountain Rockies through the extended, Friday to
Monday, 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 toward the central CA coast 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. Isolated SH/TS over Sierra this
afternoon, with slight chance moving into foothills and southern
Sac/northern San Joaquin valley after 00Z Tue. Weak convective
could continue tonight w/ TS over mountains Tue afternoon. JClapp