Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 280501
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1001 PM PDT Sun Jul 27 2014

.Synopsis...
Moisture surge will bring a few sprinkles and isolated
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 the Central Valley the next few days.

&&

.Previous Discussion...
Mid-level monsoon moisture continues to increase this evening with
preciptable water values approaching 1.00 inches. Skies are partly
cloudy and can`t rule out an isolated sprinkle over southern areas
as debris cloudiness from southern Sierra thunderstorms moves
north after midnight. Weak delta breeze not offering much cooling
with temperatures similar to 24 hrs ago. Current forecast is on
track and no evening update will be needed.

.Discussion...
Band of clouds along the western edge of the monsoon surge of mid
and upper-level moisture continues to move up from the south
through the middle portion of the forecast area. Virga and a few
sprinkles have been occurring with some of the deeper convection,
but so far thunderstorm activity along the band has remained
along the coast or offshore to the south and southwest of the Bay
Area. A few storms have begun to develop over the northern Sierra
to the south of Lake Tahoe at mid-afternoon.

Clouds have held temperatures down through much of the day through
the Central Valley, but readings are rallying at mid-afternoon as
more sunshine has peeked through and are now mostly in the 90s.
Looks like we`ll still end up shy of the century mark today in
Sacramento, but it may be close.

Tricky forecast the next few days with plenty of mid and upper-
level moisture remaining over the area with elevated instability.
Looks like the entrance region of the upper jet arcing over the
western US ridge will remain overhead, and any weak perturbations
coming up from the south may be enough to kick off a few showers
and thunderstorms. Water vapor imagery shows a few stronger waves
to our south - one originating from the large thunderstorm complex
over SW AZ last night and another moving up the west coast of Baja
- that bear watching over the day or so. Latest timing of these
would place them up around the Sacramento area Monday night and
early Tuesday.

Temperatures will also be tricky depending on cloud cover (and the
strength of the Delta Breeze for the Sac region), but will likely
remain rather hot through at least the early portion of the week.

&&

.Extended Discussion (Thursday through Sunday)

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

&&

.Aviation...

Mainly VFR next 24 hours, except areas of smoke near the Sand
Fire. Winds will remain below 10kt across Valley TAF sites. Near
Delta, SW winds 20 kt continue.

&&

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

$$






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