Area Forecast Discussion
Issued by NWS Sacramento, CA

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897
FXUS66 KSTO 200357
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
857 PM PDT Tue May 19 2015

.Synopsis...
Variable clouds with mainly mountain showers and afternoon
thunderstorms through the week as the west coast remains under
the influence of a low pressure system. Daytime highs forecast to
remain below normal.

&&

.Discussion...
Lingering showers over the mountains with most of the activity
over the far northern part of the state this evening.  Low
pressure system will stay off the coast through Wednesday so
expect little change in conditions for tomorrow.

The low will begin to move south to off the central coast for
Thursday and then move into Southern California for Friday. In
general most of the activity will stay over the mountains but a
few showers or isolated thunderstorms may be able to work its way
into the valley as the low transitions into Southern California.
No major changes in temperatures with below normal highs
continuing through Friday. Decent flow through the delta will
continue as well.

&&

.Extended Discussion (Saturday through Tuesday)

Area will be sandwiched between ridging building over eastern
Pacific and trough departing to the east for the start of the weekend.
Models continue to differ on the track and speed of the trough as
it departs. GFS moves the trough off faster to the east with
riding across the area for the weekend into Tuesday, which would
lead to a dry forecast. ECMWF/GEM are slower with the departure
and continue the chance for mountain showers and thunderstorms
through at least Sunday. Given uncertainty, have not made major
changes to going forecast. Feel that there may be enough
instability present to continue the chance for daily showers and
thunderstorms across higher terrain through Sunday for now. May
then see a break in convection for Monday and Tuesday. Regardless,
valley should remain dry in either scenario. Temperatures will
hover within a few degrees of normal with valley highs generally
in the 80s and foothills/mountains in the 50s to 60s. CEO


&&

.Aviation...

Mainly VFR conditions next 24 hours for interior NorCal except
during showers and afternoon/evening thunderstorms that bring
periods of MVFR. Best chance for showers/thunderstorms is across
higher terrain and far northern portions of Sacramento valley.
Delta breeze will be 10-20 kts with gusts up to 25 kts.


&&

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

$$







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