Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 192230
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
330 PM PDT Sat Apr 19 2014

.Synopsis...
A weak system well to the north will bring slightly cooler
temperatures today. Building high pressure on Sunday will result
in northerly winds and warmer temperatures. A stronger Pacific
trough will approach the coast Monday bringing increasing clouds
and a chance of rain and higher elevation snow on Monday night and
Tuesday. Some areas may also see isolated thunderstorms. Weak high
pressure will dry things out some Wednesday and Thursday but a
threat of precipitation will continue across the far northern
sections of the state. Another trough will bring another chance of
rain to all of interior Northern California Friday into Saturday.

&&

.Short Term Discussion...
Temperatures running a few degrees cooler this afternoon in most
locations compared to yesterday due to synoptic cooling and
onshore flow with a system moving through the Pacific Northwest
Onshore flow with delta breeze with SUU winds around 20 mph and
southerly winds in the Sacramento Valley. The onshore flow will
decrease and flow will become Northerly tonight as surface high
pressure moves into the Pacific Northwest. Although the MFR-SAC
gradient expected to be about 7 MB and 925 MB winds about 20 kts
tomorrow morning so Northerly winds not expected to be very
strong. The Northerly downslope winds will locally keep some
overnight temperatures warmer tonight than last night. Weak ridge
over the area tomorrow as the system shifts east and a stronger
system approaches the west coast. This will bring warmer
temperates in the mid 80s in the valley and around 80 in the
delta and 60s and 70s in the mountains Sunday afternoon. Temperatures
cool down on Monday into the mid to upper 70s in the Valley and
50s and 60s in the mountains with the trough off the California
coast bringing synoptic cooling and onshore flow. Temperatures
cool down to below normal for this time of the year on Tuesday
with highs in the mid 60s to around 70 in the valley and 40s and
50s in the mountains as the trough moves through the area.

Cooler and possibly wet weather Monday into Tuesday with a
stronger trough affecting Northern California. The timing of
trough has been varying some between the models and model runs.
the 18z NAM is a little slower than the 12z NAM but the 18z GFS
is a little faster than 12Z. The quicker timing may bring
precipitation into the Coastal range and Shasta County during the
day on Monday. The best chance of precipitation will be Monday
night into early Tuesday. The trough moving through Tuesday
morning makes convection less favorable than moving through
in afternoon.  Slight chance of thunderstorms Tuesday morning then
the best instability spreads east Tuesday afternoon for a threat of
thunderstorms over the east side of Sacramento Valley and into
Western Plumas County as trough shifts east. Snow levels will
start out around 7000 ft Monday night and lowering to around 5000
ft Tuesday morning. Snow accumulations generally expected to be
less than 4 inches near pass levels.


.Extended Discussion (Wednesday through Saturday)

The upper level trough will be exiting to the east on Wednesday,
with drying conditions and high temperatures warming to near
normal levels. Could see a few lingering showers over the northern
mountains, with dry weather elsewhere. Ridging on Thursday will
bring a return to above normal highs, with Valley highs in the mid
to upper 70s to near 80. A shortwave with a surface cold front is
expected to move into the area on Friday, spreading chances of
precipitation over much of the area by afternoon. Although there
are timing differences, models continue to show a trough pattern
with unsettled and cool conditions for the end of the week.
Additional shortwaves will continue through the weekend, with more
widespread precipitation and below normal temperatures. Models are
hinting that late Saturday and Sunday could be potentially quite
wet, with a significant moisture plume. A caveat to this is the
12z GFS, which, contrary to earlier runs, is trying to build in
some weak ridging in by late Sunday. Will be watching this system
closely to see how it evolves over the coming days. EK

&&

.Aviation...

VFR conditions will continue the next 24 hours across interior
Northern California. South to west winds 5-15 kt with local gusts
to 30 kt near the Delta will become light tonight. Winds will
shift around to the north 5-15 kt with local gusts to 25 kt across
the Valley on Sunday.

Dang


&&

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

$$







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