Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 301608
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
908 AM PDT SAT APR 30 2016

.Synopsis...
Strong Northerly wind over Interior NorCal today. Warming over
the weekend with above normal temperatures continuing into early
next week. Afternoon showers and thunderstorms possible over the
mountains Sunday and Monday. Mostly dry Tuesday, then more
widespread showers and thunderstorms possible Wednesday into
Friday.

&&

.Discussion...
Winds have begun to mix down over the last hour or so with more
widespread gusts through the Central Valley. MFR to SAC gradient
holding steady at around 11.5 to 12 mbs past several hours and
KDAX VWP still showing 40 kts at 2K feet, so 40-50 mph likely
the max gust potential today - wind advisory continues. Minor
updates issued.

&&

.Previous Discussion...
Water Vapor imagery showing vort max tracking southeast of the CWA
this morning along with associated showers. Ridging aloft off the
West Coast will begin building inland today. Weak vort maxes
along leading edge of ridge will continue to track over Eastern
portions of the CWA today keeping a slight chance of showers over
the higher terrain of the Sierra Nevada. KMFR-KSAC surface
pressure gradient above 11 mb this morning with KDAX VAD profiler
showing 40 kts of North wind at 2k ft. Breezy Northerly already
occurring at numerous spots in the Central Valley and winds will
continue to increase this morning after sunrise as stronger
momentum aloft mixes down. Wind advisory in place to cover
potential impacts. AMS begins warming today in response to
increased subsidence and downslope flow. High temps this afternoon
expected in the lower 80s with 50s to 70s for the mountains and
foothills.

Gusty wind continues over Interior NorCal tonight, but expected to
drop below advisory criteria as low level gradient begins to turn
NE-SW and starts to become out of phase with winds aloft. By
Sunday morning, low level pressure gradient is oriented E-W and
northerly flow aloft turns cyclonic as meso upper low, rotating
around main low over Desert SW, slowly begins to swing into
Interior NorCal. Feature will keep a chance of afternoon/evening
showers and thunderstorms over the mountains Sunday and Monday.
High temps continue to bump up into the mid 80s for the Central
Valley Sunday into Monday.

As Omega block shifts east, upstream upper trough approaches
California Tuesday with mostly dry weather and max temps trending
down. Threat of more widespread showers and thunderstorms through
midweek as upper low digs along CA coast and impacts the forecast
area. PCH

&&

.Extended Discussion (Wednesday thru Saturday)...
A Pacific low pressure system forecast to move across the state
will bring cooler temperatures and scattered showers across to the
forecast area Wednesday through the end of the week. Main
precipitation threat on Wednesday will be over the northern CWA
and over the Sierra Cascade range where southerly flow will bring
the best orographics. Stability proggs show instability over most
of the north state Wednesday afternoon so included slight chance
of thunderstorms in these areas. Cloud cover and cooler airmass
will bring daytime highs Wednesday back down closer to normal for
early May. Main upper low center moves onshore by Thursday
afternoon or evening. Cyclonic flow over entire north state will
bring a shower threat to all areas of the CWA on Thursday
afternoon with instability over the higher elevations bringing
isolated thunderstorms. Upper low continues eastward on Friday but
norcal remains under cyclonic flow so shower threat continues.
Main instability shifts to the far eastern CWA so limited
thunderstorm threat to the Sierra on Friday. By next Saturday,
all models shift main upper low into Great Basin. Upper ridging
next weekend should bring decreasing shower threat.

&&

.Aviation...
VFR all TAF sites next 24 hours. Isolated showers possible this
afternoon over the northern Sierra. North to east winds 10 to 20
knots gusts to 45 knots west side of Sacramento valley and over
Sierra. Winds decreasing slowly after 00z.

&&

.STO Watches/Warnings/Advisories...
Wind Advisory until 5 PM PDT this afternoon for Carquinez Strait
and Delta-Central Sacramento Valley-Clear Lake/Southern Lake
County-Mountains Southwestern Shasta County to Northern Lake
County-Northern Sacramento Valley-Northern San Joaquin Valley-
Southern Sacramento Valley.

&&

$$



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