Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 031613

913 AM PDT Sun May 3 2015

Warm temperatures with a slight chance of mountain thunderstorms
continue through Tuesday. Cooler and more unsettled weather will
set in mid-to-late this week.


No updates to morning forecast. Current temperatures are running
1-6 degrees cooler than 24 hours ago thanks to the onshore flow of
cooler marine air earlier. The onshore gradient/delta breeze is
starting to relax now and satellite imagery shows that marine
stratus is slowly retreating from the Delta region. Daytime highs
will be above normal again today.

.Previous Discussion...
Mainly clear skies persist across interior Northern California as
a weak and baggy trough remains situated off the California coast.
This trough has aided in deepening the marine layer (now at 2000
ft at Fort Ord) and strengthening the onshore gradient. At this
hour, marine stratus has pushed inland through the Carquinez
Strait, and may reach the eastern Delta by sunrise.

A slow and gradual cooling trend is in store the next few days,
though warmer than normal temperatures will likely continue. The
most noticeable cooling will probably be near the Delta, where a
stronger Delta Breeze will be blowing the next few days. All told,
expect a couple degrees or so of cooling each day through midweek.
With the enhanced onshore flow, we may also see some marine
stratus reach the Sacramento metro area Monday morning.

A few showers and thunderstorms are likely to pop across the
interior mountains the next few days, but southwest flow aloft
will likely carry any convection into Nevada.

A low originating from the Gulf of Alaska will be moving through
the Pacific Northwest on Tuesday, dropping south toward California
mid-to-late this week. We may begin to see some showery weather
mainly over the mountains beginning Wednesday.


.Extended Discussion (Thursday through Sunday)

Mid range models still struggling a bit on exact track of cold
upper low dropping out of the Gulf of Alaska. Models seem to be
zeroing in on upper low center tracking somewhere over Norcal on
Thursday. Cold air aloft associated with this low will likely
generate enough instability to make mountain showers or
thunderstorms a good possibility. Valley showers or thunderstorms
might also be a possibility if upper low center tracks over it but
uncertainty in models still too high to be confident in a valley
shower scenario. Cooling daytime temperatures are a likely outcome
with daytime highs Thursday cooling to near or several degrees below normal
for this time of year. Models shift upper low slightly eastward on
Friday and have adjusted precipitation chances accordingly. Models
in good agreement in shifting upper low center into the Great
Basin by next Saturday with small scale ridging over the west
coast. Not enough instability on Friday for T-storms but wrap
around moisture from low could bring a few mountain showers north
and east. Most areas currently appear will be dry next Sunday with
daytime highs bouncing back to several degrees above normal but
overrunning moisture could allow a few light showers northern



Generally VFR conditions the next 24 hours across interior
Northern California. A few thunderstorms may form along the Sierra this
afternoon and early evening. Winds generally below 15 knots except
southwest 15 to 20 knots gusting to 25 kt through the Delta and
locally gusty in vicinity of Sierra thunderstorms.


.STO Watches/Warnings/Advisories...

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