Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 261016

Area Forecast Discussion
National Weather Service Sacramento CA
316 AM PDT Thu Apr 26 2018

Warm and dry today except a slight threat of isolated mountain
showers or thunderstorms. Cooler Friday through the weekend with
increasing chances for mainly mountain showers and thunderstorms.


One last day of above normal temperatures expected today as the
west coast remains under upper level high pressure ridging. Main
ridge axis has shifted east of the state however ahead of a
Pacific low pressure system edging towards the coast. Models are
indicating a slight threat of convective showers over the Sierra
and Coast range this afternoon as the north state edges under
cyclonic flow. A fairly sturdy delta breeze has developed and is
expected to continue through the day. Therefore temperatures will
cool today in the delta and near delta areas more significantly
than elsewhere while still remaining a little above normal. Main
upper low is forecast to push into the Pacific Northwest and
Norcal on Friday bringing cooling to all areas. Daytime highs will
drop to a little below normal thanks to cooler airmass and cloud
cover especially over the northern most portion of the state.
Areas closest to the low center over the northwest portion of the
state will see another threat of afternoon showers. This threat
will shift eastward Friday night as the upper low continues to
shift inland. Stability progs indicate enough instability for a
chance of thunderstorms as well. The upper low continues to shift
inland on Saturday bringing still more cooling and spreading the
shower threat over most of the CWA. Stability progs indicating
most unstable areas Saturday afternoon will be far north state and
over the Sierra Cascade crest so have limited thunderstorm threat
to these areas. Only minor changes are expected on Sunday as the
upper low continues to slowly lift northeastward. Showers or
thunderstorms will remain a possibility over the northeast half of
the forecast area Sunday but areas southwest of about Marysville
should remain dry.


Northern California will likely remain under cyclonic flow on
Monday and potentially into Tuesday, with a longwave trough
centered over the Pacific Northwest. As such, the chance for a few
high Sierra showers and thunderstorms will persist.

This upper troughing will shift eastward toward the middle of next
week as the eastern Pacific ridge builds into California. This
will result in warmer and drier weather across the region. Longer
range models hint at a broad area of low pressure returning to the
West Coast late next week, bringing a modest cooling trend and
potentially a few mountain showers.




Mainly VFR conditions the next 24 hours across the region. Local
IFR conditions possible near the Bay / Delta region this morning.
Isolated thunderstorms possible over the high Sierra this

South to west winds 5 to 15 kt will continue today across Valley
TAF sites. Local gusts up to 30 kt near the Delta.




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