Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 251557

857 AM PDT Mon May 25 2015

Gradually warmer temperatures this week with mainly mountain
showers and thunderstorms afternoons and evenings through the
middle of the week. High pressure dries things out by late in the
week, with high temperatures peaking at 10 to 15 degrees above


A cooler start to this Memorial Day, especially in Delta Breeze
influenced areas, where temperatures are 3 to 6 degrees lower than
Sunday Morning. Marine stratus clouds from Sacramento eastward
have quickly burned off, while some low clouds linger over the
Delta and along I5 between Dunnigan and Orland. These will
diminish by later this morning.

The southern end of a trough extends down over the area from a low centered
over the Pacific Northwest. This will brush through the area today
firing up more showers and thunderstorms over the mountains by this
afternoon. The best instability and potential for convection in
the forecast area appears to be focused over the northern Coastal
Range and over eastern Shasta County, and western Plumas/Lassen
National Park, with activity also along the Sierra crest.
Convection over the Coastals should peak late afternoon/early
evening, while over the mountains to the east at that point much
of the activity should shift to the east of the crest. Mesoscale
models continue to show a few cells potentially tracking eastward into
northern Sacramento Valley late this afternoon.

A diminished potential for afternoon mountain showers and thunderstorms
continues on Tuesday and Wednesday. Upper level ridging builds in
by Thursday, with warmer and drier weather moving in. Many Valley
locations will be in the 90s Thursday, peaking on Friday with well
above normal temperatures persisting into the weekend. EK


.Extended Discussion (Friday through Monday)

High pressure ridge will be centered across NorCal on Friday
making for what should be the warmest day of the period. Dry
weather is expected across the area with above normal afternoon
temperatures reaching into the upper 80s to mid 90s in the valley
and 60s to 70s in the mountains. Benign weather and mostly sunny
skies will continue through the weekend as high pressure remains
in control. As the ridge shifts east, increasing onshore flow will
cool temperatures a degree or two Saturday and a few more degrees
Sunday but still above normal for the end of May. Models hinting at
next system approaching NorCal by next Monday/Tuesday with a
chance for precip across the north, but substantial differences remain
this far out.         CEO



Generally VFR conditions expected for the next 24 hours. A few
showers and thunderstorms across higher terrain this afternoon and
evening may lead to local MVFR restrictions. Marine stratus this
morning has largely burned off execept for some lingering patches
in the Delta, which will diminish through the rest of the morning. Locally
gusty winds will continue through the Delta with gusts to 30 kts.


.STO Watches/Warnings/Advisories...

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