Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 240001

401 PM PST Mon Feb 23 2015

Decreasing winds and dry this evening. Lighter winds and clear
skies may bring some Valley frost for early Tuesday. Dry and
warmer weather mid-week, then a pattern change by the end of the
week, bringing cooler and wetter weather Friday into the weekend.
There is the potential for snow impacting travel in the mountains
above 4000 feet.


.Discussion...Mostly clear skies over the area with a few spots
such as Marysville, Sacramento Executive Airport and McClellan
Airfield still seeing some marginal advisory level winds
(sustained 25 mph). The surface gradient has decreased and will
weaken further tonight. Will continue the Wind Advisory through 5
pm this afternoon, with breezy winds expected to wind down, except
locally in the mountains. Isolated showers east of Modesto and Turlock
have ended, with dry weather returning across the forecast area.

The upper low which brought the wind and showers south of Highway
5 is shifting to the south and east. Lighter winds combined with clear
skies and a cold airmass tonight into early Tuesday will allow
temperatures to drop quite a bit, possibly to levels not seen
since early January. The northern Sacramento Valley may have
enough wind to keep temperatures warmer, through mixing. Overnight
temperatures are tricky, but locations in the Valley and foothills
further south could see freezing temperatures. There could possibly
be some lows dropping into the upper 20s in a few sheltered areas
on the east side of the Valley. A Frost Advisory is in effect
Tuesday morning from 3 am to 9 am. People are urged to take steps
to protect sensitive plants and give outdoor pets shelter.

Upper level ridging with dry northwesterly flow will bring dry
conditions and warming temperatures through early Thursday.
Some northerly winds overnight should allow more mixing overnight,
so this and the warming airmass should end the short term frost
concerns on Tuesday. A rather cool system dropping down from
British Columbia begins to spread into the southern Cascades and
possibly into the northern Sacramento Valley Thursday night.


.Extended Discussion (Friday through Monday)

Wetter weather looks to make a return for Friday into the weekend
as wave moves SE from the Pac NW in NW flow over the weekend.
Differences remain in handling of this system with ECMWF depicting
a faster, further east solution than GFS or GEM. Regardless, think
everywhere has a decent shot at seeing some showers. Amounts
should remain light, especially in the Valley, as moisture is
limited. Early QPF amounts range from less than a tenth of an
inch in the valley to around an inch at higher elevations. Item of
note though will be colder air associated with system. This may
produce lower snow levels than previous systems we`ve seen this
winter. As system moves in snow levels will start out around 5000
feet but could drop as low as 3500 by Saturday into Sunday. This
may lead to some travel headaches below pass levels and will be
one to watch. Setup also favorable for isolated thunderstorms on
Friday, especially if afternoon timing holds up. Shear profiles
are favorable and development will hinge on how much instability
is realized. Next system progged to move SE from Pac NW by early
next week. Large differences in model solutions lead to low
confidence at this point.



VFR conditions the next 24 hours. Gusty north winds to 30 kt
across the Valley will subside around sunset, and be generally
below 10 kt tonight into Tue. Gusty NE winds will continue across
the Sierra tonight.



.STO Watches/Warnings/Advisories...
wind advisory until 5 pm pst this afternoon carquinez strait and
delta...central sacramento valley...clear lake/southern lake
county...mountains southwestern shasta county to northern lake
county...northeast foothills/sacramento valley...northern
sacramento valley...southern sacramento valley.

frost advisory from 3 am to 9 am pst tuesday central sacramento
valley...motherlode...northern san joaquin valley...southern
sacramento valley.


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