Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 172219
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
319 PM PDT Fri Oct 17 2014

.Synopsis...
Weak weather systems will continue precipitation chances tonight and
Saturday morning and again Monday and Tuesday. Heavy precipitation
is not expected. Seasonable temperatures through the weekend.

&&

.Short Term Discussion (Tonight through Monday)...
Mostly cloudy tonight over NorCal as the Upper level moves over
the area. This system has continued to weaken as it moved onshore,
and precipitation has mainly stayed west of the Coastal Range
crest. Areas of rain are possible mainly over the Coastal Range
this evening into Sat morning as the trough and weak cyclonic
circulation sink southeastward along the CA coast. Later Sat and
into Sun, ridging returns to NorCal with clearing skies and milder
temps.

A slightly deeper Pacific trough is forecast to impact NorCal on
Mon into Tue with the bulk of the precip remaining N of I-80. Even
so, models still only show up to 0.30 inches in the Shasta
mountains and Sierra. While the northwest coast should get a
decent amount of rain, interior NorCal will apparently be short
changed due to shallow moisture. As long as the persistent upper
High over the Intermountain West and Great Plains remains, the
parent Gulf of Alaska Low isn`t progressing east. The spawned
short waves from the parent Low weaken as they move inland, thus
limiting precipitation amounts.     JClapp


.Extended Discussion (Tuesday through Friday)
Model differences in timing have decreased with Pacific frontal
system progged to impact Interior NorCal Monday. Precip forecast
to spread into the Coastal Range Monday morning, then expand east
across the Central Valley into the Sierra, during the afternoon
into night. Snow levels overnight Monday look to be just above
7000 feet in the Shasta mountains to near 8000 feet along the I-80
corridor. Light snow accumulations possible over the highest
terrain. Secondary weak upper trough moves through Tuesday morning
keeping a slight chance of showers, mainly over the mountains,
then increasing subsidence into Tue afternoon. High temperatures
Mon/Tue expected to be around 5 to 10 degrees below normal.

Extended models showing greater differences beyond Tuesday. EC/GEM
gradually increase heights through the remainder of the week while
the GFS keeps westerlies farther south into far northern CA
Wed/Thu. GFS also entrains remnant moisture from T.S. Ana into the
polar jet during this time and generates some light QPF over the
Coastal range and Shasta county late Wed through Thu. EC keeps the
track farther north. With ADJMRA/CONs data showing some POPs, will
hold onto a slight chance over the northwestern mountains of
Interior NorCal during that period for now. Temperatures expected
to trend up over the latter part of next week, returning to near or
slightly above normal by next Friday.    PCH

&&

.Aviation...
Wkng Pac cdfnt movg onshr attm flwd by assocd upr trof tngt into
Sat mrng. Mnly VFR conds ovr Intr NorCal exc lcl MVFR/IFR poss
omtns ovngt. SWly flow alf vrg to Nly Sat mrng. Lcl SWly sfc wnd
gsts to 30 kts poss ovr hyr mtn trrn til 06z Sat.


&&

.STO Watches/Warnings/Advisories...
None.
&&

$$






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