Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 021620
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
920 AM PDT Tue Sep 2 2014

.Synopsis...
Cooling trend early this week with near normal daytime highs
Wednesday through Saturday. Dry weather continues.

&&

.Discussion...
Morning temps running much cooler (7-13 deg as of 14z) across the
far Nrn zones due to a lack of adiabatic warming effects from Nly
winds...but running warmer elsewhere before a cooling Delta Breeze
developed by 16z. Onshore gradients are beginning to increase and
are forecast to increase to 3 to 4 mbs by the end of the day with a
slowly deepening marine layer. Thus...cooling is expected elsewhere
as the afternoon wears on...especially in the Delta influenced areas
as the Delta Breeze increases late afternoon/evening.

A positively tilted trof is forecast to move through the Pac NW and
suppress the strong ridging over Norcal leading to cooling to near
normal temps by mid week. Cyclonic flow aloft will continue for the
rest of the week as the trof expands SWwd with a possible weak low
forming over the far Nrn zones by the end of the week.

The marine layer has made a return along the coast and it looks more
promising for a stratus intrusion into the Sac Vly Wed morning as
the NAM has forecast for the past couple of days. Would like to see
the marine layer (currently 1200-1800 ft) deepen to over >=2 kft
with good onshore momentum by Wed morning for this scenario to occur
and this still remains a possibility.

The Nly gradients are then forecast to increase again during the day
on Wed and continue Thu/Fri with the trof moving through the Pac NW
and offshore flow prevailing in its wake. This will suppress the
marine layer and limit the Delta Breeze Thu morning.

The wind pattern will allow some smoke from the Beaver WF to affect
our Nrn zones including Shasta Co at times...but the bigger smoke
plume from the more active Happy Camp WF complex may spread over
Shasta Co Wed morning per the NAM Hysplit model run. More NEly flow
Thu/Fri mornings from higher pressures to our NE may spread the
smoke back to a SWwd trajectory during that time sparing Shasta Co.

With the tail end of the weak positively-tilted trof lingering over
Norcal later this week and through the weekend...max temps will be
close to normal for early Sep.   JHM

&&

.Aviation...
General VFR conditions with clear skies over the next 24 hours.
LCL vsbys down to around 5 miles possible in smoke over north end
of Sac Valley and along Coastal range through around 18z. Then,
mixing and a shift to southerly winds expected to improve vsbys.
Local SW gusts to 25 kt possible over Sierra crest after 18z and
gusting up to 30 kt through the Delta. EK

&&

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

&&

$$





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