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000 
FXUS66 KSTO 251045
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
345 AM PDT Sun Jun 25 2017


.SYNOPSIS...
Cooling expected for the entire region today with cooler but still
above normal temperatures through the week. Isolated 
afternoon/evening thunderstorms possible over portions of 
mountains today. 

&&

.Discussion...Upper ridge which brought the Norcal heat wave for 
the last week is finally shifting inland. Upper level southeast
flow pulling some mid/high moisture out of the sub-tropics for
scattered clouds over parts of the forecast area this morning. A 
small disturbance pivoting northward is squeezing out a shower in 
the Chico area at this time but this cell will likely disperse in 
the next hour or two. Upper ridge axis currently shifting east of 
the CWA allowing for a stiff delta breeze this morning. Travis AFB
showing gusts to over 30 knots. Onshore flow and airmass cooling 
will bring a significant drop in daytime temperatures. Even with 
this cooling, daytime highs will still come in a few to several 
degrees above normal. Isolated thunderstorms will be a possibility
again over the mountains this afternoon with GFS showing the most
instability over parts of the coast range, over the Lassen area 
and Sierra crest south of Tahoe. 

Week upper troughing over the west coast will bring more cooling
on Monday with daytime highs forecast to come in just a little
above normal. A continued strong delta breeze will likely bring
another morning of scattered coastal stratus to the delta. Stable
southwest flow aloft should keep skies mainly fair through the
day. One exception might be far northwest Shasta county which
might pick up an isolated shower if the upper trough digs far
enough south. Fair skies and a bit more cooling expected on
Tuesday as weak upper troughing lingers along the west coast.
Upper ridge begins to rebuild by mid-week bringing the beginning
of a warming trend. 

&&

.EXTENDED DISCUSSION (Thursday THROUGH Sunday)

High pressure returns to the region Thursday and Friday this
week, bringing a brief period of hot temperatures. A weak upper
trough then passes through the Pacific Northwest. This system
looks rather dry, with precipitation expected to remain well to
our north. As such, the primary impacts with this weather system
will likely be modest cooling and stronger onshore flow through
the Delta.

Dang

&&

.AVIATION...

VFR conditions across Valley TAF sites the next 24 hours. Isolated
showers & thunderstorms across NorCal mountains this afternoon
into early evening. SW wind gusts up to 35 kt possible near the
Delta.

Dang

&&

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