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000
FXUS66 KSTO 131150
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
450 AM PDT MON MAY 13 2013

.SHORT TERM DISCUSSION...

LOW PRESSURE SYSTEM OFFSHORE FROM THE PACIFIC NW AND CANADIAN
COASTLINE WILL TRACK EASTWARD TODAY WITH THE BASE OF THE TROUGH
BRUSHING FAR NORCAL. MOISTURE FROM THIS SYSTEM IS EXPECTED TO STAY
NORTH OF OUR CWA. HOWEVER...THIS SYSTEM WILL IMPACT OUR REGION WITH
COOLER TEMPERATURES AND ENHANCED ONSHORE FLOW INTO THE CENTRAL VALLEY.

THE ONSHORE GRADIENT FROM SFO-SAC IS ABOUT 3 MB AND DELTA WINDS
SHOULD PEAK LATER TODAY BETWEEN 20-25 MPH WITH LOCALLY HIGHER
GUSTS. THE INFLUX OF COOLER, MOIST MARINE AIR MEANS MUCH OF THE VALLEY
WILL ONLY WARM INTO THE UPPER 80S/LOW 90S. THIS IS COOLER THAN
YESTERDAY BUT STILL 5-10 DEGREES ABOVE NORMAL. LITTLE CHANGE ON
TUESDAY AS FLOW ALOFT BECOMES ZONAL.

WEDNESDAY WILL BE A TRANSITION DAY AS ANOTHER STORM SYSTEM MOVES
TOWARDS OUR FORECAST AREA. EXPECT SLIGHTLY COOLER TEMPERATURES
AND INCREASING CLOUDS.

.EXTENDED DISCUSSION (THURSDAY-SUNDAY)...

THE REAL CHANGE OCCURS THURSDAY AND FRIDAY AS A TROUGH DEEPENS
OVER THE WEST COAST. SYNOPTIC COOLING COUPLED WITH ENHANCED
ONSHORE FLOW WILL MAKE DAYTIME HIGHS NOTABLY COOLER (VALLEY TEMPS
IN THE UPPER 70S/LOW 80S). THIS TROUGH WILL TAP INTO A GOOD
MOISTURE PLUME AND SPREAD A CHANCE OF RAIN ACROSS THE COASTAL
RANGE, NORTHERN MOUNTAINS, SIERRA AND INTO THE NORTHERN SACRAMENTO
VALLEY. INSTABILITY WILL INCREASE AS THE TROUGH MOVES
OVERHEAD...HOWEVER THE BEST INSTABILITY LOOKS TO BE ON THE EAST
SIDE OF THE SIERRA CREST SO HAVE NOT PUT THUNDERSTORMS IN OUR CWA.

DRIER AND WARMER OVER THE WEEKEND AS WEAK RIDGING DEVELOPS.
TEMPERATURES WILL REACH 4-10 DEGREES ABOVE NORMAL BY SUNDAY.
JBB


&&

.AVIATION...

VFR CONDITIONS CONTINUE THRU THE NEXT 24HRS WITH EXCEPTION OF
EARLY MORNING MFR/IFR CIGS INTO VALLEJO/BENECIA. MARINE LAYER TOO
SHALLOW (LESS THAN 800 FT) FOR ANY INLAND PENETRATION. MARINE
LAYER WILL DEEPEN TONIGHT INTO TUE MORNING. DECENT COASTAL
PRESSURE GRADIENT CONTINUES BRINGING SOME BREEZY SW TO W WINDS
OVER COASTAL RANGE AND UPPER SIERRA AND DELTA...LIGHT ELSEWHERE.
JCLAPP

&&

.STO WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$