Area Forecast Discussion
Issued by NWS Sacramento, CA

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000
FXUS66 KSTO 031051
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
351 AM PDT FRI JUL 3 2015

.SYNOPSIS...
A LITTLE ABOVE NORMAL TEMPERATURES WILL SLOWLY COOL TO NEAR NORMAL
BY THE MIDDLE OF NEXT WEEK AS HIGH PRESSURE OVER THE SOUTHWEST
U.S. SLOWLY GIVES WAY TO A OFFSHORE LOW PRESSURE SYSTEM. ISOLATED
MOUNTAIN SHOWERS OR THUNDERSTORMS WILL REMAIN A POSSIBILITY OVER
THE MOUNTAINS MAINLY AFTERNOON AND EVENING HOURS THROUGH THE
COMING WEEK.

&&

.DISCUSSION...
NORCAL REMAINS UNDER AN UPPER LEVEL RIDGE SPANNING FROM THE FOUR
CORNERS AREA TO NORCAL. SOUTHEAST FLOW BETWEEN THIS RIDGE AND A
LARGE PACIFIC LOW OFF THE SOCAL COAST PIVOTING A SHORTWAVE
DISTURBANCE ACROSS NORCAL THIS MORNING. THIS DISTURBANCE IS
BRINGING CLOUDS AND A FEW LIGHT SHOWERS TO MOST OF THE FORECAST
AREA. ISOLATED THUNDERSTORMS MAY ALSO BE POSSIBLE THIS MORNING
OVER THE NORTHERN SIERRA AS ANOTHER SMALL SCALE DISTURBANCE PIVOTS
THROUGH THE MOIST SOUTHEAST FLOW. CONDITIONS REMAIN MOIST AND
UNSTABLE ENOUGH FOR THE THREAT OF ISOLATED THUNDERSTORMS ALL
MOUNTAIN AREAS THIS AFTERNOON. A SLIGHTLY COOLER AIRMASS COMBINED
WITH CLOUD COVER WILL BRING A LITTLE COOLING MOST AREAS ALTHOUGH
HIGHS TODAY WILL STILL COME IN A FEW DEGREES ABOVE NORMAL. MOST
AREAS WILL NOT SEE MUCH CHANGE ON SATURDAY WITH SIMILAR
TEMPERATURES AND ANOTHER SHOT OF SCATTERED AFTERNOON THUNDERSTORMS
OVER THE MOUNTAINS. AN INCREASED DELTA BREEZE SHOULD BRING JUST A
BIT OF COOLING IN THE DELTA AND DELTA INFLUENCED AREAS. STILL NOT
LOOKING FOR A LOT OF CHANGE ON SUNDAY WITH ISOLATED AFTERNOON
MOUNTAIN SHOWERS AND DAYTIME HIGHS A BIT ABOVE NORMAL. WITH THE
OFFSHORE UPPER LOW EDGING COASTWARD HOWEVER THERE WILL BE SUBTLE
CHANGES AS THE UPPER FLOW SHIFTS FROM SOUTHEAST OR EAST TO A MORE
SOUTHERLY DIRECTION. THIS SHOULD BRING SLIGHTLY MORE STABLE
CONDITIONS WHICH SHOULD MAKE FOR SOME REDUCTION IN AFTERNOON
MOUNTAIN THUNDERSTORM ACTIVITY. TEMPERATURES CONTINUE TO EDGE
DOWNWARD ON MONDAY AS THE OFFSHORE UPPER LOW BRINGS MORE AND MORE
INFLUENCE TO THE NORTH STATE. INCREASED ONSHORE FLOW WILL BRING
DAYTIME HIGHS DOWN CLOSE TO NORMAL SOME AREAS. AFTERNOON
THUNDERSTORMS WILL REMAIN A SLIGHT POSSIBILITY OVER THE SIERRA
CREST BUT ELSEWHERE SHOULD SEE MAINLY FAIR SKIES.

&&
.EXTENDED DISCUSSION (TUESDAY THROUGH FRIDAY)

BOTH THE EC AND GFS SHOW THE EASTERN PACIFIC UPPER LOW STRADDLING
THE NORTHERN CA COASTLINE TUESDAY AND WEDNESDAY. MOISTURE WRAPPING
AROUND THE LOW WILL BRING SLIGHT CHANCE TO CHANCE OF SHOWERS AND
THUNDERSTORMS, MAINLY OVER THE MOUNTAINS. BY THURSDAY, THE EC
MOVES THE LOW EASTWARD ACROSS NORCAL UNTIL IT WEAKENS AND LIFTS
NORTHEASTWARD ON FRIDAY. THE 06Z GFS ALSO HAS THE LOW MOVING
ACROSS NORCAL ON THURSDAY, BUT TRACKING A BIT SLOWER AND MAINTAINING
BETTER STRUCTURE. HAVE KEPT A FEW AREAS OF POSSIBLE SHOWERS FOR
THURSDAY, BUT TRENDED DRIER FOR FRIDAY.

AS STATED IN THE PRIOR DISCUSSION: THE MODELS HAVE A DIFFICULT
TIME FORECASTING THE TRACK OF THESE OFFSHORE UPPER LOWS, SO THE
AREA OF THUNDERSTORMS MAY CHANGE AS THE EXTENDED PERIOD DRAWS
CLOSER. (JCLAPP)

HIGH TEMPERATURES WILL REMAIN NEAR TO BELOW NORMAL FROM TUES INTO
FRIDAY AS THE LOW IMPACTS NORCAL. MAX TEMPERATURES TUESDAY EXPECTED
MAINLY IN THE 90S FOR THE CENTRAL VALLEY, 80S FOR THE DELTA AND
FOOTHILLS, AND 70S FOR THE MOUNTAINS...WHICH IS NEAR NORMAL.
DAYTIME HIGHS WILL BE 2-7 DEGREES BELOW NORMAL WEDNESDAY-FRIDAY
AS THAT LOW MOVES ACROSS NORCAL.  JBB


&&

.AVIATION...

PREDOMINANTLY VFR CONDITIONS TODAY, EXCEPT FOR POTENTIAL MVFR
IN MOUNTAIN THUNDERSTORMS. DELTA BREEZE WINDS STILL GOING STRONG
THIS MORNING WITH SPEEDS 20-30 KTS...EXPECT THEM TO WEAKEN AFTER
14Z BECOMING 10-20 KTS, THEN RE-STRENGTHEN AGAIN AFTER 00Z THIS
AFTERNOON. SURFACE WINDS AT TAF SITES WILL BE ONSHORE FLOW UP TO
12 KTS WITH OCCASIONAL GUSTS UP TO 18 KTS THIS AFTERNOON WHEN THE
DELTA BREEZE INCREASES.  JBB
&&

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

$$


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