Area Forecast Discussion
Issued by NWS Sacramento, CA

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FXUS66 KSTO 071559
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
859 AM PDT TUE JUL 7 2015

.SHORT TERM DISCUSSION...

.SYNOPSIS...
COOL WEEK WITH DAILY AFTERNOON AND EVENING THUNDERSTORMS MAINLY
OVER MOUNTAINS. GREATEST THUNDERSTORM COVERAGE APPEARS TO BE THIS
EVENING THROUGH THURSDAY EVENING.

&&

.DISCUSSION (TODAY THROUGH FRIDAY)...
UPPER LOW STILL ON TRACK TO SLOWLY DRIFT OVER CALIFORNIA BY
THURSDAY AFTERNOON. AFTERNOON CONVECTION WITH THE UPPER LOW SHOULD
BE PRETTY SIMILAR TO YESTERDAY, REMAINING MOSTLY ON THE CREST AND
EAST. STEERING WINDS DO TURN A BIT TO THE SOUTHEAST THOUGH IN THE
LASSEN PARK AREA THIS EVENING SO IF ANY WHERE DOES SEE CONVECTION
WOULD BE THERE. MAIN THREAT TODAY WILL ONCE AGAIN BE HEAVY RAIN AS
PRECIPITABLE WATER VALUES UP PRETTY HIGH TODAY. IMPACT THREAT
APPEARS TO BE ISOLATED ENOUGH TO HOLD OFF ON ANY HIGHLIGHTS AT
THIS TIME.

LATE TONIGHT INTO TOMORROW MORNING NAM SHOWING SOME MID LEVEL
INSTABILITY TO DRIFT OVER CENTRAL VALLEY. MIGHT SEE SOME SPRINKLES
OR MAYBE A STRAY LIGHTNING STRIKE IN CENTRAL VALLEY BUT NEED TO
LOOK CLOSER AT DATA TO CHANGE CURRENT FORECAST WHICH DOESN`T
MENTION ANY PRECIPITATION. MAIN THREAT FOR VALLEY PRECIPITATION
WILL BE ACROSS THE NORTH LATER TOMORROW AND THIS IS COVERED WELL
IN CURRENT FORECAST. MORE INTERESTING IS HEAVY RAIN THREAT ALONG
THE NORTHERN MOUNTAINS JUST NORTH OF SACRAMENTO FORECAST AREA
TOMORROW AFTERNOON AND EVENING INTO THURSDAY. AT THIS POINT
DOESN`T LOOK LIKE WE WILL NEED TO ISSUE A FLASH FLOOD
PRODUCT...BUT WILL CONTINUE TO HIGHLIGHT THE ISOLATED THREAT OF
THIS AS IF YOU DO GET UNDER A THUNDERSTORM IT MORE THAN LIKELY
WILL HAVE HEAVY RAIN. RASCH

.PREVIOUS DISCUSSION...
COOL, PLEASANT CONDITIONS CONTINUE THIS
WEEK WITH A MODERATE DELTA BREEZE INTO THURSDAY. VERY MOIST
MONSOONAL MOISTURE WILL CONTINUE TO MOVE NORTHWARD OVER THE AREA
THIS WEEK. VERY SLOW- MOVING MOUNTAIN STORMS AND ABUNDANT MOISTURE
COULD MAKE FOR SOME HAZARDOUS FLASH FLOODING CONDITIONS OVER THE
HIGHER TERRAIN WEDNESDAY AND THURSDAY. MEANWHILE, CHANCES EXIST
FOR SOME THUNDERSTORMS TO EITHER MOVE INTO OR DEVELOP WITHIN THE
NORTHERN SACRAMENTO VALLEY THIS EVENING AND EXPAND POTENTIAL
COVERAGE OVER MUCH OF THE SACRAMENTO VALLEY WEDNESDAY AND THURSDAY
AFTERNOON/EVENINGS. HOWEVER, WE DON`T EXPECT NEAR AS MUCH RAINFALL
INTO THE VALLEY.

THE LOW MOVES NORTHEAST AND BECOMES ABSORBED INTO THE MAIN
SOUTHWEST UPPER FLOW ON FRIDAY. POTENTIAL AFTERNOON/EVENING
THUNDERSTORMS STILL CONTINUE OVER MOUNTAINS AND NORTHERN
SACRAMENTO VALLEY, BUT INSTABILITY IS WEAKENED.    JCLAPP

&&
.EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)

FOR THE EXTENDED PERIOD, MODELS REMAIN CONSISTENT THAT OUR REGION
WILL BE UNDER THE INFLUENCE OF A BROAD SYNOPTIC TROUGH PATTERN.
OVER THE WEEKEND, THE TROUGH AXIS WILL REMAIN OFFSHORE THEN
GRADUALLY NUDGE INLAND EARLY NEXT WEEK. SOME AREAS OF THE SIERRA
WILL HAVE LINGERING MOUNTAIN SHOWERS/ THUNDERSTORMS OVER THE
WEEKEND. FOR MONDAY AND TUESDAY, THE GFS AND EC MODELS DIFFER ON
THE STRENGTH AND TRACK OF THE TROUGH. THE GFS SHOWS THE DESERT SW
HIGH PRESSURE CELL STRENGTHENING INTO CA CAUSING A WARMING TREND
WITH DRY WEATHER WHILE THE EC HAS THE TROUGH AXIS LINGERING OVER
CA. HAVE KEPT A GRADUAL WARM UP IN THE EXTENDED, SIMILAR TO THE
GFS SOLUTION. THROUGHOUT THE EXTENDED, DAYTIME HIGHS WILL START
OFF 5-8 DEGREES BELOW NORMAL AND THEN GRADUALLY WARM UP TO NORMAL
BY MONDAY & TUESDAY. JBB

&&

.AVIATION...

VFR CONDITIONS PERSIST. ONSHORE FLOW CONTINUES WITH SW WIND GUSTS
20-30 KT NEAR THE DELTA. TAF SITES WILL GENERALLY BE LIGHT EXCEPT BETWEEN
23-04Z WITH WINDS 10-20 KTS FOR KSAC, KSMF, KMHR, KSAC. LOCAL MVFR
CONDITIONS POSSIBLE DUE TO STRATUS FROM THE DELTA REGION INTO THE
SOUTHERN SACRAMENTO VALLEY THROUGH 17Z. SHOWERS AND THUNDERSTORMS
WILL START DEVELOPING NEAR THE SIERRA CREST AFTER 18Z THEN SPREAD
DOWN THE WESTERN SLOPES WITH IFR CONDITIONS IN STRONGER STORMS.
JBB

&&

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

$$


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