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000
FXUS66 KSTO 130507
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1007 PM PDT SUN MAY 12 2013

.SHORT TERM DISCUSSION...

UPPER RIDGE IS OVER CALIFORNIA THIS EVENING WITH GENERALLY CLEAR
SKIES. A LOW PRESSURE SYSTEM IS JUST OFFSHORE WASHINGTON AND
BRITISH COLUMBIA AND WILL MOVE EAST THROUGH THOSE AREAS TOMORROW.
THIS WILL BRING SLIGHTLY COOLER TEMPS AND GUSTY WINDS TO NORCAL
TOMORROW. WEAK/MODERATE DELTA BREEZE THIS EVENING WITH COOLER
TEMPS OVER THE SRN VALLEY/DELTA. AT 10 PM TEMPS ARE IN THE LOW
80`S TO UPPER 60`S OVER VALLEY LOCATIONS...WARMEST NORTH. THESE
VALUES ARE 3-7 DEGREES COOLER VERSUS YESTERDAY AT THIS TIME.
FORECASTED LOWS FROM THE MID 50`S TO LOW 60`S ARE ON TRACK AND
NO EVENING UPDATE WILL BE MADE.

PREVIOUS DISCUSSION...

A RIDGE OF HIGH PRESSURE OVER THE REGION WILL GIVE WAY TO A
TROUGH OF LOW PRESSURE ON MONDAY. SOME HIGH CLOUDS WILL DRIFT
THROUGH THE REGION OVERNIGHT AND MONDAY AS THAT THROUGH MOVES
NORTHWEST. SOME SHOWERS MIGHT DEVELOP OVER EXTREME NORTHERN
CALIFORNIA BUT LOOK TO STAY NORTH OF SHASTA COUNTY AT THIS TIME.

THE TROUGH WILL HELP BRING A STRONGER DELTA BREEZE TO THE INTERIOR
OVERNIGHT AND MONDAY. THAT COMBINED WITH SOME SYNOPTIC COOLING
OVER THE REGION WILL COOL TEMPERATURES OFF ON MONDAY INTO THE
MIDDLE 80S FOR MOST VALLEY LOCATIONS.

ZONAL FLOW OVER THE REGION TUESDAY WILL BRING ONLY SLIGHT CHANGES
TO THE WEATHER OVER MONDAYS HIGHS. WEDNESDAY MAY BE A FEW DEGREES
COOLER WITH SOME HIGH CLOUDS EXPECTED TO DRIFT OVER THE REGION
AHEAD OF SYSTEM THAT WILL DIP OVER THE FAR NORTHERN SECTIONS ON
THURSDAY WITH A CONTINUED DECENT INFLUENCE FROM THE DELTA
EXPECTED.

.EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)

THE WEATHER PATTERN SHIFTS TRANSITIONING INTO THE EXTENDED PERIOD
AS A DISORGANIZED...LOW AMPLITUDE TROUGH DEVELOPS OVER THE PACNW
AND NORCAL. THE LOW PRESSURE TROUGHS OVERALL DYNAMICS ARE WEAK AND
WILL HINDER THE POTENTIAL OF THIS SYSTEM...HOWEVER THIS SYSTEM
WILL BE ACCOMPANIED BY A 1.05IN PWAT PLUME AND A MOISTENED
ATMOSPHERE WHICH SHOULD BE SUFFICENT TO SUPPORT LIGHT SHOWERS
GIVEN THE WEAK LIFT. PREVIOUS FORECAST RUNS KEPT PRECIPITATION
NORTH OF CWA... AND THE GFS REMAINS ON THE DRIER SIDE... HOWEVER
THE EURO MODEL HAS PERSISTENTLY NUDGED THESE LIGHT SHOWERS DEEPER
INTO INTERIOR NORTHERN CALIFORNIA OVER THE LAST FEW DAYS. THUS
CONFIDENCE RISEN ENOUGH TO EXTEND SHOWERS INTO THE EXTREME
NORTHERN PORTION OF THE SACRAMENTO VALLEY...INCLUDING REDDING...
THURSDAY INTO FRIDAY. FOR THE REST OF THE VALLEY... INCREASED
CLOUD COVERAGE AND SLIGHTLY COOLER AIRMASS WILL LEAD TO SEVERAL
DEGREES OF COOLING INTO THE WEEKEND. TEMPERATURES RECOVER SEVERAL
DEGREES SATURDAY AND SLIGHTLY FURTHER SO ON SUNDAY.

&&

.AVIATION...

VFR CONDITIONS CONTINUE THRU THE NEXT 24HRS WITH EXCEPTION OF
EARLY MORNING MFR/IFR CIGS THROUGH DELTA. ONSHORE FLOW CONTINUES
BRINGING LIGHT SOUTH TO SOUTHWESTERLY WINDS INTO THE SACRAMENTO
VALLEY (KSAC, KSMF, KMHR, KRBL, KRDD) AND LIGHT WEST TO NORTHWEST
WINDS INTO THE NORTHERN SAN JOAQUIN VALLEY (KSCK, KMOD). WIND
SPEEDS WILL BE UP TO 12 KTS IN THE VALLEYS BUT UP TO 20 KTS WITHIN
THE DELTA. LIGHT TO MODERATE WEST-SOUTHWEST WINDS ACROSS MOUNTAINS
WITH GUSTS UP TO 30 KTS.

&&

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

$$