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000
FXUS66 KSTO 171632
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
932 AM PDT FRI MAY 17 2013

.SHORT TERM DISCUSSION...

UPPER LEVEL TROUGH IS MOVING EAST INTO THE GREAT BASIN THIS
MORNING. ALTHOUGH...LINGERING MOISTURE OVER THE SIERRA AND SHASTA
COUNTY WILL LEAD TO ISOLATED TO SCATTERED SHOWERS. JUST ENOUGH
INSTABILITY WILL ALSO BE PRESENT FOR SLIGHT THUNDERSTORM CHANCES
OVER THE SIERRA. THE BEST CHANCES WILL BE OVER THE NRN SIERRA
NORTH OF QUINCY. SKIES WILL BE PARTLY CLOUDY OVER THE REST OF THE
AREA WITH HIGH TEMPERATURES A FEW DEGREES BELOW NORMAL GENERALLY
TOPPING OUT IN THE UPPER 70`S. WEAK DELTA BREEZE WILL DEVELOP LATE
THIS AFTERNOON WITH A FEW GUSTS TO 30 MPH OVER THE DELTA. TROUGH
WILL CONTINUE EAST TONIGHT WITH DRIER AIR FILTERING INTO NORCAL
ENDING THE SHOWER CHANCES. CURRENT FORECAST IS ON TRACK AND NO
MORNING UPDATE WILL BE NEEDED.

PREVIOUS DISCUSSION...

UPPER LEVEL TROUGH MOVING TO THE EAST OF THE AREA TODAY LEADING
TO DECREASING THE CLOUDS AND SHOWERS. AREA OF SHOWERS AND
THUNDERSTORMS THAT WAS NEARLY STATIONARY AROUND THE RED BLUFF AREA
AROUND 10 PM HAS WEAKENED AND SHIFTED EAST INTO THE FOOTHILLS AND
WESTERN PLUMAS COUNTY THIS MORNING. CHANCE OF SHOWERS AND AN
SLIGHT CHANCE OF THUNDERSTORMS WILL LINGER OVER EASTERN SHASTA
COUNTY AND DOWN THE SIERRA THIS AFTERNOON AND EVENING.
TEMPERATURES WILL BE SIMILAR TO A LITTLE WARMER THAN YESTERDAY
THIS AFTERNOON WITH MORE SUN AND A LITTLE WARMING OF THE AIRMASS.
ALTHOUGH TEMPERATURES ARE STILL SEVERAL DEGREES BELOW NORMAL FOR
THIS TIME OF THE YEAR WITH HIGHS IN THE MID TO UPPER 70S IN THE
VALLEY AND LOWER 50S TO LOWER 60S IN THE MOUNTAINS. WARMING TREND
EXPECTED OVER THE WEEKEND AND INTO MONDAY AS HIGH PRESSURE BUILDS
OVER THE AREA. TEMPERATURES WILL WARM TO SEVERAL DEGREES ABOVE
NORMAL BY MONDAY WITH HIGHS IN THE MID TO UPPER 80S IN THE VALLEY
AND MID 60S TO MID 70S IN THE MOUNTAINS. BREEZY AND GUSTY
NORTHERLY WINDS ARE POSSIBLE...ESPECIALLY ALONG THE WEST SIDE OF
THE SACRAMENTO VALLEY SUNDAY INTO EARLY MONDAY AS SURFACE HIGH
PRESSURE BUILDS INTO THE PACIFIC NORTHWEST.

.EXTENDED DISCUSSION (TUESDAY THROUGH FRIDAY)

RIDGE WEAKENS LATE MONDAY INTO TUESDAY AS AN UPPER LEVEL LOW
DROPS DOWN OFF THE PACIFIC NORTHWEST COAST. THE LOW IS EXPECTED TO
LINGER ALONG THE WEST COAST THROUGH FRIDAY. THE LOW WILL BRING
COOLER TEMPERATURES WITH HIGH TEMPERATURES DROPPING TO NEAR NORMAL
ON TUESDAY (WITH HIGHS IN THE LOW TO MID 80S IN THE VALLEY AND 60S
IN THE MOUNTAINS) AND DOWN TO ABOUT 10 DEGREES BELOW NORMAL BY
THURSDAY. THERE IS DIFFERENCES IN THE DETAILS OF THE LOW AS THE
WEEK PROGRESSES LEADING TO SOME UNCERTAINTY IN THE TEMPERATURES AND
THREAT OF PRECIPITATION.  THE LOW MAY DIG FURTHER SOUTH BY
THURSDAY BRINGING A THREAT OF PRECIPITATION TO THE NORTHERN
SACRAMENTO VALLEY AND SURROUNDING MOUNTAINS. ALTHOUGH THERE IS
UNCERTAINTY IN THE EXTENT AND TIMING OF THE PRECIPITATION.

&&

.AVIATION...

EXPECT LOCAL MVFR/IFR CIGS OVER SHASTA COUNTY DOWN OVER THE
SIERRA WITH A CHANCE OF AFTN SHOWERS/TSTMS...OTHERWISE VFR NEXT 24
HRS. STEADY COASTAL PRESSURE GRADIENT WILL KEEP WINDS BREEZY
THROUGH THE DELTA AND OVER HIGHER COASTAL MTNS AND SIERRA NEVADA
TODAY. NRN AND CENTRAL SAC VALLEY WINDS LIKELY SHIFT FROM NW LATER
TONIGHT.   JCLAPP


&&

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

$$