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000
FXUS66 KSTO 190416
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
916 PM PDT SAT MAY 18 2013

.SHORT TERM DISCUSSION...

BREEZY NORTH WINDS EXPECTED ACROSS THE CENTRAL VALLEY SUNDAY...AND
DOWN FAVORED SIERRA SLOPES SUNDAY NIGHT. WARM WEATHER CONTINUES ON
MONDAY...THEN SUBSTANTIAL COOLING BY TUESDAY AND CONTINUING
THROUGH THE REST OF THE WEEK. A CHANCE OF SHOWERS WILL BE POSSIBLE
NEAR THE OREGON BORDER TUESDAY THROUGH SATURDAY.

NOW AND TONIGHT...
NORTHERN CALIFORNIA REMAINS IN NORTHWESTERLY FLOW ALOFT WITH AN
AMPLIFYING RIDGE OF HIGH PRESSURE OVER THE EASTERN PACIFIC. A WEAK
SHORTWAVE CLIPPED THE NORTHEASTERN PORTION OF THE STATE THIS
AFTERNOON...AND WAS ENOUGH TO KICK OFF A FEW SHOWERS AND
THUNDERSTORMS. THIS ACTIVITY HAS QUIETED DOWN...AND SKIES ARE
GENERALLY CLEAR ACROSS THE REGION THIS EVENING. TEMPERATURES
ACROSS THE FORECAST AREA ARE RUNNING SEVERAL DEGREES WARMER THAN
24 HOURS AGO...OWING TO SYNOPTIC WARMING AS THE OFFSHORE RIDGE
STRENGTHENS. WILL UPDATE THE FORECAST TO FRESHEN WORDING...BUT
TEMPERATURE TRENDS ARE ON TRACK.

SUNDAY...
SURFACE HIGH PRESSURE WILL BUILD INTO THE PACIFIC NORTHWEST EARLY
IN THE DAY...STRENGTHENING THE NORTHERLY PRESSURE GRADIENT. UPPER
LEVEL SUPPORT FOR WIND IS RATHER LIMITED...BUT THE PRESSURE
GRADIENT ITSELF SHOULD BE STRONG ENOUGH TO BRING BREEZY NORTH
WINDS ACROSS THE VALLEY. GENERALLY EXPECT SUSTAINED WINDS 20 TO 25
MPH WITH GUSTS UP TO 35 MPH THROUGH THE COURSE OF THE DAY. THE
WEST SIDE OF THE VALLEY MAY SEE CONTINUED GUSTY WINDS SUNDAY
NIGHT. THE GRADIENT WILL BECOME NORTHEASTERLY SUNDAY
NIGHT...BRINGING LOCALLY GUSTY WINDS DOWN FAVORED SIERRA CANYONS.
HIGH TEMPERATURES LOOK TO WARM A BIT FURTHER FROM WHERE THEY WERE
TODAY.

MONDAY...
WINDS WILL SUBSIDE ALONG THE WESTERN SACRAMENTO VALLEY BY MIDDAY.
THE HIGH PRESSURE RIDGE ALOFT WILL SHIFT OVER CALIFORNIA MONDAY...
BRINGING WHAT WILL LIKELY BE THE WARMEST TEMPERATURES OF THE NEXT
7 DAYS. LOOK FOR VALLEY HIGHS IN THE LOWER 90S.

TUESDAY...
COOLING TREND WILL BEGIN AS A DEEP LOW PRESSURE SYSTEM APPROACHES
THE PACIFIC NORTHWEST. THIS WILL ALSO ENHANCE ONSHORE FLOW. EXPECT
A MODIFIED MARINE AIRMASS TO COOL TEMPERATURES NEAR THE DELTA AND
INTO THE SOUTHERN SACRAMENTO VALLEY. DANG


.EXTENDED DISCUSSION (WEDNESDAY THROUGH SATURDAY)

A CLOSED UPPER-LOW ROTATES INTO THE PACIFIC NW BY
WEDNESDAY...BRINGING COOLER WEATHER TO MUCH OF THE WEST COAST AND
CHANCES OF PRECIPITATION AS FAR SOUTH AS NORCAL. MODELS CONTINUE
TO SHOW HIGH CERTAINTY IN THE FORMATION OF THE LOW AND SLOWING OF
ITS PROGRESSION AS IT MOVES INLAND. THE FORECAST BECOMES LESS
CERTAIN LATER INTO THE WEEK AS SECONDARY WAVES OR EVEN SECONDARY
LOWS ROTATE AROUND THE PARENT LOW AND BRUSH NORCAL. IN
GENERAL...CHANCES OF PRECIP WILL INCREASE FURTHER NORTH. SHASTA
COUNTY HAS THE BEST CHANCE CURRENTLY OF OUR FORECAST AREA TO SEE
SOME RAIN SHOWERS...PARTICULARLY FRIDAY MORNING ACCORDING TO THE
ECMWF. TEMPERATURES WILL DROP BY AROUND 10 DEGREES WEDNESDAY AS
COOLER MOVES IN...AND LOOK TO REMAIN ON THE COOL SIDE OF AVERAGE
THROUGH THE PERIOD.

LOOKING ON TOWARDS NEXT WEEKEND...THE ECMWF FLATTENS THE LOW INTO
A BROAD TROUGH ALONG THE WEST COAST...WHICH WOULD DRY OUR AREA
BUT KEEP US COOL. THE GFS MEANWHILE HAS BEEN TRENDING DEEPER WITH
A SECONDARY WAVE AND AS OF THE 12Z RUN TODAY IS CREATING ANOTHER
CLOSED LOW JUST OFFSHORE...SUPPORTING CONTINUED UNSETTLED WEATHER
OVER OUR NORTHERN AREAS. AS A RESULT OF MODELS INDICATING SOME
ACTIVITY BUT A LACK OF CONSENSUS...HAVE GONE WITH NEAR TO
SLIGHTLY ABOVE CLIMATOLOGICAL CHANCE OF PRECIP FOR THE MOUNTAINS
FROM AROUND RED BLUFF NORTHWARD...WITH COOL TEMPERATURES FOR ALL
AREAS. -DVC


&&

.AVIATION...

VFR CONDITIONS CONTINUE OVER INTERIOR NORCAL NEXT 24 HOURS. A
WEAK LOW PRESSURE SYSTEM WILL BRUSH THE AREA WITH A FEW MID-LEVEL
CLOUDS FROM AROUND KRBL NORTH AND SOME ISOLATED SHOWERS IN SHASTA
COUNTY THROUGH THE EARLY EVENING. NORTH WINDS WILL INCREASE IN THE
CENTRAL VALLEY TOMORROW MORNING...WITH LOCAL GUSTS OVER 30KTS IN
THE AFTERNOON. -DVC

&&

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

$$