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000
FXUS66 KSTO 192243
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
343 PM PDT SUN MAY 19 2013

.SHORT TERM DISCUSSION...

TEMPERATURES CURRENTLY RUNNING AROUND 4 TO 7 DEGREES WARMER THAN
24 HOURS AGO AND RANGE FROM THE LOWER TO MID 80S IN THE VALLEY TO
MAINLY THE 60S IN THE MOUNTAINS. BREEZY CONDITIONS CONTINUE THIS
AFTERNOON ACROSS THE CENTRAL VALLEY WITH MANY LOCALES REPORTING
GUSTS OF 20 TO 25 MPH. WINDS WILL SUBSIDE ALONG THE EAST SIDE OF
THE VALLEY BY THIS EVENING AS THE SURFACE DECOUPLES...BUT WILL
PICK UP ACROSS THE HIGHER ELEVATIONS OF THE NORTHERN SIERRA NEVADA
AND WEST FACING CANYONS OVERNIGHT AND WILL CONTINUE ALONG THE WEST
SIDE OF THE SACRAMENTO VALLEY AS EASTERLY SURFACE GRADIENTS
TIGHTEN.

UPPER RIDGE CURRENTLY OVER THE EPAC SHIFTS OVER NORCAL MONDAY
WHICH WILL RESULT IN THE WARMEST TEMPERATURES OF THE WEEK AS
NORTH AND EAST WINDS DROP OFF AND THE OVERALL AIRMASS CONTINUES TO
WARM. HIGHS IN THE VALLEY ARE EXPECTED TO CLIMB INTO THE LOWER 90S
WHILE THE MOUNTAINS WILL BE MAINLY IN THE UPPER 60S AND 70S.

A MAJOR CHANGE TOWARD COOLER AND BREEZIER WEATHER IS FORECAST TO
BEGIN TUESDAY AS THE UPPER TROUGH PRESENTLY OVER THE GOA DROPS
SOUTHEASTWARD INTO THE PACNW AND CLOSES OFF. THE COLD UPPER LOW IS
FORECAST TO BE JUST OFFSHORE THE MOUTH OF THE COLUMBIA RIVER BY
LATER TUESDAY...THEN ONLY SHIFTING SLIGHTLY EAST BY WEDNESDAY.
APPEARS AT THIS TIME THAT THIS SYSTEM WILL BE RELATIVELY DRY FOR
NORCAL WITH SHOWER CHANCES MAINLY LIMITED TO THE MOUNTAINS NORTH
OF REDDING WHILE THE MAIN IMPACTS WILL BE MUCH COOLER TEMPERATURES
AND BREEZY CONDITIONS FOR MID-WEEK.

&&

.EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)

CLOSED UPPER LOW OVER THE PACIFIC NW WILL IMPACT OUR AREA FROM
MIDWEEK INTO THE WEEKEND AS SECONDARY VORTMAXES ROTATE AROUND THE
PARENT LOW AND BRUSH THE NORTHERN REACHES OF OUR FORECAST AREA.
ALTHOUGH MODELS ARE HIGHLY CONFIDENT IN PLACEMENT OF PRIMARY UPPER
LOW...CONFIDENCE IS MUCH LESS IN INDIVIDUAL VORTMAXES PIVOTING
AROUND IT. THE ECMWF CONTINUES TO INDICATE ONE STRONG VORTMAX
SWINGING THROUGH OUR AREA THURSDAY AFTERNOON...WITH ENOUGH
DYNAMICS TO GENERATE A FEW SHOWERS OVER THE SIERRA FROM AROUND
TAHOE NORTHWARD. THE GFS MEANWHILE IS MUCH WEAKER WITH THIS
FEATURE...AND LIMITS ANY CHANCES OF SHOWERS MOUNTAINS FROM AROUND
SHASTA COUNTY NORTHWARD. HAVE EXTENDED A SLIGHT CHANCE OF RAIN
SHOWERS THURS NIGHT FARTHER SOUTH ALONG THE SIERRA SOUTH TO AROUND
BLUE CANYON SINCE THE ECMWF HAS BEEN MORE CONSISTENT. EITHER
WAY...THE MAIN MESSAGE IS STILL COOLER TEMPERATURES THROUGH THE
END OF THE WORKWEEK.

BY NEXT WEEKEND...THE CLOSED LOW WEAKENS INTO AN OPEN WAVE ALONG
THE WEST COAST. ADDITIONAL WEAK SHORTWAVES LOOK TO MOVE ONSHORE TO
NORCAL...BRINGING THE POSSIBILITY OF ISOLATED SHOWERS TO THE
MOUNTAINS AROUND THE NORTHERN SAC VALLEY. TEMPERATURES SHOULD
MODERATE TO AROUND NORMAL...WITH POSSIBLE DELTA BREEZE
MODIFICATION IN THE SAC METRO AREA GIVEN ONSHORE GRADIENT. -DVC

&&

.AVIATION...

VFR CONDITIONS CONTINUE OVER INTERIOR NORCAL NEXT 24 HOURS. GUSTY
NORTH TO NORTHWEST WINDS IN THE CENTRAL VALLEY WILL DECREASE INTO
THE EVENING...BECOMING 10KTS OR LESS BY SUNSET. -DVC


&&

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

$$