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000
FXUS66 KSTO 200446
AFDSTO

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

.SHORT TERM DISCUSSION...

TEMPERATURES CURRENTLY RUNNING AROUND 2 TO 7 DEGREES WARMER THAN 24
HOURS AGO...EXCEPT IN THE SOLANO CO AREA...ALONG WITH DECREASING NW
WINDS FROM THE AFTERNOON. ENOUGH NW WIND EXPECTED TO CONTINUE LOWER
LEVEL MIXING OVER MOST LOCALES THROUGHOUT THE NITE ELEVATING MINS
FROM PREVIOUS NITES.

UPPER LOW OVER THE YUKON TERRITORY WILL BE THE DOMINATING FACTOR IN
NORCAL WX THIS WEEK...AS IT ENHANCES RIDGING OVER NORCAL ON MON...
AND THEN BRINGS A COOLING TREND AND WINDIER WX TO NORCAL FOR THE
REST OF THE WEEK AS IT DROPS SWD INTO THE PAC NW. HIGHS IN THE
VALLEY ARE EXPECTED TO CLIMB INTO THE LOWER 90S WHILE THE MOUNTAINS
WILL BE MAINLY IN THE UPPER 60S AND 70S ON MON.    JHM

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 VORT MAXES 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 VORT MAXES PIVOTING
AROUND IT. THE ECMWF CONTINUES TO INDICATE ONE STRONG VORT MAX
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 SKC CONDITIONS CONTINUE OVER INTERIOR NORCAL NEXT 24 HOURS. NW
WINDS 5-15 KTS AT TAF SITES THROUGH 00Z TUE.

&&

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

$$