Areal Flood Warning 2, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
933 AM PST SAT FEB 20 2016

.SYNOPSIS...SHOWERS WILL TAPER TODAY AND END BY THIS EVENING AS
AN UPPER RIDGE BUILDS OVER THE AREA. A FRONT WILL BRING RAIN AND
BREEZY WEATHER SUNDAY. A FEW LINGERING SHOWERS ARE EXPECTED
MONDAY. DRY WEATHER WILL PREVAIL FROM MONDAY NIGHT THROUGH MOST
OF NEXT WEEK...WITH HIGH PRESSURE IN CONTROL.

&&

.SHORT TERM...UPPER HEIGHTS RISING QUICKLY NOW AS AN UPPER RIDGE
AXIS THAT IS CURRENTLY BETWEEN THE COAST AND 130W MOVES EAST. THE
AS A RESULT...THE MID-LEVEL AIR MASS WILL STABILIZE AND LARGE-
SCALE SUBSIDENCE WILL STRENGTHEN. CROSS-CASCADE GRADIENTS WILL
BECOME EASTERLY LATER TODAY. ALL THIS WILL CONTINUE TO DECREASE
SHOWER COVERAGE FOR THE REST OF TODAY...WITH AN END TO SHOWER
ACTIVITY BY THIS EVNG. THIS WILL LEAD TO A PRECIP-FREE SAT NGT.

ONCE THE UPPER RIDGE AXIS MOVE EAST THIS EVNG...SW FLOW ALOFT WILL
DEVELOP...OPENING THE DOOR FOR THE FRONT AND UPPER TROUGH
CURRENTLY BETWEEN 140W/150W TO ADVANCE TO THE B.C. AND WA COAST.
RAIN WILL SPREAD ONTO THE COAST AROUND 7-10 AM SUNDAY...THEN
REACH THE INTERIOR OF WRN WA ARND 10 AM-NOON. DEPENDING ON
LOCATION...STEADY RAIN WILL LAST FOR 3-6 HOURS...THEN QUICKLY
TAPER TO A FEW WEAK SHOWERS ON SUNDAY AFTN. IN TYPICAL
FASHION...THE SUNDAY FRONT WILL BE PRECEDE BY INCREASING E/SE
WINDS...THEN FOLLOWED BY A QUICK SHIFT TO S/SW GRADIENTS AND
WINDS.

A SECONDARY...TRAILING UPPER TROUGH WILL THEN ARRIVE SUNDAY
NIGHT...WITH COLDER AIR ALOFT ARRIVING. THE INCOMING TROUGH WILL
PROVIDE SOME LIFT...AND THE COLDER AIR ALOFT WILL DESTABILIZE THE
MID-LEVEL AIR MASS LATER SUNDAY NIGHT AND MONDAY MORNING. SO A
RENEWED ROUND OF SHOWERS IS FORECAST...WITH THE POSSIBILITY OF A
LIGHTNING STRIKE NEAR THE NORTH COAST DURING THE PRE-DAWN HOURS
MONDAY. LINGERING SHOWERS WILL THEN CONTINUE THROUGH MON
AFTN...WITH NW FLOW ALOFT FOCUSING SHOWERS IN THE MTNS AND
POSSIBLY IN A PUGET SOUND CONVERGENCE ZONE.

A SUBSTANTIAL UPPER RIDGE WILL AMPLIFY ALONG 130W ON MON
NGT...ENDING SHOWERS OVER WRN WA.		HANER

.LONG TERM...FROM PREVIOUS DISCUSSION...AN UPPER RIDGE WILL BE
OVER THE AREA TUESDAY THROUGH FRIDAY FOR GENERALLY DRY AND MILD
WEATHER. A WEAK SHORT WAVE COULD BRING A FEW SHOWERS WEDNESDAY BUT
THIS LOOKS PRETTY INCONSEQUENTIAL. THE CURRENT FORECAST HAS CHANCE
POPS WEDNESDAY AND AGAIN FRIDAY WHICH IS PROBABLY A BIT OVERDONE.
LOW LEVEL OFFSHORE FLOW WILL ALLOW HIGHS TO WARM INTO THE 50S EACH
DAY WITH PLENTY OF SUNSHINE. 	SCHNEIDER

&&

.AVIATION...ISOLATED SHOWERS ARE LINGERING ACROSS WESTERN WA THIS
MORNING...BUT MAINLY IN THE CASCADES. SHOWERS WILL DIMINISH THIS
AFTERNOON AS AN UPPER LEVEL RIDGE MOVES IN. THE FLOW ALOFT IS
WESTERLY. CIGS ARE MAINLY VFR. HIGH CLOUDS WILL INCREASE TONIGHT AS
THE NEXT FRONT APPROACHES. THIS FRONT WILL BRING RAIN TO THE COAST
SUNDAY MORNING...WITH RAIN SPREADING TO THE INTERIOR EARLY
AFTERNOON. 33

KSEA...VFR CONDITIONS TODAY. S WIND TO 10 KT...BECOMING LIGHT N/NE
01-04Z TONIGHT. 33

&&

.MARINE...HIGH PRESSURE WILL BRING LIGHT OFFSHORE FLOW TODAY.
MEANWHILE WEST SWELLS 10-13 FEET TODAY OVER THE COASTAL WATERS AND
WEST ENTRANCE - A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS REMAINS IN
EFFECT. THE NEXT PACIFIC FRONTAL SYSTEM WILL ARRIVE ON SUNDAY AND
THE COASTAL WATERS MAY SEE SE GALES WITH THE COLD FRONT. OFFSHORE
FLOW WILL PREVAIL EARLY NEXT WEEK WITH HIGH PRESSURE OVER INTERIOR
B.C. AND EASTERN WA. 33

&&

.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.

PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COASTAL WATERS AND WEST
     STRAIT OF JUAN DE FUCA.

     GALE WATCH OUTER COASTAL WATERS.

     SMALL CRAFT ADVISORY FOR ROUGH GRAYS HARBOR BAR.

&&

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