AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
337 AM PDT SUN JUL 12 2020

.SYNOPSIS...SOME LINGERING SHOWERS POSSIBLE THIS MORNING WITH SKIES
STARTING TO CLEAR IN THE AFTERNOON. DRY CONDITIONS WILL CONTINUE
INTO AT LEAST MID-WEEK WITH SUNNY SKIES AND WARMER TEMPERATURES.
SOME WEAK SYSTEMS PASSING TO THE NORTH OF THE AREA MAY ALLOW FOR
SCATTERED SHOWERS AT TIMES FOR THE SECOND HALF OF THE WEEK.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...CURRENT SATELLITE SHOWS MOSTLY
LOW CLOUDS OVER THE AREA WHILE RADAR IS STILL PICKING UP SOME WEAK
ECHOES HERE AND THERE OVER W WA THIS MORNING...SO SOME STRAY DRIZZLE
OR LIGHT SPRINKLES ARE STILL OUT THERE IN SOME PLACES.

THE UPPER LEVEL LOW RESPONSIBLE FOR THIS UP IN CANADA LOOKS TO
CONTINUE TO SLOWLY MOVE EASTWARD...ALLOWING FOR THE PROSPECT OF
SHOWERS TO DIMINISH EVEN FURTHER AS THE DAY PROGRESSES. UPPER LEVEL
RIDGING WILL BUILD OVER THE W PACIFIC WITH THE LEADING EDGE OF THIS
RIDGE ENTERING INTO W WA THIS EVENING. THIS RIDGE WILL CONTINUE TO
MOVE EASTWARD SLOWLY OVER THE REMAINDER OF THE SHORT TERM
PERIOD...ALLOWING FOR DRY CONDITIONS TO PERSIST AND TEMPERATURES TO
WARM TO MORE SUMMER-LIKE VALUES.

HIGH TEMPS TODAY WILL STILL REMAIN A LITTLE ON THE MILD SIDE OF
THINGS WITH MOST INTERIOR LOWLAND LOCATIONS GETTING INTO THE MID TO
UPPER 60S...ALTHOUGH THE SW INTERIOR MAY GET UP INTO THE LOWER 70S.
COASTAL TEMPS WILL GENERALLY SIT IN THE LOWER 60S. HIGHS MONDAY WILL
SEE THE EFFECTS OF THE RIDGE KICK IN PRETTY QUICKLY WITH LOWER TO
MID 70S FOR THE INTERIOR WHILE COASTAL AREAS WILL WARM INTO THE MID
60S. TUESDAY SEES THIS TREND CONTINUE AS INTERIOR HIGHS WILL CLIMB
INTO THE UPPER 70S WHILE THE COAST LINGERS IN THE MID 60S.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...THE OFFSHORE RIDGE STILL
EXPECTED TO FLATTEN OUT IN THE WED/THU TIMEFRAME. THE ECMWF LOOKS TO
TRY AND BRING A SYSTEM DOWN INTO W WA THURSDAY...BUT IT REALLY ONLY
DROOPS DOWN ENOUGH TO IMPACT THE NORTHERN TWO-THIRDS OF THE CWA. THE
GFS DOES NOT REALLY ALLOW THIS FEATURE TO DIP DOWN FAR ENOUGH TO
HAVE ANY EFFECT AT ALL. ENSEMBLES TEND TO SPLIT THE DIFFERENCE HERE
WITH BRINGING SOME PRECIP IN...BUT NOT TERRIBLY MUCH...THUS HAVE
OPTED FOR RELATIVELY WEAK POPS IN THE FORECAST. BEYOND THAT...THE
DETERMINISTIC MODELS FLIP ROLES...WITH THE GFS BRINGING IN SOME WEAK
SHORTWAVES THAT COULD PRODUCE SOME WEAK POPS HERE AND THERE WHILE
THE ECMWF LOOKS TO BRING IN ANOTHER RIDGE. ENSEMBLES SEEM TO ONCE
AGAIN TRY TO SPLIT THE DIFFERENCE.

WEDNESDAY LOOKS TO BE THE WARMEST DAY OF THE WEEK WITH INTERIOR
LOCATIONS GETTING CLOSE TO 80 BEFORE THE FLATTENING RIDGE WILL ALLOW
THINGS TO COOL A BIT BACK DOWN INTO THE LOWER TO MID 70S FOR THE
REMAINDER OF THE WEEK.  18

&&

.AVIATION...WESTERLY FLOW ALOFT BECOMING NORTHWESTERLY THIS
AFTERNOON AND TONIGHT AS UPPER LEVEL TROUGH MOVES EAST OF THE
AREA. IN THE LOWER LEVEL ONSHORE FLOW CONTINUING INTO MONDAY.

CEILINGS MOSTLY IN THE 1500-2500 FOOT RANGE WITH CEILINGS BELOW
1000 FEET OVER THE KITSAP PENINSULA AND IN A WEAK CONVERGENCE ZONE
AROUND KPAE UNTIL 17Z. CEILINGS IMPROVING QUICKLY MIDDAY WITH VFR
CEILINGS IN THE 4000-5000 FOOT RANGE BY 20Z. CLOUDS SCATTERING OUT
BY 00Z. STRATUS DEVELOPING ALONG THE COAST AND NEAR THE PUGET
SOUND 09Z-12Z MONDAY WITH CEILINGS NEAR 1500 FEET.

KSEA...CEILINGS 1500-2500 FEET RISING TO 4500 FEET MIDDAY. CLOUDS
SCATTERING OUT LATER THIS AFTERNOON WITH MOSTLY CLEAR SKIES
OVERNIGHT. SOUTH WIND 6 TO 10 KNOTS BECOMING NORTHERLY 4 TO 8
KNOTS THIS AFTERNOON. FELTON

&&

.MARINE...VARYING DEGREES OF ONSHORE FLOW THIS WEEK WITH HIGH
PRESSURE OVER THE COASTAL WATERS AND LOWER PRESSURE INLAND. SMALL
CRAFT ADVISORY WESTERLIES EXPECTED EACH EVENING IN THE CENTRAL AND
EAST ENTRANCE OF THE STRAIT OF JUAN DE FUCA. FELTON

&&

.HYDROLOGY...THE DAILY HYDROLOGY DISCUSSION HAS ENDED UNTIL THE
START OF THE NEXT RAINY SEASON; IT WILL ONLY BE UPDATED AS NEEDED.

&&

.CLIMATE...WITH AN AVERAGE HIGH TEMPERATURE OF 70.4 DEGREES FOR
THE FIRST 11 DAYS OF JULY THIS IS THE COLDEST START TO THE MONTH
SINCE 2005 AND THE 3RD COLDEST START IN THE LAST 25 YEARS. THE
TWO COLDER YEARS 2000 WITH AN AVERAGE HIGH OF 69.0 DEGREES
THROUGH THE FIRST 11 DAYS AND 2005 WITH AN AVERAGE HIGH OF 69.5.
SINCE RECORDS STARTED AT SEATTLE-TACOMA AIRPORT IN 1945 THERE
HAVE ONLY BEEN TWO JULYS WITHOUT A DAY WITH A HIGH 80 DEGREES OR
WARMER. THOSE TWO YEARS WERE 1993 AND 1963. COMPARING THE COLDER
YEAR STARTS, 2005 ENDED UP WITH 9 DAYS WITH HIGHS 80 DEGREES PLUS
AND 2000 HAD 6 DAYS. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 5 AM PDT MONDAY
     FOR CENTRAL U.S. WATERS STRAIT OF JUAN DE FUCA-EAST
     ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA.

&&