Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 120443
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
940 PM PDT FRI JUL 11 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION THROUGH
MONDAY FOR WELL ABOVE NORMAL OR POSSIBLY NEAR RECORD HIGH
TEMPERATURES. A WEAK UPPER LEVEL LOW WILL DEVELOP OFF THE OREGON
COAST SUNDAY AND MOVE INLAND SUNDAY NIGHT CREATING A CHANCE OF
SHOWERS FOR THE SOUTHERN PORTION OF THE AREA.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS HIGH AMPLITUDE UPPER LEVEL
RIDGE ALONG THE WEST COAST EXTENDING NORTH INTO THE NORTHWEST
TERRITORIES WITH AN UPPER LEVEL TROUGH OVER CENTRAL CANADA. MID
LEVEL CLOUDS ASSOCIATED WITH A FIZZLING SHORTWAVE HAVE MOVED OVER
THE SOUTHERN PORTION OF THE AREA IN THE LAST COUPLE OF HOURS.
STRATUS AND FOG ALONG THE COAST BURNED BACK OFFSHORE THIS AFTERNOON
BUT HAS RETURNED TO THE CENTRAL COAST FROM ABOUT MOCLIPS SOUTHWARD
IN THE EVENING HOURS. WIDE VARIETY OF TEMPERATURES AT 9 PM WITH
UPPER 50S AND LOWER 60S ALONG THE COAST ON THE  LOW END AND LOWER
80S OVER THE CENTRAL SOUND ON THE HIGH END.

WITH THE SHORTWAVE FIZZLING OUT OVER OREGON THIS EVENING WILL MAKE A
SMALL CHANCE TO THE FORECAST TO TAKE OUT THE CHANCE OF SHOWERS OVER
THE SOUTHERN PORTION OF THE AREA LATER TONIGHT INTO SATURDAY
MORNING. NO OTHER CHANGES TO THE FORECAST THIS EVENING. UPPER LEVEL
RIDGE PRETTY MUCH ENTRENCHED ALONG THE WEST COAST FOR THE NEXT FEW
DAYS WITH THE DEEP COOL TROUGH OVER CENTRAL CANADA SAGGING SOUTH
OVER THE WEEKEND. SURFACE GRADIENTS REMAINING FLAT OVER THE WEEKEND
WITH A TREND TOWARD ONSHORE LATE IN THE DAY. 500 MB HEIGHTS
REMAINING IN THE UPPER 580 DMS THROUGH THE WEEKEND WITH
SOUTHWESTERLY FLOW ALOFT. MODEL 850 MB TEMPERATURES WARM A DEGREE OR
TWO TOMORROW INTO THE PLUS 18 TO 20C AND AGAIN ON SUNDAY TO THE PLUS
20 TO 22C RANGE. ON THE FLIP SIDE THE INCREASE IN THE ONSHORE
GRADIENTS LATE IN THE DAY WILL CAP ANY WARMING EVEN WITH A SMALL
INCREASE IN THE TEMPERATURES ALOFT. LOOK FOR HIGHS IN THE 70S ALONG
THE COAST AND NEAR THE STRAIT WITH 80S TO LOWER 90S FOR THE INTERIOR
BOTH DAYS. 00Z MODEL RUNS STAYING WITH THE IDEA THAT A WEAK UPPER
LEVEL LOW WILL DEVELOP OFF THE OREGON COAST SUNDAY AND MOVE INLAND
SOUTH OF THE AREA SUNDAY NIGHT SO WILL HAVE TO KEEP A CHANCE OF
SHOWERS IN THE FORECAST FOR THE SOUTHERN PORTION OF THE AREA AT THAT
TIME.

LITTLE CHANGE ON MONDAY AS THE WEAK UPPER LEVEL LOW MOVES WELL TO
THE EAST OF THE AREA AND THE 500 MB HEIGHTS REMAIN NEAR 590 DMS.
ONCE AGAIN SURFACE GRADIENTS GO ONSHORE LATE IN THE DAY. PERSISTENCE
LOOKS LIKE A GOOD FORECAST FOR MONDAY WITH ANOTHER ROUND OF 80S AND
LOWER 90S FOR THE INTERIOR AND 70S FOR THE COAST AND STRAIT.

A HEAT ADVISORY WAS ISSUED EARLIER IN THE DAY FOR THE CENTRAL SOUND
AND SOUTHWEST INTERIOR OVER THE WEEKEND. GIVEN THE CURRENT MODEL
SOLUTIONS THE HEAT ADVISORY WILL LIKELY BE EXTENDED INTO MONDAY AND
TUESDAY OF NEXT WEEK. FELTON

.LONG TERM...PREVIOUS DISCUSSION FOLLOWS. THE UPPER RIDGE WILL
REMAIN OVER THE REGION THROUGH MIDWEEK FOR CONTINUED ABOVE NORMAL
TEMPS ACROSS MUCH OF THE CWA. THE RIDGE WILL WEAKEN SOME OR SHIFT
WELL EAST OF THE AREA...DEPENDING ON WHICH MODEL ONE
PREFERS...DURING THE LATTER PART OF THE PERIOD. THE GFS WAS QUITE
AGGRESSIVE IN DEVELOPING AN UPPER TROF OVER THE PACIFIC NORTHWEST
WHEREAS THE ECMWF KEPT AN UPPER RIDGE OVER THE REGION. CHOSE TO
COMPROMISE BETWEEN THESE TWO EXTREMES. IN OTHER WORDS...THE FORECAST
SHOWED TEMPS COOLING TO NEAR OR SLIGHTLY ABOVE NORMAL.

&&

.CLIMATE...THE RECORD FOR CONSECUTIVE DAYS WITH HIGHS 90 DEGREES
PLUS IN SEATTLE IS 5. IT HAS HAPPENED TWICE ONCE AT SEA-TAC 8/7-11,
1981 AND ONCE AT THE FEDERAL BUILDING DOWNTOWN 7/14-18, 1941. THE
RECORD FOR CONSECUTIVE DAYS 85 DEGREES PLUS IS 9, 8/5-13, 1977 AND
8/12-20, 1967. THE RECORD FOR CONSECUTIVE DAYS 80 DEGREES PLUS IS
15, 7/30-8/13, 1977.

&&

.AVIATION...FLOW ALOFT IS BECOMING LIGHT SLY AND WILL REMAIN THAT
WAY THROUGH SAT EVENING WHEN IT WILL SWITCH TO LIGHT SWLY. THE AIR
MASS IS STABLE. MARINE STRATUS AND FOG ALONG THE COAST WILL PUSH
INTO THE STRAIT OF JUAN DE FUCA AND THE CHEHALIS GAP OVERNIGHT...THE
NORTH BEND OREGON TO SEATTLE GRADIENT WAS OVER 2MB AT 8PM THIS
EVENING...SO THERE IS A CHANCE THAT MARINE AIR AND STRATUS WILL MAKE
IT INTO SHELTON AND OLYMPIA. OTHERWISE...JUST SOME HIGH CLOUDS ARE
EXPECTED TO ARRIVE FROM THE THUNDERSTORMS OVER OREGON THIS
AFTERNOON.

KSEA...CIRRUS IS MOVING IN FROM SOUTH. SEATAC SHOULD STAY VFR
OVERNIGHT...HOWEVER LOW CLOUDS AND FOG PUSHING INLAND WILL POSSIBLY
MOVE INTO THE SOUTH SOUND. EXPECT A NLY BREEZE TO PICK UP SAT
AFTERNOON AND EVENING. JSMITH

&&

.MARINE...HIGHER PRESSURE IS OFFSHORE WITH LOWER PRESSURE
INLAND...BUT PRESSURE GRADIENTS ARE WEAK. THE PATTERN OF AFTERNOON
AND EVENING ONSHORE FLOW WILL CONTINUE THROUGH EARLY NEXT WEEK.
SMALL CRAFT ADVISORY WEST WINDS ARE POSSIBLE IN THE STRAIT TOMORROW
AFTERNOON/EVENING BUT UNCERTAINTY IS HIGH SO AN ADVISORY HAS NOT
BEEN ISSUED. STRATUS AND FOG ON THE COAST WILL PUSH INLAND TONIGHT
AND MAY REACH THE WESTERN STRAIT OR SOUTH PUGET SOUND WATERS. JSMITH

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HEAT ADVISORY IN EFFECT FOR MUCH OF THE PUGET SOUND REGION
     AND SOUTHWEST INTERIOR FROM 11 AM SATURDAY UNTIL 6 AM MONDAY.

PZ...NONE.

&&

$$

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