Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS66 KSEW 271028
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT SUN JUL 27 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION THROUGH
MUCH OF NEXT WEEK FOR DRY WEATHER WITH ABOVE NORMAL DAYTIME
TEMPERATURES.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS SOME LOWE CLOUDS ALONG THE
NORTH COAST AND MOVING DOWN THE STRAIT OF JUAN DE FUCA OTHERWISE
CLEAR SKIES ACROSS WESTERN WASHINGTON AT 10Z/3 AM. TEMPERATURES WERE
IN THE 50S AND LOWER 60S.

NO CHANGES TO THE FORECAST THIS MORNING. UPPER LEVEL RIDGE OVER
WESTERN WASHINGTON WITH THE RIDGE AXIS EAST OF THE AREA. 500 MB
HEIGHTS WILL CONTINUE TO SLOWLY RISE THROUGHOUT THE DAY IN RESPONSE
TO AN UPPER LEVEL TROUGH DIGGING SOUTH WELL OFFSHORE. BY 00Z MON/5
PM SUN 500 MB HEIGHTS WILL BE IN THE MID 580 DMS. 850 MB
TEMPERATURES WILL ALSO SLOWLY RISE TODAY FROM PLUS 12-14C THIS
MORNING TO PLUS 15 TO 18C BY LATE THIS AFTERNOON. AT THE SURFACE
WEAK LOW LEVEL ONSHORE FLOW WILL CONTINUE. WITH THE WARMING
TEMPERATURES ALOFT EXPECT ABOUT 5 DEGREES OF WARMING FOR INTERIOR
LOCATIONS. AN AFTERNOON SEA BREEZE WILL KICK UP WITH THE WEAK
ONSHORE GRADIENTS KEEPING THE COAST AND AREAS ALONG THE STRAIT
TEMPERATURES NEAR SATURDAYS READINGS. IN GENERAL UPPER 70S AND 80S
WILL COMMON OVER THE INTERIOR WITH LOWER TO MID 70S COAST AND
STRAIT.

LITTLE CHANGE IN THE PATTERN TONIGHT INTO MONDAY. TEMPERATURES ALOFT
DO WARM A TOUCH...850 MB TEMPERATURES FROM PLUS 16 TO 19C LATE
MONDAY AFTERNOON. SURFACE GRADIENTS REMAIN LIGHT ONSHORE. WITH THE
WARMER TEMPERATURES ALOFT A COUPLE MORE DEGREES OF HEATING IS
POSSIBLE ON MONDAY PUSHING THE WARMER LOCATIONS IN THE INTERIOR
INTO THE LOWER 90S. FOR THE MOST PART 80S WILL BE COMMON FOR THE
INTERIOR WITH LOWER TO MID 70S ONCE AGAIN FOR THE COAST AND STRAIT.

VIRTUALLY NO CHANGE IN THE PATTERN ON TUESDAY WITH SOUTHWESTERLY
FLOW ALOFT CONTINUING WITH WESTERN WASHINGTON ON THE BACK SIDE OF
THE UPPER LEVEL RIDGE. 500 MB HEIGHTS REMAIN IN THE MID 580 DMS AND
TEMPERATURES ALOFT ARE SIMILAR TO MONDAY TEMPERATURES. SURFACE
GRADIENTS ARE A LITTLE FLATTER BUT STILL WEAKLY ONSHORE. PERSISTENCE
IS A GOOD FORECAST FOR TUESDAY WITH THE WARMEST LOCATIONS OVER THE
INTERIOR ONCE AGAIN PUSHING 90 DEGREES.

WITH THE LIGHT ONSHORE GRADIENTS EACH DAY PATCHY MORNING LOW CLOUDS
AND FOG WILL FORM ALONG THE COAST AND OVER THE STRAIT OF JUAN DE
FUCA.

.LONG TERM...EXTENDED MODELS IN GOOD AGREEMENT WITH LITTLE CHANGE IN
THE FORECAST WEDNESDAY THOUGH FRIDAY WITH WESTERN WASHINGTON
ON THE BACK SIDE OF THE UPPER LEVEL RIDGE WITH SOUTHWESTERLY FLOW
ALOFT AND 500 MB HEIGHTS IN THE MID 580 DMS. SURFACE GRADIENTS
REMAIN LIGHT ONSHORE. THE ECMWF IS STARTING TO HINT AT THE
POSSIBILITY OF SOME CONVECTION OVER THE CASCADES ON FRIDAY WHILE THE
GFS DOES NOT HAVE THIS FEATURE. WILL LEAVE THE MENTION OF CONVECTION
FOR THE CASCADES OUT OF THE FORECAST AT THIS POINT. ONSHORE
GRADIENTS INCREASING A LITTLE OVER THE WEEKEND WITH THE UPPER LEVEL
RIDGE WEAKENING A TOUCH. THIS WILL HELP PUSH THE MORNING LOW CLOUDS
ALONG THE COAST FURTHER INLAND ON SATURDAY WITH SOME SLIGHT
COOLING...5 DEGREES OR SO...FOR THE HIGHS FOR THE INTERIOR. FELTON

&&

.AVIATION...THE UPPER LEVEL RIDGE OVER THE ROCKY MOUNTAINS WILL
CONTINUE TO BUILD THROUGH THE MUCH OF THE NEXT WEEK. FLOW ALOFT WILL
REMAIN SOUTHWESTERLY AND LIGHT TODAY. RISING HEIGHTS OVER THE REGION
WILL ALSO HELP KEEP THE AIR MASS OVER WESTERN WASHINGTON DRY AND
STABLE. LOW LEVEL ONSHORE FLOW WILL BRING VERY LIMITED LOW CLOUDS TO
THE COAST AND STRAIT LATE AROUND DAYBREAK. SATELLITE IMAGERY AND
SURFACE OBSERVATIONS AT 10Z HINTING AT DEVELOPMENT OVER THE WEST
STRAIT AND NORTH COAST. SKIES WILL REMAIN CLEAR AND VFR ALL OTHER
AREAS. LOW CLOUDS AND OR FOG WILL REMAIN VERY SHALLOW OVER THE COAST
AND STRAIT AND CLEAR QUICKLY BY MID MORNING.

KSEA...CLEAR SKIES AND VFR CONDITIONS THROUGH SUNDAY EVENING.
NORTHEASTERLY WINDS 8 TO 10 KTS WILL WEAKEN AROUND
DAYBREAK...BECOMING NORTHWESTERLY 8 TO 10 KTS BY EARLY AFTERNOON.

&&

.MARINE...THE PERSISTENT PATTERN OF HIGH PRESSURE OVER THE COASTAL
WATERS AND LOWER PRESSURE INLAND WILL CONTINUE THROUGH MID
WEEK...SUPPORTING VARYING DEGREES ONSHORE FLOW. STRONGEST WINDS WILL
OCCUR THROUGH THE CENTRAL AND EAST STRAIT...LIKELY REACHING SMALL
CRAFT ADVISORY LEVELS DURING THE LATE AFTERNOON AND EVENING HOURS.
NORTHWESTERLY WINDS OVER THE COASTAL WATERS WILL STRENGTHEN THIS
AFTERNOON AND EVENING WITH WESTERLY SWELL 4 TO 5 FEET AT 8 SECONDS.
AREAS OF FOG WILL DEVELOP EARLY THIS MORNING OVER THE COASTAL WATERS
AND STRAIT...PERSISTING INTO LATE MORNING BEFORE CLEARING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS...CENTRAL AND EAST STRAIT.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.