Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 130441
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
940 PM PDT SAT JUL 12 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION
THROUGH SUNDAY FOR CONTINUED WELL ABOVE NORMAL TEMPERATURES. A
LOW PRESSURE SYSTEM WILL MOVE ACROSS THE AREA SUNDAY NIGHT FOR
A RISK OF SHOWERS OR THUNDERSTORMS. THIS SYSTEM WILL MOVE EAST
OF THE AREA ON MONDAY. HIGH PRESSURE ALOFT WILL PREVAIL ON
TUESDAY.

&&

.SHORT TERM...WARM SUMMER WEATHER. SHOULD BE A PRETTY STRAIGHT
FORWARD FORECAST. NOT SO FAST. THIS HAS NOT BEEN A TYPICAL WARM
SPELL FOR WESTERN WASHINGTON AND THERE IS ANOTHER SOMEWHAT UNUSUAL
PATTERN SETTING UP FOR LATER TOMORROW INTO TOMORROW NIGHT.

FIRST OFF THIS EVENING. SATELLITE IMAGERY SHOWS STRATUS RIGHT ALONG
THE COAST INTO GRAYS HARBOR. LOCATIONS RIGHT ON THE OCEAN LIKE
PACIFIC BEACH NEVER SAW THE SUN TODAY WITH TEMPERATURES REMAINING IN
THE LOWER TO MID 60S. STRATUS ALREADY MOVING DOWN THE STRAIT OF JUAN
DE FUCA ALL THE WAY TO OFF OF NEW DUNGENESS AT 04Z. CLEAR SKIES OVER
THE REMAINDER OF THE AREA. TEMPERATURES ARE COOLING OFF A LITTLE
QUICKER TONIGHT WITH MOSTLY 70S OVER THE INTERIOR AND MID 50S TO
LOWER 60S NEAR THE STRAIT AND ALONG THE COAST.

WEAK ONSHORE GRADIENTS TONIGHT CONTINUING INTO SUNDAY MORNING
WITH THE LOW STRATUS AND FOG GETTING INTO THE SAN JUANS AND WHIDBEY
ISLAND. THE LOW STRATUS AND FOG COULD MAKE IT AS FAR INLAND AS THE
EVERETT AREA. SOUTHERLY ONSHORE GRADIENTS NOT THAT STRONG WITH
KHQM-KSEA ONLY AROUND PLUS 1 MB SO EXPECT THE STRATUS OVER THE SOUTH
END OF THE AREA TO NOT GET MUCH FARTHER INLAND THAN SHELTON. LOWS
OVERNIGHT WILL BE IN THE MID 50S TO MID 60S.

SOME WRINKLES IN THE FORECAST FOR SUNDAY AS A WEAK UPPER LEVEL LOW
NEAR 40N/130W THIS EVENING MOVES SLOWLY NORTHEAST. MODEL SOLUTIONS
HAVE BEEN PRETTY CONSISTENT IN MOVING THE LOW AROUND 150 NM WEST OF
NEWPORT OREGON BY 00Z MONDAY. AS THE LOW APPROACHES THE FLOW ALOFT
WILL BECOME MORE DIFFLUENT CREATING A SLIGHT CHANCE FOR
THUNDERSTORMS FROM ABOUT HOQUIAM TO CHEHALIS SOUTHWARD AND OVER THE
CENTRAL AND SOUTHERN WASHINGTON CASCADES IN THE AFTERNOON. THERE IS
SOME INSTABILITY ALOFT WITH THE LOW. THE STORM PREDICTION CENTER HAS
A SMALL...5 PERCENT...CHANCE OF SEVERE THUNDERSTORMS OVER THE
WILLAMETTE VALLEY TOMORROW. TEMPERATURE WISE THE 850 MB TEMPERATURES
FOR 00Z MON ARE SIMILAR TO WHAT WE HAD TODAY. SURFACE GRADIENTS
REMAIN SIMILAR AS WELL. WITH THE POSSIBILITY OF CONVECTION FIRING UP
IN THE AFTERNOON THERE COULD BE SOME MID LEVEL CLOUD COVER THAT
COULD CUT DOWN ON THE TEMPS A TOUCH. AT THIS POINT THE BEST CHANCE
FOR THIS WILL BE OVER THE SOUTHERN PORTION OF THE AREA SO WILL STAY
WITH THE IDEA OF SLIGHTLY COOLER HIGHS OVER THE SOUTHWEST INTERIOR
WITH PERSISTENCE OVER THE REMAINDER OF THE AREA. THIS STILL LEAVES
THE WARMER LOCATIONS IN THE LOWER 90S ON SUNDAY WITH MID 70S TO MID
80S NORTH OF SEATTLE AND 60S STILL ALONG THE COAST.

UPPER LEVEL LOW MOVING OVER WESTERN WASHINGTON SUNDAY NIGHT WITH A
CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE ENTIRE AREA. IT WILL BE
A MUGGY NIGHT WITH THE CLOUD COVER AND POSSIBLE PRECIPITATION. LOWS
WILL MOSTLY BE NEAR 60 DEGREES.

UPPER LEVEL LOW MOVING OFF TO THE EAST MONDAY MORNING. IN ITS WAKE A
WEAK MARINE PUSH WILL DEVELOP WITH THE POSSIBILITY OF THE STRATUS
DECK GETTING AS FAR EAST AS THE CASCADE FOOTHILLS. THE MARINE LAYER
WILL BE SHALLOW AND BURN BACK TO THE COAST QUICKLY LATER MONDAY
MORNING INTO MONDAY AFTERNOON. HIGH TEMPERATURES ON MONDAY ARE A
LITTLE TRICKY AS THE TEMPERATURES ALOFT REBOUND BACK TO NEAR WHAT
WILL HAVE SEEN OVER THE WEEKEND. A WEAK PUSH SCENARIO USUALLY
RESULTS IN 5 TO 10 DEGREES OF COOLING FOR THE INTERIOR BUT WITH THE
TEMPERATURES ALOFT WARMING QUICKLY COOLING COULD BE MORE ON THE
ORDER OF ONLY A COUPLE OF DEGREES FOR THE INTERIOR. THIS WILL PUT
HIGHS MOSTLY IN THE MID 70S TO UPPER 80S FOR THE INTERIOR WITH
MOSTLY 60S ONCE AGAIN FOR THE COAST.

UPPER LEVEL RIDGE REBOUNDS MONDAY NIGHT WITH THE 500 MB HEIGHTS BACK
UP TO NEAR 590 DMS ON TUESDAY. SURFACE GRADIENTS ONCE AGAIN REMAIN
LIGHT ONSHORE BUT WITH THE 850 MB TEMPERATURES ABOVE PLUS 20C
TUESDAY LOOKS TO BE SIMILAR TO SATURDAY WITH THE WARMER LOCATIONS
GETTING BACK INTO THE LOWER 90S.

THE HEAT ADVISORY WILL REMAIN IN EFFECT AT LEAST THROUGH TOMORROW.
CURRENT FORECAST HAS THE TRENDS COVERED. NO UPDATE THIS EVENING.
FELTON

.LONG TERM...PREVIOUS DISCUSSION FOLLOWS.
THE MEDIUM RANGE SOLUTIONS APPEAR TO BE LATCHING ONTO THE IDEA OF
RETROGRADING THE RIDGE FARTHER OFFSHORE DURING THIS PERIOD. THE
MAIN IMPACT THIS WILL HAVE ON OUR WEATHER WILL BE TO TIGHTEN THE
ONSHORE PRESSURE GRADIENT...LEADING TO COOLER TEMPS AND MORE
NIGHT/MORNING LOW CLOUDS. WED WILL LIKELY BE THE WARMEST DAY OF
THIS PERIOD. AFTER WED...ANTICIPATE TEMPS TO FALL BACK TO NEAR
NORMAL BEFORE REBOUNDING SOMEWHAT ABOVE NORMAL ON DAY 7.

&&

.AVIATION...THE FLOW ALOFT IS LIGHT TO MODERATE SOUTH TO SOUTHWEST.
THE AIR IS DRY EXCEPT FOR COASTAL MARINE LAYER STRATUS AND FOG WHICH
WILL PUSH INLAND TO CREATE IFR CONDS IN SOME AREAS
OVERNIGHT...ESPECIALLY ALL AROUND WHIDBEY ISLAND AND A GOOD PART OF
THE SAN JUANS. ALSO PORTIONS OF SW WA WILL SEE LOW STRATUS AND FOG
AGAIN LATE TONIGHT AND SUN MORNING. OTHERWISE...JUST A FEW HIGH
CLOUDS. SCATTERED THUNDERSTORMS SHOULD DEVELOP ON SUNDAY OVER
OREGON...AND THOSE ARE LIKELY TO WORK NORTH INTO THE WA
CASCADES...SO THERE WILL BE MORE MID AND HIGH CLOUD DEBRIS FROM THAT
OVER WRN WA ON SUNDAY AND SUNDAY NIGHT. TSTORMS THAT DEVELOP SHOULD
STAY OVER THE MOUNTAINS AND LIGHTNING WILL NOT AFFECT TAF SITES.

KSEA...LIGHT NLY SURFACE WINDS WILL PICK UP SUNDAY AFTERNOON BEFORE
SWITCHING TO SLY AROUND 5Z MON. MARINE FOG AND LOW CLOUDS SHOULD NOT
MAKE IT TO SEATAC SUNDAY MORNING...BUT THERE MIGHT BE SOME PATCHES
OF FOG DOWN ON THE WATER FOR A FEW HOURS. SOME MID AND HIGH CLOUDS
ARE LIKELY SUNDAY AND SUNDAY NIGHT...CONVECTIVE DEBRIS FROM
SCATTERED THUNDERSTORMS OVER OREGON AND THE SRN WA CASCADES. JSMITH

&&

.MARINE...IT LOOKS LIKE THE NEXT FEW DAYS WILL FEATURE THE MARINE
LAYER ALONG THE COAST AND A PRETTY GOOD WESTERLY PUSH IN THE EVENING
FOR THE STRAIT EACH DAY WITH SMALL CRAFT ADVISORY LEVEL WINDS. THE
FOG AND LOW CLOUDS SHOULD BE MORE EXTENSIVE SUNDAY
MORNING...ESPECIALLY ALL AROUND WHIDBEY AND THE PART OF THE SAN
JUANS. IT MIGHT MAKE IT AS FAR NORTH AS BELLINGHAM BAY. PATCHY FOG
COULD MAKE IT INTO PARTS OF PUGET SOUND...BUT THAT WILL BE MORE OF A
STRUGGLE. THE MARINE LAYER IS STILL PRETTY SHALLOW.

SUNDAY NIGHT INTO MONDAY MORNING AN UPPER LEVEL LOW WILL MOVE
THROUGH THE AREA ENHANCING THE PUSH AS WELL. JSMITH

&&

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

PZ...SMALL CRAFT ADVISORY IN EFFECT TONIGHT FOR THE CENTRAL AND
     EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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