Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 252152
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PDT SAT JUL 25 2015

.SYNOPSIS...AN UPPER LEVEL TROUGH WILL KEEP SHOWERS IN THE FORECAST
THROUGH SUNDAY...WITH A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND
EVENING. THE TROUGH WILL MOVE EAST OF THE CASCADES MONDAY ENDING THE
SHOWERS AND BRINGING WARMER CONDITIONS. AN UPPER LEVEL RIDGE WILL
BUILD TUESDAY AND KEEP CONDITIONS DRY AND WARM THROUGH THE END OF
THE WEEK.

&&

.SHORT TERM...THERE HAVE BEEN A FEW SUN BREAKS TODAY AND KSEA MAY
WELL REACH 70 DEGREES...SOME PLACES ALREADY HAVE. SKIES WILL REMAIN
MOSTLY CLOUDY TONIGHT WITH SCATTERED SHOWERS. A BROAD UPPER TROUGH
WILL SWING ACROSS WASHINGTON ON SUNDAY. THIS WILL BRING THE COOLEST
AIR MASS OF THE SUMMER WITH HEIGHTS FALLING TO THE MID 560S.
TEMPERATURES WILL AGAIN STRUGGLE TO REACH 70 BUT ALL IT SHOULD TAKE
IS ONE GOOD SUN BREAK...WHICH IS SOMEWHAT MORE LIKELY IN AN UNSTABLE
AIR MASS.

SHOWER ACTIVITY WILL BE ENHANCED BY THE UPPER TROUGH AND HAVE
BOOSTED POPS ESPECIALLY FOR THE AFTERNOON. LIFTED INDICES ARE
NEGATIVE OVER THE SOUTH PART AND THE MOUNTAINS SUNDAY AFTERNOON SO
THERE IS ALSO A CHANCE OF THUNDERSTORMS IN THE AFTERNOON AND
EVENING. HAVE NOT CHANGED THE AREA THAT MIGHT GET A THUNDERSTORM...
IT IS STILL THE MOUNTAINS AND ALSO THE LOWLANDS FROM ABOUT SEATTLE
SOUTH.

THE UPPER TROUGH MOVES AWAY SUNDAY NIGHT AND BY MONDAY AFTERNOON IT
WILL BE IN IDAHO AND NOT AFFECTING WESTERN WASHINGTON. SKIES WILL
BEGIN TO CLEAR UNDER DRY NORTHERLY FLOW ALOFT WHILE AN UPPER RIDGE
BUILDS OFFSHORE. WITH HEIGHTS RISING...TEMPERATURES WILL ALSO
REBOUND. HIGHS MONDAY WILL BE MOSTLY IN THE LOW TO MID 70S OVER
INLAND AREAS.

TEMPERATURES WILL RISE FURTHER ON TUESDAY AS THE UPPER RIDGE MOVES
EAST AND THE RIDGE AXIS IS BROADLY OVER WESTERN WASHINGTON. HAVE
FORECAST 80S OVER THE INTERIOR FROM ABOUT SEATTLE SOUTH WITH 70S
COAST AND NORTH. BURKE

.LONG TERM...HEIGHTS REMAIN HIGH THROUGH THE END OF THE WEEK...IN
THE 580S. THURSDAY LOOKS LIKE THE WARMEST DAY. HIGHS EACH DAY WILL
BE WELL INTO THE 80S OVER THE INTERIOR...WITH LOW 90S OVER THE SOUTH
INTERIOR. ON THURSDAY 90S COULD REACH AS FAR NORTH AS THE SEATTLE
AREA. THERE IS LITTLE CHANGE IN THE PATTERN INTO THE WEEKEND. BURKE

&&

.AVIATION...AN UPPER TROUGH WILL BE OVER THE AREA THROUGH SUNDAY
WITH WESTERLY FLOW ALOFT. AT THE SURFACE...LOW LEVEL ONSHORE FLOW
WILL PREVAIL WITH HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND.
AIR MASS MOIST AND STABLE. MOSTLY MID LEVEL CLOUDS THIS
EVENING...THEN LOW CLOUDS SHOULD REDEVELOP TONIGHT AND PERSIST
THROUGH MUCH OF THE DAY SUNDAY. AIR MASS BECOMING UNSTABLE SUNDAY
AFTERNOON.

KSEA...MOSTLY MID LEVEL CLOUDS THIS EVENING...THEN LOW CLOUDS
DEVELOPING AGAIN LATE TONIGHT. SOUTHWEST WIND 5-10 KNOTS EXPECTED
THIS EVENING...ALTHOUGH THERE IS A CHANCE WINDS COULD SWITCH TO
NORTHERLY AT TIMES EARLY IN THE EVENING. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL PREVAIL THROUGH TUESDAY WITH HIGH
PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. SMALL CRAFT
ADVISORY WEST WINDS ARE LIKELY EACH EVENING FOR THE CENTRAL
AND EASTERN STRAIT OF JUAN DE FUCA.

ONSHORE FLOW WILL WEAKEN AND TURN MORE NORTHERLY WEDNESDAY AND
THURSDAY AS A THERMAL TROUGH BUILDS NORTH ALONG THE COAST. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION CAN BE SEEN AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML


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