Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 201029
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
329 AM PDT WED AUG 20 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM ALOFT WILL INFLUENCE THE WEATHER
PATTERN OVER THE AREA THROUGH FRIDAY. THIS WILL RESULT IN SOMEWHAT
UNSETTLED CONDITIONS AND BELOW NORMAL DAYTIME TEMPERATURES. HIGH
PRESSURE ALOFT WILL RETURN THIS WEEKEND.

&&

.SHORT TERM...
THE STRATUS WAS FORMING IN PLACE INSTEAD OF ADVECTING INLAND FROM
THE PACIFIC...THUS THE LOW CLOUDS WERE NOT AS WIDESPREAD ACROSS
THE LOWLANDS AS ONE WOULD EXPECT WITH THE ONSHORE GRADIENT.
HOWEVER...THERE WAS A 5-7K FT CLOUD DECK OVER THE CWA EARLY THIS
MORNING...THUS IT LOOKS LIKE THERE WILL BE QUITE A BIT OF CLOUD
COVER AROUND THROUGH AT LEAST THIS MORNING.

MEANWHILE...THE AXIS OF AN UPPER TROF WILL REMAIN OVER THE NORTHERN
GREAT BASIN THROUGH TONIGHT...RESULTING IN NORTHWEST FLOW ALOFT
AND CONTINUED LOW LEVEL ONSHORE FLOW. IN GENERAL...TEMPS TODAY
SHOULD BE 5-15 DEGREES COOLER THAN YESTERDAY...WITH THE GREATEST
AMOUNT OF COOLING OCCURRING OVER THE LOWLAND INTERIOR.

THE MODELS WERE IN AGREEMENT THAT AN UPPER TROF WILL DIG OVER THE
REGION ON THU...WITH AN UPPER LOW DEVELOPING OVER WESTERN WA THU
NIGHT. THIS LOW WILL THEN MOVE OVER EASTERN WA/EASTERN OREGON
DURING THE DAY FRI...WITH STRONG NORTHERLY FLOW ALOFT DEVELOPING
OVER WESTERN WA IN ITS WAKE. THERE SHOULD BE SOME LIGHT PRECIP
OVER THE CWA THU AND THU NIGHT...WITH POSSIBLY A BETTER CHANCE OF
PRECIP OVER THE INTERIOR ON FRI.

PREDICTING TEMPS THU AND FRI WILL BE SOMEWHAT OF A CHALLENGE.
THERE IS A CHANCE THAT TEMPS COULD END UP A FEW DEGREES COOLER
THAN PREDICTED FOR BOTH DAYS...ESPECIALLY IF THERE IS NOT MUCH
CLEARING IN THE AFTERNOONS.

.LONG TERM...
NO CHANGES WERE MADE TO THE INHERITED FORECAST...WHICH ESSENTIALLY
REFLECTED NEAR CLIMO. THE MEDIUM RANGE SOLUTIONS APPEARED TO BE IN
BETTER AGREEMENT AND SHOWED THE CWA UNDER THE INFLUENCE OF AN
AMPLIFIED UPPER RIDGE CENTERED OFFSHORE.

&&

.AVIATION...NORTHWEST FLOW ALOFT WILL PREVAIL THROUGH TONIGHT WITH
AN UPPER TROUGH OVER EASTERN WASHINGTON. AT THE SURFACE... ONSHORE
FLOW WILL CONTINUE WITH HIGH PRESSURE OFFSHORE AND LOWER PRESSURE
INLAND. AIR MASS GENERALLY STABLE.

THERE IS WIDESPREAD AREAS OF MID LEVEL CLOUDS ABOUT 4-5K OVER MUCH
OF THE REGION EARLY THIS MORNING. THERE ARE ALSO SOME AREAS OF LOWER
CLOUDS IN THE 1K-2.5K LEVEL.  EXPECT THE LOWER CLOUDS TO LIFT AND
DISSIPATE BY AFTERNOON WITH THE MID DECK BECOMING SCATTERED TO
BROKEN BY LATE AFTERNOON.

KSEA...THE MID DECK AROUND 4.5K IS PRESENT NOW...BUT THERE ARE LOW
CLOUDS NEAR BY AT KPWT. THE LOW CLOUDS AT ABOUT 1-2K ARE EXPECTED TO
FORM OR DRIFT NEAR THE AIRPORT THIS MORNING. LOWER CLOUDS SHOULD
LIFT OR DISSIPATE BY EARLY AFTERNOON. 13

&&

.MARINE...ONSHORE FLOW WILL PREVAIL FOR THE NEXT SEVERAL DAYS WITH
HIGH PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. THIS WILL PRODUCE
WINDS NEAR SMALL CRAFT ADVISORY LEVELS IN THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA MOST EVENINGS. RIGHT NOW WE ARE EXPECTING
ABOUT 20 KTS THROUGH THE STRAIT THIS EVENING.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE CENTRAL/EASTERN STRAIT
     OF JUAN DE FUCA AND THE COASTAL WATERS FROM CAPE FLATTERY TO
     CAPE SHOALWATER 10 NM OUT TO 60 NM.


&&

$$

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD...VISIT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML




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