Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 190333
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
833 PM PDT THU SEP 18 2014

.SYNOPSIS...A WEAK DISTURBANCE WILL MOVE ACROSS THE AREA OVERNIGHT
INTO EARLY FRIDAY MORNING. LOOK FOR HIGH PRESSURE ALOFT TO BEGIN
BUILDING OVER THE REGION ON FRIDAY. STRONG HIGH PRESSURE ALOFT
ALONG WITH LOW LEVEL OFFSHORE FLOW WILL RESULT IN WELL ABOVE
NORMAL DAYTIME TEMPERATURES THIS WEEKEND.

&&

.SHORT TERM...
ZONAL FLOW ALOFT WILL PREVAIL ACROSS THE AREA TONIGHT. A WEAK
SHORT WAVE TROF EMBEDDED IN THIS FLOW WILL BRING PRECIP TO MAINLY
THE NORTHERN PART OF THE CWA OVERNIGHT INTO FRI MORNING. KLGX
DOPPLER RADAR CURRENTLY SHOWED THE LEADING EDGE OF THE RAIN SHIELD
NOT TOO FAR OFF THE NORTH COAST.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION ON FRI FOR
CLEARING SKIES. THE RIDGE WILL AMPLIFY FURTHER THIS WEEKEND. THIS
COMBINED WITH LOW LEVEL OFFSHORE FLOW WILL RESULT IN WELL ABOVE
NORMAL DAYTIME TEMPS ACROSS MUCH OF THE CWA.

.LONG TERM FROM THE PREV DISCUSSION...
THE UPPER RIDGE AXIS WILL MOVE OVER THE INTERMOUNTAIN WEST ON MON
AND THIS WILL ALLOW A WEAKENING OCCLUDED FRONT TO APPROACH THE
COAST. THIS FRONT WILL LIKELY DISSIPATE AS IT MOVES ONSHORE. THE
MAIN IMPACT WILL BE COOLER AND CLOUDIER WEATHER MON AND TUE.

BEYOND TUE...A STRONGER SYSTEM WILL IMPACT THE PACIFIC NORTHWEST
DURING THE LATTER PART OF THE EXTENDED PERIOD...RESULTING IN BELOW
NORMAL DAYTIME TEMPS AND BREEZY CONDITIONS. THIS SYSTEM IS
EXPECTED TO REMAIN OFF THE COAST THRU THU.

&&

.AVIATION...WESTERLY FLOW ALOFT TONIGHT AND FRIDAY. A WEAKENING
FRONT WILL REACH THE COAST FRIDAY MORNING AND DISSIPATE OVER THE
AREA LATER IN THE DAY. WEAK ONSHORE FLOW WILL CONTINUE WITH HIGH
PRESSURE ALONG THE COAST AND LOWER PRESSURE INLAND. AIR MASS MOIST
AND SLIGHTLY UNSTABLE. THERE WILL BE A MIX OF LOW AND MID CLOUDS
ACROSS THE AREA TONIGHT. THE TREND SHOULD BE FOR LOW CLOUDS TO
INCREASE OVERNIGHT.

KSEA...3000-4000 FOOT CEILINGS THIS EVENING SHOULD LOWER TO
1000-2000 FEET TONIGHT. SOUTHERLY WIND 4-8 KNOTS. SCHNEIDER

&&

.MARINE...WEAK HIGH PRESSURE WILL BE OVER THE COAST WITH LOWER
PRESSURE INLAND TONIGHT AND FRIDAY. SMALL CRAFT ADVISORY WEST WINDS
ARE POSSIBLE FOR THE CENTRAL AND EASTERN STRAIT THROUGH THE EARLY
MORNING HOURS FRIDAY BUT THE EVENT LOOKS MARGINAL AT BEST.

A DISSIPATING FRONT WILL MOVE THROUGH THE WATERS ON FRIDAY. OFFSHORE
FLOW WILL QUICKLY DEVELOP FRIDAY NIGHT AND CONTINUE THROUGH SUNDAY
MORNING AS A TROUGH BUILDS NORTH ALONG THE WEST COAST. SMALL CRAFT
ADVISORY EAST WINDS ARE POSSIBLE FOR THE WESTERN STRAIT SUNDAY
MORNING.

A WEAKENING TROUGH WILL REACH THE COASTAL WATERS MONDAY. A STRONGER
FRONTAL SYSTEM WELL OFFSHORE WILL BE APPROACHING FROM THE WEST ON
TUESDAY. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 2 AM FRIDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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