Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 182246
AFDSEW

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

.SYNOPSIS...A WEAK DISTURBANCE WILL MOVE ACROSS THE AREA LATER
TONIGHT THROUGH EARLY FRIDAY MORNING. HIGH PRESSURE ALOFT WILL
BEGIN BUILDING OVER THE REGION ON FRIDAY. LOOK FOR HIGH PRESSURE
ALOFT AND LOW LEVEL OFFSHORE FLOW TO PREVAIL THIS WEEKEND FOR WELL
ABOVE NORMAL DAYTIME TEMPERATURES.

&&

.SHORT TERM...
ZONAL FLOW ALOFT WILL PREVAIL ACROSS THE AREA TONIGHT. A WEAK
SHORT WAVE TROF EMBEDDED IN THIS FLOW WILL RESULT IN SOME SHOWERS
ACROSS MAINLY THE NORTHERN PART OF THE CWA. THE SHOWERS WILL
PERSIST INTO FRI MORNING.

AN UPPER RIDGE WILL BEGIN BUILDING OVER THE REGION ON FRI. THE
RIDGE WILL AMPLIFY THIS WEEKEND. THIS COMBINED WITH LOW LEVEL
OFFSHORE FLOW WILL RESULT IN WELL ABOVE NORMAL DAYTIME TEMPS.
SOME PLACES COULD END UP TYING OR BREAKING DAILY RECORDS.

.LONG TERM...
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...THE FLOW ALOFT IS WESTERLY AS AN UPPER LEVEL TROUGH
PUSHES INTO EASTERN WA. A WEAK WARM FRONT WILL SPREAD SPOTTY LIGHT
RAIN TO THE AREA TONIGHT. THE AIR MASS IS MOIST AND STABLE. CEILINGS
WILL LOWER TONIGHT WITH MVFR CONDITIONS LIKELY. A COLD FRONT WILL
CROSS THROUGH WESTERN WA FRI MORNING FOR A FEW MORE SHOWERS. 33

KSEA...CIGS LIKELY REMAINING IN MVFR RANGE TONIGHT WITH SPOTTY LIGHT
PRECIP IN THE VICINITY. SURFACE WINDS WILL REMAIN LIGHT SLY. 33

&&

.MARINE...SURFACE WINDS WILL BE MAINLY LIGHT ACROSS THE WATERS
TONIGHT WITH WEAK HIGH PRES ALONG THE COAST. HOWEVER...A WESTERLY
ONSHORE PUSH WILL BRING A FEW HOURS OF SMALL CRAFT ADVISORY WINDS
THROUGH THE CENTRAL AND EAST STRAIT OF JUAN DE FUCA THIS EVENING. A
WEAK COLD FRONT WILL CROSS THROUGH WESTERN WA ON FRIDAY. WINDS WILL
FLIP TO OFFSHORE FRI NIGHT THROUGH SAT AS A THERMALLY INDUCED TROUGH
OF LOW PRES FORMS ALONG THE COAST. THE WINDS WILL THEN TURN
SOUTHERLY ON SUN AS A SURFACE TROUGH DEVELOPS OVER THE OFFSHORE
WATERS. THIS TROUGH WILL CROSS THROUGH THE COASTAL WATERS ON MON. 33

&&

.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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