Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 100127 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED AVIATION AND MARINE SEGMENTS
NATIONAL WEATHER SERVICE SEATTLE WA
238 PM PDT WED APR 9 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL PREVAIL OVER THE REGION
THROUGH THURSDAY. EXPECT THE TAIL END OF A WEAK DISTURBANCE
PASSING TO OUR NORTH TO CLIP THE AREA ON FRIDAY. HIGH PRESSURE
ALOFT WILL BUILD STRONGLY OVER THE REGION THIS WEEKEND FOR DRY
WEATHER WITH ABOVE NORMAL DAYTIME TEMPERATURES.

&&

.SHORT TERM...
WEAK HIGH PRESSURE ALOFT WILL PREVAIL OVER THE REGION THROUGH THU.
EXPECT THE TAIL END OF A SHORT WAVE TROF PASSING TO OUR NORTH TO
CLIP THE AREA ON FRI. THE MAIN IMPACT THIS WILL HAVE ON OUR WEATHER
WILL BE TO STRENGTHEN THE ONSHORE FLOW. THERE WILL ALSO BE A CHANCE
OF SHOWERS OVER THE COAST AND NORTH CASCADES. IT SHOULD REMAIN DRY
ELSEWHERE.

AN UPPER RIDGE WILL BUILD OVER THE PACIFIC NORTHWEST ON SATURDAY.
THIS COMBINED WITH LOW LEVEL NORTHERLY FLOW WILL RESULT IN
SOMEWHAT ABOVE NORMAL DAYTIME TEMPS AT A NUMBER OF PLACES...
ESPECIALLY THOSE AREAS FARTHEST FROM THE MAJOR WATER BODIES.

.LONG TERM...
THE MEDIUM RANGE SOLUTIONS WERE COMING INTO BETTER AGREEMENT IN
REGARDS TO THE SYNOPTIC FEATURES IMPACTING THE PACIFIC NORTHWEST
DURING THE EARLY PART OF THIS PERIOD...OR SUNDAY AND MON. THE
UPPER RIDGE IS ANTICIPATED TO REMAIN OVER THE AREA ON SUNDAY. THIS
COMBINED WITH LOW LEVEL OFFSHORE FLOW WILL RESULT IN WELL ABOVE
NORMAL TEMPS AT A NUMBER OF PLACES. DAYTIME READINGS COULD END UP
AS WARM AS THEY WERE THIS PAST MON.

IT LOOKS AS THOUGH MON WILL BE THE TRANSITION DAY. THE RIDGE AXIS
IS EXPECTED TO SHIFT EAST...ALLOWING ONSHORE FLOW TO RETURN. THUS
ANTICIPATE COOLER TEMPS ON MON AS WELL AS AN INCREASE IN CLOUDS.
HAVE CHOSEN TO FOLLOW MODEL TRENDS AND BACKED OFF ON THE RISK OF
PRECIP MON NIGHT. THE FORECAST NOW CONFINES IT TO MAINLY WITHIN A
PUGET SOUND CONVERGENCE ZONE.

BEYOND MON...THE MODELS DIVERGED CONCERNING THE DETAILS...SO
CONFIDENCE WAS NOT VERY HIGH. DECIDED TO LIMIT THE CHANCE OF
PRECIP TO MAINLY THE MOUNTAINS ON TUE. BEYOND TUE...THE OVERALL
PATTERN APPEARED UNSETTLED. DAYTIME TEMPS SHOULD FALL BACK TO
NEAR OR SLIGHTLY BELOW CLIMO BY THE MIDDLE OF NEXT WEEK.

&&

.HYDROLOGY...
RIVER FLOODING IS NOT EXPECTED ON AREA RIVERS...EXCEPT THE
STILLAGUAMISH...THE NEXT 7 DAYS.

A FLOOD WARNING REMAINS IN EFFECT UNTIL FURTHER NOTICE FOR THE
NORTH FORK OF THE STILLAGUAMISH RIVER IN SNOHOMISH COUNTY JUST
UPSTREAM OF THE SR 530 LANDSLIDE. FLOODING CONTINUED AS A RESULT
OF WATER POOLED BEHIND THE DEBRIS DAM THAT PARTIALLY BLOCKS THE
RIVER.

THE NORTH FORK OF THE STILLAGUAMISH NEAR ARLINGTON AND THE POOL
UPSTREAM OF THE SR 530 SLIDE WILL CONTINUE FALLING THROUGH THIS
WEEKEND.

&&

.AVIATION...THE FLOW ALOFT WILL BE NORTHWEST WITH LOW LEVEL ONSHORE
FLOW TONIGHT AND THURSDAY. SLIGHTLY UNSTABLE AIR HAS ALLOWED CUMULUS
CLOUDS TO BUBBLE UP OVER THE AREA. SKIES SHOULD CLEAR THIS EVENING
WITH THE AIR MASS BECOMING STABLE.

KSEA...SOME 5000 FOOT CEILINGS AT TIMES LATE THIS AFTERNOON...THEN
CLOUDS WILL DECREASE IN THE EVENING WITH MOSTLY HIGH CLOUDS AT
TIMES. NORTHWEST 4-8 KNOTS THIS EVENING WILL BECOME LIGHT NORTHEAST
OVERNIGHT. SCHNEIDER

&&

.MARINE...ONSHORE FLOW WILL PREVAIL THROUGH FRIDAY WITH HIGH
PRESSURE OFFSHORE AND LOWER PRESSURE INLAND. SMALL CRAFT ADVISORY
WEST WINDS SHOULD OCCUR IN THE CENTRAL AND EAST STRAIT EACH
DAY...STRONGEST IN THE EVENING HOURS. IT IS NOT OUT OF THE QUESTION
THAT MARGINAL WESTERLY GALES COULD OCCUR IN THE CENTRAL AND EAST
STRAIT EACH EVENING BUT THE FORECAST IS 20-30 KNOTS FOR NOW. THERE
IS ALSO A CHANCE NORTHWEST WINDS OVER THE INNER COASTAL WATERS COULD
HIT SMALL CRAFT THE NEXT FEW EVENINGS.

OFFSHORE FLOW WILL DEVELOP NEXT WEEKEND WITH A WEAK THERMAL TROUGH
BUILDING ALONG THE COAST AND HIGHER PRESSURE OVER INTERIOR BRITISH
COLUMBIA. THE TROUGH WILL SHIFT INLAND MONDAY WITH MODERATE ONSHORE
FLOW RETURNING. SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WARNING REMAINS IN EFFECT FOR THE NORTH FORK OF THE
     STILLAGUAMISH RIVER EAST OF THE SR 530 LANDSLIDE.

PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 5 AM THURSDAY FOR THE
     CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

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