Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 020020 CCA
AFDSEW

AREA FORECAST DISCUSSION...CORRECTED WARNINGS SECTION
NATIONAL WEATHER SERVICE SEATTLE WA
230 PM PST SUN MAR 1 2015

.SYNOPSIS...A WEAK WEATHER SYSTEM WILL MOVE SOUTHEAST THROUGH THE
AREA TONIGHT FOR AREAS OF LIGHT PRECIPITATION. DRY WEATHER WILL
PREVAIL THE REMAINDER OF THE WEEK UNDER THE INFLUENCE OF AN UPPER
RIDGE AND LOW LEVEL OFFSHORE FLOW.

&&

.SHORT TERM...A WEAK UPPER LEVEL DISTURBANCE WILL DROP DOWN FROM THE
NORTHWEST TONIGHT. THIS WILL BRING CLOUDS WITH A LITTLE RAIN AT THE
COAST AND A CHANCE OF RAIN FARTHER INLAND.

RAIN CHANCES WILL END QUICKLY MONDAY MORNING AS THE UPPER LEVEL
DISTURBANCE MOVES SOUTH OF THE AREA. LOW LEVEL NORTH TO NORHTEAST
OFFSHORE FLOW WILL INCREASE AS A 1040 MB SURFACE HIGH DROPS SOUTH
INTO BRITISH COLUMBIA. THIS WILL HELP DRY THE LOW LEVELS OUT AND
CLOUDS SHOULD BE ON THE DECREASE LATER IN THE DAY. THERE WILL ALSO
BE SOME BREEZY NORTH WINDS DURING THE DAY...ESPECIALLY OVER THE
NORTH INTERIOR.

AN UPPER RIDGE OVER THE NORTHEAST PACIFIC WILL BRING DRY AND MAINLY
SUNNY WEATHER TUESDAY AND WEDNESDAY ALTHOUGH THERE COULD BE SOME
HIGH CLOUDS AT TIMES...ESPECIALLY ON TUESDAY. SCHNEIDER

.LONG TERM...AN UPPER RIDGE WILL REMAIN OVER THE AREA THURSDAY
THROUGH SUNDAY...KEEPING THE WEATHER MAINLY DRY. SHORT WAVE ENERGY
COMING OVER THE TOP OF THE RIDGE THURSDAY THROUGH FRIDAY COULD BRING
A FEW SHOWERS TO THE FAR NORTHERN ZONES BUT THIS DOES NOT LOOK LIKE
IT WILL AMOUNT TO MUCH FOR NOW. OTHERWISE...IT LOOKS LIKE A FAIRLY
DIRTY RIDGE THURSDAY AND FRIDAY WITH HIGH CLOUDS AND PARTLY SUNNY
SKIES. SCHNEIDER

&&

.HYDROLOGY...FLOODING IS UNLIKELY FOR THE NEXT 7 DAYS.

&&

.AVIATION...A LARGE UPPER LEVEL RIDGE CENTERED OFFSHORE ALONG 140W
WILL MAINTAIN N-NW FLOW ACROSS W WA TONIGHT THROUGH MONDAY. AN UPPER
LEVEL SHORTWAVE TROUGH EMBEDDED IN THE N FLOW AND APPROACHING
NORTHERN VANCOUVER ISLAND AT 22Z WILL MOVE SE OVER W WA BY 06Z. MID
LEVEL CLOUDS WILL BEGIN SPREADING OVER W WA AHEAD OF THE TROUGH
AFTER 00Z WITH CIGS LOWERING TO AROUND BKN050 WITH SOME LIGHT RAIN
OVER THE N AROUND 03Z. LOWERING CIGS AND AREAS OF LIGHT RAIN WILL
SPREAD S WITH THE SHORTWAVE TROUGH...WITH AREAS OF MVFR CIGS
EXPECTED TO DEVELOP ANYWHERE FROM 06Z-18Z.

KSEA...MID AND HIGH CLOUDS WILL SPREAD S OVER THE TERMINAL THROUGH
03Z WITH CIGS BKN100 AND HIGHER. MID LEVEL MOISTURE AROUND 5000 FEET
WITH A LITTLE LIGHT RAIN SHOULD REACH THE AREA BETWEEN 04Z-09Z. MVFR
CIGS ARE LIKELY MONDAY MORNING. SURFACE WINDS WILL BE S-SW 4-7 KT
THROUGH 03Z BUT A WIND SHIFT TO N-NE 4-8 KT IS EXPECTED SOMETIME
BETWEEN 03Z-05Z. KAM

&&

.MARINE...AN UPPER LEVEL SHORTWAVE TROUGH APPROACHING NORTHERN
VANCOUVER ISLAND AT 2 PM WILL MOVE SE ACROSS W WA TONIGHT. NORTHERLY
FLOW WILL INCREASE OVER WA WATERS EARLY THIS EVENING...WITH WINDS
REACHING SMALL CRAFT ADVISORY LEVELS OVER THE COASTAL WATERS BEFORE
DIMINISHING LATE TONIGHT.

BEHIND THE UPPER LEVEL TROUGH...A 1044 MB SURFACE HIGH WILL MOVE S
ACROSS INTERIOR B.C. ON MONDAY. RISING PRESSURES OVER B.C. WILL
INCREASE THE NORTHERLY PRESSURE GRADIENT ACROSS THE NORTHERN
INTERIOR OF W WA STARTING MONDAY MORNING. NORTH WINDS WILL INCREASE
OVER THE INLAND WATERS ZONES FROM BELLINGHAM DOWN THROUGH PUGET
SOUND ON MONDAY...WITH LOCAL SMALL CRAFT ADVISORY WINDS EXPECTED
MONDAY AFTERNOON.

AS THE B.C. SURFACE HIGH MOVES SE THE PRESSURE GRADIENT ACROSS W WA
WILL SHIFT MORE E-NE AND STRENGTHEN MONDAY NIGHT AND TUESDAY. THIS
SHOULD ALLOW MODERATE TO STRONG E-NE FLOW TO DEVELOP ACROSS THE N
INLAND WATERS...EXTENDING OUT THROUGH THE STRAIT AND ACROSS THE
NORTHERN COASTAL WATERS. THE 12Z NWS ARW MODEL PUT WINDS IN THE
30-35 KT RANGE OVER THE NORTH INLAND WATERS MONDAY NIGHT...WITH SCA
LEVEL WINDS THROUGH THE STRAIT OF JUAN DE FUCA AND OVER THE NORTHERN
COASTAL WATERS. THIS TIME AROUND THE 12Z CANADIAN MESOSCALE MODEL
WAS WEAKER KEEPING WINDS IN THE 25-30 KT RANGE. THE UW WRF-GFS
WAS NOT AVAILABLE IN TIME FOR THE FORECAST. NE OFFSHORE FLOW SHOULD
WEAKEN BY TUESDAY AFTERNOON AS THE SURFACE HIGH CONTINUES SE AND
WEAKENS. KAM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS TONIGHT.
     GALE WATCH NORTH INLAND WATERS MONDAY NIGHT.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML















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