Small Craft Advisory 149, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT TUE JUL 14 2015

.SYNOPSIS...A WEAK UPPER TROUGH WILL SHIFT EAST TONIGHT. ANOTHER LOW
PRESSURE TROUGH WILL APPROACH ON WEDNESDAY...THEN MOVE ACROSS THE
REGION WEDNESDAY NIGHT AND THURSDAY. NORTHERLY FLOW WITH A FEW
MOUNTAIN SHOWERS DEVELOP ON FRIDAY. OFFSHORE THIS WEEKEND WILL
PRODUCE DRY CONDITIONS AND WARMER TEMPERATURES. ONSHORE FLOW RESUMES
EARLY NEXT WEEK WITH MORE CLOUDS AND COOLER TEMPERATURES.

&&

.SHORT TERM...A WEAK SPLIT TROUGH AXIS OVER THE REGION WILL SHIFT
EWD TONIGHT. THE LAST VISIBLE PICTURE OF THE DAY SHOWS JUST A FEW CU
OVER THE MOUNTAINS WHICH WILL DIE OFF AFTER SUNSET. PATCHY LOW
CLOUDS OR FOG COULD FORM ALONG THE COAST...ESPECIALLY NORTH NEAR THE
WEST ENTRANCE TO THE STRAIT. OTHERWISE...THE LACK OF STRATUS
OFFSHORE AND NORTHERLY FLOW OVER THE INTERIOR SHOULD GIVE MOSTLY
CLEAR SKIES TO WRN WA TONIGHT INTO WEDNESDAY MORNING.

ANOTHER TROUGH WILL APPROACH THE REGION WEDNESDAY WITH ONSHORE
WESTERLY GRADIENT INCREASING THROUGH THE AFTERNOON INTO THE EVENING.
THE COMBINATION OF STRONGER ONSHORE FLOW AND FALLING 500 MB HEIGHTS
THROUGH THE DAY MEAN HIGH TEMPERATURES AROUND PUGET SOUND SHOULD BE
NEAR OR A COUPLE DEGREES LOWER THAN TODAY'S HIGH TEMPERATURES.
BREEZY WINDS WILL DEVELOP ALONG OR NEAR THE STRAIT OF JUAN DE FUCA
BY EVENING AND STRATUS SHOULD REACH THE COAST...THEN PUSH INLAND
OVERNIGHT INTO THURSDAY MORNING. MOST OF THE AREA WILL LIKELY START
OFF WITH CLOUDS ON THURSDAY WITH SLOW PARTIAL CLEARING IN THE
AFTERNOON. HIGHS ON THURSDAY WILL ONLY BE IN THE LOW 70S AROUND
PUGET SOUND AND THE SW INTERIOR...AND ONLY 60S TO AROUND 70
ELSEWHERE. CURRENT FORECAST HIGHS MAY BE A COUPLE DEGREES ON THE
WARM SIDE.

A TROUGH AXIS SHIFTS ACROSS THE AREA THURSDAY WITH A SHORT WAVE ON
THE BACK SIDE OF THE TROUGH DIGGING SW USHERING IN NORTHERLY FLOW ON
FRIDAY. THERE COULD BE A FEW SHOWERS OVER THE MOUNTAINS PER THE
12/18Z GFS BUT THE SYSTEM WILL LACK DEEP MOISTURE AND AMOUNTS WILL
BE MINIMAL. CLOUDS WILL CLEAR OUT ON FRIDAY AS NORTHERLY FLOW
BECOMES MORE OFFSHORE DURING THE AFTERNOON. EXPECT SOME WARMING WITH
HIGHS INTO THE MID/UPPER 70S INLAND AND EVEN SOME LOW 70S POSSIBLE
AT THE COAST.

OFFSHORE FLOW DEVELOPS OVER THE WEEKEND. THE GFS/ECMWF INDICATE MUCH
MOSTLY CLEAR SKIES AND MUCH WARMER TEMPERATURES ARE POSSIBLE...EVEN
AT THE COAST.

.LONG TERM...FROM PREVIOUS DISCUSSION...MODELS ARE IN FAIR AGREEMENT
ABOUT THE BROAD PATTERN. AN UPPER RIDGE WILL BUILD OFFSHORE SATURDAY
AND SUNDAY WITH HEIGHTS OVER WASHINGTON WELL INTO THE 580S. HEIGHTS
WILL REMAIN HIGH MONDAY EVEN AS AN UPPER TROUGH MOVES SOUTHEAST OFF
BRITISH COLUMBIA. ALL THREE DAYS ARE LIKELY TO BE DRY AND WARM. BY
TUESDAY THE EURO... GFS...AND CANADIAN MODELS ALL SHOW SOME VERSION
OF AN UPPER TROUGH MOVING CLOSE TO WASHINGTON...WITH LOWER HEIGHTS
AND PERHAPS EVEN SOME SHOWERS. FOR NOW HAVE LEFT POPS OUT OF DAY 7.
BURKE

&&

.AVIATION...A WEAK UPPER LEVEL TROUGH OVER THE AREA WILL MOVE INLAND
THROUGH TONIGHT. ANOTHER WEAK UPPER TROUGH WILL REACH THE AREA WED
NIGHT. WLY FLOW ALOFT. THE AIR MASS IS DRY AND STABLE. AREAS OF LOW
LEVEL MOISTURE WILL DEVELOP ALONG THE COAST OVERNIGHT AND MOVE INTO
THE STRAIT OF JUAN DE FUCA. THE STRATUS WILL BURN BACK TO THE
COASTAL WATERS MIDDAY WED. THE MAJORITY OF THE INTERIOR WILL REMAIN
GOOD VFR THROUGH WED EVENING.  ALBRECHT

KSEA...GOOD VFR CONDITIONS THROUGH WED EVENING. N TO NW WIND 6-8 KT
WILL BECOME NELY 07Z THEN BECOMING LIGHT AND VARIABLE AFTER 12Z.
EXPECT NWLY WIND 6-10 KT TO REDEVELOP AROUND 19Z WED. ALBRECHT

&&

.MARINE...A RIDGE OF HIGH PRES CENTERED ALONG 145W COMBINED WITH
LOWER PRES E OF THE CASCADES IS GIVING MODERATE TO STRONG ONSHORE
FLOW THIS EVENING. EXPECT THE ONSHORE FLOW TO STRENGTHEN SOMEWHAT
WED EVENING AS AN UPPER LEVEL TROUGH MOVES ACROSS THE REGION
TIGHTENING LOW LEVEL PRES GRADIENTS. FLOW WILL BECOME OFFSHORE ON
FRIDAY OR FRIDAY NIGHT AS HIGH PRES DEVELOPS OVER BRITISH COLUMBIA
AND A THERMAL TROUGH OF LOW PRES DEVELOPS OVER THE COASTAL WATERS.

GALE WARNINGS ARE IN EFFECT FOR THE CENTRAL AND EASTERN STRAIT OF
JUAN DE FUCA THROUGH 3 AM PDT WED. GALES ARE EXPECTED TO REDEVELOP
WED AFTERNOON AND CONTINUE THROUGH WED NIGHT. SMALL CRAFT ADVISORIES
ARE IN EFFECT FOR ADMIRALTY INLET AND THE COASTAL WATERS FOR NWLY
WINDS THIS EVENING AND WILL LIKELY BE NEEDED AGAIN ON WED EVENING.
ALBRECHT

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...GALE WARNING CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA SMALL
     CRAFT ADVISORY UNTIL MIDNIGHT PDT FOR ADMIRALTY INLET

AND THE WASHINGTON COASTAL WATERS.

&&

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