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ZCZC SEAGPHAFD ALL
TTAA00 KSEA 130410
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
915 PM PDT MON MAY 12 2008
.SYNOPSIS...A WARM FRONT WILL BRING RAIN TO THE AREA TUESDAY AND
TUESDAY NIGHT (image)...THEN SLOWLY LIFT NORTH ON WEDNESDAY. A STRONG
UPPER RIDGE WILL PROVIDE WARM AND SUNNY WEATHER THURSDAY (image)
THROUGH SATURDAY (image)...WITH NEAR RECORD HIGH TEMPERATURES
POSSIBLE. A WEAK WEATHER SYSTEM WILL REACH THE AREA SUNDAY (image).
&&
.SHORT TERM...SOME VERY LIGHT PRECIPITATION HAS MOVED ONTO THE NORTH
COAST THIS EVENING (image) AHEAD OF AN ADVANCING WEATHER SYSTEM
MOVING THROUGH THE OFFSHORE WATERS (image). A LARGE AREA OF MOISTURE
ROUNDING THE BASE OF THE UPPER TROUGH NOW CENTERED NEAR 170W (image)
WILL SWING NE INTO THE AREA LATER TUE AND TUE NIGHT...THEN LIFT
NORTH THROUGH THE AREA AS A WARM FRONT WED (image). A QUICK LOOK AT
THE NEW 00Z GUIDANCE SHOWS SOME VERY LIGHT PRECIPITATION MOVING ONTO
THE COAST THROUGH TUE MORNING...FOLLOWED BY THAT MORE SIGNIFICANT
SLUG OF MOISTURE THAT MOVES THROUGH THE AREA IN STRONG WESTERLY FLOW
ALOFT LATE TUE THROUGH EARLY WED...CONSISTENT WITH PREVIOUS MODEL
SOLUTIONS.
WITH ALL OF THE WESTERLY FLOW...EXPECT HEAVIEST PRECIPITATION
AMOUNTS TO BE ALONG THE COAST AND IN THE CASCADES (image). THE PUGET
SOUND AREA WILL SEE ONLY VERY LIGHT AMOUNTS AS THE AREA GETS
SHADOWED BY THE OLYMPICS. RAINFALL TOTALS IN THE CASCADES AND
OLYMPICS FOR THE 24 HOUR PERIOD NOON TUE THROUGH NOON WED ACCORDING
TO THE NEW 00Z NAM WILL BE NEARLY AN INCH...LOCALLY OVER 1.5 INCHES
(image). MOST AREAS AROUND THE CENTRAL PUGET SOUND AREA WILL SEE LESS
THAN A TENTH OF AN INCH (image). LOW LEVEL SOUTHERLY FLOW ALONG THE
COAST AND IN THE PUGET SOUND AREA WILL BE ENHANCED BY THE
INTERACTION OF THE STABLE FLOW WITH THE TERRAIN...AND IT MAY BECOME
BREEZY TO LOCALLY WINDY TUE NIGHT AND EARLY WED.
THE WARM FRONT LIFTS NORTH OF THE AREA DURING THE AFTERNOON
WED...BRINGING AN END TO THE PRECIPITATION AND THE BEGINNING OF A
RATHER SIGNIFICANT WARM SPELL. RECORD TO NEAR RECORD HIGH
TEMPERATURES CAN BE EXPECTED ACROSS THE AREA FRI...AND ESPECIALLY
SAT.
CURRENT FORECASTS LOOK GOOD. NOT UPDATES WILL BE MADE THIS EVENING.
ALBRECHT
.LONG TERM...PREVIOUS LONG TERM DISCUSSION FOLLOWS...THE GFS/ECMWF
MAINTAIN A STRONG UPPER RIDGE OVER THE AREA ON FRIDAY WITH THERMALLY
INDUCED LOW PRESSURE FORMING ALONG THE COAST. LARGE SCALE SUBSIDENCE
ALOFT AND LOW LEVEL OFFSHORE FLOW SHOULD PRODUCE MUCH WARMER
TEMPERATURES...POSSIBLY REACHING NEAR RECORD HIGHS BY FRIDAY AND
POSSIBLY SATURDAY. IF CURRENT MODEL RUNS ARE CORRECT...THE THERMAL
TROUGH WILL BE LOCATED ALONG THE COAST FRIDAY PRODUCING THERE
WARMEST TEMPS THERE...PROBABLY EVEN A FEW DEGREES WARMER THAN THE
INTERIOR. ON SATURDAY...LIGHT ONSHORE GRADIENTS DEVELOP ALONG THE
COAST WITH COOLER TEMPS BUT THE THERMALLY INDUCED TROUGH SHIFTS OVER
INTERIOR WRN WA GIVING THE WARMEST TEMPS TO THE PUGET SOUND/FOOTHILL
AREAS. THIS MAY BE A BIT MUCH DETAIL FOR DAY 5...BUT THATS HOW
THINGS LOOK AT THIS POINT. UPPER HEIGHTS ABOVE 5990 CERTAINLY
SUPPORT A POTENTIAL OF A FEW 90+ DEGREE TEMPS...HOWEVER WILL PLAY IT
MORE CONSERVATIVE FOR NOW WITH 80S IN THE FORECAST...STILL WELL
ABOVE CLIMO AND MOS. IT REMAINS UNCLEAR WHEN A MARINE PUSH WILL
ARRIVE BUT MOST LIKELY SOMETIME SATURDAY EVENING OR SUNDAY. ONCE THE
RIDGE SHIFTS OFF TO THE EAST...A COOL AND SHOWERY PATTERN WILL
RETURN THE END OF THE WEEKEND INTO EARLY NEXT WEEK. MERCER
&&
.AVIATION...WEAK SURFACE HIGH PRESSURE WILL REMAIN OVER THE AREA
THROUGH TONIGHT () WHILE A WARM FRONT APPROACHES THE COAST.
HIGHER CLOUDS ASSOCIATED WITH THE APPROACHING WARM FRONT WILL
CONTINUE TO THICKEN AND LOWER OVERNIGHT WITH RAIN DEVELOPING ALONG
THE COAST TONIGHT AND OVER THE INTERIOR TUESDAY.
.KSEA...VFR CEILINGS THROUGH THE NIGHT TONIGHT WITH A THREAT OF
LIGHT RAIN AFTER 10Z-12Z TUE MORNING. LIGHT AND VARIABLE WIND WILL
CONTINUE UNTIL 07Z OR SO...THEN BECOME LIGHT SOUTHERLY.
&&
.MARINE...WARM FRONT APPROACHING THE REGION () WILL INCREASE
THE SOUTHERLY FLOW ALONG THE COAST TONIGHT AND ALL AREAS TUESDAY.
PROBABLY SEE LOW END SMALL CRAFT ADVISORY WINDS ALONG THE COAST...
AND POSSIBLY AT THE WEST ENTRANCE. WINDS BECOME SOUTHERLY ALL WATERS
OVERNIGHT BUT EVEN WITH FRONTAL PASSAGE TUESDAY AFTERNOON SMALL
CRAFT ADVISORY WINDS ELSEWHERE NOT A SURE BET. WILL REASSESS THIS
FOR 3 AM ISSUANCE. CHB
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ....SMALL CRAFT ADVISORY TO THE COASTAL WATERS TUE AND TUE
EVENING.
$$
WEATHER.GOV/SEATTLE
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