Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS66 KSEW 250447
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
947 PM PDT TUE MAR 24 2015

.SYNOPSIS...A WARM FRONT WILL BRING RAIN TO THE AREA OVERNIGHT
THROUGH WEDNESDAY. HIGH PRESSURE ALOFT WILL BUILD OVER THE REGION
WEDNESDAY NIGHT...CAUSING THE RAIN TO BE SHOVED NORTH OF THE AREA.
DRY AND WARM WEATHER WILL PREVAIL ON THURSDAY. THE HIGH WILL MOVE
EAST ON FRIDAY...ALLOWING A COLD FRONT TO APPROACH FROM THE WEST.

&&

.SHORT TERM...
THE RAIN ASSOCIATED WITH A WARM FRONT PRESENTLY OFFSHORE WAS
OVERSPREADING THE CWA FASTER THAN PREVIOUSLY ANTICIPATED. WILL
UPDATE THE FORECAST TO ACCOUNT FOR THIS TREND. IT SHOULD BE
RAINING OVER THE ENTIRE CWA BY SUNRISE.

MEANWHILE...THE AIR MASS WAS QUITE MOIST OFFSHORE. THE SATELLITE-
DERIVED TOTAL PRECIPITABLE WATER /TPW/ PRODUCT INDICATED THAT
SUBTROPICAL MOISTURE HAS BECOME ENTRAINED INTO THE SYSTEM. TPW
VALUES WERE IN THE ONE TO JUST SHY OF TWO INCH RANGE...WHICH WAS
OVER 200 PERCENT OF NORMAL PER THE SATELLITE-DERIVED PERCENT OF
NORMAL TPW. IT LOOKS LIKE THE HEAVIEST RAIN WILL PROBABLY FALL ON
VANCOUVER ISLAND BUT THE NORTH COAST AND MOUNTAINS SHOULD RECEIVE
A DECENT AMOUNT OF PRECIP FROM THIS SYSTEM.

THE WARM FRONT WILL LIFT NORTH ACROSS THE CWA DURING THE DAY WED.
BY LATE WED EVENING...IT SHOULD BE IN BRITISH COLUMBIA. AN UPPER
RIDGE WILL AMPLIFY OVER THE REGION WED NIGHT...THEREBY CAUSING THE
PRECIP TO BE SHOVED NORTHWARD. THE UPPER RIDGE WILL REMAIN OVER
THE AREA ON THU FOR DRY WEATHER WITH ABOVE NORMAL TEMPS.

LOOK FOR THE RIDGE TO MOVE EAST ON FRI...ALLOWING A SHORT WAVE
TROF AND ASSOCIATED COLD FRONT TO APPROACH FROM THE WEST. IT LOOKS
LIKE THE LATEST SOLUTIONS WERE TRENDING FASTER WITH THIS SYSTEM...
THUS IT COULD BE RAINING ON AT LEAST THE NORTHWEST HALF OF THE
CWA FRI AFTERNOON. THE FRONT SHOULD BE EAST OF THE CWA BY LATE FRI
NIGHT.

.LONG TERM FROM THE PREV DISCUSSION...
SATURDAY MAY START OUT DAMP AND DRIPPY BUT OVERALL THE WEEKEND
SHOULD TURN OUT DRY. THE UPPER LEVEL RIDGE THAT BUILDS OVER THE
AREA FOR THE WEEKEND IS NOT NEARLY AS STRONG AS THE RIDGE ON
THURSDAY. ANOTHER FRONT SHOULD APPROACH THE AREA MONDAY OR MONDAY
NIGHT.

&&

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

&&

.AVIATION...AN UPPER RIDGE WILL MOVE OVER WESTERN WASHINGTON TONIGHT
AND WEDNESDAY WITH WESTERLY FLOW ALOFT. A WARM FRONT WILL MOVE
THROUGH THE AREA LATER TONIGHT AND WEDNESDAY. AIR MASS STABLE AND
BECOMING INCREASINGLY MOIST AT ALL LEVELS LATER TONIGHT AS THE WARM
FRONT SPREADS RAIN ONSHORE.

KSEA...MID AND HIGH LEVEL CLOUDS THROUGH EARLY WEDNESDAY MORNING...
THEN LOW CLOUDS AND RAIN SHOULD DEVELOP. SOUTHERLY WIND 5-10 KNOTS.
SCHNEIDER

&&

.MARINE...A WARM FRONT WILL MOVE THROUGH THE AREA LATER TONIGHT AND
WEDNESDAY...BRINGING SMALL CRAFT ADVISORY WINDS TO MOST WATERS.
WEAK HIGH PRESSURE WILL MOVE OVER WESTERN WASHINGTON WEDNESDAY
NIGHT AND THURSDAY. A WEAK COLD FRONT WILL CROSS THE AREA FRIDAY
AFTERNOON OR EVENING. ONSHORE FLOW WILL PREVAIL ON SATURDAY.
SCHNEIDER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR ALL WATERS EXCEPT THE
     CENTRAL STRAIT OF JUAN DE FUCA.

&&

$$

WWW.WEATHER.GOV/SEATTLE

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




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.