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

000
FXUS66 KSEW 302218
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
318 PM PDT THU OCT 30 2014

.SYNOPSIS...A MOIST LOW PRESSURE SYSTEM WILL BRING LOCALLY HEAVY
RAIN TO THE AREA THROUGH EARLY FRIDAY MORNING. LOOK FOR THE STEADY
RAIN TO TAPER OFF TO SCATTERED SHOWERS ON FRIDAY BEHIND THE COLD
FRONT. UNSETTLED CONDITIONS WILL PERSIST OVER THE AREA THIS
WEEKEND. ALAS...ANOTHER PERIOD OF SIGNIFICANT RAINFALL IS EXPECTED
NEXT WEEK.

&&

.SHORT TERM...
A PLUME OF SUBTROPICAL MOISTURE WAS DIRECTED AT WESTERN WA AT
THIS TIME. THIS COMBINED WITH STRONG UPPER FORCING AND OROGRAPHIC
LIFT HAVE RESULTED IN PERIODS OF HEAVY RAIN ON THE SOUTH FACING
SLOPES OF THE OLYMPIC RANGE TODAY. RAIN HAS BEEN FALLING LOCALLY
AT A RATE OF 0.25 TO 0.3 INCH PER HOUR AT TIMES ON THE OLYMPICS.
DURING THE PAST 6 HOURS...ENDING AROUND 315 PM PDT...ABOUT 1 TO
1.5 INCHES OF RAIN HAS FALLEN LOCALLY ON THE OLYMPICS.

THE COLD FRONT WAS ABOUT 85 MILES OFFSHORE BASED ON SATELLITE
IMAGERY AND LIMITED MARINE OBSERVATIONS. THIS FRONT WILL CONTINUE
MOVING SLOWLY EAST AND WILL MOVE ACROSS THE CWA LATE TONIGHT OR
EARLY FRI. THE STEADY RAIN WILL BECOME LIGHT BEHIND THE FRONT
BEFORE TAPERING OFF TO SCATTERED SHOWERS FRI AFTERNOON AS A COOLER
AIR MASS BEGINS TO INVADE THE REGION.

LOOK FOR THE UPPER TROF TO MOVE OVER THE PACIFIC NORTHWEST FRI
NIGHT AND THEN MOVE SLOWLY EAST ON SATURDAY. THE TROF IS
ANTICIPATED TO BE EAST OF THE CWA SATURDAY EVENING. PER SATELLITE
IMAGERY...THE AIR MASS ASSOCIATED WITH THE UPPER LOW WAS QUITE
UNSTABLE...THUS HAVE BUMPED UP POPS FOR FRI NIGHT AND INCLUDED A
CHANCE OF SHOWERS OVER THE ENTIRE CWA FOR SATURDAY.

A DIRTY RIDGE WILL PREVAIL OVER THE REGION ON SUNDAY. IT ALSO
APPEARED THAT A WARM FRONT WILL APPROACH THE CWA DURING THE DAY.
DECIDED TO GO WITH CLIMO POPS FOR SUNDAY. CANNOT RULE OUT A THREAT
OF LIGHT RAIN OVER THE ENTIRE CWA DUE TO WEAK WARM AIR ADVECTION
OR ISENTROPIC LIFT.

.LONG TERM...
CONFIDENCE IN THIS PERIOD WAS NOT HIGH DUE TO CONTINUED
DISAGREEMENT AND LACK CONTINUITY IN THE MEDIUM RANGE SOLUTIONS. IT
DID APPEAR THAT WESTERN WA WILL PROBABLY RECEIVE SIGNIFICANT
RAINFALL DURING THIS PERIOD. THE MEDIUM RANGE SOLUTIONS SEEMED TO
BE CONVERGING ON THE IDEA OF A SIGNIFICANT RAINFALL PRODUCER
IMPACTING THE CWA DURING THE MON/TUE TIME FRAME. HAVE KEPT POPS
ABOVE CLIMO DURING THE EXTENDED PERIOD.

&&

.HYDROLOGY...
RAIN HAS BEEN FALLING LOCALLY AT A RATE OF 0.25 TO 0.3 INCH PER
HOUR AT TIMES ON THE OLYMPIC RANGE THIS AFTERNOON. THIS HAS
RESULTED IN STEEP RISES ON THE SKOKOMISH RIVER. ANOTHER 1.5 TO
2.5 INCHES OF RAIN IS FORECAST ON THE SOUTH FACING SLOPES OF THE
OLYMPIC RANGE DURING THE 18-HOUR PERIOD ENDING AT 11 AM PDT FRI.
THIS SHOULD BE ENOUGH TO CAUSE THE SKOKOMISH RIVER TO RISE ABOVE
THE FLOOD STAGE OF 16.5 FEET LATE TONIGHT OR EARLY FRI MORNING.

AT THIS TIME...IT APPEARED THAT THE NOOKSACK RIVER WILL REMAIN
BELOW FLOOD STAGE DURING THIS EVENT BUT WILL NEED TO KEEP AN EYE
ON THE GAGES IN CASE MORE RAIN FALLS THAN PREDICTED.

FLOODING IS NOT EXPECTED ON THE REMAINING RIVERS THE NEXT 7 DAYS.

&&

.MONDAY NIGHT AND TUESDAY...RAIN. LOWS IN THE 40S TO LOWER 50S.
HIGHS IN THE 40S TO UPPER 50S. CHANCE OF RAIN 80 PERCENT.

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FLOOD WATCH IN EFFECT FROM 6 PM PDT THIS EVENING THROUGH LATE
     FRIDAY NIGHT FOR MASON COUNTY.

PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 5 PM THIS AFTERNOON FOR
     ALL WATERS EXCEPT THE ADMIRALTY INLET AND PUGET SOUND/HOOD
     CANAL.


&&

$$

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.