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 191006
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
305 AM PDT TUE MAY 19 2015

.SYNOPSIS...ONSHORE FLOW WILL CONTINUE THROUGH THE WEEKEND...
INCREASING A BIT TOWARD THE END OF THE WEEK. UNSTABLE AIR WILL
MAINTAIN A CHANCE OF AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS
OVER THE MOUNTAINS EACH DAY.

&&

.SHORT TERM...LOW LEVEL ONSHORE FLOW WILL BE A BIT STRONGER TODAY...
THEN WEAKEN AND TURN A BIT MORE NORTHERLY WEDNESDAY AND THURSDAY. A
MODEST PUSH IS UNDERWAY EARLY THIS MORNING WITH STRATUS AND PATCHY
FOG MOVING INTO THE INTERIOR. MOST OF THIS SHOULD BURN BACK TO THE
COAST LATER TODAY. HIGHS WILL BE A FEW DEGREES COOLER TODAY WITH THE
MORNING CLOUDS AND STRONGER ONSHORE FLOW.

LOW CLOUDS SHOULD PUSH AT LEAST PARTIALLY INTO THE INTERIOR TONIGHT
WITH ONSHORE FLOW CONTINUING. THE BURN OFF WILL PROBABLY BE A LITTLE
EARLIER ON WEDNESDAY AS LOW LEVEL ONSHORE FLOW WEAKENS. HIGHS WILL
WARM A FEW DEGREES AS WELL. LOW CLOUDS SHOULD BE LIMITED MOSTLY TO
THE COAST THURSDAY MORNING. HIGHS THURSDAY WILL BE ABOUT THE SAME AS
WEDNESDAY.

THE AIR MASS WILL REMAIN UNSTABLE OVER THE MOUNTAINS FOR A CHANCE OF
AFTERNOON AND EVENING THUNDERSTORMS THE NEXT THREE DAYS. SCHNEIDER

.LONG TERM...A NONDESCRIPT UPPER PATTERN WILL CONTINUE OVER THE
PACIFIC NORTHWEST THURSDAY THROUGH EARLY NEXT WEEK WITH LOW LEVEL
ONSHORE FLOW. A WEAK UPPER LOW IS EXPECTED TO DROP DOWN FROM THE
NORTHWEST OVER THE WEEKEND...PERHAPS BRINGING A CHANCE OF SHOWERS TO
THE AREA. OTHERWISE...IT SHOULD BE DRY EXCEPT FOR AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS EACH DAY. HIGHS
WILL BE NEAR NORMAL. SCHNEIDER

&&

.AVIATION...WEAK LOW PRESSURE WITH LIGHT FLOW ALOFT TODAY WITH LOW
LEVEL ONSHORE FLOW CONTINUING. SATELLITE IMAGERY SHOWS STRATUS DECK
ALONG THE COAST...DOWN THE STRAIT INTO SNOHOMISH COUNTY AND AS FAR
EAST AS BREMERTON. CEILINGS ARE LESS THAN 1000 FEET. ONSHORE
GRADIENTS STRONG ENOUGH TO BRING STRATUS INTO ALL BUT THE BELLINGHAM
TERMINAL IN THE NEXT THREE HOURS. CEILINGS BELOW 1000 FEET WILL BE
COMMON WITH THE HIGHER TERMINALS...KPAE AND KSEA...HAVING THE
POTENTIAL OF REDUCED VISIBILITIES IN FOG. THE MARINE LAYER WILL BE
SHALLOW WITH TOPS 1000-1500 FEET OVER THE INTERIOR. WITH THE SHALLOW
MARINE LAYER EXPECT THE STRATUS TO BURN BACK TO THE COAST BY NOON.
JUST SOME HIGH CLOUDS FOR THE REMAINDER OF THE DAY. THE AIR MASS
WILL ONCE AGAIN BECOME UNSTABLE IN THE LATE AFTERNOON AND EVENING
HOURS BUT ANY CONVECTION THAT DEVELOPS WILL STAY OVER THE HIGHER
TERRAIN.

KSEA...STRATUS JUST TO THE WEST OF THE TERMINAL AT 09Z. CURRENT TAF
HAS CEILINGS BELOW 500 FEET BEGINNING AT 13Z. MIGHT NEED TO MOVE UP
THE ARRIVAL TIME BY A HOUR IN NEXT ISSUANCE OF THE TAF. WITH THE
SHALLOW MARINE LAYER WILL STAY WITH THE 17Z-18Z BREAKOUT WITH JUST
HIGH CLOUDS FOR THE REMAINDER OF THE DAY. LIGHT AND VARIABLE OR
LIGHT...5 KNOTS OR LESS...SOUTHERLY WINDS WILL SWITCH TO NORTHERLY 6
TO 10 KNOTS MIDDAY. FELTON

&&

.MARINE...A STABLE PATTERN WILL PERSIST THROUGH SATURDAY WITH
VARYING DEGREES OF ONSHORE FLOW THROUGH THE PERIOD DUE TO A 1025 MB
HIGH WELL OFFSHORE AND LOWER PRES INLAND. SMALL CRAFT ADVISORY WINDS
ARE POSSIBLE EACH DAY DURING THE LATE AFTERNOON AND EVENING HOURS
FOR THE CENTRAL AND EASTERN STRAIT. FOR THE REMAINDER OF THE WATERS
EXPECT WINDS TO REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA...20
KNOTS OR LESS. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY EARLY THIS MORNING FOR THE CENTRAL STRAIT
     OF JUAN DE FUCA.
     SMALL CRAFT ADVISORY TONIGHT FOR THE CENTRAL AND EASTERN 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.