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 270357 AAA
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT TUE APR 26 2016

.SYNOPSIS...A WEAK WEATHER SYSTEM OFF THE COAST WILL MOVE SOUTHEAST
INTO OREGON TONIGHT. LIGHT RAIN IS LIKELY ON THE COAST WITH CLOUDS
AND A CHANCE OF RAIN INLAND THROUGH WEDNESDAY. HIGH PRESSURE WILL
BRING DRY WEATHER THURSDAY. ANOTHER WEAK FRONT WILL ARRIVE FRIDAY
WITH A POSSIBLE CONVERGENCE ZONE LINGERING INTO FRIDAY EVENING. DRY
WEATHER AND A WARMING TREND IS EXPECTED SATURDAY THROUGH MONDAY.

&&

.SHORT TERM...RADAR SHOWS LIGHT RAIN OFF THE COAST BUT LITTLE OVER
THE LAND. NEITHER KUIL NOR KAST HAS RECEIVED ANY RAIN YET. THIS
PATTERN AGREES WITH MODELS THAT TAKE A PARENT UPPER LOW SOUTHEAST
INTO OREGON TONIGHT AND WEDNESDAY. CHANCE POPS REMAIN OVER MOST OF
THE AREA THROUGH WEDNESDAY.

AN UPPER RIDGE BRIEFLY BUILDS OVER THE REGION THURSDAY GIVING DRY
WEATHER. A WEAK WEATHER SYSTEM WILL APPROACH THE COAST THURSDAY
NIGHT THEN GET ENERGIZED SOMEWHAT AS AN UPPER LEVEL LOW DEVELOPS
RIGHT OVER WASHINGTON. SHOWERS SEEM LIKELY FRIDAY AND SOME BUT NOT
ALL GUIDANCE IS POINTING THAT WAY. HIGHS WILL BE NEAR AVERAGE
THROUGH THE PERIOD...IN THE UPPER 50S TO MID 60S WITH THURSDAY THE
WARMEST DAY. BURKE

.LONG TERM...PREVIOUS DISCUSSION...LONG RANGE MODELS REMAIN IN GOOD
AGREEMENT THAT A STRONG RIDGE OF HIGH PRESSURE BUILDS OVER THE PAC
NW THIS WEEKEND INTO AT LEAST MONDAY OF NEXT WEEK. 500 MB HEIGHTS
BUILD OVER THE WEEKEND BUT ONSHORE FLOW SATURDAY WILL INITIALLY HOLD
BACK POTENTIAL HIGHS. TEMPERATURES WILL STRUGGLE TO GET MUCH ABOVE
60 ALONG THE COAST...STRAIT...AND NORTH INTERIOR NEAR THE WATER.
FURTHER INLAND AND AROUND PUGET SOUND IT SHOULD WARM INTO THE LOW TO
MID 60S AFTER MORNING CLOUDS BURN OFF.

THE POSITIVE TILT RIDGE BUILDS MORE DIRECTLY OVER WA ON SUNDAY
ALLOWING THERMALLY INDUCED LOW PRESSURE TO BUILD NORTH ALONG THE
OREGON COAST AND INTO SW WA. SOME MODELS SHOW THE HEAT LOW SHIFTING
ALONG THE WA COAST OR EVEN JUST OFF THE COAST MONDAY WHICH WOULD
INDUCE STRONG OFFSHORE FLOW AND USHER IN DRIER DOWNSLOPE FLOW.
FORECAST HIGHS WERE BOOSTED TO WELL ABOVE AVERAGE SUNDAY AND MONDAY
WITH WIDESPREAD 70S A GOOD BET. I WOULD NOT BE SURPRISED TO SEE SOME
LOW 80S BY THE END OF THIS NEXT ROUND OF WARM TEMPERATURES. THE
GFS/ECMWF/CANADIAN VARY ON WHEN THE NEXT SYSTEM ARRIVES OR AT LEAST
WHEN ONSHORE FLOW RESUMES. TUESDAY SEEMS THE MOSTLY LIKELY DAY WITH
GFS/CANADIAN SHOWING EITHER SW FLOW ALOFT INDUCING SOME LOW LEVEL
ONSHORE FLOW OR POSSIBLY SOME SHOWERS WITH A FRONT PER THE CANADIAN
SOLUTION. KEPT SOME LOW POPS IN THE FORECAST AND LOWERED HIGHS BY
ROUGHLY 10 DEGREES WHICH WOULD STILL BE ABOVE AVERAGE. THIS APRIL
COULD VERY WELL END AS THE WARMEST ON RECORD.  MERCER

&&

.AVIATION...A WEAK UPPER LEVEL TROF WILL MOVE OVER THE AREA
OVERNIGHT. THE FLOW ALOFT WILL BE LIGHT AND VARIABLE. WEAK LOW
LEVEL ONSHORE FLOW WILL PERSIST. VFR CONDITIONS ARE EXPECTED TO
PREVAIL OVERNIGHT.

KSEA...VFR. WINDS WILL BE LIGHT AND VARIABLE OVERNIGHT.

&&

.MARINE...
A WEAKENING OCCLUDED FRONT OVER THE OFFSHORE WATERS WILL DISSIPATE
BEFORE REACHING THE COASTAL WATERS LATE TONIGHT OR EARLY WED.
BUILDING HIGH PRES OVER THE OFFSHORE WATERS ON WED WITH LOWER PRES
E OF THE CASCADES WILL RESULT IN STRENGTHENING ONSHORE OR WESTERLY
FLOW. ONSHORE FLOW WILL CONTINUE ON THU.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

WWW.WEATHER.GOV/SEATTLE

AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION CAN BE SEEN 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.