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 250450
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PST TUE FEB 24 2015

.SYNOPSIS...A WEAK SYSTEM WILL BRING SOME SPOTTY LIGHT RAIN OR
SPRINKLES TO PARTS OF WESTERN WASHINGTON TONIGHT. THE NEXT TRAILING
SYSTEM WILL BRING LIGHT RAIN TO THE COAST WEDNESDAY
AFTERNOON...SPREADING INLAND WEDNESDAY NIGHT. A SHOWERY PATTERN WILL
PERSIST THROUGH FRIDAY. DRY OFFSHORE FLOW WILL DEVELOP THIS
WEEKEND...THEN A CHANCE OF RAIN WILL RETURN EARLY NEXT WEEK.
TEMPERATURES WILL BE LOWER THAN THEY HAVE BEEN RECENTLY...CLOSER TO
NORMAL.

&&

.SHORT TERM...THE FLOW IS ONSHORE THIS EVENING AS A WEAK SURFACE
TROUGH DIVING SE THROUGH THE AREA. LOW CLOUDS ALONG THE COAST SHOULD
SPREAD INLAND OVERNIGHT. COASTAL RADAR IS PICKING UP ON SOME SPOTTY
SHOWERS BUT SO FAR THIS ACTIVITY REMAINS ALONG THE COAST. THERE IS
NOT MUCH LIFT WITH THIS INITIAL PUSH OF MOISTURE BUT SPOTTY LIGHT
MEASURABLE RAINFALL IS POSSIBLE...MAINLY ALONG THE COAST. WILL LEAVE
POPS IN PLACE AROUND PUGET SOUND BUT THE TREND APPEARS LESS
FAVORABLE FOR MEASURABLE RAIN INLAND.

THE NEXT SYSTEM TO AFFECT THE REGION WILL ARRIVE IN NW FLOW
WEDNESDAY. MODELS STILL DEVELOP LIGHT RAIN ALONG THE COAST BY MIDDAY
AND SPREAD IT INLAND DURING THE AFTERNOON. RAIN AT TIMES IS LIKELY
WEDNESDAY NIGHT INTO THURSDAY AS THE WARM FRONTAL WAVE IS FOLLOWED
BY THE MAIN TROUGH. PRECIPITATION WILL TRANSITION TO A MORE SHOWERY
PATTERN THURSDAY AFTERNOON THROUGH FRIDAY AS THE TROUGH SHARPENS AND
DIGS SE ACROSS THE AREA. THIS WILL USHER IN COLDER AIR ALOFT WITH
SNOW LEVELS FALLING TO THE PASSES. THE 850 MB FLOW WILL BE LIGHT SO
SNOW AMOUNTS WILL PROBABLY NOT BE ALL THAT IMPRESSIVE. STILL...A FEW
INCHES AT THE SKI RESORTS WILL BE WELCOME. HIGHS IN THE LOWLANDS
WILL BE NEAR AVERAGE IN THE LOW 50S. MERCER

.LONG TERM...FROM PREVIOUS DISCUSSION...THE WEEKEND LOOKS DRY AS ANY
RESIDUAL SHOWERS MOVE OFF TO THE SOUTH AND THE UPPER RIDGE WELL
OFFSHORE NOSES INLAND. A WEAK SYSTEM MAY BRING A LITTLE RAIN MONDAY
OR TUESDAY. HIGHS BOTH DAYS ARE FORECAST TO BE MOSTLY IN THE UPPER
40S...WHICH COULD BE THE FIRST TIME SINCE FEBRUARY 1 THAT THE
DAYTIME HIGH DOES NOT EXCEED THE NORMAL HIGH. BURKE

&&

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

&&

.AVIATION...NORTHWEST FLOW ALOFT. THE AIR MASS IS STABLE WITH
INCREASING LOW LEVEL MOISTURE FROM THE NW. LOW LEVEL ONSHORE THIS
EVENING WILL DIMINISH LATE TONIGHT THROUGH WED AS A WEAK UPPER RIDGE
MOVES ACROSS THE AREA. A WEAK FRONTAL SYSTEM WILL MOVE ACROSS THE
AREA WED NIGHT.

MULTISPECTRAL SATELLITE IMAGERY SHOWS A SOLID STRATUS DECK FROM THE
WESTERN OLYMPIC PENINSULA OUT INTO THE PACIFIC. THE BASES ARE AROUND
010 ALONG THE COAST AND SOME VERY LIGHT RAIN IS BEING REPORTED AT
KUIL. THE LATEST 03Z RUN OF THE HRRR KEEPS THE PRECIPITATION
CONFINED TO THE IMMEDIATE COASTLINE THROUGH WED MORNING. CIGS ON THE
COAST WILL LIKELY REMAIN BKN010-020 WITH POCKETS OF CIGS BLO
BKN010 THROUGH WED MORNING.

STRATUS WILL PUSH INLAND AND ACROSS THE AREA TONIGHT...BUT
CONDITIONS IN THE INTERIOR WILL LIKELY REMAIN IN THE VFR CATEGORY
WITH CLOUD BASES 030-035 THROUGH ABOUT 10Z. STRATUS BASES 10Z-18Z
ARE EXPECTED TO AVERAGE FL010-015 IN THE INTERIOR WITH POCKETS OF
BKN005-009 NEAR THE STRAIT OF JUAN DE FUCA AND FROM KPWT SW THROUGH
THE CHEHALIS GAP.

THE STRATUS MAY BREAK SOMEWHAT IN THE INTERIOR WED AFTERNOON AS WEAK
SHORT WAVE RIDGING ALOFT MOVES ACROSS THE AREA. BUT STRATUS WILL
FILL BACK IN WED EVENING AND VIS MAY FALL TO 3-5SM -RA BR AS A
FRONTAL SYSTEM MOVES SE ACROSS THE REGION. ALBRECHT

KSEA...CLOUDS WILL LIKELY INCREASE BY 06Z WITH STRATUS BASES
030-035. EXPECT BKN010-015 OVC030 10Z-18Z WED. LOWER LAYERS MAY
BECOME SCATTERED WED AFTERNOON. LIGHT S WIND WILL BECOME VARIABLE TO
4 KT TONIGHT THROUGH WED. ALBRECHT

&&

.MARINE...ONSHORE FLOW IS DIMINISHING THIS EVENING. WINDS IN THE
CENTRAL AND EASTERN PORTIONS OF THE STRAIT OF JUAN DE FUCA HAVE
DIMINISHED TO BELOW 20 KNOTS...SO WILL CANCEL THE SMALL CRAFT
ADVISORY THAT WAS IN EFFECT THERE.

EXPECT LIGHT PRES GRADIENTS LATER TONIGHT INTO WED AS A WEAK UPPER
LEVEL RIDGE OF HIGH PRES MOVES ACROSS THE AREA. THEN A WEAK COLD
FRONT WILL PUSH SE ACROSS THE WATERS WED NIGHT INTO
EARLY THU MORNING. AT THIS TIME IT APPEARS THAT WINDS
THROUGHOUT THE WATERS WILL REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA.

A WEAK 1012 MB LOW WILL DROP S OVER THE COASTAL WATERS LATE THU
NIGHT INTO FRI. PRES GRADIENTS ARE EXPECTED TO REMAIN LIGHT OVER THE
WATERS AS THE LOW PASSES SOUTHWARD ACROSS THE AREA.

HIGH PRES WILL DEVELOP OVER BRITISH COLUMBIA FRI INTO FRI NIGHT. THE
COMBINATION OF THE BUILDING HIGH AND THE DEPARTING LOW WILL RESULT
IN STRONG NE FLOW OVER THE WATERS LATER FRI OR FRI NIGHT INTO SAT
WITH SMALL CRAFT ADVISORY CONDITIONS EXPECTED EVERYWHERE EXCEPT IN
ADMIRALTY INLET AND PUGET SOUND/HOOD CANAL. PRES GRADIENTS WILL
RELAX ON SUN AS HIGH PRES MOVES OVER THE WATERS. ALBRECHT

&&

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


&&

$$

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.