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 211014
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT MON JUL 21 2014

.SYNOPSIS...THE AIR MASS WILL DRY AND ONSHORE FLOW WILL WEAKEN TODAY
AND TUESDAY FOR PARTLY SUNNY SKIES. AN UPPER LOW WILL BRING
WIDESPREAD SHOWERS WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE WILL
BUILD OVER THE AREA LATE IN THE WEEK AND INTO THE WEEKEND FOR
SUNNIER WARMER WEATHER.

&&

.SHORT TERM...WITH LIGHT CONVERGENCE STILL GOING ON IN THE CENTRAL
PUGET SOUND AREA...HAVE INCLUDED A CHANCE OF SHOWERS FOR THIS
MORNING WHICH WILL FIZZLE OUT. OTHERWISE...EXPECT PARTLY TO MOSTLY
SUNNY SKIES IN THE AFTERNOON AND EVENING AS ONSHORE FLOW DIES DOWN
TODAY. TUESDAY WILL HAVE PARTLY SUNNY SKIES IN THE MORNING BUT IT
WILL CLOUD UP AS AN UPPER LOW APPROACHES THE AREA.

SPOTTY SHOWERS ARE POSSIBLE BEGINNING TUESDAY AFTERNOON...BUT THEY
WILL BECOME WIDESPREAD ON WEDNESDAY AND WEDNESDAY NIGHT AS THE LOW
MOVES DIRECTLY OVER WESTERN WASHINGTON. A MODERATE LEVEL OF
INSTABILITY OVER THE MOUNTAINS WITH NAM12 CAPE VALUES IN THE 500
J/KG RANGE...COMBINED WITH 0 TO 6 KM BULK SHEAR VALUES AVERAGING 40
KT...AND UPPER LEVEL SUPPORT FROM THE OVERHEAD LOW...HAS CONVINCED
ME TO ADD A SLIGHT CHANCE OF THUNDERSTORMS FOR THE MOUNTAINS
WEDNESDAY AFTERNOON AND EVENING. UNCERTAINTY FOR THUNDERSTORMS IS
STILL HIGH AT THIS POINT. JSMITH

.LONG TERM...THE UPPER LOW WILL MOVE NORTHEAST INTO ALBERTA ON
THURSDAY...AND AN UPPER RIDGE WILL BEGIN TO BUILD OFFSHORE.
LINGERING SHOWERS AND CLOUDY SKIES ON THURSDAY MORNING WILL GIVE WAY
TO A PARTLY TO MOSTLY SUNNY AFTERNOON. THE GFS40 AND ECMWF HAVE BEEN
RATHER CONSISTENT WITH THE UPPER RIDGE BUILDING INTO THE AREA
TOWARDS THE END OF THE WEEK AND INTO THE WEEKEND. SUNNY AND WARM
DAYS TOWARDS THE END OF THE WEEK ARE A GOOD BET. JSMITH

&&

.AVIATION...UPPER LEVEL TROUGH WELL OFFSHORE DIGGING SOUTH TODAY
WITH THE FLOW ALOFT BECOMING SOUTHWESTERLY. AT THE SURFACE...HIGH
PRESSURE WILL BE OFFSHORE WITH LOWER PRESSURE INLAND. AIR MASS MOIST
AND STABLE...WITH DRYING THIS AFTERNOON.

WIDE VARIETY OF CEILINGS EARLY THIS MORNING. CONVERGENCE OVER THE
CENTRAL SOUND HAS KEPT CEILINGS IN THE 2000-3000 FOOT RANGE INTO THE
EARLY MORNING HOURS. OUTSIDE OF THE CONVERGENCE OVER THE INTERIOR
CEILINGS GENERALLY AOA 5000 FEET TO THE NORTH WITH JUST A SCATTERED
TO BROKEN LAYER AROUND 5000 FEET OVER THE SOUTHWEST INTERIOR AND
ALONG THE CENTRAL COAST. OTHER THAN CEILINGS LOWERING ALONG THE
CENTRAL COAST DOWN TO NEAR 2000 FEET LITTLE CHANGE FOR THE NEXT FEW
HOURS. CEILINGS OVER THE CENTRAL SOUND LIFTING LATER THIS MORNING
WITH THE CLOUDS SCATTERING OUT OVER THE ENTIRE AREA THIS AFTERNOON.

KSEA...CEILINGS AROUND 2000 FEET IMPROVING LATE MORNING WITH THE
CLOUDS SCATTERING OUT MID TO LATE AFTERNOON. VARIABLE WINDS LESS
THAN 6 KNOTS BECOMING SOUTHWESTERLY LATE MORNING. WINDS BECOMING
NORTHWEST 5-10 KNOTS LATE THIS AFTERNOON. FELTON

&&

.MARINE...HIGH PRESSURE WILL BE OFFSHORE WITH LOWER PRESSURE INLAND
FOR THE NEXT SEVERAL DAYS...RESULTING IN VARYING DEGREES OF ONSHORE
FLOW. THE EXCEPTION TO THIS WILL BE TUESDAY NIGHT WHEN A WEAK
SURFACE LOW MOVES INTO THE COASTAL WATERS WEAKENING THE ONSHORE FLOW
FOR A SHORT TIME. THIS PATTERN WILL GENERALLY PRODUCE SMALL CRAFT
ADVISORY WEST WINDS FOR THE CENTRAL AND EASTERN STRAIT OF JUAN DE
FUCA EACH EVENING INTO THE EARLY MORNING HOURS WITH THE EXCEPTION OF
TUESDAY EVENING AND EARLY WEDNESDAY MORNING. FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE 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.