Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 121039
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
336 AM PDT FRI SEP 12 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL MAINTAIN DRY WEATHER INTO EARLY
NEXT WEEK. ABUNDANT SUNSHINE AND LOW LEVEL OFFSHORE FLOW WILL
SUPPORT A VERY GRADUAL WARMING TREND THROUGH THE WEEKEND INTO EARLY
NEXT WEEK. COOLER AND MORE UNSETTLED WEATHER WILL RETURN WEDNESDAY
NIGHT AND THURSDAY.

&&

.SHORT TERM...THE UPPER LEVEL RIDGE JUST INSIDE OF 140W WILL SLOWLY
SHIFT EAST THROUGH THE WEEKEND KEEPING SUNNY SKIES OVER THE REGION.
OFFSHORE FLOW WILL ALSO CONTINUE...HELPING BOOST DAYTIME HIGH
TEMPERATURES A FEW DEGREES EACH DAY WITH MANY AREAS REACHING THE
LOWER TO MID 80S THIS WEEKEND. CLEAR SKIES WILL HELP OVERNIGHT
TEMPERATURES DROP INTO THE 30S IN SHELTERED VALLEYS WHILE HIGHER
SPOTS OR LOCATIONS PRONE TO EAST WINDS WILL REMAIN IN THE 50S.

NOTE...THE STRONG SOLAR FLARE THAT OCCURRED YESTERDAY AND CONTINUED
CLEAR SKIES WILL INCREASE THE CHANCES OF OBSERVING AURORA BOREALIS
OVER WESTERN WASHINGTON TONIGHT AND INTO THE WEEKEND. FOR MORE
INFORMATION GO TO WWW.SWPC.NOAA.GOV

.LONG TERM...THE UPPER LEVEL RIDGE AXIS WILL CONTINUE TO SHIFT EAST
SUNDAY EVENING AND EAST OF THE CASCADES DURING THE DAY MONDAY. AT
LOW LEVELS THE THERMALLY INDUCED TROUGH WEAKENS AND SHIFTS
INLAND...ENDING OFFSHORE FLOW. ACCORDINGLY BOOSTED TEMPERATURES
MONDAY...ESPECIALLY OVER THE INTERIOR...FOR ANOTHER WARM AND SUNNY
DAY WITH HIGHS IN THE INTERIOR RISING INTO THE LOW TO MID 80S.
A WEAK UPPER LEVEL SHORT WAVE TROUGH TRACKING NORTH THROUGH WESTERN
WA EARLY TUESDAY MORNING WILL DO LITTLE MORE THAN BRING A FEW MID
AND HIGH CLOUDS...TUESDAY WILL REMAIN PARTLY TO MOSTLY SUNNY WITH
TEMPERATURES IN THE 70S. COOLER AND UNSETTLED WEATHER WILL RETURN
WEDNESDAY OR WEDNESDAY EVENING THROUGH THURSDAY. MEDIUM RANGE MODELS
CONTINUE TO DIFFER A BIT ON THE TIMING OF THIS SYSTEM WITH THE ECMWF
BRINGING A MORE CONSOLIDATED SYSTEM ONSHORE A BIT EARLIER THAN THE
GFS. FOR NOW THE CURRENT FORECAST HIGHLIGHTS CHANCE POPS FOR THE
COAST DURING THE DAY WEDNESDAY...SPREADING INLAND WEDNESDAY NIGHT
AND THURSDAY.

&&

.FIRE WEATHER...PREVIOUS DISCUSSION...A STRONG EAST WIND EVENT IS
UNDERWAY THIS AFTERNOON. CRITICAL COMBINATIONS OF WIND...LOW
HUMIDITY AND DRY FUELS ARE TAKING PLACE OVER A LARGE PORTION OF
WESTERN WASHINGTON... ESPECIALLY OVER THE OLYMPIC PENINSULA AND OVER
THE INTERIOR SOUTH OF I-90. FOR THE NORTHWEST OLYMPIC PENINSULA AND
THROUGH THE CASCADES...EAST WINDS WILL NOT BE AS STRONG ON FRIDAY AS
THEY HAVE BEEN TODAY...BUT LOCALIZED GUSTS AROUND 20 TO 35 MPH WILL
STILL BE A CONCERN. MEANWHILE...THE PUGET SOUND LOWLANDS AND THE
CHEHALIS GAP SHOULD SEE SIMILARLY BREEZY CONDITIONS ON FRIDAY
AFTERNOON AS THIS AFTERNOON...WITH GUSTS AROUND 20 TO 25 MPH AND
HUMIDITY WELL UNDER 30 PERCENT.

EAST WINDS WILL CONTINUE UNTIL MONDAY...BUT SPEEDS WILL EASE A
LITTLE BIT EACH DAY THROUGH MONDAY. EVEN WITH WEAKENING EAST WINDS
OVER THE WEEKEND...THE AIR MASS WILL CONTINUE TO BE WARM AND DRY
THROUGH TUESDAY MORNING. POOR NIGHTTIME HUMIDITY RECOVERY WILL
CONTINUE...AND MID-LEVEL HAINES 5-6 CONDITIONS ON SUNDAY AND MONDAY
WILL SUPPORT AN ACTIVE BURNING ENVIRONMENT. MID-LEVEL HAINES 5-6
MEANS THAT THE 850-700 MB LAYER OF THE ATMOSPHERE WILL BE VERY DRY
AND SOMEWHAT UNSTABLE.   HANER

&&

.AVIATION...UPPER LEVEL RIDGE OFFSHORE BETWEEN 130-140W WITH
NORTHWESTERLY FLOW ALOFT OVER WESTERN WASHINGTON THROUGH SATURDAY.
AT THE SURFACE...A THERMALLY INDUCED TROUGH OF LOW PRESSURE OVER THE
WASHINGTON AND OREGON COASTAL WATERS WITH HIGHER PRESSURE OVER
EASTERN WASHINGTON GIVING LOW LEVEL OFFSHORE FLOW THROUGH SATURDAY.
AIR MASS DRY AND STABLE WITH CLEAR SKIES.

KSEA...CLEAR SKIES. NORTHEAST WINDS 6-10 KT BECOMING NORTHERLY 8 TO
12 KNOTS THIS AFTERNOON. FELTON

&&

.MARINE...THERMALLY INDUCED TROUGH OF LOW PRESSURE OVER THE COASTAL
WATERS WHILE A RIDGE OF HIGH PRES EXTENDS FROM CENTRAL BRITISH
COLUMBIA SE INTO MONTANA AND NORTH DAKOTA. THE PATTERN IS PRODUCING
MODERATE OFFSHORE FLOW WITH LITTLE CHANGE THROUGH SUNDAY.

THE THERMALLY TROUGH WILL WEAKEN ON MONDAY AND SHIFT INLAND LATER
MONDAY INTO TUESDAY. A NARROW RIDGE OF HIGH PRESSURE WILL DEVELOP
RIGHT ALONG THE COAST MONDAY NIGHT AND TUESDAY WITH THE LOW LEVEL
FLOW GOING ONSHORE. FELTON

&&

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









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