Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 011550
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT SAT AUG 1 2015

.SYNOPSIS...AN UPPER RIDGE WILL GRADUALLY WEAKEN OVER THE NEXT
COUPLE OF DAYS. ONSHORE FLOW WILL RETURN EARLY NEXT WEEK FOR
COOLER WEATHER. AN UPPER TROUGH WILL BRING A CHANCE OF SHOWERS
LATER IN THE WEEK.

&&

.SHORT TERM...VISIBLE SATELLITE IMAGERY SHOWS LOW CLOUDS ALONG THE
COAST HAVE SPREAD INLAND UP THE CHEHALIS RIVER VALLEY AND ALSO DOWN
THE STRAIT. STRATUS IS PROBABLY AT ITS GREATEST EXTENT THIS MORNING
WITH ALL AREAS LIKELY TO BE CLEAR BY NOON OR SO. OF INTEREST IS THE
LARGE AREA OF SMOKE FROM THE PARADISE FIRE IN THE QUEETS RIVER
VALLEY OVER WESTERN JEFFERSON COUNTY. THIS SMOKE WILL BE VISIBLE
FROM MANY PLACES IN THE WESTERN OLYMPIC PENINSULA TODAY AND COULD
GIVE A NICE SUNSET IN SEATTLE TONIGHT.

EVEN MORE IMPRESSIVE IS THE SMOKE FROM THE WOLVERINE FIRE NEAR LAKE
CHELAN THAT HAS COVERED A SIGNIFICANT PART OF EASTERN WASHINGTON
THIS MORNING. THE FIRE APPEARS TO HAVE GREATLY EXPANDED OVERNIGHT.
THANKFULLY THE WOLVERINE FIRE IS NOT IN THE CWA BUT TRAVELERS
TO EASTERN WASHINGTON...ESPECIALLY THE LAKE CHELAN AREA...SHOULD
TAKE NOTE.

THE UPPER LEVEL RIDGE OVER THE AREA THAT HAS PERSISTED FOR SEVERAL
DAYS WILL NOT MOVE TODAY. THIS WILL RESULT IN ANOTHER HOT DAY FOR
THE INTERIOR. SURFACE GRADIENTS ARE FLAT AND TEMPERATURES ALOFT ARE
SIMILAR TO FRIDAY. TEMPERATURE GUIDANCE IS GOING FOR A FEW DEGREES
OF COOLING TODAY BUT WITH LITTLE CHANGE IN THE PATTERN WILL GO MORE
ALONG THE LINES OF PERSISTENCE FOR HIGHS TODAY WITH THE WARMEST
LOCATIONS ONCE AGAIN IN THE MID TO UPPER 90S AND THE COOL SPOT BEING
THE COAST WITH 70S AND LOWER 80S.

SOME SMALL CHANGES BEGIN TO TAKE PLACE TONIGHT INTO SUNDAY. THE
UPPER LEVEL RIDGE BEGINS TO WEAKEN AND SHIFT EAST. BY 00Z MONDAY THE
THERMALLY INDUCED SURFACE TROUGH IS OVER EASTERN WASHINGTON. THIS
WILL MODERATE TO STRONG SOME LOW LEVEL ONSHORE FLOW IN WESTERN
WASHINGTON SUNDAY AFTERNOON. TEMPERATURES ALOFT WILL COOL WITH
850 MB TEMPERATURES LOWERING FROM PLUS 20C TO PLUS 18C. THE
COMBINATION OF THESE TWO VARIABLES WILL BE SLIGHTLY LOWER MAX
TEMPERATURES ON SUNDAY...WITH LOWER 90S FROM SEATTLE SOUTHWARD. 80S
WILL BE COMMON NORTH OF SEATTLE WITH 70S ALONG THE COAST. EVEN WITH
THE SLIGHTLY COOLER TEMPERATURES THE HEAT ADVISORY WILL REMAIN UP
THROUGH SUNDAY EVENING FOR THE SEATTLE AREA...SOUTHWEST INTERIOR AND
EAST PUGET SOUND LOWLANDS.

ON SUNDAY NIGHT THE UPPER LEVEL RIDGE AXIS AND THERMALLY INDUCED
SURFACE TROUGH WILL BE EAST OF THE AREA. A MARINE PUSH WILL DEVELOP
OVER WESTERN WASHINGTON. MODEL ONSHORE GRADIENTS ARE NOT VERY
IMPRESSIVE AND INDICATE A WEAK PUSH INTO MONDAY. TEMPERATURES ALOFT
CONTINUE TO COOL WITH 850 MB TEMPERATURES DOWN TO PLUS 14 OR 15C
BY 00Z TUESDAY AS A WEAK UPPER LEVEL TROUGH MOVES INTO THE AREA.
MODEL CROSS SECTIONS ALSO SHOW THE WINDS RIGHT OFF THE GROUND UP
THROUGH 700 MB REMAINING NORTHWESTERLY SUNDAY NIGHT INTO MONDAY.
THIS ALSO SUPPORTS THE WEAK PUSH SCENARIO. IN GENERAL WILL GO FOR 5
TO 10 DEGREES OF COOLING ON MONDAY VERSUS THE SUNDAY MAX TEMPS. THIS
WILL PUT MAX TEMPERATURES IN THE INTERIOR MOSTLY IN THE 70S TO LOWER
80S WITH 60S AND LOWER 70S ALONG THE COAST. FELTON/BURKE

.LONG TERM...PREVIOUS DISCUSSION...IF YOU ARE NOT A FAN OF THE HOT
WEATHER WE HAVE BEEN EXPERIENCING THE LAST FEW DAYS THEN YOU WILL
LIKE THE EXTENDED FORECAST. WHILE THERE IS NOT A LOT OF CONSISTENCY
IN THE MODELS THE GENERAL IDEA OF COOLER WEATHER IS EVIDENT IN ALL
OF THE EXTENDED SOLUTIONS. THE ECMWF IS THE MORE OPTIMISTIC OF THE
MODELS WITH NORTHWESTERLY FLOW ALOFT OVER THE AREA UNTIL A WEAK
RIDGE BUILDS LATE IN THE WEEK. THE GFS AND CANADIAN BRING AN UPPER
LEVEL LOW DOWN FROM THE NORTHWEST AND MOVE THE LOW INTO SOUTHERN
BRITISH COLUMBIA/WESTERN WASHINGTON THURSDAY WITH THE CANADIAN MODEL
ABOUT 12 HOURS SLOWER WITH THIS FEATURE VERSUS THE GFS. THE CANADIAN
KEEPS SOME WEAK TROFINESS OVER THE AREA FRIDAY WHILE THE GFS DOES
SHOW SOME WEAK RIDGE BY LATER FRIDAY INTO SATURDAY. EVEN THROUGH IT
IS THE CLIMATOLOGICALLY DRIEST TIME OF THE YEAR WITH THE LACK OF
CONSENSUS IN THE MODELS WILL STAY WITH THE CURRENT FORECAST THAT HAS
A CHANCE OF SHOWERS FORECAST FOR MOST OF THE AREA THURSDAY AND
FRIDAY WITH HIGH TEMPERATURES NEAR OR A LITTLE BELOW NORMAL...IN THE
70S FOR THE INTERIOR AND 60S FOR THE COAST. FELTON

&&

.CLIMATE...JULY 2015 WAS THE WARMEST MONTH ON RECORD IN SEATTLE WITH
AN AVERAGE TEMPERATURE OF 71.2 DEGREES. THE OLD RECORD WAS 71.1
DEGREES SET IN AUGUST OF 1967. THIS RECORD INCLUDES THE FEDERAL
BUILDING RECORDS WHICH GO BACK TO THE 1890S.

IT WAS THE WARMEST JULY ON RECORD AT BOTH HOQUIAM AND FORKS. AT
HOQUIAM THE AVERAGE TEMPERATURE FOR JULY WAS 63.9 DEGREES BREAKING
THE RECORD OF 63.0 DEGREES SET IN 1958. AT FORKS THE AVERAGE
TEMPERATURE WAS 63.0 DEGREES BREAKING THE RECORD OF 61.4 SET IN
1990. RECORDS BEGAN IN HOQUIAM IN 1953 AND AT FORKS IN 1966.

OTHER LOCATIONS AROUND WESTERN WASHINGTON...AT BELLINGHAM IT WAS THE
2ND WARMEST JULY ON RECORD WITH AN AVERAGE TEMPERATURE OF 67.2. THE
RECORD IS 68.0 DEGREES SET IN 1958. OLYMPIA ALSO HAD THE SECOND
WARMEST JULY ON RECORD WITH AN AVERAGE TEMPERATURE OF 68.0 DEGREES.
THE RECORD IS 69.1 SET ALSO IN 1958. FELTON

&&

.AVIATION...A BROAD UPPER RIDGE WILL REMAIN OVER THE REGION THROUGH
TONIGHT WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS WILL BE STABLE
AND DRY...EXCEPT FOR SHALLOW MARINE MOISTURE MAINLY ALONG THE COAST.

THERE IS MARINE STRATUS ALONG THE COAST AND IN THE LOWER CHEHALIS
VALLEY THIS MORNING...WHICH SHOULD BURN OFF BY LATE MORNING AND
RETURN TONIGHT. OTHERWISE SKIES WILL REMAIN CLEAR ACROSS THE
FORECAST AREA.

KSEA...NORTH TO NORTHWEST WIND MOSTLY 4-10 KT.   MCDONNAL

&&

.MARINE...HIGH PRESSURE OFFSHORE AND LOW PRESSURE EAST OF THE
CASCADES WILL RESULT IN STRONGER ONSHORE FLOW THROUGH THE MIDDLE OF
NEXT WEEK. SMALL CRAFT ADVISORY NORTHWEST WINDS ARE LIKELY OVER THE
OUTER COASTAL WATERS THROUGH SUNDAY MORNING...WITH SMALL CRAFT
ADVISORY NORTHWESTERLIES THIS EVENING OVER THE SOUTHERN TWO COASTAL
INNER COASTAL WATERS ZONES. HIGH END SMALL CRAFT ADVISORY WESTERLIES
ARE LIKELY IN THE CENTRAL STRAIT OF JUAN DE FUCA AND EAST ENTRANCE
STRAIT TONIGHT AND SUNDAY NIGHT...AND GALES ARE NOT OUT OF THE
QUESTION. GALE FORCE WESTERLIES ARE A GOOD BET THERE MONDAY AND
TUESDAY NIGHTS.

&&

.FIRE WEATHER...THE 12Z QUILLAYUTE SOUNDING SHOWED EXTREMELY DRY AIR
THIS MORNING ATOP A SHALLOW 500-FOOT DEEP MARINE LAYER.
INDEED...WEATHER OBSERVATIONS FROM THE OLYMPIC MOUNTAINS THIS
MORNING WERE SHOWING RELATIVE HUMIDITY VALUES WELL UNDER 20 PERCENT
AT SUNRISE. LOOKING AT ONE MORE DAY AND NIGHT OF A VERY DRY AIR
MASS...COMBINED WITH A LITTLE BIT OF MID-LEVEL INSTABILITY. MANY
LOWLAND OBSERVATION SITES WILL AGAIN SEE THEIR RELATIVE HUMIDITY
VALUES DIP DOWN NEAR OR BELOW 20 PERCENT THIS AFTERNOON. ONSHORE
FLOW WILL STRENGTHEN ON SUNDAY AND SHOULD TAKE THE EDGE OFF THE
DRYNESS OF THE AIR MASS.

THE RED FLAG WARNING REMAINS IN EFFECT THROUGH THIS EVENING ABOVE
2000 FEET. ONCE THE RED FLAG WARNING DOES EXPIRE LATE THIS
EVENING...IT JUST MEANS THAT WEATHER WILL BE LESS OF AN AGGRAVATING
FACTOR IN THE FIRE ENVIRONMENT. BACKGROUND FIRE DANGER WILL STILL BE
ELEVATED DUE TO DRY FUELS. HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...HEAT ADVISORY REMAINS IN EFFECT TIL 8 PM SUNDAY FOR PARTS OF
 THE PUGET SOUND REGION AND SOUTHWEST INTERIOR.

     RED FLAG WARNING IN EFFECT TIL 10 PM SATURDAY NIGHT FOR THE
 CASCADES AND OLYMPICS ABOVE 2000 FEET.

PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS AND TWO SOUTHERN
      INNER COASTAL WATERS ZONES...CENTRAL STRAIT OF JUAN DE
FUCA...EAST ENTRANCE STRAIT.

&&

$$

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.