Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 262234
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
315 PM PDT FRI JUN 26 2015

.SYNOPSIS...A STRONG UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION
THROUGH THE WEEKEND BRINGING HOT WEATHER TO WESTERN WASHINGTON. AN
UPPER LEVEL DISTURBANCE APPROACHING THE REGION WILL BRING A CHANCE
OF THUNDERSTORMS TO PARTS OF WESTERN WASHINGTON LATE SATURDAY
THROUGH SUNDAY. THE UPPER LEVEL RIDGE WILL WEAKEN EARLY NEXT WEEK
WHILE A RETURN TO WEAK ONSHORE FLOW WILL BRING A LITTLE COOLING TO
THE AREA. DRY WEATHER AND A TREND BACK TO MUCH WARMER TEMPERATURES
IS POSSIBLE LATER NEXT WEEK.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS MOSTLY CLEAR SKIES ACROSS WRN
WA WITH THE EXCEPTION OF LOW STRATUS ALONG THE COAST AND IN THE
STRAIT. HIGH PRESSURE ALOFT OVER THE GREAT BASIN IS EXPANDING NWD
OVER THE PAC NW AS EXPECTED BRINGING WARM TEMPERATURES TO MOST OF
INTERIOR WRN WA. TEMPERATURES AT 2 PM WERE ALREADY IN THE 80S ACROSS
MOST OF PUGET SOUND BUT NLY GRADIENTS ARE INCREASING WITH SEA-BREEZE
EFFECTS LIKELY TO SLOW THE RATE OF WARMING AT PLACES NEAR THE WATER.
THIS IS CERTAINLY THE CASE ON THE COAST AND STRAIT WHERE NWLY FLOW
IS HOLDING TEMPERATURES BACK IN THE UPPER 60S TO LOW 70S. THE UPPER
RIDGE IS EXPECTED TO AMPLIFY FURTHER TONIGHT ALLOWING THE THERMALLY
INDUCED TROUGH CENTERED OVER OREGON AND ERN WA TO BROADEN OVER ALL
OF WA ON SATURDAY. WHILE THE THERMALLY INDUCED TROUGH NEVER BECOMES
ESTABLISHED ALONG THE COAST IT WILL BECOME CENTERED OVER THE
INTERIOR OF WRN WA FOR A TIME LATER TONIGHT AND SATURDAY. THIS WILL
RESULT IN LIGHTER FLOW AND LESS MODERATION FROM SEA-BREEZE EFFECTS.
THIS WILL ALLOW AREAS NEAR THE WATERS LIKE SEA-TAC TO SURGE A FEW
DEGREES WARMER THAN TODAY...INTO THE LOW 90S WHICH WOULD BE A
RECORD. HIGHS SHOULD EVEN REACH THE LOW 80S AT THE COAST WITH
LIGHTER ONSHORE FLOW THAN TODAY. LOW TEMPERATURES WILL ALSO BE QUITE
WARM WITH LOWS IN THE I-5 URBAN AREAS ONLY FALLING BELOW 70 FOR A
SHORT TIME THE NEXT COUPLE MORNINGS. DUE TO A COMBINATION OF HOT
DAYTIME TEMPERATURES AND WARM OVERNIGHT LOWS...THE EXCESSIVE HEAT
WARNING WILL REMAIN IN EFFECT THROUGH SUNDAY MORNING.

THE FORECAST BECOMES MORE COMPLICATED STARTING LATER SATURDAY
AFTERNOON THROUGH SUNDAY AS THE FLOW ALOFT TURNS MORE SLY. THIS
OPENS THE DOOR TO INCREASING MID AND HIGH LEVEL MOISTURE WHICH WILL
BE ENCOUNTERING A HOT AND UNSTABLE AIR MASS OVER WRN WA. MODELS
GENERALLY AGREE THAT THERE WILL BE TWO DISTINCT SURGES OF MOISTURE.
THE FIRST ARRIVES LATE SATURDAY AFTERNOON THROUGH SATURDAY NIGHT
WITH MODELS INDICATING A RATHER SHALLOW MOISTURE LAYER ABOVE 700 MB.
WHILE THIS MAY INITIALLY PRODUCE NOTHING MORE THAN SOME AC
CLOUDS...CONVECTION SHOULD BECOME MORE SIGNIFICANT OVERNIGHT GIVEN
THE STEEP LAPSE RATES AND CONTINUING MOISTURE ADVECTION FROM THE
SOUTH. TIME-HEIGHTS SHOW VERY DRY AIR IN THE LOW LEVELS BELOW 700 MB
SO BASES ON CONVECTION WILL BE QUITE HIGH ABOVE 10K FT. THIS MEANS
ANY LIGHTNING PRODUCED BY THUNDERSTORMS WILL NOT BE ACCOMPANIED BY
MUCH IF ANY RAINFALL.

AN UPPER LOW OFF THE CA COAST KICKS NWD ON SUNDAY WHICH WILL BRING
ANOTHER SURGE OF DEEPER MOISTURE INTO WRN WA DURING THE DAY. THE
FLOW REMAINS SLY OR EVEN S-SELY WITH VORTICITY ADVECTION PRODUCING
FAVORABLE DYNAMICS FOR THUNDERSTORMS ACROSS WRN WA. THE LOWER LEVELS
EVENTUALLY MOISTENS UP SUNDAY AFTERNOON AND NIGHT BUT CONVECTION
WILL BE WEAKER WITH JUST LIGHT RAIN SHOWERS LATER SUNDAY NIGHT WITH
INSIGNIFICANT RAIN AMOUNTS. CERTAINLY NOT ENOUGH TO IMPROVE THE DRY
FUEL CONDITIONS ACROSS THE AREA.

THE UPPER LOW WILL INDUCE A MARINE PUSH BUT THE TIMING OF THIS
REMAINS HIGHLY UNCERTAIN. SOME MODELS SHOW A SLY SURGE ALONG THE
COAST JUST BARELY PENETRATING THE SW INTERIOR SUNDAY AFTERNOON. THIS
SCENARIO WOULD RESULT IN ANOTHER DAY OF HOT TEMPERATURES FROM
CENTRAL/N PARTS OF PUGET SOUND NWD. OTHER MODELS BRING COOLER AIR IN
QUICKER ON SUNDAY MODERATING HIGH TEMPERATURES SIGNIFICANTLY. THE
FORECAST REFLECTS A MODEL BLEND BUT IS STILL QUITE WARM IN THE 80S
ACROSS THE INTERIOR. THE ADDED HUMIDITY WILL MAKE IT FEEL EVEN
WARMER. IT IS POSSIBLE THE EXCESSIVE HEAT WARNING MAY NEED TO BE
EXTENDED IF TEMPERATURES REMAIN ON THE WARMER ON SUNDAY.

STRATUS WILL EVENTUALLY FILL IN ACROSS INTERIOR WRN WA MONDAY
MORNING AS SHOWERS END ACROSS THE AREA. THIS SHOULD FINALLY MODERATE
HIGH TEMPERATURES DOWN 5-10 DEGREES. THE UPPER TROUGH AXIS LIFTS NE
OF THE AREA DURING THE DAY WITH DRY WEATHER EXPECTED BY AFTERNOON.

.LONG TERM...MODELS ARE IN GOOD AGREEMENT THAT THE UPPER RIDGE
BUILDS STRONGER ON TUESDAY AND PERSISTS THROUGH THE END OF NEXT
WEEK. THIS WILL ALLOW FOR A GRADUAL WARMING TREND AND PERSISTENT DRY
CONDITIONS. HIGH TEMPERATURES ARE EXPECTED TO REMAIN WELL ABOVE
AVERAGE THROUGH THE WEEK. SOME MODELS ARE SUGGESTING ANOTHER BOUT OF
EXCESSIVELY HOT WEATHER IS POSSIBLE TOWARD THE FORTH OF JULY HOLIDAY
WEEKEND. FORECASTS SHOULD BE MONITORED GIVEN THE DRY CONDITIONS AND
ELEVATED FIRE POTENTIAL.  MERCER

&&

.CLIMATE...THE FOLLOWING ARE THE RECORD AND FORECAST HIGH
TEMPERATURES FOR SELECT SITES ON SATURDAY JUNE 27 2015...

LOCATION    RECORD HIGH            FORECAST HIGH

SEA-TAC     88 DEGREES IN 2000     91
OLYMPIA     91 DEGREES IN 2000     94
EVERETT     84 DEGREES IN 2000     85
BELLINGHAM  82 DEGREES IN 2000     84

IN ADDITION...THE RECORD FOR THE ENTIRE MONTH OF JUNE IN TERMS OF
AVERAGE HIGH TEMPERATURES AT SEA-TAC IS 75.8 DEGREES SET IN 1992.
WITH MOST OF JUNE ALREADY HAVING ABOVE NORMAL HIGH TEMPS...WE ARE ON
TRACK TO SHATTER THIS RECORD WITH THE ANTICIPATED HEAT WAVE OVER THE
NEXT FEW DAYS. MERCER

&&

.AVIATION...AN UPPER RIDGE CENTERED FROM WESTERN ALBERTA INTO THE
THE DESERT SOUTHWEST WILL BUILD NORTHWARD THROUGH SATURDAY NIGHT.
SOUTHWEST FLOW ALOFT WILL BECOME SOUTHERLY ON SATURDAY. AT THE
SURFACE...EXPECT LOW LEVEL NORTHERLY FLOW IN THE INTERIOR VALLEYS
WITH NORTHWESTERLY FLOW ALONG THE COAST AND THROUGH THE STRAIT OF
JUAN DE FUCA. THE AIR MASS WILL BE STABLE THROUGH MIDDAY SATURDAY
THEN BECOME UNSTABLE LATE SATURDAY AFTERNOON INTO SATURDAY NIGHT AS
MID AND UPPER LEVEL MOISTURE PUSHES INTO THE AREA FROM THE SOUTH.

LOW STRATUS AND FOG OVER THE COASTAL WATERS AND IN THE WESTERN
STRAIT OF JUAN DE FUCA WILL PUSH INTO THE COASTAL ZONES AND EASTWARD
THROUGH THE STRAIT OF JUAN DE FUCA TO AROUND THE EAST ENTRANCE OF
THE STRAIT OVERNIGHT. EXPECT STRATUS TO BE SIMILAR IN COVERAGE
SATURDAY MORNING AS IT WAS THIS MORNING. GOOD VFR WILL DOMINATE IN
THE INTERIOR AND IN THE MOUNTAINS THROUGH SATURDAY AFTERNOON.
ALBRECHT

KSEA...ONLY A FEW HIGH CIRRUS CLOUDS THROUGH SATURDAY AFTERNOON.
NORTH WINDS 9-13 KT WITH SOME GUSTS TO 20 KT WILL BECOME NNE 10KT
AFTER 03Z. ALBRECHT

&&

.MARINE...A 1024 MB RIDGE IS SITTING OVER THE OFFSHORE WATERS WHILE
A 1011 MB THERMAL LOW SITS OVER THE BASINS OF EASTERN WASHINGTON.
WEAK THERMAL TROUGHING EXTENDS FROM THE OLYMPICS SOUTHEASTWARD INTO
THE SOUTH WASHINGTON CASCADES. THE PATTERN WILL RESULT IN SMALL
CRAFT ADVISORY NORTHWEST FLOW OVER THE COASTAL WATERS
TONIGHT...THROUGH THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA
THROUGH THIS EVENING...AND SMALL CRAFT ADVISORY NORTHERLY FLOW THIS
EVENING IN PUGET SOUND AND HOOD CANAL. WHILE LITTLE CHANGE IN THE
PATTERN IS EXPECTED SATURDAY AFTERNOON THROUGH SATURDAY
NIGHT...PRESSURE GRADIENTS ARE EXPECTED TO RELAX SOMEWHAT.

A WEAK TO MODERATE SOUTHWESTERLY MARINE PUSH IS EXPECTED TO DEVELOP
SUNDAY AND CONTINUE INTO MONDAY OR EARLY TUESDAY. THIS WILL RESULT
IN A TURN OF THE WIND TO A MORE WEST TO SOUTHWEST DIRECTION AT
LIGHTER WIND SPEEDS. THE EXCEPTION WILL BE IN THE STRAIT OF JUAN DE
FUCA WHERE HIGH END SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY
DURING THE LATE AFTERNOON THROUGH OVERNIGHT HOURS. ALBRECHT

&&

.FIRE WEATHER...WITH A GREATER LIKELIHOOD OF ABUNDANT LIGHTNING
SPREADING OVER MUCH OF THE LOWLANDS OF WESTERN WASHINGTON...WILL
ISSUE A FIRE WEATHER WATCH FOR SATURDAY NIGHT INTO SUNDAY EVENING.
THANKS TO THE DRY CONDITIONS...ANY LIGHTNING ORIENTED FIRE STARTS
HAVE THE POTENTIAL TO GROW RAPIDLY IN THIS CONDUCIVE ATMOSPHERE. THE
DEVIL WILL BE IN THE DETAILS. ANY UPPER LEVEL TRIGGERING MECHANISM
CAN SET OFF THE CONVECTION. NEED TO MONITOR THE DEVELOPING SITUATION
IN NORTHERN CALIFORNIA AND OREGON TONIGHT TO GET A BETTER FEEL FOR
WHAT MAY TRANSLATE FURTHER NORTH SATURDAY.

WILL CONTINUE THE WATCH FOR THE MOUNTAINS GIVEN DEVELOPING HOT AND
UNSTABLE AIR MASS SITUATION. THE NICE THERMAL BELT BETWEEN ABOUT 2K
AND 4K IN THE MOUNTAINS REMAINS ON TRACK.

AS NOTED EARLIER...FUEL CONDITIONS THROUGHOUT WESTERN WASHINGTON -
FROM THE CASCADES TO THE COAST - ARE BEYOND CRITICAL VALUES - QUITE
DRY. SO FOR THE FIRE AND EMERGENCY RESPONSE COMMUNITY...READINESS TO
RESPOND TO ANY FIRE STARTS - LIGHTNING OR FIREWORKS OR OTHER SOURCES
- IS IMPERATIVE. BUEHNER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...FIRE WEATHER WATCH ZONES - ALL FIRE WEATHER ZONES

     EXCESSIVE HEAT WARNING FOR THE GREATER PUGET SOUND REGION AND
     THE SOUTHWEST INTERIOR FRIDAY AFTERNOON THROUGH SATURDAY NIGHT.

PZ...SMALL CRAFT ADVISORY COASTAL WATERS...CENTRAL AND EAST STRAIT
     OF JUAN DE FUCA...AND PUGET SOUND AND HOOD CANAL.

&&

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THIS FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML



































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