Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 261619
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM 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 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 WARMER TEMPERATURES IS POSSIBLE LATER NEXT WEEK.

&&

.SHORT TERM...SKIES ARE MOSTLY CLEAR ACROSS WRN WA THIS MORNING AND
TEMPERATURES ARE RUNNING ANYWHERE FROM +2 TO +7 DEGREES WARMER OVER
YESTERDAY. A 5950M UPPER LEVEL HIGH IS CENTERED OVER THE GREAT BASIN
EXTENDING NWD OVER THE PAC NW. THE RIDGE WILL MAINTAIN A WARMING AIR
MASS OVER OUR REGION THROUGH THE WEEKEND BUT PERIODS OF CLOUDS AND
CHANGES IN THE SURFACE FLOW PATTERN WILL RESULT IN LARGE VARIATIONS
IN HIGH TEMPERATURES EACH DAY ACROSS WRN WA.

THERMALLY INDUCED LOW PRESSURE WILL REMAIN CENTERED OVER WRN OREGON
INTO ERN WA TODAY GIVING NWLY ONSHORE ALONG THE COAST AND NLY FLOW
INLAND. THE BREEZY NLY WINDS OVER PUGET SOUND THIS AFTERNOON MAY
HINDER POTENTIAL HIGHS NEAR THE WATER LIKE AT SEA-TAC. HOWEVER...THE
STRONG RIDGE...CLEAR SKIES...AND WARMER START TO THE DAY SHOULD
STILL TRANSLATE WARMER TEMPERATURES TODAY. HIGHS NEAR THE WATER MAY
TREND A COUPLE DEGREES WARMER BUT PERHAPS +5 DEGREES WARMER FURTHER
INLAND. EXPECT WIDESPREAD 80S WITH SOME LOW 90S POSSIBLE AROUND THE
E PUGET SOUND LOWLANDS AND SW INTERIOR. IT WILL ONLY REACH THE 70S
ALONG THE COAST AND STRAIT WHERE ONSHORE FLOW IS STRONGER.

HIGH PRESSURE SHIFTS A BIT FURTHER W TONIGHT ALLOWING THE THERMALLY
INDUCED TROUGH TO BROADEN OVER WA. THIS WILL MAINTAIN WARMER
NIGHTTIME TEMPERATURES...ONLY DIPPING INTO THE 60S IN THE URBAN
AREAS SATURDAY MORNING. MODELS SHOW ABOUT +4C WARMING AT 850 MB AND
THE NLY SURFACE FLOW WILL BE WEAKER SATURDAY AFTERNOON THAN TODAY.
THEREFORE...SATURDAY STILL LOOKS ON TRACK TO BE HOT WITH RECORD
BREAKING TEMPERATURES EXPECTED AT SOME LOCATIONS. A SHORT WAVE OFF
THE CA COAST WILL BE LIFTING NWD ON SATURDAY SPREADING MID/HIGH
LEVEL MOISTURE INTO WA DURING THE AFTERNOON BUT THIS WILL LIKELY
ARRIVE TOO LATE AND PROBABLY NOT BE INITIALLY THICK ENOUGH TO AFFECT
HIGH TEMPERATURES.

MOISTURE IN THE 700-500 MB LAYER CONTINUES TO INCREASE LATE SATURDAY
AFTERNOON/SATURDAY NIGHT AS THE FLOW ALOFT TURNS MORE SLY. IT IS
STILL NOT CLEAR IF THIS INITIAL SURGE OF MOISTURE WILL BE DEEP
ENOUGH TO TRIGGER ELEVATED CONVECTION BUT THE POSSIBILITY IS THERE.
THE CURRENT FORECAST LOOKS GOOD WITH JUST A CHANCE OF LATE DAY
THUNDERSTORMS OVER THE MOUNTAINS SATURDAY...THEN POSSIBLY EXPANDING
INTO THE LOWLANDS SATURDAY NIGHT. THIS IS A DRY THUNDERSTORM PATTERN
WITH THE ASSOCIATED LIGHTNING INCREASING THE FIRE DANGER OVER THE
AREA. THE LOW CHANCE POPS LOOK GOOD GIVEN THE DRY LOW LEVELS AND
DIFFICULTY MEASURING EVEN IF CONVECTION DOES DEVELOP. SOME TIMING
ADJUSTMENTS MIGHT BE NEEDED BUT WILL WAIT FOR ALL THE 12Z GUIDANCE
TO ARRIVE.

THE PRIMARY SHORT WAVE FEATURE OFF THE CA COAST LIFTS NWD ON SUNDAY
WITH THE TROUGH AXIS OVER WA BY MONDAY MORNING. AHEAD OF THE TROUGH
AXIS...MOISTURE WILL DEEPEN IN THE MID/UPPER LEVELS AND THERE WILL
BE SOME ADDED DYNAMICS FROM VORT MAX FEATURES EMBEDDED IN THE SLY
FLOW. SUNDAY WILL HAVE THE BEST CHANCE OF THUNDERSTORMS OVER WRN WA
BUT MODELS TIME-HEIGHT SECTIONS INDICATE THE LOW LEVELS WILL NOT
MOISTEN UP UNTIL SUNDAY EVENING. IN ADDITION...MESO MODELS SHOW THE
MAIN PUSH OF MARINE AIR MOVES NWD ALONG THE COAST AND PENETRATES THE
SW INTERIOR BUT MAY NOT QUITE REACH CENTRAL PUGET SOUND NWD. THIS
SCENARIO IMPLIES HIGH TEMPERATURES MAY BE A BIT COOLER BUT IT WILL
WILL FEEL MUGGY WITH THE ADDED HUMIDITY. THE LARGEST DROP IN
TEMPERATURES WILL OCCUR ALONG THE COAST AND THE SW INTERIOR WHERE
THE FLOW TURNS ONSHORE SOONER IN THE DAY.

THE HEAT WARNING/ADVISORY FOR PARTS OF INTERIOR WRN WA REMAINS IN
EFFECT THROUGH SUNDAY MORNING FOR THE COMBINATION OF HOT DAYTIME
TEMPERATURES....WARM OVERNIGHT LOWS...AND INCREASED HUMIDITY BY
SUNDAY. THIS MAY NEED TO BE EXTENDED THROUGH SUNDAY NIGHT IF NEW
MODELS TODAY CONTINUE TO TREND WARMER FOR SUNDAY. MERCER


.LONG TERM...NO UPDATES FROM PREVIOUS DISCUSSION...A MORE
SIGNIFICANT UPPER LEVEL SHORTWAVE TROUGH MOVES NE ACROSS THE AREA
MONDAY MORNING...WITH DRIER AND MORE STABLE SW FLOW ALOFT MOVING
OVER W WA BEHIND IT. COOLING ALOFT WITH THE TROUGH COMBINED WITH
INCREASING ONSHORE FLOW SHOULD END THE HOT SPELL. THE AIR MASS WILL
STILL BE WARMER THAN NORMAL SO THE WARMEST MAX TEMPERATURES WILL
STILL REACH THE LOWER TO MID 80S. THE UPPER LEVEL RIDGE OVER THE
REGION WILL GRADUALLY STRENGTHEN AGAIN FROM MIDWEEK ONWARD...AND LOW
LEVEL ONSHORE FLOW BEGINS TO WEAKEN. TEMPERATURES WILL RISE AGAIN
BUT WITH THE MODELS SHOWING MORE INCONSISTENCY IT IS NOT CERTAIN
JUST HOW HOT IT WILL GET. IT DOES LOOK LIKE DAILY MAX TEMPERATURES
WILL STILL BE IN THE 80S AROUND MUCH OF THE INTERIOR. KAM

&&

.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     92
OLYMPIA     91 DEGREES IN 2000     94
EVERETT     84 DEGREES IN 2000     85
BELLINGHAM  82 DEGREES IN 2000     84
QUILLAYUTE  86 DEGREES IN 2000     85


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
DESERT SOUTHWEST WILL BUILD NORTHWARD TODAY THROUGH SATURDAY.
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.

LOW STRATUS AND FOG OVER THE COASTAL WATERS AND IN THE WESTERN TWO
THIRDS OF THE STRAIT OF JUAN DE FUCA EXTENDS ONSHORE OVER THE
COASTAL ZONES AND INTO THE CHEHALIS GAP TO WEST OF KSHN. THE FOG AND
STRATUS WILL BURN BACK TO THE COASTLINE BY AROUND NOON. PRESSURE
GRADIENTS ARE EXPECTED TO HAVE A WEAKER WESTERLY COMPONENT TONIGHT
THAN THEY WERE ON THURSDAY NIGHT...SO EXPECT THE STRATUS AND FOG TO
NOT PUSH AS FAR INLAND LATE TONIGHT AS THEY DID LAST NIGHT AND THIS
MORNING. ALBRECHT

KSEA...ONLY A FEW HIGH CIRRUS CLOUDS THROUGH MIDDAY SATURDAY. NORTH
WINDS WILL INCREASE TO 9-13 KT MIDDAY AND CONTINUE THROUGH THIS
EVENING. ALBRECHT

&&

.MARINE...A 1025 MB RIDGE IS SITTING OVER THE OFFSHORE WATERS THIS
MORNING WHILE A 1011 MB THERMAL LOW SITS OVER THE BASINS OF EASTERN
WASHINGTON. 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 THIS AFTERNOON AND TONIGHT...THROUGH THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA THIS EVENING...AND SMALL CRAFT ADVISORY
NORTHERLY FLOW LATE THIS AFTERNOON AND TONIGHT IN PUGET SOUND AND
HOOD CANAL. LITTLE CHANGE IN THE PATTERN IS EXPECTED SATURDAY
AFTERNOON THROUGH SATURDAY NIGHT.

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 SOUTHWEST TO SOUTH DIRECTION AT
LIGHTER WIND SPEEDS. THE EXCEPTION WILL BE IN THE STRAIT OF JUAN DE
FUCA WHERE HIGH END SMALL CRAFT ADVISORY CONDITIONS CAN BE EXPECTED
DURING THE LATE AFTERNOON THROUGH OVERNIGHT HOURS. ALBRECHT

&&

.FIRE WEATHER...DEVELOPING HOT AND UNSTABLE AIR MASS SITUATION
REMAINS ON TRACK FOR THE MOUNTAINS STARTING SATURDAY AFTERNOON. FIRE
WEATHER WATCH CONTINUES.

NEXT QUESTION IS WILL THE WATCH NEED TO TRANSLATE TO AT LEAST PART
OF THE WESTERN WASHINGTON LOWLANDS FOR LIGHTNING SATURDAY NIGHT INTO
SUNDAY. LATEST GUIDANCE CONTINUES MAINTAINING A LOW LEVEL
TEMPERATURE INVERSION - QUITE WARM ALOFT - ON THE FORECAST
SOUNDINGS. NICE THERMAL BELT BETWEEN ABOUT 2K AND 4K IN THE
MOUNTAINS. WILL EXAMINE THE LIGHTNING SITUATION FURTHER TODAY.

AS NOTED YESTERDAY...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 652 661 658 AND 659

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

     HEAT ADVISORY FOR HOOD CANAL AND THE LOWER CHEHALIS VALLEY
     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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