Severe Thunderstorm Warning 3, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
350 PM PDT SAT JUL 25 2009

.SYNOPSIS...AN UPPER LEVEL LOW OVER EASTERN WASHINGTON WILL MAINTAIN
A THREAT OF THUNDERSTORMS ACROSS MOST OF WESTERN WASHINGTON THROUGH
SUNDAY.  THEN TEMPERATURES WILL CONTINUE TO RISE ACROSS THE REGION
THROUGH WEDNESDAY AS A STRONG UPPER LEVEL RIDGE BUILDS OVER THE
PACIFIC NORTHWEST.  THIS WILL RESULT IN TEMPERATURES NEAR RECORD
LEVELS MONDAY THROUGH THURSDAY.  AN UPPER LEVEL LOW WILL BEGIN TO
APPROACH THE WEST COAST LATE IN THE WEEK ALLOWING TEMPERATURES TO
GRADUALLY COOL BUT BRING A THREAT OF THUNDERSTORMS TO THE MOUNTAINS
NEXT WEEKEND.

&&

.SHORT TERM...PROBLEM OF THE DAY IS THE THUNDERSTORM THREAT OVER THE
NEXT 24-36 HOURS.  THE SHORTWAVE THAT WAS EXITING NORTHERN IDAHO
THIS MORNING IS NOW MOVING WEST ACROSS SOUTHERN BRITISH COLUMBIA AND
THUNDERSTORMS ARE ERUPTING IN WITH AND AHEAD OF IT AND ARE RIGHT ON
OUR BORDER.  AS THIS CONTINUES TO SWING AROUND THE LOW IT WILL MOVE
SW ACROSS WESTERN WASHINGTON TONIGHT AND THUNDERSTORMS WILL MOVE IN
AHEAD OF IT.  CASCADES ARE A GIVEN AT THIS POINT AND HAVE LIKELY
POPS THERE.  NW INTERIOR LOOKS GOOD AS WELL AND SHOULD HAVE SOME
SPREAD INTO THE LOW LANDS OVERNIGHT.  LAST NIGHT WE HAD ONE SEVERE
THUNDERSTORM NEAR BAKER LAKE AND WILL NEED TO KEEP AN EYE ON THINGS
THIS EVENING AS WELL AS WE HAVE PLENTY OF INSTABILITY AND A FORCING
MECHANISM.

WITH WARM AIR MASS OVERHEAD...RELATIVELY HIGH DEWPOINTS AND SOME
CLOUDS MOVING IN WE WILL HAVE ANOTHER MILD NIGHT TONIGHT AS COOLING
WILL BE SLOW.  LOWS WILL RANGE FROM THE MID 50S IN THE COOLEST
LOCATIONS TO LOWER 60S METRO AREA.

SUNDAY...WE WILL LIKELY HAVE SOME LINGERING THUNDERSTORMS OVER THE
EASTERN HALF OF THE AREA AND POSSIBLY OVER THE OLYMPICS AS THE UPPER
LEVEL LOW WILL BE NEAR ENOUGH TO CAUSE PROBLEMS.  JUST NOT THE
THREAT WE WILL HAVE TONIGHT.  WITH THE SUN COMING OUT AND A WARM
START TO THE DAY...TEMPERATURES SHOULD CREEP UPWARD A FEW MORE
DEGREES AND WE SHOULD START TO SEE OUR FIRST 90 IN THE HOTTEST AREAS
OF THE LOWLANDS...MAINLY SW INTERIOR.

FOR MONDAY...UPPER LOW MOVES WELL EAST OF THE REGION AND UPPER LEVEL
RIDGE BUILDS OVERHEAD.  MEANWHILE A SURFACE TROUGH WILL DEVELOP
ALONG THE WEST COAST ALL THE WAY UP THROUGH BRITISH COLUMBIA.  THIS
IS THE SETUP THAT WILL BRING ABOUT THE EXPECTED HOT WEATHER OF THE
COMING WEEK.  ON MONDAY...TEMPERATURES WILL BE IN THE 80S COOLER
AREAS NEAR THE WATER TO MID 90S INLAND.  AFTER ANOTHER VERY MILD
NIGHT...TUESDAY SHOULD BE A FEW DEGREES WARMER AS THE AIR MASS
CONTINUES TO HEAT UP.  SO BREAK OUT THE ICED TEA AND GET READY.

THIS BRINGS UP A COUPLE ADDITIONAL POINTS THAT NEED TO BE CONSIDERED
OVER THE NEXT FEW DAYS...HEAT ADVISORY AND AIR STAGNATION PROBLEMS.
AS FAR AS THE HEAT ADVISORY GOES...WE ARE NOT BEING FLAGGED IN OUR
GUIDANCE AS NEEDING ONE JUST YET AND THAT MAY BE DUE TO THE FACT
THAT WE ARE IN JULY AND HAVE ALREADY HAD A WARM SPELL AND SHOULD BE
USED TO IT.  SO WILL LEAVE THAT ALONE FOR NOW.  THE AIR MASS WILL
BECOME STAGNANT AS LITTLE FLOW WILL OCCUR THROUGH THE REGION TO
CLEAR IT OUT.  THEN ADD HIGH TEMPERATURES AND STRONG SUNSHINE AND
ELEVATED POLLUTION PROBLEMS COULD RESULT.  CERNIGLIA

EACH DAY WILL BE SEVERAL DEGREES HOTTER THAN THE PREVIOUS THROUGH
WEDNESDAY AS WE NEAR RECORD HIGH TEMPERATURES.  AT ITS HEIGHT...THIS
COULD END UP BEING THE WARMEST WE HAVE SEEN IT SINCE 2007 WHEN IT
HIT 98 AT THE SEATAC AIRPORT.

.LONG TERM...THE PATTERN WILL CONTINUE TO HOLD THROUGH WEDNESDAY
WITH WEDNESDAY LOOKING TO BE THE HOTTEST DAY FOR MOST OF THE AREA.
THIS COULD END UP BEING THE WARMEST WE HAVE SEEN IT SINCE 2007 WHEN
IT HIT 98 AT THE SEATAC AIRPORT AS WE ARE FORECASTING MID TO UPPER
90S IN MANY AREAS.  FOR THURSDAY THE RIDGE BEGINS TO WEAKEN SOME
WITH THE LOW LEVEL TROUGH MOVING TO THE INTERIOR WHICH WILL ALLOW
COOLER TEMPERATURES FOR THE COAST AND SLIGHTLY COOLER FURTHER
INLAND...STILL PLENTY OF 90S THOUGH.

BEYOND THAT...THERE IS A QUESTION OF TIMING.  AN UPPER LOW IS
EXPECTED TO APPROACH THE WEST COAST AT THE END OF THE WEEK AND THE
MODELS ARE IN AGREEMENT WITH THAT BASIC IDEA.  QUESTION IS TIMING
WITH THE GFS EARLIER AND THE ECMWF LATER.  THE CANADIAN LOOKS TO
LEAN LATER AS WELL.  SO FOR THIS FORECAST I HELD ONTO WARMER
TEMPERATURES A BIT LONGER THAN WHAT THE GFS WOULD SUGGEST.  THE GFS
WOULD SLAM COOLER TEMPERATURES IN HERE SATURDAY WHICH IS QUITE
COMMON AFTER A HOT SPELL LIKE THIS WHILE THE ECMWF IS SLOWER AND
MORE GRADUAL.  IT WILL LIKELY BE A RAPID COOL DOWN...JUST NOT SURE
IF IT WILL BE SATURDAY OR SUNDAY.  THE OTHER PROBLEM WITH THE UPPER
LOW IS THAT IT RENEWS THE THREAT OF THUNDERSTORMS FOR THE
MOUNTAINS.  STAY TUNED.  CERNIGLIA

&&

.AVIATION...STNRY UPPER LOW OVR ERN WA W/ UNSTABLE AIR MASS OVER WA.
EXPECTING SCATTERED STORMS TO MOVE DOWN OVER WRN WA AGAIN IN THE NE
FLOW...MOST OVER THE NRN CASCADES AGAIN THIS EVENING. A CHANCE OF
STORMS FOR THE LOWLANDS AS WELL...MORE ISOLATED. LOW MARINE STRATUS
OR FOG FOR THE COAST...SPREADING ONLY A LITTLE INLAND
OVERNIGHT...POSSIBLY REACHING SHELTON AND PARTWAY DOWN THE STRAIT.

KSEA...MID LEVEL CLOUDS INCREASE W/ A CHANCE OF TSTMS TNGT...MOVING
OFF THE CASCADES ARND SKAGIT COUNTY. THE STORMS MOVED AT ABOUT 20
MPH YESTERDAY...AND ALTHOUGH THEY DID NOT QUITE REACH THE METRO AREA
THE AIR MASS IS MOISTURE TODAY HERE AND ESPECIALLY UPSTREAM SO THERE
IS A BETTER CHANCE TNGT. A VCTS PROBABLY AGAIN FOR THE TAF...THEN
UPDATING AS NEEDED. NORMAL SUMMER DIURNAL WINDS...NLY IN THE
AFTERNOON AND EVENING WILL BECOME MORE VARIABLE IF STORMS APPROACH.
19

&&

.MARINE...LIGHT GRADIENTS...JUST A 15-25KT WLY PUSH IN THE STRAIT
THIS EVENING...AND LESS SUN-WED AS THERMAL LOW PRES SETS UP OVER THE
REGION.

&&

.FIRE WEATHER...VERY CRITICAL FIRE WEATHER SETUP OVER THE NEXT FEW
DAYS. THUNDERSTORMS ARE ALREADY FORMING TO THE NORTHEAST OVER
SOUTHERN B.C.. THESE WILL SWING SOUTHWEST FOR THE REST OF THIS
AFTERNOON AND TONIGHT...BRINGING NUMEROUS CLOUD-TO-GROUND LIGHTNING
STRIKES TO SOME AREAS. HIGHEST LIGHTNING RISK WILL BE TO THE
NORTHEAST OVER THE NORTH CASCADES AND NORTH INTERIOR...TAPERING OFF
AS YOU MOVE SOUTHWEST OF THE OLYMPIC MTNS. GIVEN FUEL DRYNESS...THIS
WILL EASILY IGNITE NEW FIRES. WITH A PROLONGED HEAT WAVE STARTING
OVER THE NEXT TWO DAYS...SLEEPERS AND LIGHTNING HOLDOVERS WILL HAVE
A MUCH GREATER CHANCE THAN USUAL OF FLARING UP AND COMING TO LIFE.
THE LOW-LEVEL AIR MASS WILL ALSO BECOME UNSTABLE FROM TUESDAY
THROUGH THURSDAY AS A THERMAL PRESSURE TROUGH BECOMES ESTABLISHED
OVER THE WRN WA INTERIOR. THIS WILL FURTHER ENHANCE THE BURNING
ENVIRONMENT FOR ANY NEW STARTS.         HANER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...RED FLAG WARNING UNTIL 5 AM FOR SCATTERED AND ABUNDANT
     LIGHTNING IN FIRE WEATHER ZONES 653 654 656 657 658 659 661 AND
     662.
PZ...SMALL CRAFT ADVISORY THIS EVENING CENTRAL AND EASTERN STRAIT.

WWW.WEATHER.GOV/SEATTLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SEATTLE WA
1146 AM PDT SAT JUL 25 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0715 PM     TSTM WND DMG     10 N CONCRETE           48.68N 121.75W
07/24/2009                   WHATCOM            WA   OTHER FEDERAL

            COUPLE OF DOZEN TREES...SOME VERY LARGE OLD GROWTH...WERE
            BLOWN DOWN ACROSS SEVERAL AREAS OF THE BAKER LAKE
            HIGHWAY. PEOPLE...ROUGHLY 50 CARS...WERE TRAPPED BEHIND
            UNTIL THE ROAD WAS CLEARED.

&&

CERNIGLIA

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE SEATTLE WA
429 PM PDT SAT JUL 25 2009

WAZ518-260015-
WEST SLOPES NORTHERN CASCADES AND PASSES-
429 PM PDT SAT JUL 25 2009

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN WHATCOM AND NORTHEAST
SKAGIT COUNTIES UNTIL 515 PM PDT...

AT 424 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS NORTHEAST OF MARBLEMOUNT UP TO ROSS
LAKE...MOVING SOUTHWEST AT 20 MPH.

HAIL UP TO THE SIZE OF NICKELS AND WIND GUSTS TO 50 MPH ARE LIKELY
WITH THIS STORM...AS WELL AS FREQUENT DANGEROUS LIGHTNING.

LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...DIABLO AND NEWHALEM.

CERNIGLIA