Lightning Strike in Washington, August 11, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 PM PDT MON AUG 11 2014

.SYNOPSIS...AN UPPER LEVEL LOW PRESSURE SYSTEM OFF THE OREGON COAST
WILL MOVE EAST TO NORTHEAST TONIGHT THROUGH WEDNESDAY. A
VERY WARM AND UNSTABLE AIR MASS ALOFT COMBINED WITH THIS APPROACHING
UPPER LEVEL SYSTEM WILL GIVE A CHANCE OF THUNDERSTORMS TO THE AREA
TONIGHT INTO TUESDAY NIGHT. TEMPERATURES WILL COOL ABOUT 15 DEGREES
ON TUESDAY AND WILL COOL FURTHER ON WEDNESDAY AS A THREAT OF SHOWERS
CONTINUES. CONDITIONS WILL DRY TOWARD THE END OF THE WEEK WITH
TEMPERATURES NEAR NORMAL FOR MID AUGUST.

&&

.SHORT TERM...IT WAS A VERY HOT DAY ACROSS CENTRAL AND SOUTHERN
PORTIONS OF THE WASHINGTON INTERIOR TODAY. AREAS FROM EVERETT
SOUTHWARD REACHED THE LOWER TO MID 90S...AND TEMPERATURES EXCEEDED
100 DEGREES AT SHELTON AND CHEHALIS IN THE SOUTH INTERIOR. THE AIR
MASS IS NOW QUICKLY DESTABILIZING THIS EVENING AS AN UPPER LEVEL LOW
OFF THE CALIFORNIA COAST...AND ANOTHER UPPER TROUGH THAT IS CLOSING
OFF INTO A NEW UPPER LOW OFF THE OREGON COAST...COMBINE TO SHIFT
MONSOONAL MOISTURE -THAT ORIGINATED OVER THE DESERT SOUTHWEST AND
MOVED INTO CENTRAL OREGON- NORTHWESTWARD INTO WESTERN WASHINGTON.

AT 845 PM TWO THUNDERSTORMS ARE SEEN OVER KING COUNTY. A PERSISTENT
AND RATHER STRONG TSTM THAT EARLIER HAD 60 DBZ RETURNS AND 0.25 INCH
HAIL ORIGINATED S OF MT RAINIER AND IS MOVING TOWARD THE BELLEVUE
AREA. A SECOND CELL IS FORMING JUST E OF SEATAC AIRPORT AND THE
RADAR IS STARTING TO LIGHT UP FROM BREMERTON SOUTHWARD THROUGH
OLYMPIA. THE EVENING FORECAST WAS UPDATED TO SHIFT THE TSTM CHANCES
NORTHWARD FASTER THIS EVENING...BUT IT APPEARS THAT ANOTHER UPDATE
TO SHIFT TSTM CHANCES NWD TO THE CANADIAN BORDER MAY BE ON TAP
SHORTLY IF THE CELLS KEEP DEVELOPING. THE COASTAL ZONES WERE UPDATED
FOR AREAS OF FOG OVERNIGHT...AS SEEN ON WEB CAMERAS THIS EVENING.

NAM BUFR SOUNDINGS FOR THE SEATAC AREA SHOWS LIFTED INDICES GETTING
TO -7.6 BY ABOUT MIDNIGHT WITH CAPE VALUES REACHING AN IMPRESSIVE
2600 J/KG. CIN VALUES OF -78 J/KG MEAN THAT THE ACTIVITY WILL BE
ELEVATED WITH A STABILIZING BOUNDARY LAYER DOING NOTHING TO STOP THE
ACTIVITY.

OCCASIONAL TSTM ACTIVITY WILL LIKELY CONTINUE INTO TUE EVENING.
CLOUDS WILL LIKELY KEEP TEMPERATURES IN THE INTERIOR ONLY AROUND
80...WHILE A MARINE LAYER ALONG THE COAST KEEPS TEMPERATURES IN THE
60S THERE.

LOW LEVEL ONSHORE FLOW WILL INCREASE TUE INTO TUE NIGHT RESULTING IN
MORE COOLING. A DEFORMATION BAND WRAPPING AROUND THE UPPER LOW THAT
MOVES BY TO THE SOUTH MAY BRING RATHER GOOD PRECIPITATION AMOUNTS TO
PORTIONS OF THE FORECAST AREA TUE NIGHT INTO WED MORNING. ALBRECHT

.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...THE UPPER LOW
WILL SHIFT SLOWLY INLAND WED NITE AND THU...THEN MOVES TO WRN MT
LATE IN THE WEEK. THE SHOWER THREAT WILL SHIFT EAST WITH THE LOW AND
WRN WA SHOULD HAVE DRY WEATHER LATE IN THE WEEK THROUGH NEXT
WEEKEND. IT IS NOT YET CLEAR WHETHER MUCH OF A RIDGE WILL
REBUILD...THE 12Z RUNS SUGGEST A BIT OF AN UPPER TROUGH SETTLING
INTO THE REGION EARLY NEXT WEEK...BUT UPPER HEIGHTS ARE STILL WELL
IN THE 570S AND IT WOULD STILL LIKELY BE MOSTLY SUNNY WITH TEMPS IN
THE MID AND UPPER 70S IN THE INTERIOR OF WRN WA.

&&

.FIRE WEATHER...FROM THE AFTERNOON FIRE WEATHER
DISCUSSION...THUNDERSTORM ACTIVITY OVER OREGON YESTERDAY AND
STARTING UP AGAIN TODAY LENDS EVEN GREATER CONFIDENCE THAT WESTERN
WASHINGTON WILL BE LOOKING AT A SIGNIFICANT EVENT STARTING UP THIS
EVENING. THAT SAID...HAVE UPGRADED ALL PREVIOUS FIRE WEATHER WATCHES
TO RED FLAG WARNINGS. HAINES INDICES...HIGH LEVEL AND MID
LEVEL...LEND THEMSELVES WELL TO DRY AND UNSTABLE CONDITIONS FOR FIRE
ZONE 662 LATE THIS MORNING INTO THE AFTERNOON...WITH LOW END 5S ON
THE HIGH LEVEL AND 6S ON THE MID. THIS LINES UP WITH FEEDBACK FROM
IMETS OUT IN THE FIELD IN THAT AREA. THIS WILL TRANSITION TO A RED
FLAG FOR LIGHTNING AS WE PROGRESS INTO THIS EVENING...ALONG WITH
MUCH OF WESTERN WASHINGTON JOINING IN. THUNDERSTORMS REMAIN IN THE
FORECAST FOR MUCH OF TUESDAY...AND WITH CONDITIONS GRADUALLY
MOISTENING...THE RISK FOR FIRE STARTS WILL DIMINISH THEN END BY
TUESDAY EVENING AS THUNDERSTORMS TRANSITION TO SHOWERS. THE QUESTION
MARK STILL REMAINS ZONE 662...AS STILL NOT SURE HOW LONG THUNDER
WILL LINGER ON EAST SIDE OF THE CASCADES. WILL KEEP CURRENT TIMING
AND LIKELY LEAVE THE DECISION AS TO WHETHER OR NOT TO EXTEND THE END
TIME FOR THEIR WARNING FOR FUTURE SHIFTS.

&&

.AVIATION...AN UPPER RIDGE WILL REMAIN OVER THE REGION THRU TUE
MORNING. CONTD SLY FLOW ALOFT. GRADUALLY INCREASING LOW LEVEL
ONSHORE OR SLY FLOW. THE AIR MASS WAS BECMG MORE UNSTABLE OVER THE
INTERIOR...RESULTING IN ISOLD TSTMS THIS EVENING. THE TSTMS WILL
PROBABLY INCREASE IN COVERAGE OVERNIGHT.

MEANWHILE...ANTICIPATE VFR CONDITIONS OVERNIGHT ACROSS MUCH OF THE
AREA. THE EXCEPTION WILL BE THE COAST WHERE THERE WILL BE AREAS OF
VSBYS AND CIGS AOB 1SM AND 500 FT...RESPECTIVELY.

KSEA...TAF WAS AMENDED TO INCLUDE TSTMS IN THE VICINITY OF THE
AIRPORT. THE TSTMS WERE MOVING TO THE NW...THUS IT IS LIKELY THAT A
TSTM WILL MOVE ACROSS THE TERMINAL BETWEEN 0400 AND 0600 UTC. THE
THREAT OF TSTMS WILL PERSIST ALL NIGHT....POSSIBLY INTO TUE MORNING.

&&

.MARINE...
HIGHER PRES OFF THE OREGON COAST AND LOWER PRES OVER BRITISH
COLUMBIA WILL RESULT IN LIGHT ONSHORE FLOW TONIGHT. ONSHORE FLOW
WILL STRENGTHEN ON TUE IN THE WAKE OF A WEAK COLD FRONT THAT WILL
MOVE ACROSS THE AREA LATE IN THE DAY. MODERATE TO STRONG ONSHORE
FLOW WILL THEN PERSIST THROUGH FRI.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...RED FLAG WARNING ALL BUT COASTAL AREAS.
PZ...SMALL CRAFT ADVISORY IN EFFECT UNTIL 2 AM TUESDAY FOR THE
     CENTRAL STRAIT OF JUAN DE FUCA.

&&

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