Lightning Strike in Washington, August 5, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
215 PM PDT MON AUG 5 2002

.SYNOPSIS...AN UPPER LEVEL LOW OVER SOUTHWEST WASHINGTON WILL LIFT
SLOWLY NORTHEAST INTO THE CENTRAL CASCADES BY EARLY TUESDAY...THEN
SHIFT EAST INTO IDAHO TUESDAY NIGHT. SCATTERED SHOWERS AND A POSSIBLE
THUNDERSTORM WILL ACCOMPANY THIS UPPER LOW. SURFACE HIGH PRESSURE AND
NORTHERLY FLOW ALOFT WILL BRING GRADUAL WARMING AND DRYING WEDNESDAY
THROUGH THE END OF THE WEEK.

.DISCUSSION...
HIGH AMPLITUDE PATTERN CONTINUES TODAY WITH RIDGING 145W AND IN THE
CENTRAL US...AND TROUGHING ALONG THE IMMEDIATE W COAST. THE PAC NW
561 DAM H5 UPPER LOW WILL WOBBLE NE FROM SW WA THIS AFTN TO KSMP AM
TUE AND EWD TO KCOE LATE TUE NIGHT AS WK IMPULSES ROTATE AROUND THE
SYS. AMS UNDER THE UPPER LOW IS MOIST/UNSTBL WITH 12Z KUIL LI OF M3
AND H5 TEMPS OF M22C UNDER THE LOW. SUFFICIENT INSTABILITY GIVES AMS
SHRA AND ISOLD TSRA TONIGHT. LESS CAPE TUE RESULTS IN SCT SHRA
LOWLANDS AND SCT SHRA WITH ISOLD TSRA OVR THE CASCDS. WED SEES
IMPROVEMENT AS H5 HGHTS RISE WITH THE LOW DEPARTING TO THE E...THOUGH
A 20 POP OVR THE CASCDS SEEMS PRUDENT WITH CONTINUED CYCLONIC FLOW
AND SOME AFTN INSTABILITY. MARINE CLOUDS WILL GRDLY SPREAD INLD FROM
THE PAC WED AS THE AMS STABILIZES AND FLOW IS MORE ONSHR. RIDGING OVR
SW BC GIVES DRY NLY FLOW AND WARMING TO SEASONABLE TEMPS THU.

.EXTENDED...12Z AVN AND ITS EXTENSION USED FOR EXTENDED PACKAGE. IT
SHOWS HIGH HGHTS AND ZONAL FLOW THU/FRI TIME FRAME WILL AMPLIFY ONCE
AGAIN NEXT WEEKEND AS A SHORTWAVE TROF DROPS FROM THE NE GLFAK INTO
THE NRN INTERMOUNTAIN STATES. THIS SHORTWAVE TROF INCREASES THE DEPTH
OF THE MARINE LAYER W OF THE CASCDS OVR THE WEEKEND AND GIVES A
CHANCE OF SHOWERS OR THUNDERSTORMS TO THE N CASCDS AS IT DRIVES SE.
MON IS UP IN THE AIR AS THE 00Z MRF SHOWS HI AMP H5 RIDGING AND
THERMALLY FORCED SFC TROF NWD INTO W WA MON. THE 12Z AVN SHOWS NW
FLOW ALF WITH DEPRESSED SFC THERMAL TROUGHING OVR OREGON. IF SYSTEMS
NEAR 170W BY LATE IN THE WEEKEND DEVELOP MORE THAN THE GLOBAL MODELS
SUGGEST...WILL LIKELY SEE AMPLIFIED RIDING ALONG 150W AND MORE
TROUGHING ALONG THE W COAST THAN MODELS SHOW. AT THIS TIME WILL STAY
WITH THE COMPROMISE 12Z AVN FOR SEASONABLY WARM AND DRY CONDITIONS.

UIL 321- SEA 5311 OLM 5311  ALBRECHT

.SEW...NONE.
.KATX...VCP21/CSR32...OPERATIONAL.