Severe Thunderstorm Warning 7, NWS Pendleton, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OREGON
200 PM PDT FRI JUN 18 2004

.SHORT TERM...CONVECTION HAS BEGUN TO FIRE THIS AFTERNOON ACROSS THE
EASTERN PARTS OF THE FORECAST AREA.  AN UPPER LOW PRESSURE SYSTEM
HAS DROPPED DOWN INTO THE PACIFIC NORTHWEST WITH COLDER AIR ALOFT.
THIS HAS CAUSED LAPSE RATES TO INCREASE OVER THE REGION.  THIS
COMBINED WITH LOW LI/S AND HIGH CAPE VALUES HAS ALLOWED THE
DEVELOPMENT OF THUNDERSTORMS.  THE THUNDERSTORMS WILL BE
CONCENTRATED OVER THE EASTERN AND NORTHEAST OREGON MOUNTAINS AS WELL
AS THE SOUTHEAST WASHINGTON MOUNTAINS.  THE UPPER LEVEL LOW PRESSURE
SYSTEM WILL PERSIST INTO SATURDAY WITH CONTINUED UNSTABLE
CONDITIONS.  AS A RESULT WILL PUT MORE SHOWERS AND THUNDERSTORMS IN
THE FORECAST AGAIN FOR SATURDAY AFTERNOON.  DURING THE LATE NIGHT
HOURS THE LOWER ATMOSPHERE WILL STABILIZE DUE TO SURFACE COOLING SO
THUNDERSTORMS WILL BE REDUCED TO MAINLY JUST SHOWERS IN THE LATE
NIGHT AND EARLY MORNING HOURS.  THE ATMOSPHERE WILL NOT BE QUITE AS
UNSTABLE SATURDAY AFTERNOON AS IT IS TODAY SO THE COVERAGE OF
THUNDERSTORM ACTIVITY WILL NOT BE AS GREAT AS TODAY.  ON SUNDAY THE
UPPER LOW WILL OPEN UP INTO A TROUGH AND WEAKEN AS IT SLIDES TO THE
SOUTHEAST.  THERE WILL AGAIN BE SOME LEFT OVER INSTABILITY ON SUNDAY
AFTERNOON SO WILL INCLUDE A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS ONCE AGAIN.  AN UPPER LEVEL RIDGE WILL TRY TO
RE-ESTABLISH ITSELF BY SUNDAY NIGHT OVER THE REGION AND WILL
CONTINUE INTO THE EXTENDED PERIOD. RSC.

.LONG TERM...MONDAY THROUGH FRIDAY...PATTERN WILL BE DOMINATED BY
UPPER RIDGE THROUGH THE EXTENDED PERIOD. EXTENDED MODELS DIFFER
SLIGHTLY ON THE POSITIONING OF THE UPPER LOW OFF THE WEST COAST LATE
NEXT WEEK...WITH THE ECMWF POSITIONING THE LOW FARTHER NORTH THAN
THE GFS/MRF. WITH EITHER SOLUTION THERE IS SOME POTENTIAL FOR THE
RIDGE TO BREAK DOWN ENOUGH FOR AN INFLUX OF MOISTURE AND A CHANCE
FOR AT LEAST ISOLATED THUNDERSTORMS...AFTER ABOUT WEDNESDAY. HAVE
CHOSEN TO MAINTAIN CONTINUITY AND DRY FORECAST FOR NOW BUT SITUATION
WILL NEED TO BE MONITORED WITH TIME. OTHERWISE...A GRADUAL WARMING
TREND IS IN THE OFFING WITH LOWER 90S ANTICIPATED AT THE LOWER
ELEVATIONS BY TUESDAY AFTERNOON. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PENDLETON (AIRPORT) 52 83 52 82 / 10 10 10 10
WALLA WALLA         55 80 55 79 / 10 10 10 10
TRI-CITIES          52 86 52 85 / 10 10 10 10
YAKIMA              52 85 52 84 / 10 10 10 10
&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
&&

88

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PENDLETON OR
515 AM PDT FRI JUN 18 2004

ORZ046-049-050-WAZ025-030-191200-
BLUE MOUNTAINS OF OREGON OR-EAST SLOPES SOUTHERN CASCADES WA-
GRANDE RONDE VALLEY OR-NORTHWEST BLUE MOUNTAINS WA-WALLOWA COUNTY OR-
515 AM PDT FRI JUN 18 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE MOUNTAINS OF NORTHEAST
OREGON AND SOUTHEAST WASHINGTON AS WELL AS THE EAST SLOPES OF THE
SOUTHERN WASHINGTON CASCADES.

.DAY ONE...TODAY AND TONIGHT

A LOW PRESSURE SYSTEM IS CURRENTLY OVER THE PACIFIC NORTHWEST.
ALTHOUGH THERE IS LIMITED MOISTURE WITH THE SYSTEM...THE AIR MASS IS
UNSTABLE.  SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CAN BE
EXPECTED OVER THE MOUNTAINS OF NORTHEAST OREGON AND SOUTHEAST
WASHINGTON.  ISOLATED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED ALONG
THE EAST SLOPES OF THE SOUTHERN WASHINGTON CASCADES.  OCCASIONAL
CLOUD-TO-GROUND LIGHTNING...HAIL...AND WINDS GUSTING TO 50 MPH ARE
POSSIBLE WITH THUNDERSTORMS TODAY AND TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

THE LOW PRESSURE SYSTEM WILL REMAIN PARKED OVER THE PACIFIC NORTHWEST
THROUGH THE WEEKEND THEN WILL GRADUALLY EXIT THE REGION EARLY NEXT
WEEK.  THIS WILL BE FOLLOWED BY WEAK HIGH PRESSURE BRINGING DRIER
CONDITIONS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

ORZ041>045-047-048-WAZ024-026>029-191200-
CENTRAL OREGON OR-EAST COLUMBIA RIVER GORGE OR-
EAST COLUMBIA RIVER GORGE WA-FOOTHILLS OF THE BLUE MOUNTAINS WA-
FOOTHILLS OF THE BLUE MOUNTAINS OR-JOHN DAY VALLEY OR-
KITTITAS VALLEY WA-LOWER COLUMBIA BASIN WA-LOWER COLUMBIA BASIN OR-
NORTH CENTRAL OREGON OR-OCHOCO-JOHN DAY HIGHLANDS OR-
YAKIMA VALLEY WA-
515 AM PDT FRI JUN 18 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND NORTHEAST OREGON
AS WELL AS SOUTH CENTRAL AND SOUTHEAST WASHINGTON.

.DAY ONE...TODAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

A LOW PRESSURE SYSTEM CURRENTLY OVER THE PACIFIC NORTHWEST HAS
LIMITED MOISTURE ASSOCIATED WITH IT.  ANY SHOWERS AND THUNDERSTORMS
ASSOCIATED WITH THE SYSTEM WILL BE CONFINED TO THE EAST SLOPES OF THE
SOUTHERN WASHINGTON CASCADES AND THE MOUNTAINS OF NORTHEAST OREGON
AND SOUTHEAST WASHINGTON.

.DAYS TWO THROUGH SEVEN...TONIGHT THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

DRY CONDITIONS WILL PREVAIL THROUGH MID WEEK.  THE LOW PRESSURE
SYSTEM WILL GRADUALLY EXIT THE REGION FOLLOWED BY WEAK HIGH PRESSURE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.