Severe Thunderstorm Warning 23, NWS Pendleton, OR

NORTHEAST OREGON/SOUTHEAST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PDT WED JUL 11 2001

CLEARING LINE BEHIND THE EXITING SHORTWAVE TO OUR NORTHEAST IS
QUICKLY FILLING IN WITH CUMULUS AND SHOWERS AND THUNDERSTORMS. VERY
HEAVY RAIN HAS BEEN REPORTED WITH THE STORMS OVER DESCHUTES
COUNTY...WHICH IS NOT A SURPRISE GIVEN THE PRECIPITABLE WATERS ON
THE 12Z SOUNDING. EXPECT THESE TO CONTINUE TO DEVELOP THROUGH THE
REMAINDER OF THE AFTERNOON...SOME WITH LOCALLY HEAVY RAIN. SECOND
SHORTWAVE CURRENTLY OVER NORTHERN NEVADA/CALIFORNIA IS SETTING OFF
MORE VIGOROUS THUNDERSTORMS OVER EXTREME SOUTH CENTRAL OREGON. THIS
SHORTWAVE WILL MOVE NORTH AND BE NEAR THE OCHOCO MOUNTAINS AND JOHN
DAY HIGHLANDS BY 03Z AND OVER THE COLUMBIA BASIN AROUND 06Z. THIS
REINFORCING WAVE WILL PROVIDE THUNDERSTORMS INTO THE EVENING WITH
STRATIFORM RAIN EXPECTED IN THE BASIN AND NORTHEAST ZONES THROUGH
09Z. PARTIAL CLEARING IS EXPECTED OVERNIGHT BEHIND THE EXITING
SHORTWAVE. A REPEAT PERFORMANCE CAN BE EXPECTED THURSDAY WITH
CUMULUS DEVELOPMENT IN THE LATER  MORNING/EARLY AFTERNOON WITH
SHOWERS AND THUNDERSTORMS INTO THE EVENING. THIS TREND WILL CONTINUE
INTO FRIDAY WITH THE INSTABILITY SHIFTING A LITTLE FURTHER EAST EACH
DAY. BY FRIDAY...THE EAST SLOPES...NORTH OF MADRAS...SHOULD REMAIN
DRY. TEMPERATURES SHOULD DROP JUST A FEW DEGREES EACH DAY. BREEZY
CONDITIONS CAN BE EXPECTED ALONG THE EAST SLOPES OF THE CASCADES AND
THROUGH THE EASTERN COLUMBIA RIVER GORGE FRIDAY AS A MARINE PUSH
BEGINS TO MAKE ITS WAY INLAND.  MEAD

EXTENDED...AN UPPER LEVEL TROUGH WILL MOVE SOUTHWARD ALONG THE
BRITISH COLUMBIA COAST ON SATURDAY. 12Z AVN RUN A LITTLE SLOWER IN
MOVEMENT OF UPPER TROUGH ON SATURDAY...SO HAVE DECIDED TO BACK OFF
ON ANY MENTION OF AFTERNOON AND EVENING CONVECTION ON SATURDAY EAST
OF THE WASHINGTON CASCADES...THE LOWER COLUMBIA BASIN AND THE
FOOTHILLS OF THE BLUES...BUT WILL HOLD ONTO A SLIGHT CHANCE OF
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS FROM CENTRAL OREGON
TO THE BLUE MOUNTAINS. THE UPPER TROUGH DEVELOPS INTO A CLOSED UPPER
LOW ALONG THE WASHINGTON/OREGON COAST ON SUNDAY...THUS BACKING FLOW
ALOFT TO THE SOUTH EAST OF THE CASCADES. THE MRF...CANADIAN AND
NOGAPS MODELS ALL SHOW THE UPPER LOW MEANDERING JUST OFFSHORE OF THE
OREGON COAST FROM MONDAY THROUGH WEDNESDAY AND HAVE DECIDED TO GO
WITH THIS SOLUTION. AMPLE MID LEVEL MOISTURE ASSOCIATED WITH THE
UPPER LOW AND COLD TEMPERATURES AT 500 MB WILL KEEP THE ATMOSPHERE
UNSTABLE OVER THE FORECAST AREA FOR SCATTERED SHOWERS AND
THUNDERSTORMS SUNDAY THROUGH WEDNESDAY.  POLAN

PDT 6262  ALW 6262  PSC 5252,  YKM 2121

.KPDT...WSR-88D...VCP21/CSR21...OPERATIONAL.

.KPDT...NONE.