Severe Thunderstorm Warning 25, NWS Pendleton, OR

NORTHEAST OREGON/SOUTHEAST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
220 PM PDT THU JUL 12 2001

ANOTHER ACTIVE NIGHT IS ON TAP FOR THE FORECAST AREA TONIGHT. TWO
FEATURES WILL BRING CONVECTIVE WEATHER TO THE FORECAST AREA. THE
UPPER LOW OVER SOUTHEAST OREGON WILL PROVIDE LOW LEVEL UPSLOPE FLOW
TO THE EAST SLOPES OF THE WASHINGTON CASCADES. THIS LOCATION IS
ALREADY UNSTABLE...HAVING HAD SOME SHOWERS EARLIER TODAY...AND
CUMULUS CLOUDS ALREADY DEVELOPING AT THIS TIME. THE SECOND WAVE...
WHICH IS NOT HANDLED WELL BY ANY OF THE MODELS...IS QUICKLY MAKING
ITS WAY NORTHEAST TOWARD OREGON. THE IR AND WATER VAPOR BOTH SHOW
GOOD CONVECTION ON THE FRONT END OF THIS WAVE OVER NORTHERN
CALIFORNIA. THIS SECOND FEATURE WILL REACH THE OCHOCO MOUNTAINS AND
JOHN DAY HIGHLANDS NEAR 00Z AND BE NEAR THE FOOTHILLS AND THE
WALLOWAS BETWEEN 03-05Z. THIS WILL KEEP CONVECTIVE ACTIVITY IN THE
EASTERN ZONES GOING THROUGH THE OVERNIGHT HOURS. WITH THE
INSTABILITY PARAMETERS AS HIGH AS THEY ARE FROM CENTRAL OREGON
THROUGH NORTHEAST OREGON...EXPECT SOME MARGINALLY SEVERE STORMS. SPC
HAS PUT CENTRAL AND EASTERN OREGON IN THE SLIGHT RISK AREA FOR
TODAY. AN UPPER TROUGH WILL SLOWLY APPROACH THE PACIFIC NORTHWEST BY
THE END OF THE SHORT TERM AS THE UPPER RIDGE OVER THE SOUTHWEST US
BEGINS TO SHIFT EAST. SINCE THE TROUGH TAKES ITS TIME APPROACHING
THE COAST...A STRONG MARINE PUSH IS NOT EVIDENT. HOWEVER EXPECT WEAK
LITTLE WAVES OF COOLER MARINE AIR TO MOVE THROUGH THE FORECAST AREA
STARTING FRIDAY EVENING. WITH THE SOUTHWEST FLOW APPROACHING...THE
UNSTABLE AIR WILL SHIFT EVER SO SLOWLY EAST AND SOUTH OVER THE NEXT
36-48 HOURS. THIS WILL RELEGATE THE THUNDERSTORM THREAT TO MAINLY
OVER THE WALLOWAS...JOHN DAY HIGHLANDS AND BAKER COUNTY BY SATURDAY.
TEMPERATURES WILL REMAIN PERSISTENT FOR ONE MORE DAY...THEN COOL
SLIGHTLY SATURDAY. THINK GUIDANCE IS A BIT TOO LOW FOR SATURDAY...SO
HAVE ADJUSTED ACCORDINGLY. MEAD

IN THE EXTENDED...AS THE UPPER LEVEL PATTERN SHIFTS EAST THIS
WEEKEND...THE UPPER TROUGH IN THE GULF OF ALASKA WILL SHIFT INTO THE
PACNW BY MONDAY. THUS CONDITIONS WILL REMAIN UNSETTLED...BUT WILL BE
10 TO 15 DEGREES COOLER AS MARINE AIR SETTLES OVER THE AREA. THIS
MOIST MARINE AIR SHOULD REDUCE THE INSTABILITY ACROSS THE AREA...
AND ONLY EXPECT SHOWERY PRECIP WITH NO THUNDERSTORMS. GKH

PDT 5221  ALW 5221  PSC 2110  YKM 3100

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

.KPDT...NONE.