Severe Thunderstorm Warning 27, NWS Pendleton, OR

NORTHEAST OREGON/SOUTHEAST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PDT TUE JUL 23 2002

CONCERN WILL BE WITH PRECIPITATION CHANCES NEXT COUPLE OF DAYS.

LATEST MSAS DATA SHOWED IMPRESSIVE INSTABILITY (MINUS EIGHT
LIS...WARM AIR ADVECTION IN THE LOW LEVELS AND MOISTURE CONVERGENCE)
OVER MOST PORTIONS OF NE OREGON ESPECIALLY IN AND AROUND THE DALLES
TO PDT. LOW PRESSURE OVER SOUTHWEST OREGON WILL REMAIN STATIONARY
SPINNING DISTURBANCES ACROSS OUR AREA THROUGH TOMORROW. LOW LEVEL
MOISTURE HAD INCREASED ACROSS SE WASHINGTON AND NE OREGON AS SURFACE
DEW POINTS HAS RISEN TO 60 DEGREES AT PDT. THEREFORE WHEN
THUNDERSTORMS DEVELOP THEY SHOULD BE OF THE WET VARIETY. WITH
DAYTIME HEATING AND LOW LEVEL MOISTURE THE ATMOSPHERE SHOULD
CONTINUE TO BECOME VERY UNSTABLE THIS LATE AFTERNOON. IN ADDITION A
DISTURBANCE/(5HMBS/VORT MAX) MOVES INTO CENTRAL OREGON AND REMAINS
OVER THE AREA TONIGHT. THEREFORE I WOULD EXPECT THE CAP TO
BREAK(HIGH CIN) AND CONVECTION TO DEVELOP THIS AFTERNOON AND PERSIST
INTO THE EVENING. WITH THE SLOW MOVEMENT OF THE STORMS...MOIST
LOW/MID LEVELS...PRECIPITABLE WATERS AROUND AN INCH(ALSO SOMEWHAT OF
A THETA E RIDGE) NEAR WALLOWA COUNTY...SOME OF THE STORMS COULD
PRODUCE LOCALLY HEAVY RAINFALL. ALSO THE WET BULB ZERO TEMPERATURES
HAD LOWERED AND SOME DIME SIZE HAIL MAY OCCUR AS WELL.

SIMILAR CONDITIONS EXIST FOR TOMORROW BUT WITH THE LACK OF A STRONG
DISTURBANCE. STILL THE ATMOSPHERE BECOMES UNSTABLE(7HMBS/POSITIVE
OMEGAS BULLSEYE IN AND AROUND JOHN DAY) AND THUNDERSTORMS SHOULD
DEVELOP AGAIN FOR WEDNESDAY. FINALLY THE LOW PRESSURE OVER SOUTHWEST
OREGON BEGINS TO MOVE INTO CENTRAL OREGON THURSDAY. DRIER AIR SLOWLY
ADVECTS/MOVES INTO THE WESTERN PORTIONS OF THE COUNTY WARNING
AREA(REDMOND/YAKIMA) BY LATE AFTERNOON AND PRECIPITATION CHANCES
SHOULD DECREASE.

BY EARLY FRIDAY ALL OF SE WASHINGTON/NE OREGON ARE IN DRIER AIR. BUT
A FAST MOVING DISTURBANCE DIVES SOUTHEAST FROM THE GULF OF ALASKA
AND ENTERS EASTERN WASHINGTON BY AFTERNOON AND SPREADS SOME MID
LEVEL CLOUDINESS ACROSS THE AREA. IN ADDITION PRESSURE GRADIENTS
TIGHTEN AND THE WESTERN PORTIONS OF THE FORECAST AREA...NEAR
ELLENSBURG/THE DALLES COULD HAVE BREEZY TO WINDY WEST TO NORTHWEST
WINDS.

AFTERNOON HIGHS FOR WEDNESDAY SHOULD BE ABOVE NORMAL RISING INTO THE
90S. BY THURSDAY LOW LEVEL TEMPERATURES(850MBS) FALL A COUPLE OF
DEGREES AND AFTERNOON HIGHS SHOULD NOT BE AS HOT. BY FRIDAY
AFTERNOON AGAIN SHOULD BE COOLER THAN THE DAY BEFORE.

EXTENDED...THE EXTENDED WILL REMAIN DRY WITH TEMPERATURES NEAR
NORMAL. THE VORTICITY MAXIMUM ASSOCIATED WITH THE FAST MOVING SYSTEM
OF FRIDAY...WILL BE LOCATED IN NORTHERN CALIFORNIA ON
SATURDAY...WITH LINGERING VORTICITY OVER MUCH OF OREGON.
HOWEVER...THIS SYSTEM IS VERY DRY AND THE ATMOSPHERE APPEARS TO BE
STABLE...WITH THICKNESS LOWERING ACROSS WASHINGTON AND OREGON.
THEREFORE...SATURDAY WILL BE DRY...WITH COOLER TEMPERATURES. AS THE
UPPER LEVEL TROUGH PUSHES OUT...A RIDGE TRIES TO BUILD INTO THE
PACIFIC NORTHWEST ON SUNDAY NIGHT INTO MONDAY. MODELS ARE VARYING ON
THE STRENGTH OF THIS RIDGE THOUGH...AND FOR NOW...WILL FOLLOW THE
MRF SOLUTION WHICH FLATTENS OUT THE RIDGE ON MONDAY NIGHT AS ANOTHER
WAVE PUSHES SOUTH FROM CANADA ON TUESDAY...PUTTING WASHINGTON IN
NORTHWESTERLY FLOW AND OREGON UNDER WESTERLY FLOW. TEMPERATURES WILL
RISE A DEGREE OR TWO ON SUNDAY AND MONDAY...WITH A SLIGHT DECREASE
ON TUESDAY WITH LOWERING THICKNESS AGAIN. PALMER

PDT 323  ALW 323  PSC 323  YKM 323

KPDT...VCP21...OPERATIONAL.

.KPDT...NONE.