FXUS66 KPDT 202126
AFDPDT

NORTHEAST OREGON/SOUTHEAST WASHINGTON FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PDT WED AUG 20 2003

A PACIFIC LOW PRESSURE SYSTEM CURRENTLY LOCATED OFF THE CALIFORNIA 
COAST WILL GRADUALLY APPROACH THE COAST OVER THE NEXT TWO DAYS.  AS 
IT APPROACHES...IT WILL DRAW DEEP MONSOON-LIKE MOISTURE NORTHWARD 
FROM NEVADA AND CALIFORNIA.  THE DEEP MOISTURE WILL REACH CENTRAL 
OREGON THURSDAY AFTERNOON AND REACH THE OR/WA BORDER BY FRIDAY 
MORNING.  THURSDAY THE AIR MASS REMAINS FAIRLY STABLE...HOWEVER 
THERE IS A SLIGHT THREAT OF THUNDERSTORMS THURSDAY MAINLY SOUTH OF A 
MADRAS TO JOHN DAY LINE.  FRIDAY A WEATHER DISTURBANCE TRACKS ACROSS 
OREGON FROM THE SOUTHWEST...INCREASING INSTABILITY AND PROVIDING 
FORCING FOR LIFT.  THE FORCING REACHES NORTHEAST OREGON IN THE 
AFTERNOON...THE TIME OF MAXIMUM DIURNAL HEATING AND 
INSTABILITY...AND AS SUCH STRONG THUNDERSTORMS AND POTENTIALLY HEAVY 
RAIN ARE POSSIBLE FRIDAY AFTERNOON AND EVENING.  MITTELSTADT    

IN THE EXTENDED STRONG LOW PRESSURE OVER WESTERN CANADA DEEPENS A 
TROUGH OVER THE WESTERN USA SATURDAY. CONVECTION THAT DEVELOPS 
EARLIER MAY PERSIST PRIMARILY OVER THE BLUES/WALLOWAS SAT/NITE. THIS 
QUICK MOVING SYSTEM ALONG WITH ITS MOISTURE WILL MOVE AWAY FROM THE 
REGION LATE SAT/NITE. BUT WITH A WESTERLY UPSLOPE FLOW LINGERING 
SHOWERS OVER THE WASHINGTON CASCADES ARE POSSIBLE INTO EARLY SUNDAY. 
MUCH DRIER AND STABLE AIR WILL FILTER INTO ALL OF THE AREA LATE 
SUNDAY. A MID LEVEL RIDGE BUILDS INTO THE REGION DURING THE 
BEGINNING OF THE WEEK AND THIS WILL KEEP THE DRY CONDITIONS AND THE 
HIGH TEMPERATURES WILL INCREASE THROUGH TUESDAY. LOW PRESSURE OFF 
THE PACNW COAST WILL NEAR THE AREA WEDNESDAY BUT WILL REMAIN TOO FAR 
OFFSHORE TO AFFECT THE REGIONS WEATHER UNTIL THURSDAY.

PDT 0000  ALW 0000  PSC 0000  YKM 0000

.KPDT...NONE.
   
$$