Flash Flood Warning 1, NWS Pendleton, OR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OREGON
230 PM PDT WED MAY 19 2004

.SHORT TERM...THROUGH FRIDAY NIGHT. CONCERN THIS PACKAGE IS WITH
THUNDER/RAIN CHANCES THROUGH THURSDAY.

LOW PRESSURE OVER SOUTHERN OREGON...MOISTURE...AND AN UNSTABLE AIR
MASS WILL PRODUCE THUNDERSTORMS INTO EARLY EVENING WITH THE BETTER
CHANCES OVER THE EASTERN SLOPES OF THE WASHINGTON CASCADES AND
WALLOWA MTNS. WITH THE LOSS OF DAYTIME HEATING THE TSRA SHUD DIMINISH
AFTER SUNSET. HOWEVER...SHRA WILL CONTINUE TONIGHT. MODEL COMPARISON
INDICATED A BETTER GFS SOLN WITH PCPN AND WILL LEAN TOWARD THIS
SOLN. INSTABILITY RETURNS TOMORROW AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP AGAIN ACROSS THE REGION. SOME OF THE STORMS MAY BECOME
STRONG TOMORROW PRIMARILY ALONG THE EAST SLOPES OF THE WASHINGTON
CASCADES AND PERHAPS INTO THE BASIN. THE TSRA SHUD WEAKEN AGAIN
AFTER SUNSET WHILE THEY DRIFT TOWARD THE EAST. A LONG WAVE TROUGH
REMAINS OVER THE AREA FOR FRIDAY AND UNSETTLED WEATHER IS EXPECTED
TO CONTINUE.  SOME DRIER AIR WORKS ITS WAY INTO THE REGION AND RAIN
CHANCES SHOULD BE ON THE DECREASE FROM WEST TO EAST. IN
ADDITION...PRESSURE GRADIENTS TIGHTEN AND WINDS MAY BECOME BREEZY
LATE FRIDAY INTO THE NIGHT ESPECIALLY IN THE GORGE/ELN/DLS AND THE
BASIN. HIGH TEMPERATURES OVER THE JOHN DAY/WALLOWA AREA SHUD MAKE A
REBOUND TOMORROW AND FOR THE REMAINDER OF THE REGION THEY SHUD BE AT
OR SLIGHTLY ABOVE NORMAL THROUGH THE END OF THE WEEK.

.LONG TERM...ANOTHER STRONG UPPER LOW PRESSURE SYSTEM WILL DROP DOWN
OUT OF WESTERN BRITISH COLUMBIA INTO THE PACIFIC NORTHWEST ON FRIDAY
NIGHT AND SATURDAY.  THE LONGER RANGE MODELS ARE IN GOOD AGREEMENT
NOW WITH THE MOVEMENT AND STRENGTH OF THIS UPPER LOW.  IT WILL BRING
A FRESH SUPPLY OF COLD AND UNSTABLE AIR ALOFT TO THE REGION TO CAUSE
SCATTERED SHOWERS AND THUNDERSTORMS.  THIS UNSETTLED WEATHER PATTERN
WILL CONTINUE THOUGH NEARLY ALL OF THE EXTENDED PERIOD AS THIS UPPER
LOW WILL BE VERY SLOW MOVING.  THERE MAY EVEN BE A PERIOD OF STEADY
PRECIPITATION AS THE UPPER LOW SLIDES SOUTHEAST AND CAUSES A WRAP
AROUND EAST TO NORTHEAST FLOW OF MOISTURE INTO THE FORECAST AREA.
TEMPERATURES WILL BE MILD AT FIRST BUT THEN WILL COOL AS THE COLDER
AIR ALOFT MOVES INTO THE REGION AND MIXES DOWN TO THE SURFACE.  RSC.

&&

.PRELIMINARY POINT TEMPS/POPS...
PENDLETON (AIRPORT) 48 76 50 76 / 30 30 30 20
WALLA WALLA         52 77 53 77 / 30 30 30 20
TRI-CITIES          52 82 53 82 / 20 20 20 20
YAKIMA              51 80 51 82 / 30 30 30 20
&&

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

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
855 AM PDT WED MAY 19 2004

ORZ041>050-WAZ024>030-201200-
BLUE MOUNTAINS OF OREGON OR-CENTRAL OREGON OR-
EAST COLUMBIA RIVER GORGE OR-EAST COLUMBIA RIVER GORGE WA-
EAST SLOPES SOUTHERN CASCADES WA-FOOTHILLS OF THE BLUE MOUNTAINS WA-
FOOTHILLS OF THE BLUE MOUNTAINS OR-GRANDE RONDE VALLEY OR-
JOHN DAY VALLEY OR-KITTITAS VALLEY WA-LOWER COLUMBIA BASIN WA-
LOWER COLUMBIA BASIN OR-NORTH CENTRAL OREGON OR-
NORTHWEST BLUE MOUNTAINS WA-OCHOCO-JOHN DAY HIGHLANDS OR-
WALLOWA COUNTY OR-YAKIMA VALLEY WA-
855 AM PDT WED MAY 19 2004

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

.DAY ONE...TODAY AND TONIGHT

A TROUGH OF LOW PRESSURE REMAINS OVER EASTERN OREGON AND WASHINGTON
TODAY...WITH PLENTY OF MOISTURE AND INSTABILITY REMAINING OVER THE
AREA.  SHOWER ACTIVITY WILL INCREASE THROUGHOUT THE DAY...AND
THUNDERSTORMS ARE POSSIBLE.  WHILE THUNDERSTORMS ARE POSSIBLE
ANYWHERE THROUGHOUT THE REGION TODAY...SOME OF THE STORMS MAY BECOME
STRONG AND PRODUCE WIND GUSTS TO 50 MPH AND HAIL PRIMARILY NORTH OF
THE STATE LINE IN WASHINGTON. MODERATE TO HEAVY RAIN MAY ALSO
ACCOMPANY THESE THUNDERSTORMS.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

UNSETTLED WEATHER WILL CONTINUE OVER THE REGION...AS THE TROUGH OF
LOW PRESSURE REMAINS IN PLACE.  ANOTHER SYSTEM WILL MOVE THROUGH THE
TROUGH FRIDAY NIGHT THROUGH SATURDAY...BRINGING GUSTY WINDS AND A
BETTER CHANCE OF SHOWERS TO THE REGION.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EARLY EVENING
PRIMARILY ALONG AND NORTH OF A LINE FROM THE DALLES OREGON TO
PENDLETON.

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