Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 050526
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1022 PM PDT TUE AUG 4 2015

.SHORT TERM...UPPER LOW MOVING INTO CENTRAL CALIFORNIA THIS
AFTERNOON AND EARLY EVENING. CLOUDS EXTEND INTO SOUTHERN OREGON.
STILL HAVE AN AREA OF CUMULUS OVER CENTRAL AND NORTHEAST OREGON
MOUNTAINS AND NOW SEEING A FEW THUNDERSTORMS. WATER VAPOR INDICATES
THE UPPER LOW IS FAIRLY STRONG AND MAY HAVE ENOUGH DYNAMICS TO
KEEP THE THREAT OF THUNDERSTORMS GOING THROUGH THE EVENING AND
INTO TONIGHT. THIS SYSTEM WILL MOVE NORTHEAST TONIGHT AND INTO
IDAHO ON WEDNESDAY. ANY LINGERING SHOWERS OR THUNDERSTORMS OVER
NORTHEAST OREGON WILL END BY LATE MORNING. MEANWHILE ANOTHER LARGE
UPPER LOW IS MOVING INTO SOUTHERN BC AND THE PACIFIC NORTHWEST
TONIGHT AND WEDNESDAY. THIS SYSTEM WILL CREATE A DRY WESTERLY FLOW
TOMORROW WITH CLEARING SKIES AND COOLER TEMPERATURES. EXPECT
WESTERLY WINDS TO BE INCREASING AS THIS LOW MOVES INTO THE REGION
WITH 15-25 MPH BY AFTERNOON FOR MANY LOCATIONS. 94

.AVIATION...WEST WINDS 5-15KT TONIGHT INCREASING TO 10-25KT
WEDNESDAY. SCT CLOUDS 100-200.

&&

.PREV DISCUSSION... /ISSUED 410 PM PDT TUE AUG 4 2015/

SHORT TERM...TONIGHT THROUGH FRIDAY...COMPLICATED WEATHER PATTERN.
THERE IS AN UPPER LEVEL LOW PRESSURE SYSTEM OVER BRITISH COLUMBIA
AND AN UPPER LEVEL LOW OFF THE COAST OF CALIFORNIA. COMBINED THEY
ARE PRODUCING A WEST TO SOUTHWEST FLOW ACROSS THE FORECAST AREA. A
PIECE OF ENERGY IS BREAKING AWAY FROM THE COASTAL LOW AND WILL MOVE
INTO NORTHERN CALIFORNIA LATE TODAY AND THEN INTO SOUTHERN IDAHO ON
WEDNESDAY WITH ITS PATH CUTTING ACROSS SOUTHEAST OREGON OVERNIGHT
AND EARLY WEDNESDAY. THIS WILL ADD A LITTLE KICK TO THE ATMOSPHERE
AND HELP PRODUCE SOME SHOWERS AND POSSIBLE THUNDERSTORMS FROM
EASTERN DESCHUTES COUNTY TO WALLOWA COUNTY OVERNIGHT. THE BRITISH
COLUMBIA LOW WILL MOVE FURTHER SOUTHWARD OVERNIGHT AND WEDNESDAY
BRINGING SOME COOLER DRY AIR INTO THE FORECAST AREA WITH
TEMPERATURES DROPPING 5 TO 10 DEGREES. ON THURSDAY THIS LOW WILL
MOVE EAST ALONG THE CANADIAN BORDER AS A FLAT RIDGE OF HIGH PRESSURE
BEGINS BUILDING BACK INTO THE REGION FROM THE WEST. THIS WILL KEEP
THE COOL DRY CONDITIONS IN PLACE. BY FRIDAY THE FLAT RIDGE WILL BE
OVER THE REGION BUT THE CALIFORNIA COASTAL LOW PRESSURE SYSTEM WILL
BEGIN MOVING INLAND INTO CENTRAL AND NORTHERN CALIFORNIA. SOME
MOISTURE ASSOCIATED WITH THIS COULD REACH SOUTHERN AND CENTRAL
OREGON FOR A CHANCE OF SHOWERS AND OR THUNDERSTORMS IN THE AFTERNOON
AND EVENING.

LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...FRIDAY NIGHT WILL SEE
AN UPPER LOW HEADING SOUTH ALONG THE NORTHERN BRITISH COLUMBIA
COAST AND A WEAK WAVE IN NORTHERN CALIFORNIA. THIS WILL GIVE US A
SOUTHERLY FLOW OF MOISTURE INTO THE AREA AND A SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS FROM CENTRAL OREGON SOUTH OF MADRAS AND
IN THE EASTERN MOUNTAINS THAT WILL TAPER OFF IN THE LATE EVENING.
SATURDAY THROUGH TUESDAY WILL SEE THE UPPER LOW SLOWLY SINK SOUTH
ALONG THE BRITISH COLUMBIA COAST AND ENDING UP OFF THE OLYMPIC
PENINSULA ON MONDAY AND THEN MOVE ASHORE OVER THE OLYMPIC
PENINSULA ON TUESDAY. OUR AREA WILL BE UNDER A TROUGH THROUGH THIS
PERIOD WITH A SOUTH TO SOUTHWEST FLOW OVER THE AREA. THIS FLOW
WILL CARRY MOISTURE INTO THE AREA AND ALONG WITH INSTABILITY FROM
DAYTIME HEATING WILL GIVE CENTRAL OREGON, THE EASTERN MOUNTAINS
AND THE CASCADES A SLIGHT CHANCE OF THUNDERSTORMS EACH AFTERNOON
AND EVENING, TAPERING OFF TO SHOWERS IN THE LATE EVENING. SUNDAY
WILL SEE GREATER MOISTURE OVER THE AREA AND THE SLIGHT CHANCE OF
THUNDERSTORMS WILL EXPAND INTO IN THE BLUE MOUNTAIN FOOTHILLS.
TEMPERATURES WILL BE NEAR NORMAL WITH HIGHS IN THE MID 80S TO
LOWER 90S WITH 70S AND LOWER 80S IN THE MOUNTAINS. PERRY

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  59  84  54  83 /   0   0   0   0
ALW  65  85  60  84 /   0   0   0   0
PSC  60  88  58  87 /   0   0   0   0
YKM  57  81  53  82 /   0   0   0   0
HRI  61  86  56  85 /   0   0   0   0
ELN  60  80  55  83 /   0   0  10   0
RDM  48  80  41  82 /  10   0   0   0
LGD  50  80  49  80 /  20  10   0   0
GCD  54  84  47  85 /  20  10   0   0
DLS  62  81  59  88 /   0   0   0   0

&&

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

&&

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

94


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