Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 301628
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
927 AM PDT TUE JUN 30 2015

.SHORT TERM...MORNING UPDATE...A WEAK DISTURBANCE WILL MOVE INTO AND
THROUGH BRITISH COLUMBIA TODAY AND TONIGHT. THIS DISTURBANCE WILL
SUPPRESS THE STRONG UPPER RIDGE OVER THE WESTERN U.S. SUCH THAT THE
FLOW OVER THE PACIFIC NORTHWEST WILL BE WESTERLY THOUGH TONIGHT.
THUS WILL SEE FAIR AND DRY CONDITIONS OVER THE AREA TODAY AND
TONIGHT. WILL BE ENOUGH INSTABILITY FOR SOME AFTERNOON/EVENING
CUMULUS CLOUDS OVER THE HIGHER TERRAIN, ESPECIALLY OVER THE WALLOWAS
AND THE WASHINGTON CASCADE EAST SLOPES. THERE SHOULD BE SUFFICIENT
CAPPING IN THESE AREAS THIS AFTERNOON/EVENING TO KEEP THESE CUMULUS
CLOUDS FROM DEVELOPING INTO THUNDERSTORMS. HIGH TEMPS WILL BE
WARMEST IN THE LOWER BASIN OF WASHINGTON, BUT GENERALLY WILL BE 103
DEGREES OR LESS. THUS THE CURRENT HEAT ADVISORY IS MARGINAL, BUT
WILL REMAIN IN EFFECT. UPDATES THIS MORNING CENTERED ON MAKING A FEW
ADJUSTMENTS TO WINDS, SKY COVER AND HIGH TEMPS. 90

.LONG TERM...PREVIOUS DISCUSSION...A WEAK AND FLAT MID/UPPER LEVEL
RIDGE OF HIGH PRESSURE WILL BE OVER THE REGION THURSDAY NIGHT. THE
RIDGE WILL GRADUALLY RECEDE SOUTHWARD IN RESPONSE TO A RIDGE
BUILDING UPSTREAM IN THE GULF OF ALASKA FRIDAY AND SATURDAY WHILE A
LARGE MID/UPPER LEVEL TROUGH DIGS SOUTHEAST ACROSS THE PRAIRIE
PROVINCES OF CANADA. SINKING AIR ALOFT ASSOCIATED WITH THE RIDGE
WILL PRODUCE DRY AND STABLE CONDITIONS THROUGH SATURDAY NIGHT. THE
MODELS SHOWS SUBTLE DIFFERENCES IN TERMS OF THE STRENGTH OF THE
RIDGE OVER THE GREAT BASIN AND THE SOUTHWEST STATES. THE 00Z ECMWF
RUN KEEPS WEAK TROUGH OVER WESTERN CANADA AND THIS KEEPS THE RIDGE
OVER THE WESTERN STATES SUPPRESSED FARTHER SOUTH THAN THE 00Z GFS
RUN INDICATES FOR SUNDAY THROUGH MONDAY NIGHT. THE GFS MODEL ALLOWS
THE RIDGE TO BUILD A TAD FARTHER NORTH INTO OREGON, WHICH RESULTS IN
A MONSOON MOISTURE PLUME ADVANCING NORTHWARD OVER CALIFORNIA
RESULTING IN MID LEVEL MOISTURE ENTERING SOUTHERN AND CENTRAL OREGON
BY LATE SATURDAY AFTERNOON WITH THE INFLUX OF MONSOON MOISTURE
CONTINUING INTO SUNDAY AND MONDAY. I CHOSE TO GO WITH THE GFS
SOLUTION. AS SUCH I HAVE A SLIGHT CHANCE OF AFTERNOON AND EVENING
THUNDERSTORMS IN CENTRAL AND NORTHEAST OREGON FOR SUNDAY AND MONDAY.

&&

.AVIATION...18Z TAFS...VFR CONDITIONS EXPECTED THROUGH THE PERIOD
WITH CLEAR SKIES. WINDS WILL BE MOSTLY NW-N AT AROUND 10 KT THIS
AFTERNOON EXCEPT 10 TO 20 KT AT KDLS. WINDS WILL DIMINISH OVERNIGHT
AND BECOME MOSTLY TERRAIN DRIVEN AFTER 06Z. 78

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  97  63  98  64 /   0   0   0   0
ALW  99  69  98  71 /   0   0   0   0
PSC 101  66 101  65 /   0   0   0   0
YKM  96  65  97  66 /   0   0   0   0
HRI 100  64 100  64 /   0   0   0   0
ELN  97  63  99  63 /   0   0   0   0
RDM  95  56  96  59 /   0   0   0   0
LGD  93  55  92  55 /   0   0   0  10
GCD  98  57  99  59 /   0   0  10  10
DLS  97  66 101  68 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...HEAT ADVISORY UNTIL 8 PM PDT THIS EVENING FOR WAZ028.

&&

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

$$

90/99/78



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