Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 061504
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
805 AM PDT FRI MAY 6 2016

.UPDATE...AN UPPER LOW PRESSURE SYSTEM OVER SOUTHERN CALIFORNIA INTO
THE GREAT BASIN AND A HIGH TO THE NORTH OF THE REGION WILL KEEP AN
EAST TO NORTHEAST LOW LEVEL FLOW OVER THE CWA TODAY. THE OVERALL
ATMOSPHERE WILL BE MORE STABLE WITH MUCH LESS SHEAR. HOWEVER
PRECIPITABLE WATER VALUES AND NEGATIVE LI`S ALONG THE SOUTHERN
BORDER OF THE CWA SUGGESTS THAT THERE WILL BE THUNDERSTORMS AGAIN
THIS AFTERNOON AND EVENING ALONG THE SOUTHEAST BORDER REGION OF THE
CWA. THIS MORNING THERE MAY BE A FEW SHOWERS BUT THEY WILL BE LIGHT
AND WITHOUT THUNDER. THE ATMOSPHERE WILL GENERALLY BECOME DRIER OVER
THE NEXT COUPLE DAYS WITH LOCALLY BREEZY CONDITIONS...ESPECIALLY IN
THE AFTERNOON AND EVENING. TEMPERATURES WILL WARM UP TO THE LOWER TO
MID 80S TODAY AND SATURDAY IN THE LOWER ELEVATIONS. 88

&&

.PREV DISCUSSION... /ISSUED 500 AM PDT FRI MAY 6 2016/

SHORT TERM...TODAY THROUGH SUNDAY...AN ELONGATED TROUGH IS LOCATED
OVER THE PACIFIC COAST WITH A CLOSED LOW IN SOUTHERN CALIFORNIA. THE
MOISTURE AND INSTABILITY IS DECREASING TONIGHT AS UPPER LEVEL FLOW
OVER EASTERN OREGON CHANGES FROM SOUTHERLY IN THE TROUGH TO
SOUTHEASTERLY AROUND THE SOUTHERN LOW. AS THIS LOW DRIFTS SOUTHEAST
TODAY AN UPPER LEVEL RIDGE WILL BUILD INTO SOUTHERN CANADA AND
NORTHERN WASHINGTON. THIS RIDGING WILL CREATE A STRONG CAP OVER
WASHINGTON AND PART OF NORTHEASTERN OREGON. THE COMBINATION OF THIS
CAP...DOWN SLOPE EASTERLY FLOW...AND DECREASING MOISTURE WILL KEEP THE
BLUE MOUNTAIN FOOTHILLS AND AREAS TO THE NORTHWEST OF THE FOOTHILLS
DRY TODAY. ALONG THE SOUTHERN BORDER OF THE CWA, ESPECIALLY IN
WALLOWA AND GRANT COUNTIES, THE CAP WILL BE WEAKER AND THERE IS
ENOUGH INSTABILITY TO BREAK IT AND FORM THUNDERSTORMS DURING THE
AFTERNOON AND EVENING. THESE THUNDERSTORMS WILL END WITH THE LOSS OF
DAYTIME HEATING. THE SURFACE GRADIENT BETWEEN THE NORTHERN RIDGE AND
THE LOW TO THE SOUTH WILL CREATE BREEZY NORTH TO NORTHEAST WINDS
OVER THE AREA IN THE AFTERNOON.

THE UPPER LOW WILL CONTINUE TO MOVE EAST SATURDAY AND SUNDAY WHICH
WILL CAUSE A GRADUAL DECREASE IN CONVECTIVE DEVELOPMENT AND
STABILIZATION OF THE ATMOSPHERE. A FEW SHOWERS AND THUNDERSTORMS ARE
STILL POSSIBLE IN EASTERN GRANT COUNTY AND WALLOWA COUNTY SATURDAY.
SUNDAY EASTERN WASHINGTON AND NORTHEASTERN OREGON WILL BE DRY. A
WEAK MARINE PUSH SUNDAY WILL BRING COOLER TEMPERATURES AND BREEZY
WINDS IN THE LOWER COLUMBIA BASIN. COONFIELD

LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...WINDY CONDITIONS WILL
PERSIST INTO SUNDAY EVENING DUE TO THE WEAK MARINE PUSH SUNDAY. A
DISTURBANCE WILL MOVE SOUTHEAST OUT OF BRITISH COLUMBIA AND ACROSS
THE AREA OVERNIGHT SUNDAY INTO MONDAY. THIS SYSTEM WILL KEEP
CONDITIONS LOCALLY BREEZY INTO MONDAY. ALSO THERE WILL BE VARYING
CHANCES OF SHOWERS OVER THE BLUE MOUNTAINS, THE ADJACENT FOOTHILLS
OF THE BLUES, THE GRANDE RONDE VALLEY AND WALLOWA COUNTY, MAINLY ON
MONDAY. FOR THE TUESDAY THROUGH THURSDAY PERIOD, EXPECT DRY AND
WARMING CONDITIONS DUE TO A WEAK UPPER LEVEL RIDGE. 90

AVIATION...12Z TAFS...MOISTURE WRAPPING AROUND AN UPPER LOW OVER
THE SOUTHERN U.S. WILL BRING ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS TO PORTIONS OF THE AREA TODAY. THESE SHOWERS AND
STORMS ARE LARGELY EXPECTED TO HAVE LIMITED IMPACT ON OUR TAF SITES.
KRDM AND KBDN COULD HAVE THE BEST CHANCES OF SEEING A SHOWER OR
STORM, THOUGH CONFIDENCE IS ONLY HIGH ENOUGH TO INDICATE UP TO 3
HOURS OF VICINITY THUNDERSTORMS. KPDT AND KALW COULD ALSO BE
AFFECTED BY A STRAY STORM DRIFTING OFF THE BLUE MOUNTAINS TO THE
EAST. AT THIS TIME CONFIDENCE IS TOO LOW TO INDICATE ANY STORMS AT
OR IN THE VICINITY OF KPDT AND KALW. EXPECT DRY CONDITIONS AT KDLS,
KPSC AND KYKM. BELOW VFR CIGS AT KBDN SHOULD GRADUALLY LIFT AND
BREAK UP WITHIN THE FIRST 3 HOURS OF THIS PERIOD. OTHERWISE EXPECT
VFR CIGS/VIS AT ALL SITES, THOUGH SCT CLOUDS WITH BASES BETWEEN 2000
AND 3000 FT AGL MAY BRIEFLY OCCUR AT KALW AND KPDT THIS MORNING.
STRONGEST WINDS WILL RUN BETWEEN 11 AND 18 KTS WITH HIGHER GUSTS
THIS AFTERNOON AND EARLY THIS EVENING. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  78  57  81  55 /  10  10  10  10
ALW  80  56  82  56 /  10  10  10  10
PSC  84  58  87  58 /  10  10   0   0
YKM  84  55  87  54 /  10  10   0   0
HRI  82  54  85  56 /  10  10  10  10
ELN  81  51  83  52 /  10  10   0   0
RDM  73  44  79  42 /  10  10  10  10
LGD  72  49  76  48 /  40  20  20  20
GCD  71  50  76  48 /  40  40  20  20
DLS  85  54  86  55 /  10  10   0   0

&&

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

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

$$

88/76/76


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