Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 021000
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
300 AM PDT SUN AUG 2 2015

.SHORT TERM...TODAY THROUGH MONDAY NIGHT...AN UPPER LEVEL HIGH
PRESSURE RIDGE WILL CONTINUE OVER THE REGION TODAY. ALSO SURFACE LOW
PRESSURE WILL BE OVER THE INTERIOR NORTHWEST. AS SUCH HIGH
TEMPERATURES WILL AGAIN BE HOT AT MOST LOCATIONS. VARYING AMOUNTS OF
HIGH LEVEL CLOUDINESS MAY HELP KEEP HIGH TEMPS A DEGREE OR TWO LOWER
THAN THEY MIGHT OTHERWISE REACH. STILL WILL CONTINUE THE EXTENDED
HEAT ADVISORIES. THERE WILL BE SOME INSTABILITY FOR POTENTIAL
THUNDERSTORM DEVELOPMENT, BUT THE UPPER HIGH LOOKS TO CAP MUCH OF
THE AREA. STILL WILL INDICATE ISOLATED STORMS OVER CENTRAL OREGON
EAST TO SOUTHERN GRANT COUNTY THIS AFTERNOON AND EVENING. ALSO A FEW
STORMS MAY PERSIST OVER CENTRAL OREGON OVERNIGHT. A FEW OF THESE MAY
MIGRATE NORTH ALONG THE CASCADE CREST AS WELL. AN UPPER LEVEL TROUGH
OF LOW PRESSURE WILL MOVE INTO BRITISH COLUMBIA MONDAY AND MONDAY
NIGHT. THIS TROUGH WILL SUPPRESS THE RIDGE OVER THE PACIFIC
NORTHWEST WHILE INSTIGATING A PUSH OF COOLER MARINE AIR INTO THE
REGION. THUS WILL SEE HIGH TEMPS MONDAY DROP ANYWHERE FROM 7 TO 12
DEGREES. THIS TROUGH WILL ALSO CAUSE THE DEVELOPMENT OF SOME SHOWERS
AND A FEW THUNDERSTORMS FROM CENTRAL OREGON EAST TO GRANT COUNTY,
AND FROM THE BLUE MOUNTAINS EAST TO WALLOWA COUNTY. ELSEWHERE,
EXPECT GENERALLY DRY CONDITIONS THOUGH A FEW SPRINKLES MAY TRACK
ACROSS THE BASIN WITH AN UPPER WAVE ASSOCIATED WITH THE TROUGH. 90


.LONG TERM...TUESDAY THROUGH SATURDAY...THE MAIN MID/UPPER LEVEL LOW
PRESSURE SYSTEM WILL BE OVER BRITISH COLUMBIA ON TUESDAY. FORECAST
AREA WILL BE ON FAR SOUTHERN FLANK OF THE LOW. AS SUCH WINDS WILL
BE FROM THE WEST-SOUTHWEST YIELDING DOWNSLOPE WINDS EAST OF THE
CASCADES AND THUS DRY AND STABLE CONDITIONS, BUT I KEPT A SLIGHT
CHANCE OF AFTERNOON/EVENING THUNDERSTORMS IN CENTRAL OREGON AND THE
EASTERN OREGON MOUNTAINS BY VIRTUE OF OROGRAPHIC LIFT. A MID/UPPER
LEVEL SHORT WAVE MOVES THROUGH THE BASE OF THE LONG WAVE TROUGH OVER
THE PACIFIC NORTHWEST TUESDAY NIGHT AND WEDNESDAY, THUS BRINGING
DYNAMIC LIFT A SLIGHT CHANCE OF SHOWERS FROM OVERNIGHT THROUGH
WEDNESDAY MORNING IN THE BLUE MOUNTAINS AND A SLIGHT CHANCE OF
THUNDERSTORMS IN THE AFTERNOON AND EVENING IN THE NORTHERN BLUE
MOUNTAINS. WEDNESDAY NIGHT THROUGH THE REMAINDER OF THE PERIOD ZONAL
WESTERLY FLOW ALOFT PERSISTS OVER THE FORECAST AREA FOR DRY
CONDITIONS. ALTHOUGH FRIDAY AND SATURDAY WE HAVE A SLIGHT CHANCE OF
THUNDERSTORMS MY CONFIDENCE IS NOT HIGH GIVEN THE AFOREMENTIONED
WESTERLY FLOW ALOFT, BUT WILL DEFER TO THE DAY SHIFT TO REMOVE
MENTION OF SLIGHT CHANCE OF THUNDERSTORMS FOR FRIDAY AND SATURDAY.
POLAN

&&

.AVIATION...12Z TAFS...VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT
24 HOURS. THERE MAY BE AN INCREASE IN WIND AT KDLS...KRDM AND KBDN
SUNDAY AFTERNOON AND EVENING. OTHERWISE, WINDS WILL BE LIGHT. POLAN

&&

.FIRE WEATHER...AN UPPER LEVEL RIDGE WILL REMAIN CENTERED OVER THE
AREA THROUGH TODAY. THE AIR MASS IS VERY DRY AND HUMIDITIES WILL
REMAIN LOW. MINIMUM RH VALUES DURING THE DAY WILL BE 5-20 PERCENT
FOR MOST LOCATIONS. RECOVERIES AT NIGHT WILL BE POOR. HAINES INDEX
VALUES WILL BE 5/6 ON TODAY. THE RED FLAG WARNINGS FOR ZONES 639 AND
640 IN WASHINGTON AND OREGON, AS WELL AS WASHINGTON ZONE 643 WILL
NOW CONTINUE UNTIL 9 PM THIS EVENING. MOISTURE MOVING INTO THE
REGION FROM THE SOUTH WILL BEGIN TO LOWER THE HAINES VALUES LATE
TONIGHT INTO MONDAY. AN UPPER LEVEL TROUGH MOVING INTO THE PACIFIC
NORTHWEST MONDAY WILL START A COOLING TREND WHICH WILL CONTINUE INTO
MID WEEK. HUMIDITIES WILL BEGIN TO RISE AS WELL. WESTERLY WINDS WILL
INCREASE SOME MONDAY AS THE TROUGH MOVES INTO THE AREA. THE
POTENTIAL FOR ISSUES WITH LIGHTNING COULD PEAK MONDAY AS WELL.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 102  69  91  61 /   0  10  10  10
ALW 103  72  93  66 /   0  10  10  10
PSC 104  65  97  65 /   0  10  10  10
YKM 100  69  95  61 /   0  10  10  10
HRI 103  67  95  63 /   0  10  10  10
ELN 103  67  94  63 /   0  10  10  10
RDM  99  59  89  50 /  20  20  30  20
LGD  99  53  88  50 /  10  10  20  30
GCD 102  60  92  54 /  10  10  20  30
DLS 103  70  94  64 /  10  10  20  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR ORZ639-641.

     HEAT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR ORZ041-044-507.

WA...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR WAZ639-641-643.

     HEAT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR WAZ024-027>029.

&&

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

$$

90/99/99/90


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