Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 011550 AAA
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
850 AM PDT SAT AUG 1 2015

.UPDATE...STRONG HIGH PRESSURE HAS A FIRM GRIP ON THE PACNW AND THE
HOT TEMPERATURES WILL PERSIST TODAY. AFTN TEMPS WILL ONCE AGAIN
CLIMB ABOVE THE CENTURY MARK ACROSS PORTIONS OF THE BASIN AND
SURROUNDING AREA AND A HEAT ADVISORY REMAINS IN EFFECT OVER PORTIONS
OF THE AREA. MEANWHILE SOME MOISTURE WAS WORKING ITS WAY NORTH AND
IS EXPECTED TO MOVE INTO PORTIONS OF CENTRAL OREGON AND THE JOHN DAY
HIGHLANDS WITH A FEW TSRA POSSIBLE LATER TODAY. IN ADDITION THE
VISIBLE SATL WAS INDICATING SOME SMOKE THAT IS DRIFTING INTO OUR
WASHINGTON ZONES THIS MORNING AND THE BENTON/FRANKLIN ZONES WERE
UPDATED TO REFLECT THIS. OTHERWISE CRITICAL FIRE CONDITIONS PERSIST
WITH MULTIPLE RED FLAG WARNINGS IN EFFECT TODAY AND THE PRESENT
SHORT TERM FORECAST APPEARS ON TRACK FOR NOW.

.FIRE WEATHER DISCUSSION...UPPER LEVEL RIDGE REMAINS CENTERED OVER
THE AREA TODAY INTO SUNDAY. THE AIRMASS IS VERY DRY AND HUMIDITIES
WILL REMAIN LOW. MINIMUM RH VALUES DURING THE DAY WILL BE 5-15
PERCENT FOR MOST LOCATIONS. RECOVERIES AT NIGHT WILL ALSO BE POOR.
HAINES INDEX TODAY IS 5/6. TEMPERATURES WILL BE WELL ABOVE NORMAL
WITH HIGHS IN THE 90S TO NEAR 105. MOISTURE MOVING INTO THE REGION
FROM THE SOUTH MAY GENERATE A FEW THUNDERSTORMS LATE IN THE DAY OVER
THE SOUTHERN PORTION OF THE DISTRICT...MAINLY 610 611 640 AND 642.

&&

.PREV DISCUSSION... /ISSUED 300 AM PDT SAT AUG 1 2015/

SHORT TERM...TODAY THROUGH SUNDAY NIGHT...AN UPPER LEVEL RIDGE OF
HIGH PRESSURE WILL PERSIST OVER THE REGION THROUGH THIS PERIOD.
HEIGHTS WILL GRADUALLY LOWER SUNDAY AND SUNDAY NIGHT AS THE RIDGE
WEAKENS DUE TO AN APPROACHING LOW PRESSURE TROUGH. THE UPPER FLOW
OVER CENTRAL AND EAST CENTRAL OREGON TODAY WILL ALLOW SUBTROPICAL
MOISTURE TO CONTINUE TO WORK INTO THIS AREA. DAYTIME HEATING WILL BE
EXCELLENT AGAIN, RESULTING IN SOME DIURNALLY INDUCED INSTABILITY.
THUS WILL INDICATE SOME LOW END CHANCES OF SHOWERS AND/OR
THUNDERSTORMS OVER OUR SOUTHERN MOST AREAS. WEST FLOW OVER MUCH OF
THE REMAINDER OF OUR AREA WILL KEEP CONDITIONS DRY. THE FLOW WILL
BECOME MORE SOUTHERLY ACROSS THE PACIFIC NORTHWEST SUNDAY. THUS WILL
SEE THE SUBTROPICAL MOISTURE BEGIN TO WORK INTO THE REMAINDER OF
NORTHEAST OREGON AND SOUTHEAST WASHINGTON. INSTABILITY AND FORCING
REMAINS WEAK SUNDAY AFTERNOON AND SUNDAY NIGHT. THUS WILL CONTINUE
TO INDICATE ONLY SLIGHT CHANCES OF SHOWERS AND THUNDERSTORMS OVER
PORTIONS OF CENTRAL, EAST CENTRAL AND NORTHEAST OREGON FOR THIS TIME
PERIOD. HIGH TEMPS WILL REMAIN HOT ACROSS THE AREA AND WILL CONTINUE
THE CURRENT HEAT ADVISORIES THROUGH TODAY. THESE ADVISORIES MAY NEED
TO BE EXTENDED INTO SUNDAY FOR A FEW ZONES. 90

LONG TERM...MONDAY THROUGH FRIDAY NIGHT...ON THE SYNOPTIC SCALE, A
SLOW MOVING MID/UPPER LEVEL TROUGH WILL BE OVER BRITISH COLUMBIA
MONDAY AS A MID/UPPER LEVEL SHORT WAVE ASSOCIATED DYNAMIC LIFT MOVES
NORTHEAST FROM CENTRAL OREGON BEGINNING AROUND DAYBREAK MONDAY TO
NORTHEAST OREGON THUS YIELDING ISOLATED THUNDERSTORMS MONDAY MORNING
THROUGH MONDAY EVENING ACROSS HIGHER TERRAIN IN EASTERN OREGON.
OVERNIGHT INTO TUESDAY MORNING THE MID/UPPER LEVEL SHORT WAVE EXITS
FORECAST AREA, BUT HELD ON TO SLIGHT CHANCE OF THUNDERSTORMS FOR
EASTERN MOUNTAINS OF OREGON THROUGH TUESDAY AFTERNOON/EVENING TO
ACCOUNT FOR DAYTIME SURFACE HEATING YIELDING MARGINAL INSTABILITY
OVER MOUNTAINS IN GRANT COUNTY AND THE BLUE MOUNTAINS TO IDAHO.
UPPER TROUGH MOVES OVER REGION ON WEDNESDAY AND THURSDAY FOR A
SLIGHT CHANCE OF THUNDERSTORMS IN THE BLUE MOUNTAINS. FRIDAY LOOKS
TO BE DRY BY VIRTUE OF WESTERLY FLOW ALOFT OVER REGION. POLAN

AVIATION...12Z TAFS...VFR CONDITIONS WITH LIGHT WINDS ARE EXPECTED
FOR THE NEXT 24 HOURS. WINDS WILL INCREASE THIS AFTERNOON TO 10-20
KTS.  POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 103  64 101  69 /   0   0  10  10
ALW 104  70 102  73 /   0   0  10  10
PSC 106  62 104  69 /   0   0   0  10
YKM 102  64 100  68 /   0   0   0   0
HRI 105  62 103  69 /   0   0   0  10
ELN 104  62 101  65 /   0   0   0   0
RDM 101  57  98  59 /  10  10  20  20
LGD  99  55  97  55 /  10  10  10  10
GCD 102  56 100  60 /  10  10  20  20
DLS 106  66 101  71 /   0   0  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 10 PM PDT THIS EVENING FOR ORZ639-640-642.

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

WA...RED FLAG WARNING UNTIL 10 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

$$

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