Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 010241
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
741 PM PDT FRI JUL 31 2015

.UPDATE...CONVECTION OVER CENTRAL OREGON IS RAPIDLY DECREASING DUE
TO THE LOSS OF DAYTIME HEATING. DEBRIS CLOUDS FROM EARLIER
CONVECTION WILL DRIFT TO THE EAST-NORTHEAST OVERNIGHT AND WILL BRING
PARTLY CLOUDY SKIES TO THE SOUTHEAST ZONES OF THE CWA OVERNIGHT.
HIGH PRESSURE ALOFT WILL CONTINUE THROUGH THE WEEKEND WITH A
CONTINUATION OF THE HOT TEMPERATURES. HIGH TEMPERATURES ON SATURDAY
WILL ONCE AGAIN REACH THE LOWER TO MID 100S IN THE LOWER ELEVATIONS
AND UPPER 80S TO UPPER 90S IN THE MOUNTAINS. A HEAT ADVISORY REMAINS
IN EFFECT FOR THE LOWER COLUMBIA BASIN...THE NORTHERN BLUE MOUNTAIN
FOOTHILLS...THE EASTERN COLUMBIA RIVER GORGE AND THE YAKIMA VALLEY
THROUGH AT LEAST SATURDAY EVENING. SOME SUBTROPICAL MOISTURE WILL
AGAIN TRY TO WORK ITS WAY NORTHWARD ON SATURDAY AFTERNOON AND
EVENING IN CENTRAL OREGON RESULTING IN ISOLATED THUNDERSTORMS AGAIN
OVER SOUTHWEST DESCHUTES COUNTY SATURDAY EVENING. THERE ARE A NUMBER
OF FIRE WEATHER WATCHES AND RED FLAG WARNINGS. PLEASE REFER TO THE
FIRE WEATHER DISCUSSION FOR MORE DETAILS. OTHERWISE FORECAST IS ON
TRACK. 88

&&

.AVIATION...06Z TAFS...VFR CONDITIONS WITH LIGHT WINDS ARE EXPECTED
FOR THE NEXT 24 HOURS EXCEPT AT KDLS WHERE GUSTY WESTERLY WINDS WILL
OCCUR THIS EVENING FOR A WHILE. THE WINDS ARE EXPECTED TO DECREASE
THERE AFTER SUNSET. 88

&&

.FIRE WEATHER...A NUMBER OF RED FLAG WARNINGS REMAIN IN EFFECT THIS
EVENING...SOME UNTIL AT LEAST SATURDAY EVENING. HOT AND DRY
CONDITIONS HAVE LED TO MODERATE TO HIGH HAINES INDEX VALUES AND
CRITICAL FIRE WEATHER CONDITIONS IN PORTIONS OF THE FIRE WEATHER
DISTRICT. IN ADDITION INCREASING WINDS THROUGH THE EASTERN COLUMBIA
RIVER GORGE COMBINED WITH THE HOT DRY CONDITIONS ARE LEADING TO
CRITICAL FIRE WEATHER CONDITIONS THERE. THE RED FLAG WARNING FOR
FIRE WEATHER ZONE OR 611 (THE DESCHUTES NATIONAL FOREST) WILL BE
CANCELLED EARLY DUE TO EARLY DISSIPATION OF THUNDERSTORMS. OTHERWISE
FIRE WEATHER FORECAST AND RED FLAG WARNINGS ARE ON TRACK. 88

&&

.PREV DISCUSSION... /ISSUED 415 PM PDT FRI JUL 31 2015/

SHORT TERM...HIGH PRESSURE CONTINUES TO DOMINATE THE AREAS WEATHER
WITH HOT AND DRY CONDITIONS AND THIS WILL PERSIST INTO THIS WEEKEND.
SOME MOISTURE WAS MOVING INTO AND NEAR CENTRAL OREGON WITH ISOLD
TSRA TRYING TO DEVELOP THIS AFTN. IF TSRA DEVELOP LITTLE RAIN MAY
ACCOMPANY THEM AND THIS WILL CREATE CRITICAL FIRE WEATHER
CONDITIONS. THEREFORE A RED FLAG WARNING WAS HOISTED FOR FIRE
WEATHER ZONE 611 INTO THIS EVENING WHERE ISOLD TSRA COULD PERSIST.
EAST OF THIS AREA ADDITIONAL RED FLAG WARNINGS WERE ISSUED ALONG
WITH WASHINGTON ZONES 639...641...643 THAT ARE LOCATED FURTHER
NORTH FOR HAINES AND WINDS AND RH IN SOME MANNER.

MEANWHILE THE HIGH PRESSURE CONTINUES TO INFLUENCE THE REGION WITH
HOT TEMPERATURES ON SATURDAY AND A ISOLD TSRA IS POSSIBLE ONCE AGAIN
ALONG THE EAST SLOPES OF THE WASHINGTON CASCADES SATURDAY AFTN/EVE.
BY SUNDAY THE HIGH PRESSURE SLOWLY MOVES EAST ALLOWING FOR A RETURN
FLOW OF MOISTURE TO MOVE INTO OUR SOUTHERN AREAS WHERE ISOLD TSRA
ARE POSSIBLE. AFTN TEMPS SHOULD BE SEVERAL DEGREES LOWER BUT STILL
REMAIN HOT AND NEARING THE CENTURY MARK.

ANY CONVECTION THAT DEVELOPS SUNDAY COULD PERSIST SUNDAY NIGHT WHILE
MOVING NORTH AND EAST MOVING INTO THE BLUE AND WALLOWA AREAS. A
DISTURBANCE IS FORECAST TO MOVE INTO THE REGION MONDAY AND THE AREA
OF TSRA ARE EXPECTED TO EXPAND IN COVERAGE TO ALSO INCLUDE PORTIONS
OF THE BASIN. IN ADDITION AFTN TEMPS ARE EXPECTED TO BE COOLER BUT
STILL REMAIN ABOVE NORMAL ON MONDAY.

LONG TERM...MONDAY NIGHT THROUGH FRIDAY NIGHT...THERE IS FAIRLY
GOOD MODEL AGREEMENT TO START THE EXTENDED...WITH BOTH THE LATEST
GFS AND EC INDICATING A SHORTWAVE TROUGH MOVING THROUGH THE AREA
MONDAY NIGHT. THIS TROUGH WILL COMBINE WITH MODERATE INSTABILITY TO
CREATE A CHANCE OF SHOWERS AND THUNDERSTORMS OVER PARTS OF THE AREA
DURING THIS TIME. BEYOND THIS THE GUIDANCE BEGINS TO SIGNIFICANTLY
DIVERGE ON THE TIMING AND PLACEMENT OF ANY UPPER DISTURBANCES THAT
MAY AFFECT THE AREA. THE LATEST EC ALONG WITH SEVERAL PREVIOUS RUNS
HAVE BEEN FAIRLY CONSISTENT IN BRINGING A MORE COHERENT AND STRONGER
UPPER LEVEL TROUGH INTO THE AREA FOR TUESDAY AND WEDNESDAY...THEN A
CLOSED UPPER LEVEL LOW ACROSS THE FAR NORTHERN PORTION OF THE CWA BY
THURSDAY. BASED ON CONSISTENCY AND COLLABORATION WITH SURROUNDING
OFFICES DECIDED TO LEAN THE FORECAST MORE TOWARD THE
WETTER/UNSETTLED EC SOLUTION. THEREFORE ADDED A CHANCE OF SHOWERS
AND A SLIGHT CHANCE OF THUNDER INTO THE FORECAST FOR TUESDAY AND
WEDNESDAY. WITH MUCH UNCERTAINTY IN THE TIMING AND EVENTUAL EXIT OF
THE TROUGH WENT AHEAD AND LEFT A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS MAINLY IN THE MOUNTAINS ON THURSDAY AND FRIDAY.
ALTHOUGH AN OUTLIER AT THIS TIME THE LATEST GFS WOULD SUGGEST THAT
CONDITIONS WOULD REMAIN DRIER AND WARMER FOR TUESDAY THROUGH
THURSDAY OVER MUCH OF THE AREA UNDER A WEAK UPPER RIDGE...THEN THE
FLOW WOULD TURN MORE SOUTHERLY WITH POSSIBLE SHOWERS AND
THUNDERSTORMS ON FRIDAY AS A WEAK AND RATHER DISJOINTED UPPER LEVEL
TROUGH MOVES THROUGH.

TEMPERATURES WILL BE ON A COOLING TREND THROUGH THE WEEK...AGAIN
LEANED TOWARD THE MORE CONSISTENT EC SOLUTION FOR TEMPERATURES.  IN
THE LOWER ELEVATIONS TUESDAY STARTS OFF IN THE UPPER 80S TO MID 90S
BEFORE DROPPING INTO THE 80S FOR WEDNESDAY THROUGH FRIDAY...THIS IS
ABOUT 5 DEGREES BELOW AVERAGE. HIGH TEMPERATURES TUESDAY THROUGH
FRIDAY WILL BE IN THE UPPER 60S AND 70S IN THE MOUNTAINS....WITH
LOWS IN THE UPPER 30S TO 40S. 77

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  64 103  65 100 /   0   0   0  10
ALW  69 104  70 100 /   0   0   0  10
PSC  60 104  64 102 /   0   0   0   0
YKM  63 100  65  98 /   0   0   0   0
HRI  61 104  63 101 /   0   0   0   0
ELN  60 102  62 100 /   0   0   0   0
RDM  55 101  56  95 /  20  10  10  20
LGD  51  98  56  97 /   0  10  10  10
GCD  55 103  56  97 /  10  10  10  20
DLS  65 102  67 100 /   0   0   0  10

&&

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

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

     RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ611.

WA...RED FLAG WARNING UNTIL 10 PM PDT SATURDAY FOR WAZ639-641-643.

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

&&

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

$$

88/77/88/88


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