Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 280505 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1005 PM PDT MON JUL 27 2015

.UPDATE...CONVECTION HAS DISSIPATED OVER THE CWA THOUGH SOME SHOWERS
STILL PERSIST NORTH AND EAST OF WALLOWA COUNTY. RIDGE WILL BUILD
INTO WASHINGTON TUESDAY. WITH CLEARING SKIES EXPECT GOOD
RADIATIONAL COOLING OVERNIGHT. CURRENT FORECAST ON TRACK. COONFIELD

&&

.AVIATION...06Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HRS. MAINLY CLEAR SKIES AREA WIDE. WINDS WILL BE LESS THAN 12 MPH.
76

&&

.PREV DISCUSSION... /ISSUED 412 PM PDT MON JUL 27 2015/

SHORT TERM...TONIGHT THROUGH THURSDAY AFTERNOON...A MID/UPPER LEVEL
LONG WAVE TROUGH HAS MOVED INTO IDAHO/WESTERN MONTANA THIS
AFTERNOON. THE WESTERN FLANK OF THE TROUGH WILL BRING A FEW MORE
HOURS OF WRAP AROUND MOISTURE INTO EARLY THIS EVENING TO THE
NORTHERN BLUE MOUNTAINS, WALLOWA COUNTY AND THE WALLOWA MOUNTAINS.
AS SUCH ISOLATED SHOWERS AND PERHAPS A FEW ISOLATED LIGHTNING
STRIKES WILL BE POSSIBLE UNTIL SUNSET THIS EVENING IN THE
AFOREMENTIONED AREAS. THE LONG WAVE TROUGH WILL USHER IN A COOLER AND
DRIER AIRMASS TONIGHT AND TUESDAY NIGHT. THE COOLER AIR WILL BE MOST
NOTICEABLE IN THE MOUNTAINS ABOVE 3000 FT ABOVE MEAN SEA LEVEL OVER
THE NEXT COUPLE OF NIGHTS. LOW TEMPERATURES AROUND DAYBREAK ON
TUESDAY AND WEDNESDAY MORNINGS WILL BE NEAR RECORD LOWS, IN THE
LOWER TO MID 30S, ESPECIALLY IN THE BLUE MOUNTAINS AND IN THE GRANDE
RONDE VALLEY, AND ALSO IN THE WALLOWA MOUNTAINS WITH BELOW NORMAL
LOWS EXPECTED IN OTHER MOUNTAINOUS AREAS. CAMPERS AND HIKERS SHOULD
PACK EXTRA WARM CLOTHING AND EXTRA WARM THERMAL SLEEPING BAGS WITH
THEM FOR OVERNIGHT SOJOURNS IN THE CASCADES MOUNTAINS OF OREGON AND
WASHINGTON, THE BLUE MOUNTAINS, THE WALLOWA MOUNTAINS, THE ELKHORN
AND STRAWBERRY MOUNTAINS, THE OCHOCO-JOHN DAY HIGHLANDS AND THE
ALDRICH MOUNTAINS BY VIRTUE OF SIGNIFICANTLY BELOW NORMAL LOW
TEMPERATURES AT HIGHER ELEVATIONS TONIGHT AND TUESDAY NIGHT.

LOOKING UPSTREAM ACROSS THE NORTHEAST PACIFIC, A RIDGE OF MID/UPPER
LEVEL HIGH PRESSURE WILL BE MOVING EAST TO THE COAST OVERNIGHT WITH
THE RIDGE AXIS MOVING INTO THE FORECAST AREA ON TUESDAY. THE RIDGE
FLATTENS OUT A BIT TUESDAY NIGHT OVER THE REGION AND THEN MERGES
WITH THE MID/UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE FOUR
CORNERS AREA ON WEDNESDAY. THE WESTERN STATES HIGH PRESSURE RIDGE
THEN AMPLIFIES NORTHWARD INTO THE PACIFIC NORTHWEST WEDNESDAY NIGHT
AND THURSDAY. THEREFORE, EXPECT DRY CONDITIONS OVERNIGHT AND ON
TUESDAY THROUGH THURSDAY AFTERNOON. A WARMING TREND COMMENCES ON
WEDNESDAY WITH DAYTIME HIGH TEMPERATURES GETTING INTO THE LOWER TO
MID 90S FOR WEDNESDAY AND THURSDAY.  POLAN

LONG TERM...THURSDAY NIGHT THROUGH MONDAY...AN UPPER LEVEL RIDGE OF
HIGH PRESSURE WILL BE FIRMLY IN PLACE OVER THE REGION FOR THURSDAY
NIGHT AND FRIDAY. THIS WILL ALLOW ABOVE AVERAGE TEMPERATURES AND
GENERALLY CLEAR/DRY CONDITIONS TO CONTINUE. TEMPERATURES WILL BE IN
THE UPPER 90S TO LOW 100S FOR THE LOWER ELEVATIONS ON FRIDAY...WHICH
IS 10-15 DEGREES ABOVE AVERAGE. BY SATURDAY...SUNDAY AND MONDAY MID
AND UPPER LEVEL MONSOONAL MOISTURE WILL BEGIN TO PIVOT INTO THE
REGION FROM THE SOUTH. THIS ADDED MOISTURE WILL LIKELY ACT TO
INCREASE THE ELEVATED INSTABILITY DURING THE AFTERNOON AND EVENING
HOURS...THEREFORE ADDED A SLIGHT CHANCE FOR SHOWERS AND
THUNDERSTORMS INTO THE FORECAST...MAINLY IN THE OREGON MOUNTAINS
DURING THIS TIME. AS IS TYPICALLY THE CASE WITH MONSOON MOISTURE
CLOUD BASES ARE PROGGED TO BE RATHER ELEVATED...LIKELY BETWEEN 10-
15K FT AGL (AT LEAST TO START). MODEL SOUNDINGS ARE SHOWING THE
CLASSIC INVERTED "V" SHAPE...WITH DRY LOW LEVEL AIR PRESENT BELOW
10K FT AGL. HOWEVER AN INDICATION OF THE INCREASED MOISTURE IS THE
RISING PWATS...WHICH ARE FORECAST TO BE BETWEEN 0.75 AND 1.10 INCHES
BY SATURDAY NIGHT AND SUNDAY. IF STORMS DO FORM DRY LIGHTNING COULD
CERTAINLY END UP BEING AN ISSUE (AGAIN AT LEAST TO START)...AND THIS
IS A THREAT THAT WILL NEED TO BE WATCHED CAREFULLY IN THE COMING
DAYS. TEMPERATURES ARE EXPECTED TO REMAIN 8 TO 15 DEGREES ABOVE
NORMAL INTO THE WEEKEND AND EARLY NEXT WEEK...WITH EXACT
TEMPERATURES LIKELY DEPENDENT ON THE AMOUNT OF CLOUD COVER OVER THE
AREA. IN GENERAL EXPECT TEMPERATURES IN THE MID-90S TO LOW 100S
THROUGH MONDAY FOR THE VALLEYS AND BASINS WITH 80S TO LOWER 90S IN
THE MOUNTAINS. OVERNIGHT LOWS WILL ALSO BE ON THE RISE FOR THE
WEEKEND WITH THE INCREASED MOISTURE AND CLOUD COVER AROUND. LOWS
WILL BE IN THE 60S FOR THE LOWER ELEVATIONS WITH UPPER 40S AND 50S
IN THE MOUNTAINS. 77

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  50  84  53  95 /   0   0   0   0
ALW  55  86  58  95 /   0   0   0   0
PSC  52  87  51  97 /   0   0   0   0
YKM  51  84  53  93 /   0   0   0   0
HRI  50  87  52  96 /   0   0   0   0
ELN  53  86  51  96 /   0   0   0   0
RDM  38  83  43  93 /   0   0   0   0
LGD  39  80  42  90 /  10   0   0   0
GCD  42  85  46  94 /   0   0   0   0
DLS  56  90  57  99 /   0   0   0   0

&&

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

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

$$

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