Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 301808 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1105 AM PDT WED JUL 30 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...UPDATE...AN UPPER RIDGE REMAINS OVER THE WESTERN U.S.
THIS MORNING. AS SUCH THE UPPER LEVEL FLOW OVER THE PACIFIC
NORTHWEST REMAINS SOUTHWEST TO WEST-SOUTHWEST. ONE WAVE WITHIN THIS
FLOW WILL SWING OUT OF THE AREA TODAY. THIS WILL CAUSE SOME DRYING
AND STABILIZING ACROSS OUR NORTHERN ZONES, ESPECIALLY OVER SOUTH-
CENTRAL WASHINGTON. WILL DECREASE SHOWER AND THUNDERSTORM COVERAGE
OVER NORTHEAST OREGON DUE TO THE DECREASING INSTABILITY BEHIND THIS
EXITING WAVE. MEANWHILE ANOTHER WAVE WILL MOVE NORTH OUT OF
CALIFORNIA THIS AFTERNOON AND EVENING. THIS WAVE WILL BRING ANOTHER
ROUND OF MOISTURE AND LIFT INTO CENTRAL AND EAST-CENTRAL OREGON.
THUS WILL CONTINUE TO INDICATE SCATTERED SHOWERS AND THUNDERSTORMS
IN THESE AREAS FOR THE AFTERNOON AND EVENING. PRECIPITABLE WATER
AMOUNTS ACROSS THE SOUTHERN HALF OF OREGON ARE RUNNING AROUND 1 INCH
SO EXPECT MEASURABLE PRECIP UNDER STORM CORES IN CENTRAL AND EAST-
CENTRAL OREGON. WILL SEE ANOTHER VERY WARM DAY AND WILL KEEP CURRENT
HEAT ADVISORIES IN PLACE. 90

&&

.AVIATION...18Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS. FEW-SCT MID AND HIGH LEVEL CLOUDS FROM THUNDERSTORM ANVIL
BLOWOFF OVER THE COLUMBIA-DESCHUTES PLATEAU THIS AFTERNOON WILL BE
POSSIBLE AT KDLS, KPDT AND KALW AFTER 22Z. THIS AFTERNOON EXPECT A
REPEAT OF THUNDERSTORMS IN CENTRAL OREGON AFTER 21Z AND HAVE VCTS IN
THE TAFS AT KBDN AND KRDM STARTING AT 22Z. SURFACE WINDS WILL REMAIN
BELOW 15 KTS FOR THE NEXT 24 HOURS, EXCEPT KDLS MAY HAVE SOME GUSTS
UP TO 26 KTS THIS AFTERNOON. KRDM AND KBDN WILL HAVE SUSTAINED
NORTHERLY WINDS OF 10-20 KTS, EXCEPT WHEN THUNDERSTORMS ARE IN
VICINITY WHICH MAY PRODUCE OUTFLOW GUST FRONTS WITH VARIABLE WINDS
20-25 KTS WITH HIGHER GUSTS TO 35-40 KTS.  POLAN

&&

.LONG TERM...PREVIOUS DISCUSSION...EASTERN OREGON AND WASHINGTON
WILL BE ON THE WESTERN SIDE OF AN UPPER LEVEL RIDGE THROUGH AT LEAST
MONDAY MORNING. SEVERAL WAVES WILL MOVE THROUGH THE AREA AND RIDE
OVER THE RIDGE. SUBSIDENCE FROM THE RIDGE WILL BRING SOUTH TO
SOUTHWEST FLOW AND HOT TEMPERATURES TO THE REGION. THIS SOUTHERLY
FLOW WILL ALSO BRING MONSOON MOISTURE INTO THE AREA AT TIMES.
THUNDERSTORMS ACTIVITY WILL BE ENHANCED BY HEATING DURING THE
AFTERNOON AND EVENING...BUT WEAK WAVES MAY TRIGGER NIGHTTIME
CONVECTION AS WELL.

SOUTHWEST FLOW WILL BE OVER THE AREA FRIDAY. THE GFS AND ECMWF BRING
A WAVE THROUGH THE AREA FRIDAY AFTERNOON. EXPECT CONVECTION TO
LINGER INTO THE EVENING BEFORE DECREASING OVERNIGHT. SATURDAY
ANOTHER WAVE WILL FORM OFFSHORE AND MOVE INTO EASTERN OREGON AND
WASHINGTON SATURDAY NIGHT AND SUNDAY. THIS WILL REINFORCE THE
SOUTHERLY FLOW AND KEEP A CHANCE OF THUNDERSTORMS OVER THE CWA.
MONDAY THE GFS KEEPS A SOUTHERLY FLOW AND BRINGS ANOTHER WEAK WAVE
TO ENHANCE THUNDERSTORM ACTIVITY. THE ECMWF DEVELOPS A WESTERLY FLOW
WITH THE BEST CONVECTIVE POTENTIAL IN SOUTHERN IDAHO AND MONTANA.
THE GFS ENSEMBLES SHOW BOTH SCENARIOS. KEPT A PERSISTENCE FORECAST
WITH SLIGHT CHANCE OF THUNDERSTORMS CENTRAL TO NORTHEAST OREGON
MOUNTAINS...BUT HAVE LOW CONFIDENCE IN DETAILS. TUESDAY BOTH 0Z
MODELS INDICATE DRY WESTERLY FLOW DEVELOPING BUT ENOUGH INSTABILITY
AND MOISTURE MAY LINGER OVER THE NORTHEAST OREGON MOUNTAINS TO
TRIGGER THUNDERSTORMS AGAIN TUESDAY AFTERNOON/EVENING.

&&

.FIRE WX...WARM AND DRY CONDITIONS WILL PERSIST AS A RIDGE OF HIGH
PRESSURE REMAINS OVER THE REGION. OVERNIGHT HUMIDITY RECOVERY WILL
BE POOR TO MODERATE. EACH DAY THIS WEEK...THUNDERSTORM CHANCES WILL
INCREASE AND SPREAD NORTH AND EAST AS SEVERAL WEAK DISTURBANCES
INTERACT WITH MONSOON FLOW. MOST THUNDERSTORMS SHOULD STAY SOUTH OF
THE WASHINGTON BORDER UNTIL FRIDAY AND SATURDAY. STORMS THAT DEVELOP
WILL BE A MIXTURE OF WET AND DRY WITH PRECIPITATION RANGING FROM A
FEW HUNDREDTHS OF AN INCH TO AROUND A QUARTER OF AN INCH. RED FLAG
WARNINGS HAVE BEEN ISSUED FOR ABUNDANT LIGHTNING ACROSS CENTRAL
OREGON TODAY THROUGH SATURDAY. OVER THE NORTHEAST MOUNTAINS...ONLY
ISOLATED THUNDERSTORMS ARE EXPECTED TODAY. SCATTERED THUNDERSTORMS
WILL THEN BE POSSIBLE ACROSS A LARGER AREA ON THURSDAY...AND RED
FLAG WARNINGS FOR THE NORTHEAST MOUNTAINS BEGIN THURSDAY AFTERNOON.
COBB

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT 103  69  98  69 /  10  10  10  10
ALW 103  72  99  73 /  10  10  10  10
PSC 105  69 101  70 /  10   0  10  10
YKM 101  67  99  69 /   0   0  10  10
HRI 105  69 100  69 /  10   0  10  10
ELN 100  62  97  62 /   0   0  10  10
RDM  96  61  93  60 /  30  30  30  30
LGD  97  64  92  62 /  20  20  30  30
GCD  99  64  92  63 /  30  30  30  30
DLS  96  67  97  68 /  10  10  10  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 11 PM PDT SATURDAY
     ORZ503-505-506-509>511.

     RED FLAG WARNING FROM 1 PM THURSDAY TO 11 PM PDT SATURDAY
     ORZ050-502-507.

     HEAT ADVISORY FROM NOON TODAY TO 9 PM PDT THIS EVENING
     ORZ044-507.

     RED FLAG WARNING FROM 1 PM THIS AFTERNOON TO 11 PM PDT SATURDAY
     ORZ049.

WA...RED FLAG WARNING FROM 1 PM THURSDAY TO 11 PM PDT SATURDAY WAZ030.

     HEAT ADVISORY FROM NOON TODAY TO 9 PM PDT THIS EVENING
     WAZ027-029.

     HEAT ADVISORY UNTIL 9 PM PDT THIS EVENING WAZ028.

&&

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

$$

90/76/99/82






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