Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 282355 AAA
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
450 PM PDT MON JUL 28 2014

.UPDATE...THE LATEST RADAR WAS SHOWING SOME SHOWERS DEVELOPING OVER
CENTRAL OREGON AND THE ZONES WERE UPDATED TO INCLUDE THIS DURING THE
EVENING. ALSO A FEW TSRA HAD DEVELOPED NEAR EASTERN GRANT COUNTY AND
THE PRESENT SHORT TERM FORECAST APPEARS ON TRACK FOR NOW.

&&

.PREV DISC... /ISSUED 336 PM PDT MON JUL 28 2014/

SHORT TERM...TONIGHT THROUGH THURSDAY...THE FOUR CORNER HIGH
PRESSURE RIDGE CONTINUES TO DOMINATE THE WEATHER PATTERN. THE FLOW
AROUND THIS HIGH PLACES THE AREA UNDER A SOUTHWEST FLOW WITH SOME
MONSOONAL MOISTURE CLIPPING THE SOUTHEAST PORTION OF THE FORECAST
AREA. THIS WILL PLACE THE SOUTH AND EASTERN PORTION OF THE FORECAST
AREA UNDER AT LEAST A SLIGHT CHANCE OF THUNDERSTORM THREAT THROUGH
THE PERIOD. MODELS ARE HAVING A HARD TIME PICKING UP THE TIMING AND
STRENGTH OF THE RIPPLES OR SHORTWAVES PROPAGATING AROUND THE HIGH.
THE LACK OF MODEL CONSISTENCY MAKES IT DIFFICULT TO FORECAST THE
POSSIBLE INCREASE IN THUNDERSTORM COVERAGE FROM SLIGHT CHANCE TO
CHANCE OR SCATTERED. ONE MODEL...THE GFS...IS HINTING AT A STRONGER
SHORTWAVE ARRIVING LATE TUESDAY INTO SOUTHERN OREGON AND THEN ACROSS
NORTHEAST OREGON WEDNESDAY. IF CORRECT THEN THIS COULD BE THE
TRIGGER TO ELEVATE THE THUNDERSTORM THREAT. PREFER TO WAIT
ANOTHER MODEL RUN OR TWO TO SEE IF IT REMAINS CONSISTENT IN THE
MODELS BEFORE ACTING ON IT. HIGH TEMPERATURES WILL REMAIN HOT AND
ABOVE NORMAL BUT AMOUNT OF CLOUD COVER WILL DETERMINE ACTUAL
TEMPERATURES EACH DAY. IF THE GFS IS CORRECT THEN CLOUD COVER WOULD
PROVIDE COOLER TEMPERATURES ON WEDNESDAY. PREFERRED TO KEEP
TEMPERATURES CONSISTENT DAY TO DAY AND TWEAK AS MODELS COME INTO
BETTER AGREEMENT ON THE TIMING AND MOVEMENT OF THE SHORTWAVES.

LONG TERM...THURSDAY NIGHT THROUGH MONDAY...OUR AREA WILL CONTINUE
TO BE ON THE WESTERN SIDE OF AN UPPER RIDGE THROUGH THE LONG TERM
PERIOD. HOWEVER, MODELS DIVERGE ON DETAILS OF THE DAY TO DAY
SITUATION SO CONFIDENCE ON ANY PARTICULAR DAY IS ON THE LOW SIDE. A
SOUTHWEST FLOW WILL BE OVER THE AREA THURSDAY NIGHT INTO FRIDAY.
BOTH THE GFS BRINGS A WAVE INTO THE AREA FRIDAY AFTERNOON WHILE THE
ECMWF DEVELOPS A CLOSED LOW OVER IDAHO, POSSIBLY FROM MOISTURE AND
ENERGY FROM TROPICAL STORM HERNAN CURRENTLY OFF THE BAJA MEXICO
COAST. HAVE KEPT A CHANCE OF THUNDERSTORMS OVER THE ENTIRE AREA ON
FRIDAY THOUGH WAS TEMPTED TO KEEP THE WASHINGTON CASCADES AND
COLUMBIA BASIN DRY. THE WAVE/UPPER LOW MOVES INTO MONTANA ON
SATURDAY AND OUR FLOW TURNS A LITTLE MORE SOUTHERLY. THERE WILL
CONTINUE TO BE A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS OVER
CENTRAL OREGON, THE CASCADES AS FAR NORTH AS MOUNT ADAMS AND THE
EASTERN OREGON MOUNTAINS. BOTH THE GFS AND ECMWF DEVELOP A WEAK LOW
OFF OF CALIFORNIA BY SUNDAY WHICH WILL REINFORCE THE SOUTHERLY FLOW
AND AID IN INCREASING THE MOISTURE FLOW ON SUNDAY AND MONDAY. HAVE
KEPT A SLIGHT CHANCE OF THUNDERSTORMS OVER THE ENTIRE AREA EXCEPT
FOR THE COLUMBIA BASIN ON SUNDAY AND MONDAY. WITH THE RIDGE
PERSISTING, TEMPERATURES WILL CONTINUE IN THE MID 90S TO LOWER 100S
WITH MID 80S TO MID 90S IN THE MOUNTAINS. PERRY

AVIATION...00Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS WITH MAINLY CLEAR SKIES THROUGH 00Z TOMORROW. AN EXCEPTION
WILL BE FEW-SCT HIGH BASED CUMULUS ABOVE 10000 FEET AGL AT KBDN AND
KRDM. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS THIS EVENING AND
AGAIN TOMORROW AFTERNOON IN CENTRAL OREGON AND THE OCHOCO-JOHN DAY
HIGHLANDS, POSSIBLY AFFECTING KBDN AND KRDM, BUT THE PROBABILITY WAS
TOO LOW TO MENTION IN THOSE TAFS. SURFACE WINDS WILL GENERALLY
REMAIN BELOW 15 KTS FOR THE NEXT 24 HOURS THOUGH KDLS MAY HAVE SOME
GUSTS TO 20 KTS EARLY THIS EVENING AGAIN TOMORROW AFTERNOON. PERRY

FIRE WX...CONDITIONS WILL CONTINUE TO BE WARM AND DRY AS A RIDGE OF
HIGH PRESSURE REMAINS OVER THE REGION. EXPECT OVERNIGHT RELATIVE
HUMIDITY RECOVERIES TO BE MODERATE TO POOR...ESPECIALLY ALONG
RIDGETOPS AGAIN TONIGHT. HIGH LEVEL MONSOON MOISTURE IS CONTINUING
TO MOVE INTO THE REGION AND THERE COULD BE AN ISOLATED THUNDERSTORM
IN CENTRAL OREGON OR OVER THE NORTHEAST MOUNTAINS THIS AFTERNOON OR
EVENING. EACH DAY THIS WEEK...SHOWER AND THUNDERSTORM CHANCES WILL
SPREAD NORTH AND EAST AS SEVERAL WEAK DISTURBANCES INTERACT WITH THE
MONSOON FLOW. HOWEVER...THUNDERSTORMS SHOULD MOSTLY STAY SOUTH OF
THE WASHINGTON BORDER. ANY STORMS THAT DO DEVELOP TODAY AND TOMORROW
WILL INITIALLY HAVE LIMITED PRECIPITATION. WILL MONITOR STORM
DEVELOPMENT AS WELL AS CHECK MODEL CONSISTENCY TO DETERMINE IF ANY
RED FLAG WARNINGS WILL NEED TO BE ISSUED IN THE COMING DAYS.  COBB

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  66  98  68  97 /   0  10  10  10
ALW  71 101  72 100 /   0   0   0  10
PSC  67 102  70 100 /   0   0   0   0
YKM  62 101  66  99 /   0   0   0   0
HRI  66 101  68 100 /   0   0   0  10
ELN  60 100  62  97 /   0   0   0   0
RDM  46  94  58  94 /  20  10  20  20
LGD  63  95  63  92 /  20  10  20  20
GCD  66  94  66  91 /  20  20  20  20
DLS  65  97  67  96 /   0   0   0  10

&&

.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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