Area Forecast Discussion
Issued by NWS Pendleton, OR

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000
FXUS66 KPDT 281703 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1003 AM PDT MON JUL 28 2014

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH TUESDAY...THE FOUR CORNER HIGH PRESSURE
RIDGE CONTINUES TO DOMINATE THE WEATHER PATTERN. THE FLOW AROUND
THIS HIGH PLACES US UNDER A SOUTHWEST FLOW WITH SOME MONSOONAL
MOISTURE CLIPPING THE FORECAST AREA. THIS WILL LEAD TO THE SLIGHT
CHANCE OF THUNDERSTORMS FROM CENTRAL OREGON OVER TO THE WALLOWA
MOUNTAIN REGION TODAY AND TUESDAY. IF STORMS DO DEVELOP THEY WILL BE
HIGH BASED AND PRODUCE VERY LITTLE RAINFALL. HIGH TEMPERATURES WILL
CONTINUE TO RUN ABOVE NORMAL BUT BELOW THE WIDESPREAD 103 DEGREES
NEEDED FOR HEAT ADVISORIES.

&&

.AVIATION...18Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT 24
HOURS WITH MAINLY CLEAR SKIES TODAY. FEW-SCT HIGH BASED CUMULUS
ABOVE 10000 FEET AGL IS POSSIBLE AFTER 21Z AT KBDN AND KRDM. THERE
IS A SLIGHT CHANCE OF THUNDERSTORMS 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. FEW-SCT MID AND
HIGH LEVEL CLOUDS ABOVE 12000 FEET AGL WILL BEGIN MOVING INTO THE
AREA AFTER 12Z TONIGHT. SURFACE WINDS WILL GENERALLY REMAIN BELOW 15
KTS FOR THE NEXT 24 HOURS THOUGH KDLS MAY HAVE SOME GUSTS TO 20 KTS
THIS AFTERNOON AND EARLY EVENING. PERRY

&&

.PREV DISC... /ISSUED 140 AM PDT MON JUL 28 2014/

SHORT TERM...TODAY THROUGH WEDNESDAY...AN UPPER RIDGE OVER THE
INLAND WEST AND A TROUGH IN THE GULF OF AK WILL CONTINUE TO KEEP A
SOUTHWEST FLOW OVER THE REGION AND CWA. THIS PATTERN WILL CAUSE HOT
AND DRY CONDITIONS TO PERSIST THROUGH THE SHORT TERM PERIOD GOING
INTO THE LONG TERM. SOME LIMITED MID LEVEL MONSOONAL MOISTURE WILL
CONTINUE TO BE PULLED NORTHWARD INTO THE CWA...ESPECIALLY SOUTHERN
AREAS. THE ATMOSPHERE WILL BECOME UNSTABLE DUE TO HEATING EACH
AFTERNOON. THIS COMBINED WITH THE MID LEVEL MOISTURE AND CAPE WILL
RESULT IN ISOLATED AFTERNOON AND EVENING THUNDERSTORMS EACH DAY OVER
PORTIONS OF CENTRAL AND NORTHEAST OREGON. TODAY ANY THUNDERSTORMS
THAT FORM WILL BE CONFINED TO CENTRAL OREGON AND THE JOHN DAY
HIGHLANDS. ELSEWHERE THE ATMOSPHERE WILL BE TOO DRY. THUNDERSTORM
POTENTIAL COVERAGE WILL INCREASE EACH DAY SPREADING SLOWLY NORTHWARD
AND EASTWARD AS THE AREA OF INSTABILITY INCREASES. THE BEST CHANCES
FOR ANY THUNDERSTORMS WILL BE OVER CENTRAL OREGON AND THE OREGON
CASCADE EAST SLOPES. THE LOWER LEVELS WILL BE QUITE DRY SO ANY
THUNDERSTORMS WILL BE HIGH BASED WITH LITTLE RAINFALL REACHING THE
GROUND. THUS THERE COULD BE A FIRE WEATHER CONCERN DUE TO LIGHTNING
IGNITING NEW WILDFIRES. TEMPERATURES WILL BE HOT...BUT NOT QUITE AS
HOT AS PREVIOUSLY EXPECTED. MAXIMUM TEMPERATURES WILL WARM TO AROUND
100-103 IN THE LOWER ELEVATIONS WITH 80S AND 90S ELSEWHERE. TUESDAY
WILL BE THE HOTTEST DAY AND THEN THERE WILL BE SLIGHT COOLING AS MID
AND HIGH CLOUDS INCREASE DUE TO CONVECTION. NIGHT TIME TEMPERATURES
WILL REMAIN WARM DUE TO THE MID AND HIGH CLOUDS PREVENTING STRONG
RADIATIONAL COOLING. HOWEVER...TEMPERATURES ARE NO LONGER EXPECTED
TO REACH HEAT ADVISORY CRITERIA ANYMORE. THIS WEATHER PATTERN WILL
PERSIST INTO THE EXTENDED FORECAST PERIOD. 88

LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...EASTERN OREGON AND
WASHINGTON WILL BE ON THE WESTERN SIDE OF AN UPPER LEVEL RIDGE
THROUGH THE LONG TERM PERIOD. 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. THERE WILL BE A THREAT FOR THUNDERSTORMS EACH DAY AS UNSTABLE
SOUTHERLY FLOW COMBINES WITH DAYTIME HEATING. THIS THREAT WILL
INCREASE LATER IN THE WEEK AS MONSOON MOISTURE INCREASES. CLOUD
DEBRIS FROM THUNDERSTORMS KEEP WILL KEEP OVERNIGHT LOWS ELEVATED
WITH 60S TO LOWER 70S EXPECTED AT LOWER ELEVATIONS.

MODELS HAVE BEEN CONSISTENT WITH THE OVERALL PATTERN AND INCREASING
INSTABILITY WITH TIME...BUT INDIVIDUAL WEAK WAVES THAT WOULD ENHANCE
INSTABILITY...CONVECTIVE ACTIVITY...AND MONSOONAL MOISTURE ADVECTION
VARY WITH EACH MODEL RUN. THUNDERSTORMS ACTIVITY WILL BE ENHANCED BY
HEATING DURING THE AFTERNOON AND EVENING...BUT WEAK WAVES MAY
TRIGGER NIGHTTIME CONVECTION AS WELL.   COONFIELD

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  99  66  98  68 /   0   0  10  10
ALW 101  71 101  74 /   0   0   0   0
PSC 101  67 102  70 /   0   0   0   0
YKM  98  62 100  68 /   0   0   0   0
HRI 101  66 101  68 /   0   0   0   0
ELN  97  60  96  65 /   0   0   0   0
RDM  96  46  94  58 /  10  10  20  20
LGD  96  63  94  61 /  10  10  10  20
GCD  96  66  94  66 /  10  20  20  20
DLS  98  65  96  68 /   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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