000
FXUS66 KPDT 232303 AAA
AFDPDT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
400 PM PDT THU MAY 23 2013

UPDATED THE AVIATION DISCUSSION

.SHORT TERM...TONIGHT THROUGH SUNDAY...INSTABILITY IS ON THE 
INCREASE THIS AFTERNOON AS SURFACE HEATING COMBINES WITH THE COLD 
AIR ALOFT TO CREATE AN UNSTABLE ENVIRONMENT OVER THE REGION. EXPECT 
INSTABILITY SHOWERS WITH POSSIBLE THUNDERSTORMS TO CONTINUE INTO THE 
EVENING THEN DECREASE AROUND SUNSET AND AFTER. OTHER CONCERN IS A 
BAND OF PRECIPITATION ROTATING AROUND THE UPPER LEVEL LOW PRESSURE. 
THIS BAND IS NOW OVER SOUTHWEST WASHINGTON AND NORTHWEST OREGON. 
MODEL PROJECTIONS INDICATE THAT THIS WILL SWEEP INTO THE WESTERN 
PORTION OF THE FORECAST AREA LATER TONIGHT THEN MOVE ACROSS THE 
FORECAST AREA LATE TONIGHT AND EARLY FRIDAY. THIS WILL BRING A MORE 
STEADY PRECIPITATION TO THE FORECAST AREA. SNOW LEVELS WILL BE 
AROUND 4000 TO 5000 FEET WITH SEVERAL INCHES EXPECTED ABOVE THESE 
ELEVATIONS BY FRIDAY MAINLY IN THE WESTERN PORTION OF THE FORECAST 
AREA. DON'T EXPECT ACCUMULATIONS IN THE POPULATED AREAS ALONG THE 
EAST SLOPES OF THE CASCADES BUT MOUNTAIN PASSES WILL BE IMPACTED. 
SHOULD BE ENOUGH CLOUD COVER OVERNIGHT TO MITIGATE THE COOL 
TEMPERATURES AND PREVENT FREEZING TEMPERATURES IN THE LOWER 
ELEVATIONS. UPPER LEVEL LOW WILL LIFT A LITTLE NORTHWARD ON FRIDAY 
WITH BEST CHANCE OF SHOWERS FOCUSED OVER THE NORTHERN PORTION OF THE 
FORECAST AREA. EXPECT ENOUGH STABLE CONDITIONS FRIDAY NIGHT THAT I 
WENT WITH A MAINLY DRY FORECAST. SATURDAY AND SUNDAY WILL SEE 
ANOTHER WEAKER UPPER LEVEL DISTURBANCE IMPACTING THE REGION WITH 
MORE SHOWERS AND POTENTIAL THUNDERSTORMS MAINLY ON SUNDAY. 
TEMPERATURES WILL BE SLOWLY WARMING WITH DAYTIME TEMPERATURES 
REACHING NEAR NORMAL BY SUNDAY BUT CONTINUED COOL OVERNIGHT
TEMPERATURES.  

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY. A DISTURBANCE IS 
EXPECTED TO TRACK ACROSS THE TWO STATE AREA SUNDAY NIGHT AND SOME 
CONVECTION IS POSSIBLE MAINLY OVER OUR EASTERN ZONES. AS THE 
DISTURBANCE MOVES EAST...A LOW PRESSURE SYSTEM IS FORECAST TO NEAR 
THE PACNW EARLY MONDAY. THIS SHOULD SPREAD CLOUDS AND SHOWERS INTO 
THE TWO STATE AREA MONDAY AND TUESDAY. AS THE SYSTEM DRIFTS AWAY... 
MOISTURE LINGERS OVER THE REGION DURING THE MIDDLE OF THE WEEK AND 
THE CLOUDS AND SHOWERS SHOULD PERSIST. ANOTHER LOW PRESSURE SYSTEM 
APPROACHES WA/OR ON THURSDAY AND WILL SPREAD ADDITIONAL MOISTURE 
INTO OUR AREA KEEPING THE UNSETTLED WEATHER IN THE FORECAST. 
TEMPERATURES WILL REMAIN NEAR NORMAL THROUGH THE PERIOD.

&&

.AVIATION...LCL MVFR CEILINGS ARE POSSIBLE AT ALL TAF SITES IN 
SHOWERS UNTIL 02Z. HOWEVER A LOW PRESSURE SYSTEM IS FORECAST TO MOVE 
INLAND AND INCREASE CLOUDS AND SHOWERS ACROSS THE AREA INTO TONIGHT. 
AREAS OF MVFR CEILINGS WILL DEVELOP AT TAF SITE KDLS IN AND NEAR 
SHOWERS. OTHERWISE DETERIORATING CEILINGS CAN BE EXPECTED AT TAF 
SITES KYKM AND KRDM THAT WILL LOWER TO AREAS OF MVFR CONDITIONS 
AROUND 02Z. AFTER 04Z THE REMAINDER OF THE TAF SITES SHOULD 
EXPERIENCE MVFR CEILINGS IN SHOWERS INTO FRIDAY. 

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  42  62  39  68 /  30  50  20  10 
ALW  42  63  42  71 /  30  50  20  10 
PSC  43  67  40  74 /  20  40  20  10 
YKM  42  63  42  69 /  20  40  20  10 
HRI  44  66  40  73 /  20  50  10  10 
ELN  38  60  40  65 /  30  40  20  10 
RDM  38  56  32  64 /  70  30  10  10 
LGD  35  55  35  64 /  40  60  20  20 
GCD  34  54  33  65 /  40  50  10  20 
DLS  44  64  43  71 /  60  40  10  10 

&&

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

THREAT INDEX
FRIDAY : GREEN
SATURDAY : GREEN
SUNDAY : GREEN

GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.

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

$$

91/97/97