012 
FXUS66 KPDT 241826 AAB
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1025 AM PST TUE NOV 24 2015

UPDATED AVIATION DISCUSSION TO ADD MORE DETAIL

.SHORT TERM...UPPER LOW MOVING ACROSS THE PACIFIC NORTHWEST TODAY
AND TONIGHT. CENTER OF THE LOW IS JUST OFF THE OREGON COAST THIS
MORNING. SATELLITE SHOWING OVERCAST CONDITIONS ACROSS THE FORECAST
AREA. PRECIPITATION IS MIXED WITH REPORTS OF RAIN FREEZING RAIN
AND SNOW AS TEMPERATURES ARE IN THE UPPER 20S TO LOWER 30S. AS THE
LOW CONTINUES TO MOVE SOUTH TODAY COLDER AIR WILL ADVECT INTO THE
REGION WITH INCREASING NORTHERLY WINDS. THIS WILL RESULT IN
PRECIPITATION CHANGING OVER TO ALL SNOW BY EVENING AND TONIGHT.
WITH THE LOW CENTERED OVER SOUTHERN OREGON AND NORTHERN CALIFORNIA
TONIGHT EXPECT SIGNIFICANT SNOW FOR CENTRAL AND NORTHEAST OREGON
THROUGH EARLY WEDNESDAY MORNING. CLEARING SKIES LATER WEDNESDAY
AS HIGH PRESSURE STARTS TO BUILD IN WITH A DRY COLD NORTH FLOW. 94

&&

.AVIATION...18Z TAFS...THE WARM LAYER ALOFT THAT HAD ALLOWED RAIN TO
REACH THE GROUND THIS MORNING IN THE LOWER COLUMBIA BASIN PRODUCING
FREEZING RAIN AT THE SURFACE HAS COOLED TO BELOW FREEZING AND THE
FORECAST VERTICAL TEMPERATURE PROFILE FOR THE COLUMBIA BASIN
AND SURROUNDING HIGHER TERRAIN WILL REMAIN BELOW FREEZING THROUGH THE
REST OF THIS STORM EVENT. THUS SNOW IS EXPECTED AT TAF SITES FROM
THIS POINT FORWARD FOR THE REMAINDER OF TODAY AND THROUGH THIS
EVENING FOR ANY PRECIPITATION THAT DOES OCCUR. CONDITIONS AT KRDM
AND KBDN ARE DOWN TO LIFR/IFR VIS DUE TO -SN/SN AND THESE CONDITIONS
ARE ALSO EXPECTED AT KPDT, KALW AND KDLS WITH THESE CONDITIONS
PERSISTING THROUGH THIS AFTERNOON INTO THIS EVENING. CONDITIONS HAVE
ALSO DETERIORATED TO IFR AT KPSC DUE TO LOW CIGS WITH -SN LIMITING
VIS TO AROUND 3SM THROUGH THIS AFTERNOON. SNOW HAS ENDED AT KYKM FOR
TODAY, ALTHOUGH MVFR VIS ARE POSSIBLE AT KYKM DUE TO MIST THIS
AFTERNOON. IN SUMMARY, LOW CLOUDS/FOG AND SNOW CONTINUING AT MOST
TAF SITES THROUGH THIS EVENING. NORTHERLY FLOW IN THE BOUNDARY LAYER
WILL CAUSE LOW CLOUDS AND SNOW TO PERSIST AT KALW AND KPDT THROUGH
THIS EVENING. MOST SITES WILL IMPROVE AFTER 25/06Z. WINDS WILL BE
NORTHERLY AND INCREASE THIS AFTERNOON AND EVENING TO 10-20 KTS AND
THESE WINDS SPEEDS WILL CONTINUE THROUGH 18Z TOMORROW MORNING.
POLAN

&&

.PREVIOUS DISCUSSION... /ISSUED 343 AM PST TUE NOV 24 2015/ 

SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...AN UPPER LEVEL LOW
WEST OF VANCOUVER ISLAND WILL MOVE SOUTH OFF THE COAST THIS
MORNING...THEN MOVE SOUTHEAST ACROSS NORTHERN CALIFORNIA AND NEVADA
TONIGHT AND WEDNESDAY. THIS WILL KEEP A MIX OF RAIN...FREEZING
RAIN...AND SNOW ACROSS EASTERN WASHINGTON AND OREGON TODAY.
WRAPAROUND MOISTURE WILL KEEP SNOW ACROSS THE AREA THIS EVENING. HIGH
PRESSURE WILL BUILD INTO SOUTHEAST WASHINGTON WEDNESDAY. 

COLD AIR IS TRAPPED IN THE LOWER COLUMBIA BASIN WITH AREAS OF LIGHT
FREEZING RAIN. FREEZING RAIN OR UNKNOWN PRECIP WITH BELOW FREEZING
TEMPERATURES HAVE BEEN REPORTED YKM, PSC, PDT, ALW, DLS, AND
PROSSER. TEMPERATURES AT MOST STATIONS IN THE COLUMBIA RIVER GORGE
HAVE RISEN ABOVE FREEZING BUT POCKETS OF COLDER AIR PROBABLY REMAIN.
ALL OTHER ZONES IN THE FREEZING RAIN ADVISORY STILL HAVE MAINLY
BELOW FREEZING TEMPERATURES. I WILL CONTINUE THE FREEZING RAIN
ADVISORIES AT THIS TIME.

SNOW OR RAIN CHANGING TO SNOW IS EXPECTED TO SPREAD ACROSS NORTHEAST
OREGON EARLY THIS MORNING. SNOW ADVISORIES ARE WILL START THIS
MORNING OVER ALL OREGON ZONES NOT COVERED BY FREEZING RAIN
ADVISORIES. 

A BACKDOOR ARCTIC FRONT WILL BRING DRIER AND MORE STABLE COLD AIR
WILL MOVE INTO NORTHERN WASHINGTON THIS EVENING AND SPREAD ACROSS
OREGON WEDNESDAY. SNOW WILL END OVER SOUTHEAST WASHINGTON EARLY
WEDNESDAY AND OVER OREGON BY WEDNESDAY NIGHT. BRISK NORTHERLY WINDS
WILL DEVELOP BEHIND THIS FRONT AND PERSIST WEDNESDAY EVENING.
COONFIELD

LONG TERM...THURSDAY THROUGH TUESDAY...DRY WEATHER WILL PREVAIL
THROUGH THE THANKSGIVING WEEKEND...BUT A NORTHEASTERLY FLOW ALOFT
WILL KEEP TEMPERATURES BELOW NORMAL. HIGH TEMPERATURES WILL BE IN
THE 20S TO MID 30S AND OVERNIGHT LOWS WILL BE IN THE SINGLE DIGITS
TO LOWER 20S. A SURFACE INVERSION WILL DEVELOP THURSDAY NIGHT AS
A RIDGE BUILDS OVER WASHINGTON. THE LONG CLEAR NIGHT AND LIGHT WINDS
WILL CREATE IDEAL CONDITIONS FOR PATCHY FREEZING FOG AND
STRATUS DEVELOPMENT IN THE LOWER COLUMBIA BASIN AND MOUNTAIN VALLEYS.
THE FOG COULD LAST THROUGH MONDAY...BUT AM NOT CONFIDENT IN THIS. A
LOBE OF ENERGY ASSOCIATED WITH THE CUTOFF LOW THAT BROUGHT SNOW TO
THE REGION COULD LINGER AND LESSEN THE CHANCES OF A PERSISTENT FOG
BY BRINGING CLOUDS TO THE AREA AND POSSIBLE EVEN SNOW SHOWERS.
HOWEVER...HAVE KEPT THE FORECAST DRY AND FOGGY FOR NOW. THE NEXT
CHANCE FOR RAIN AND SNOW WILL BE MONDAY NIGHT AND TUESDAY.
SLIGHTLY WARMER TEMPERATURES CAN ALSO BE EXPECTED TUESDAY. COBB

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  35  25  32  12 /  70  60  20   0 
ALW  38  26  35  15 /  70  60  10   0 
PSC  38  28  39  17 /  70  50  10   0 
YKM  37  25  38  14 /  60  40   0   0 
HRI  38  28  38  14 /  70  50  10   0 
ELN  35  22  34  13 /  60  30   0   0 
RDM  38  18  26   5 /  80  80  30   0 
LGD  40  25  29  12 /  80  60  30   0 
GCD  40  22  28   8 /  80  70  40  10 
DLS  40  29  40  19 /  70  60  10   0 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY FOR ORZ049-050-
     502-503-505-506-509-511.

     FREEZING RAIN ADVISORY UNTIL 10 AM PST THIS MORNING FOR ORZ041-
     044-507-508-510.

WA...WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY FOR WAZ030.

     FREEZING RAIN ADVISORY UNTIL 10 AM PST THIS MORNING FOR WAZ024-
     027>029.

     WINTER WEATHER ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR WAZ520.

&&

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

$$

94/99/76/82