619  
FXUS66 KPDT 230554 AAA  
AFDPDT  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE PENDLETON OR  
954 PM PST TUE JAN 22 2019  
 
UPDATED AVIATION DISCUSSION  
   
UPDATE
 
AN UPPER LEVEL RIDGE REMAINS OFFSHORE THIS EVENING BUT  
A SYSTEM IS RIDING OVER THE TOP OF IT INTO OUR AREA. A WARM FRONT  
HAS MOVED INTO THE AREA WITH WIDESPREAD PRECIPITATION. THIS WARM  
FRONT IS BRINGING WARMER AIR INTO THE AREA AND EXPECT  
TEMPERATURES TONIGHT TO REMAIN STEADY OR SLOWLY RISE. SNOW LEVELS  
SHOULD RISE AS WELL BUT HAVE BEEN SLOW TO DO SO. ALREADY EXTENDED  
THE WINTER WEATHER ADVISORY ALONG THE EAST SLOPES OF THE  
WASHINGTON CASCADES BEFORE LETTING IT EXPIRE AT 8 PM. LIGHT SNOW  
CONTINUES BUT DO NOT EXPECT MUCH ADDITIONAL SNOW IN THE NEXT FEW  
HOURS. A HEAVIER BAND OF PRECIPITATION HAS COME ASHORE IN  
WASHINGTON BUT BY THE TIME IT ARRIVES, AM ANTICIPATING THAT SNOW  
LEVELS WILL BE HIGH ENOUGH BY THEN FOR THE SNOW TO SWITCH TO RAIN.  
ELSEWHERE MODERATE RAIN CONTINUE IN THE COLUMBIA BASIN AND BLUE  
MOUNTAIN FOOTHILLS AND SNOW FROM THE BLUE MOUNTAINS EASTWARD. SNOW  
AMOUNTS HAVE BEEN HEAVIER THAN EXPECTED AND WILL HAVE TO LOOK AT  
THE NEED FOR ADDITIONAL ADVISORIES, PARTICULARLY IN THE GRANDE  
RONDE VALLEY. CURRENT WINTER WEATHER ADVISORY IN THE BLUE  
MOUNTAINS LOOKS GOOD. ADDITIONALLY, WINDS ARE STARTING TO SHOW  
SIGNS OF INCREASING AND EXPECT THAT THE CURRENT HIGH WIND WARNING  
FOR THE SIMCOE HIGHLANDS AND THE WIND ADVISORY FOR NORTH CENTRAL  
OREGON WILL PROVE WARRANTED. THE COLUMBIA BASIN SHOULD INCREASE TO  
15 TO 25 MPH LATE TONIGHT AND EARLY TOMORROW MORNING BEFORE  
BEGINNING TO DECREASE. MADE A FEW WIND AND TEMPERATURE  
ADJUSTMENTS. FORECAST UPDATE ALREADY OUT. PERRY  
 

 
   
AVIATION...06Z TAFS
 
A STORM CROSSING THE AREA IS BRINGING RAIN  
WITH SNOW IN THE MOUNTAINS TO THE AREA TONIGHT THOUGH CENTRAL OREGON  
INCLUDING KRDM AND KBDN ARE MOSTLY DRY. RAIN WILL END AT OTHER TAF  
SITES BY 12Z THOUGH IT MAY LINGER ON THROUGH 15Z-18Z AT KALW.  
CEILINGS AND VISIBILITIES WILL BE PRIMARILY VFR THOUGH KALW COULD  
HAVE MVFR CEILINGS AND VISIBILITIES THROUGH 12Z. WINDS WILL BE  
INCREASING IN THE NEXT FEW HOURS AND WESTERLY WINDS OF 10 TO 20 KTS  
WITH GUSTS TO 30 KTS ARE EXPECTED THROUGH AROUND 18Z BEFORE  
DECREASING BELOW 12 KTS BY 00Z. PERRY  
 

 
   
PREV DISCUSSION
 
/ISSUED 200 PM PST TUE JAN 22 2019/  
 
SHORT TERM...AN UPPER LEVEL RIDGE IS PRESENT OFF THE EASTERN  
PACIFIC WITH THE AXIS OF THE RIDGE ALONG 130W. A STRONG SHORTWAVE  
IS SLIDING DOWN THE EAST SIDE OF THE RIDGE AND WILL BE OVER  
VANCOUVER ISLAND THIS EVENING THEN ACROSS EASTERN WA AND NORTHEAST  
OR TONIGHT AND WEDNESDAY MORNING. THERE ARE SEVERAL WEATHER  
CONCERNS EXPECTED WITH THE SHORTWAVE. A WARM FRONT AHEAD OF THE  
SHORTWAVE IS BRINGING WIDESPREAD PRECIPITATION ACROSS WESTERN WA AND  
NORTHWEST OR, AND PRECIPITATION IS ALONG THE EAST SLOPES OF THE  
CASCADES. BASED ON SURFACE TEMPS AND DEWPOINTS, SNOW LEVELS RANGE  
FROM AROUND 2500 FEET IN SOUTH CENTRAL WA TO 4000 FEET IN CENTRAL  
OR. CURRENT WINTER WEATHER ADVISORY FOR THE WA CASCADE EAST SLOPES  
EXPIRES AT 4 PM. THIS LOOKS REASONABLE AS SNOW LEVELS WILL CONTINUE  
TO CLIMB OVERNIGHT TO ABOVE PASS LEVELS. PRECIPITATION WILL QUICKLY  
SPREAD ACROSS THE FORECAST AREA LATE THIS AFTERNOON AND EVENING, AND  
THE NORTHERN BLUE MOUNTAINS WILL BEGIN TO RECEIVE SNOW BY SUNSET.  
WINTER WEATHER ADVISORIES FOR SNOW ARE IN EFFECT FOR THE NORTHERN  
BLUES ABOVE 4000 FEET. 4-8 INCHES ARE EXPECTED WITH THE HEAVIEST  
ACCUMULATION ABOVE 5000 FEET. SNOW ACCUMULATIONS ELSEWHERE WILL BE  
LIGHT, AND AREAS SOUTH OF THE BLUE MOUNTAINS AND ACROSS CENTRAL OR  
WILL HAVE LITTLE TO NO PRECIPITATION WITH THIS SYSTEM.  
 
IT WAS A TOUGH DECISION ON THE HIGH WIND WATCHES THAT WERE ISSUED  
FOR AREAS ACROSS SOUTH CENTRAL WA. MOUNTAIN WAVES WILL DEVELOP  
ALONG THE RIDGETOPS WHERE MANY OF THE EXPOSED RIDGES AND WIND PRONE  
AREAS OF THE WA AND NORTHERN OR CASCADES WILL HAVE VERY STRONG  
WINDS. THE QUESTION IS WHETHER THE MOUNTAIN WAVES WILL PROPAGATE  
INTO THE VALLEYS WITH A POTENTIAL FOR FOEHN WINDS. THERE IS A WELL-  
DEFINED LEE SIDE TROUGH, BUT FORECAST CROSS SECTIONS WOULD INDICATE  
TRAPPED LEE WAVES RATHER THAN PROPAGATING WAVES. THE ONLY EXCEPTION  
WILL BE IN THE SIMCOE HIGHLANDS WHERE DAMAGING WINDS MAY REACH THE  
SURFACE, AND THE WATCH WAS UPGRADE TO A WARNING FOR THIS ZONE. ALL  
OTHER WATCHES WERE CANCELLED. A WIND ADVISORY WAS ALSO ISSUED FOR  
NORTH CENTRAL OREGON (ZONE 510) AS THE HIGHWAY 97 CORRIDOR FROM MORO  
TO MOUNT IDENTIFIER MAY HAVE GUSTS 45-55 MPH. BLOWING SNOW WAS  
ADDED TO SEVERAL OF THE MOUNTAIN ZONES THIS EVENING, BUT THE IMPACTS  
WILL NOT BE SIGNIFICANT DUE TO INCREASING SNOW LEVELS AND POTENTIAL  
FOR COMPACTED SNOW.  
 
A STRONG NORTHWEST FLOW ALOFT WILL REMAIN OVER WA/OR WEDNESDAY FOR  
CONTINUED OROGRAPHIC MOUNTAIN SNOW SHOWERS AND BREEZY TO WINDY  
CONDITIONS. SURFACE WINDS WILL DECOUPLE FROM WINDS ALOFT WEDNESDAY  
NIGHT AND WILL DIMINISH. MOUNTAIN SHOWERS WILL ALSO END WEDNESDAY  
NIGHT. THURSDAY AND THURSDAY NIGHT WILL BE DRY AS HIGH PRESSURE  
REBUILDS. ANOTHER SHORTWAVE IS PROGGED TO DIVE SOUTH ACROSS WA/OR  
THURSDAY NIGHT BUT SHOULD DO LITTLE EXCEPT INCREASE CLOUD COVER.  
WISTER  
 
LONG TERM...FRIDAY THROUGH TUESDAY...AN UPPER LEVEL RIDGE  
WILL BUILD OFFSHORE AND PERSIST THROUGH THE LONG TERM PERIOD. THIS  
WILL CREATE DRY CONDITIONS WITH LATE NIGHT AND MORNING FOG IN THE  
COLUMBIA BASIN AND SURROUNDING VALLEYS. ON FRIDAY AND SUNDAY  
DISTURBANCES WILL DIVE DOWN THE BACKSIDE OF THE RIDGE FROM NW CANADA  
TO MT. THIS WILL INCREASE CLOUD COVER OVER THE CWA BUT NO  
PRECIPITATION IS EXPECTED SINCE THE TRAJECTORY IS TOO FAR EAST.  
TEMPERATURES WILL BE QUITE MILD WITH HIGHS IN THE MID 40S TO LOWER  
50S. COONFIELD  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 39 50 36 47 / 80 40 10 0  
ALW 39 50 38 48 / 90 60 20 0  
PSC 40 53 36 48 / 70 10 0 0  
YKM 34 49 32 45 / 40 20 0 0  
HRI 40 55 36 49 / 60 10 10 0  
ELN 33 45 31 41 / 60 20 0 0  
RDM 34 51 30 50 / 10 30 10 0  
LGD 30 45 35 44 / 80 80 30 0  
GCD 30 48 34 47 / 50 40 20 0  
DLS 39 53 37 49 / 50 40 10 0  
 

 
   
PDT WATCHES/WARNINGS/ADVISORIES
 
 
OR...WIND ADVISORY FROM MIDNIGHT TONIGHT TO 8 AM PST WEDNESDAY FOR  
ORZ510.  
 
WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY FOR ORZ502.  
 
WA...WINTER WEATHER ADVISORY UNTIL 4 AM PST WEDNESDAY FOR WAZ030.  
 
HIGH WIND WARNING FROM MIDNIGHT TONIGHT TO 8 AM PST WEDNESDAY  
FOR WAZ521.  
 

 
 

 
 
83/76/83  
 
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