887  
FXUS66 KPDT 221754  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
954 AM PST MON JAN 22 2018  
   
SHORT TERM
 
A GENERALLY WESTERLY FLOW ALOFT REMAINS OVER THE  
AREA THIS MORNING. A COUPLE OF WEAK RIPPLES IN THE FLOW WILL KEEP  
SCATTERED LIGHT SNOW SHOWERS IN THE MOUNTAINS TODAY AND A SLIGHT  
CHANCE OF RAIN SHOWERS IN THE BLUE MOUNTAIN FOOTHILLS. THE REST OF  
THE COLUMBIA BASIN AND CENTRAL OREGON SHOULD REMAIN DRY. HAVE  
ADJUSTED RAIN AND SNOW CHANCES THIS MORNING DOWNWARD DUE TO THE  
LACK OF RETURNS RIGHT NOW ON RADAR. ALSO REDUCED CLOUD COVER  
SOMEWHAT TODAY AND LOWERED TEMPERATURES A DEGREE OR SO AS THEY  
LOOKED A LITTLE TOO WARM COMPARED TO GUIDANCE. OTHERWISE FORECAST  
IS IN GOOD SHAPE. MAIN FORECAST CHALLENGE TODAY WILL BE THE SYSTEM  
ARRIVING TOMORROW INTO WEDNESDAY. SNOW LEVELS WILL REMAIN LOW  
INTO TUESDAY NIGHT BEFORE RISING DUE TO WARM AIR ADVECTION. THE  
SNOW LEVELS WILL BE CRITICAL TO HOW MUCH SNOW WILL FALL ALONG THE  
CASCADE CREST REGION TUESDAY THROUGH WEDNESDAY. MAY NEED TO ISSUE  
A WINTER WEATHER ADVISORY FOR THE WASHINGTON CASCADES WITH THE  
AFTERNOON FORECAST PACKAGE. THE OREGON CASCADES LOOK LIKE THEY  
WILL REMAIN BELOW ADVISORY AMOUNTS. FORECAST UPDATE ALREADY OUT.  
PERRY  
 

 
   
AVIATION...18Z TAFS
 
VFR CONDITIONS SHOULD PREVAIL THE NEXT 24  
HOURS. HOWEVER, KDLS MAY SEE IFR/MVFR CONDITIONS BY 23/12Z DUE TO  
FOG AND LOW CLOUDS. A SYSTEM WILL BEGIN TO SPREAD PRECIPITATION  
ACROSS THE AREA BY SUNRISE TUESDAY. WINDS WILL GENERALLY BE LESS  
THAN 12 KTS. EARLE  
 

 
   
PREV DISCUSSION
 
/ISSUED 938 AM PST MON JAN 22 2018/  
 
SHORT TERM...TODAY THROUGH WEDNESDAY...THE UPPER LEVEL FLOW WILL  
CONTINUE TO BE ONSHORE WESTERLY TODAY. A WEAK DISTURBANCE WITHIN  
THIS FLOW WILL MOVE ACROSS THE REGION TODAY. THE COMBINATION OF THE  
ONSHORE FLOW AND THE DISTURBANCE WILL CAUSE ISOLATED TO SCATTERED  
SHOWERS OVER THE AREA AT TIMES. BEST CHANCES WILL BE THE ALONG THE  
CASCADE EAST SLOPES WHERE NUMEROUS SHOWERS WILL BE POSSIBLE THIS  
MORNING. SNOW LEVELS THIS MORNING RANGE FROM NEAR 1000 FEET TO NEAR  
3000 FEET. SNOW LEVELS WILL RISE TO BETWEEN 2500 AND 3600 FEET THIS  
AFTERNOON. OVERALL, SNOW ACCUMULATIONS SHOULD BE LIGHT AND SPOTTY  
DUE TO THE SHOWERY NATURE OF THE PRECIP. A WEAK UPPER LEVEL RIDGE  
WILL BUILD OVER THE REGION TONIGHT. THUS WILL SEE CHANCES OF SHOWERS  
DECREASE, BECOMING VERY LIMITED BY MIDNIGHT. THE NEXT PACIFIC SYSTEM  
WILL THEN PUSH PRECIP INTO THE REGION TUESDAY MORNING, WITH MUCH OF  
THE AREA HAVING DECENT CHANCES THROUGH THE DAY. SNOW LEVELS WILL BE  
LOW AGAIN TUESDAY MORNING, BUT WILL GRADUALLY RISE DURING THE  
AFTERNOON AND EVENING. THE WASHINGTON CASCADE EAST SLOPES AND THE  
KITTITAS VALLEY WILL SEE THE SLOWEST RISE IN SNOW LEVELS, THUS THESE  
AREAS WILL MOST LIKELY SEE SNOW THROUGH THE DAY TUESDAY. COULD SEE  
UP TO 2 INCHES IN THE KITTITAS VALLEY AND 2 TO 6 INCHES IN THE  
WASHINGTON CASCADE EAST SLOPES. WINDS WILL BECOME BREEZY TO LOCALLY  
WINDY OVER PORTIONS OF CENTRAL OREGON, THE GRANDE RONDE VALLEY AND  
THE BLUE MOUNTAIN FOOTHILLS ON TUESDAY. A MOIST SOUTHWEST FLOW WILL  
KEEP PRECIP CHANCES HIGH LATE TUESDAY NIGHT INTO WEDNESDAY. SNOW  
LEVELS WILL CONTINUE TO RISE OVERNIGHT TUESDAY AND WEDNESDAY  
MORNING, THEN FALL SLIGHTLY WEDNESDAY AFTERNOON. 90  
 
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...A FAST MOVING  
DISTURBANCE PUSHES A COLD FRONT ACROSS THE REGION WEDNESDAY NIGHT  
WITH SNOW LEVELS LOWERING TO 2000-3000 FEET OVERNIGHT AND CONTINUING  
LOWER DURING THE DAY ON THURSDAY THUS DECREASING TO 1000-2000 FEET.  
ANOTHER DISTURBANCE MOVES INTO THE REGION THURSDAY NIGHT AND FRIDAY  
AND FRIDAY MORNING FOR ANOTHER ROUND OF A MIX OF RAIN/SNOW IN THE  
COLUMBIA BASIN AND ADDITIONAL SNOW IN THE MOUNTAINS. A WARM FRONT  
BRINGS VALLEY RAIN AND MOUNTAIN SNOW TO THE REGION OVER THE WEEKEND.  
POLAN  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 48 31 46 39 / 20 10 50 70  
ALW 48 34 47 41 / 20 10 40 70  
PSC 50 32 43 39 / 10 10 60 70  
YKM 45 30 40 35 / 10 10 60 70  
HRI 49 31 44 38 / 10 10 60 60  
ELN 41 27 36 31 / 20 10 80 70  
RDM 43 27 45 36 / 10 10 40 60  
LGD 43 30 39 37 / 30 20 50 70  
GCD 42 27 39 36 / 10 10 60 70  
DLS 47 34 42 37 / 20 10 80 80  
 

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

 
 

 
 
83/81/81  
 
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