235  
FXUS66 KPDT 261141  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
440 AM PDT WED APR 26 2017  
 
UPDATED AVIATION DISCUSSION  
   
SHORT TERM...TODAY THROUGH FRIDAY
 
AN UPPER LEVEL STORM SYSTEM  
IS MOVING OUT OF THE CWA THIS MORNING AND ANOTHER ONE IS EXPECTED TO  
MOVE INTO CENTRAL OR THIS MORNING. THIS WILL BRING ANOTHER ROUND OF  
PRECIPITATION TO EASTERN WA AND OR. THE PRECIPITATION WILL BE  
HEAVIEST IN OREGON. THE SNOW LEVELS WILL BE 4500-6000 FT SO MOST OF  
THE PRECIPITATION WILL BE RAIN. IT WILL BECOME WINDY/VERY WINDY  
AFTER THE COLD FRONT PASSAGE THIS AFTERNOON. WIND ADVISORIES HAVE  
BEEN ISSUED FOR THE KITTITAS VALLEY AND SIMCOE HIGHLANDS FOR GUSTY W-  
NW WINDS. MODELS HAVE BACKED OFF ON WIND SPEEDS ACROSS THE LOWER  
COLUMBIA BASIN, BUT I KEPT THE WIND SPEEDS SIMILAR TO THE PREVIOUS  
FORECAST BECAUSE MODELS FREQUENTLY UNDERESTIMATE HOW MUCH WINDS MIX  
TO THE SURFACE AFTER A COLD FRONT PASSAGE. UPPER LEVEL FLOW WILL  
TURN NORTHWEST THIS AFTERNOON AS A RIDGE BUILDS OFFSHORE. MULTIPLE  
WAVES IN THE NORTHWEST FLOW WILL KEEP SHOWERY PRECIPITATION OVER THE  
AREA TONIGHT AND THURSDAY. UPSLOPE REGIONS OF THE EASTERN MOUNTAINS  
WILL GET THE MOST RAIN/SNOW. SNOW LEVELS WILL DROP TO 2500-3000 FT  
BY THURSDAY MORNING. HOWEVER THE SHOWERY PRECIPITATION WILL PROBABLY  
NOT PRODUCE ENOUGH WIDESPREAD SNOW TO JUSTIFY A WINTER ADVISORY  
THOUGH LOCAL ACCUMULATIONS MAY REACH ADVISORY CRITERIA. THIS WILL  
NEED TO BE MONITORED. FRIDAY A DRIER NORTHERLY FLOW WILL DEVELOP  
WITH DECREASING CHANCES FOR SHOWERS. COONFIELD  
   
LONG TERM
 
FRIDAY NIGHT THROUGH TUESDAY. A WEAK TRANSITORY RIDGE  
WILL PUSH INLAND FRIDAY NIGHT...AND SHOWERS WILL END AFTER MIDNIGHT.  
A DRY FORECAST IS IN STORE SATURDAY...BUT SHOWERS WILL RETURN  
SATURDAY NIGHT WHEN THE RIDGE FLATTENS AND ALLOWS A PACIFIC FRONT TO  
GRADUALLY TRAVEL SOUTH ACROSS WA/OR. A WESTERLY FLOW WILL REMAIN ON  
SUNDAY FOR CONTINUED SHOWERS BUT ALSO BREEZY WINDS.  
MODELS...PARTICULARLY THE ECMWF...ARE HAVING SOME DIFFICULTY WITH A  
SHORTWAVE TROUGH PROGGED TO MOVE SOUTH ON MONDAY. THE ECMWF HAS  
BEEN FLIP FLOPPING ON THE STRENGTH...AND THE LATEST RUN DAMPENS THE  
WAVE WITH LITTLE TO NO PRECIPITATION. LEANING TOWARDS THE MORE  
CONSISTENT GFS AND CANADIAN WITH A STRONGER WAVE. HOWEVER, RAIN AND  
MOUNTAIN SNOW SHOWERS (SNOW LEVELS AROUND 4000-5000 FEET) WILL  
MAINLY DEVELOP ALONG THE CASCADES AND FAR NORTHEAST OREGON AND  
SOUTHEAST WASHINGTON. THE MODELS ARE IN AGREEMENT WITH AN UPPER  
LEVEL RIDGE BUILDING TUESDAY AND A HIGHLY AMPLITUDE RIDGE ON  
WEDNESDAY. PEOPLE WANTING MORE SUN AND LESS RAIN WILL LIKELY GET  
THEIR WISH TUESDAY AND WEDNESDAY. WISTER  
 

 
   
AVIATION
 
12Z TAFS. THE FORECAST AREA IS BETWEEN FRONTS AT THIS  
TIME WITH THE NEXT FRONT SPREADING PRECIPITATION ACROSS EASTERN OR  
THIS MORNING THEN SOUTHEAST WA THIS AFTERNOON. CIGS ARE CURRENTLY  
VFR WITH BASES AROUND 4K-10K FT AGL. CONFIDENCE IS FAIRLY HIGH THAT  
LIGHT TO MODERATE RAIN WILL OCCASIONALLY BRING CIGS/VSBY DOWN TO  
MVFR AT KALW AND KPDT...AND THIS WAS INCLUDED IN THE 12Z TAFS. KDLS,  
KYKM AND KPSC MAY SEE LITTLE TO NO RAINFALL WITH THIS UPCOMING FRONT  
AND WILL REMAIN VFR FOR THE NEXT 24 HOURS. KRDM AND KBDN SHOULD  
REMAIN VFR BUT LIGHT RAIN MAY BRIEFLY LOWER CIGS TO MVFR. THE MAIN  
AVIATION CONCERN WILL BE THE INCREASING WIND. SW-W WINDS INCREASING  
TO 15-25 KNOTS WITH GUST 25-35 KNOTS ARE EXPECTED AT ALL TAF  
SITES THIS AFTERNOON AND EVENING...POSSIBLY OVERNIGHT. WISTER  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 57 40 55 37 / 60 20 30 30  
ALW 59 43 58 42 / 60 40 30 30  
PSC 64 44 63 41 / 30 10 10 20  
YKM 63 38 61 37 / 30 10 10 10  
HRI 61 43 60 41 / 40 10 20 20  
ELN 57 38 56 38 / 20 10 10 10  
RDM 53 30 51 24 / 70 10 30 30  
LGD 52 37 50 35 / 80 30 40 40  
GCD 50 32 48 28 / 90 30 50 60  
DLS 59 43 58 42 / 50 20 30 20  
 

 
   
PDT WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...WIND ADVISORY FROM 11 AM THIS MORNING TO 9 PM PDT THURSDAY FOR  
WAZ026-521.  
 

 
 

 
 
76/85/85  
 
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