157  
FXUS66 KPDT 300547 AAA  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
1040 PM PDT SAT APR 29 2017  
 
UPDATED THE AVIATION DISCUSSION  
   
UPDATE
 
THE LATEST RADAR WAS SHOWING AN AREA OF RAIN STRIKING  
THE CASCADES AND SOME OF THE MOISTURE WAS ATTEMPTING TO MAKE IT  
ACROSS AND INTO THE INTERIOR PORTIONS OF WA/OR. A WEAK DISTURBANCE  
IS FORECAST TO TRACK ACROSS THE REGION OVERNIGHT AND THE SHOWERS  
SHOULD INCREASE SOME ACROSS THE ENTIRE AREA ESPECIALLY INTO THE  
WA/OR BLUE MOUNTAINS OVERNIGHT. POPS WERE ADJUSTED SOME TO REFLECT  
THIS TREND AND MINOR CHANGES WERE ALSO PERFORMED TO TEMPS.  
MEANWHILE PRESSURE GRADIENTS WILL TIGHTEN TOMORROW AND BREEZY  
WINDS ARE EXPECTED WITH WINDY CONDITIONS IN AND NEAR ELN. OTHERWISE  
THE PRESENT SHORT TERM FORECAST FOR TONIGHT APPEARS ON TRACK FOR  
NOW.  
   
AVIATION
 
VFR CONDITIONS WILL CONTINUE UNTIL A STORM SYSTEM BRINGS  
SHOWERS TO THE REGION AND MVFR CONDITIONS MAY BE APPROACHED AT TAF  
SITE KDLS AFTER 08Z AND THEN THE OTHER TAF SITES AFTER 10Z.  
MEANWHILE WIND GUSTS BETWEEN 25 KTS TO 30 KTS IS POSSIBLE AT ALL TAF  
SITES AFTER 12Z BEFORE DIMINISHING AFTER 02Z AND ALL TAF SITES WILL  
REMAIN VFR.  
 

 
   
PREV DISCUSSION
 
/ISSUED 300 PM PDT SAT APR 29 2017/  
 
SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...A RIDGE OF HIGH  
PRESSURE WILL REMAIN OFFSHORE FOR THE NEXT COUPLE OF DAYS THOUGH  
THERE WILL BE A COUPLE OF FRONTAL SYSTEMS RIDING OVER THE RIDGE AND  
THROUGH THE AREA. ONE WILL ARRIVE TONIGHT WITH A CHANCE OF LIGHT  
RAIN MAINLY DURING THE OVERNIGHT HOURS. DURING THE DAY TOMORROW A  
CHANCE OF RAIN SHOWERS WILL REMAIN OVER THE MOUNTAINS WHILE THE  
LOWER ELEVATIONS DRY OUT. RAIN AMOUNTS WILL BE JUST A FEW HUNDREDTHS  
OF AN INCH WITH UP TO A TENTH OF AN INCH IN THE MOUNTAINS. SNOW  
LEVELS WILL BE AROUND 6000-6500 FEET. BEHIND THE FRONT TOMORROW,  
PRESSURE GRADIENTS WILL TIGHTEN UP AND HEATING WILL HELP MIX DOWN 30-  
45 KT 850 MB WINDS TO THE SURFACE. MOST OF THE AREA WILL HAVE 20-30  
MPH WINDS BUT THE KITTITAS VALLEY IS EXPECTED TO HAVE 25-40 MPH  
WINDS WITH GUSTS TO 50 MPH. HAVE ISSUED A WIND ADVISORY FOR THAT  
ZONE FROM TOMORROW MORNING THROUGH EARLY EVENING. WINDS WILL  
DECREASE AFTER SUNDOWN. SUNDAY NIGHT AND MONDAY MORNING WILL BE A  
BREAK BEFORE THE NEXT SYSTEM. ANY PRECIPITATION WILL BE CONFINED TO  
THE WASHINGTON CASCADES. MONDAY AFTERNOON ANOTHER SYSTEM WILL MOVE  
THROUGH THE AREA WITH MORE LIGHT SHOWERS MAINLY OVER THE MOUNTAINS.  
PRECIPITATION AMOUNTS WILL BE JUST A FEW HUNDREDTHS OF AN INCH. SNOW  
LEVELS WILL BE 4500-5500 FEET. NOT EXPECTING ANY SIGNIFICANT WINDS  
WITH THIS SYSTEM. TEMPERATURES WILL BE IN THE 60S WITH MAINLY 50S IN  
THE MOUNTAINS. PERRY  
 
LONG TERM...TUESDAY THROUGH THURSDAY NIGHT...A SHORTWAVE TROUGH  
WILL MOVE EAST OF THE AREA TUESDAY FOLLOWED BY A BUILDING UPPER  
LEVEL RIDGE FOR WEDNESDAY INTO EARLY THURSDAY. THE RIDGE WILL BEGIN  
TO BREAK DOWN BY THURSDAY EVENING. EXPECT FAIR CONDITIONS WITH  
WARMING TEMPERATURES THROUGH THE PERIOD. HIGH TEMPERATURES WITHIN A  
FEW DEGREES OF 70 TUESDAY IN THE LOWER ELEVATIONS WILL WARM TO THE  
LOWER TO MID 80S BY THURSDAY AFTERNOON. BY LATE THURSDAY AFTERNOON  
AND EVENING THERE WILL BE AT LEAST A SLIGHT CHANCE OF SHOWERS AND  
THUNDERSTORMS...AS THE RIDGE BEGINS TO BREAK DOWN AND INSTABILITY  
INCREASES. THE ACTIVITY WILL TEND TO FORM FIRST NEAR THE CASCADE  
CREST AND THEN SPREAD EASTWARD DURING THE EVENING AND OVERNIGHT  
HOURS. 78  
 
FRIDAY MORNING THROUGH SUNDAY...FORECAST MODEL SOLUTIONS DIVERGE  
BEYOND FRIDAY WITH DEPTH AND EXACT PLACEMENT OF LONGWAVE TROUGH  
ACROSS THE NW PAC COAST. THE GFS HAS MOVED TOWARD THE ECMWF AND  
CANADIAN SOLUTIONS BUT IS STILL THE WEAKEST AND LEAST PROGRESSIVE  
WITH THIS FEATURE. HAVE LEANED MORE TOWARD THE ECMWF SOLUTION FOR  
NOW. THERE WILL BE A SLIGHT CHANCE OF SHOWERS ACROSS THE BLUE  
MOUNTAINS THROUGH SATURDAY EVENING AS THE TROUGH AND ASSOCIATED COLD  
FRONT SLOWLY SHIFTS TO THE EAST. WITH THE PASSAGE OF THE COLD FRONT  
ON FRIDAY HIGH TEMPERATURES WILL DROP INTO THE INTO THE UPPER 60S IN  
THE LOWER ELEVATIONS FOR BOTH FRIDAY AND SATURDAY. 74  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 49 61 38 59 / 30 30 0 10  
ALW 52 65 43 62 / 40 40 0 10  
PSC 52 67 40 65 / 20 10 0 10  
YKM 46 64 38 62 / 20 0 0 10  
HRI 50 65 39 63 / 20 10 0 10  
ELN 44 58 38 58 / 30 10 10 10  
RDM 42 59 30 59 / 20 20 0 20  
LGD 47 59 37 57 / 30 50 10 20  
GCD 43 60 34 57 / 20 30 0 10  
DLS 50 61 42 62 / 30 20 0 20  
 

 
   
PDT WATCHES/WARNINGS/ADVISORIES
 
 
OR...NONE.  
WA...WIND ADVISORY FROM 7 AM TO 9 PM PDT SUNDAY FOR WAZ026.  
 

 
 

 
 
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