733  
FXUS66 KPDT 261734 AAA  
AFDPDT  
 
AREA FORECAST DISCUSSION...UPDATE  
NATIONAL WEATHER SERVICE PENDLETON OR  
1033 AM PDT SUN MAR 26 2017  
 
UPDATED AVIATION DISCUSSION  
   
SHORT TERM...TODAY AND TONIGHT
 
A WEATHER SYSTEM IS MOVING INTO  
THE REGION THIS MORNING. A WARM FRONT WILL LIFT THROUGH THE FORECAST  
AREA TODAY FOLLOWED BY A COLD FRONT THIS EVENING AND OVERNIGHT.  
LIGHT RAIN IS ALREADY FALLING IN CENTRAL OREGON AND EXPECT THIS TO  
SPREAD ACROSS THE FORECAST AREA THROUGH THE DAY. SNOW LEVELS WILL  
RISE TODAY BUT COULD SEE A LITTLE LIGHT SNOWFALL IN PORTIONS OF  
CENTRAL OREGON THIS MORNING AS WELL AS ALONG THE EAST SLOPES OF THE  
CASCADES BEFORE SNOW LEVELS RISE. HIGHER ELEVATIONS OF THE BLUE  
MOUNTAINS WILL ALSO SEE SOME LIGHT SNOW ACCUMULATIONS. THE COLD  
FRONT WILL WILL MOVE OVER THE CASCADES EARLY THIS EVENING. MODELS  
ARE INDICATING THAT A SHORTWAVE MOVING UP THE FRONT WILL HELP TO  
ENHANCE PRECIPITATION FROM CENTRAL OREGON TO NORTHEAST OREGON FROM  
THIS EVENING AND OVERNIGHT SO HAVE KEPT CHANCE OF PRECIPITATION HIGH  
FOR THESE AREAS AHEAD OF THE FRONT. BEHIND THE FRONT PRECIPITATION  
WILL DECREASE RAPIDLY.  
   
AVIATION...18Z TAFS
 
VFR AND TEMPO MVFR CONDITIONS ARE EXPECTED TO  
PREVAIL AT ALL TERMINALS THROUGH THE DAY TODAY. CONDITIONS SHOULD  
IMPROVE TO VFR FOR MOST TERMINALS OVERNIGHT AND INTO MONDAY MORNING.  
RAIN SHOWERS WILL BE MOVING THROUGH THE AREA TODAY AND INTO THIS  
EVENING...THE SHOWERS COULD BE MODERATE AT TIMES, ESPECIALLY THIS  
AFTERNOON, AS THE ATMOSPHERE WILL AGAIN HAVE SOME MARGINAL  
INSTABILITY. THUNDERSTORMS ARE NOT EXPECTED. CIGS WILL MAINLY RANGE  
FROM ABOUT 4K TO 8K FEET AGL IN THE RAIN SHOWERS, BUT COULD  
OCCASIONALLY DROP TO BETWEEN 2.5K TO 4K FEET AGL IN ANY HEAVIER  
SHOWERS...VIS COULD ALSO OCCASIONALLY DROP TO 3-5SM IN THESE  
SHOWERS. CIGS/VIS SHOULD TEND TO LIFT AND IMPROVE TONIGHT AS THE  
MAIN AXIS OF PRECIPITATION MOVES EAST. EXPECT SCT TO BKN CLOUDS  
MAINLY BETWEEN 5K TO 10K FEET AGL OVERNIGHT AND INTO MONDAY MORNING.  
IF SKIES CLEAR ENOUGH OVERNIGHT, THERE IS THE POTENTIAL FOR SOME  
LOCALIZED POCKETS OF SHALLOW FOG TO FORM, DUE TO THE WET GROUND  
CONDITIONS. NOT ENOUGH CONFIDENCE ON WHERE, WHEN OR IF THIS FOG WILL  
FORM YET TO INCLUDE IN THE TAFS. WINDS WILL REMAIN LIGHT THROUGH THE  
PERIOD...AOB 15KTS FOR MOST LOCATIONS. 77  
 

 
   
PREV DISCUSSION
 
/ISSUED 300 AM PDT SUN MAR 26 2017/  
 
SHORT TERM...TODAY THROUGH TUESDAY...AN UPPER LEVEL TROUGH HAS  
MOVED INTO IDAHO TONIGHT AND A BRIEF TRANSITORY RIDGE IS OVER THE  
REGION EARLY THIS MORNING. THIS IS LEADING TO THE CURRENT DRY  
CONDITIONS. THIS WILL NOT LAST LONG AS A SYSTEM IS APPROACHING THE  
PACIFIC NORTHWEST COAST. THE WARM FRONT OF THIS SYSTEM WILL CROSS  
THE CASCADES LATER THIS MORNING AND BRING A CHANCE OF SHOWERS TO THE  
CASCADES AND CENTRAL OREGON IN THE MORNING AND A CHANCE OF SHOWERS  
ACROSS THE AREA IN THE AFTERNOON. THE COLD FRONT WILL ARRIVE SUNDAY  
EVENING AND SHOWERS WILL BE LIKELY BEFORE STARTING TO TAPER OFF LATE  
IN THE EVENING WITH JUST A SLIGHT CHANCE OF SHOWERS IN THE COLUMBIA  
BASIN AND NORTH CENTRAL OREGON OVERNIGHT. PRECIPITATION WILL BE  
MAINLY RAIN WITH SNOW LEVELS RISING FROM AROUND 4500 FEET THIS  
MORNING TO AROUND 5500-6000 FEET THIS EVENING BEFORE DROPPING DOWN  
TO 3500 TO 4000 FEET BEHIND THE FRONT BY TOMORROW MORNING.  
PRECIPITATION AMOUNTS WILL BE AROUND A TENTH OF AN INCH IN THE  
COLUMBIA BASIN, UP TO A QUARTER OF AN INCH IN THE REST OF THE LOWER  
ELEVATIONS AND UP TO A HALF INCH IN THE MOUNTAINS. SNOW AMOUNTS IN  
THE MOUNTAINS WILL BE UP TO 3 INCHES IN THE HIGHER MOUNTAIN PASSES.  
ON MONDAY AS THE FRONT DEPARTS, THE ASSOCIATED TROUGH WILL CROSS THE  
AREA. INSTABILITY WITH THE FRONT WILL KEEP A CHANCE OF RAIN AND SNOW  
SHOWERS IN THE MOUNTAINS IN THE AFTERNOON AND A SLIGHT CHANCE OF  
RAIN SHOWERS IN THE LOWER ELEVATIONS. SNOW LEVELS WILL REMAIN AROUND  
3500-4000 FEET AND PRECIPITATION AMOUNTS WILL BE LESS THAN A TENTH  
OF AN INCH. MONDAY NIGHT AND TUESDAY A RIDGE WILL BE OVER THE AREA  
FOR MAINLY DRY CONDITIONS. ANOTHER SYSTEM WILL BE TRYING TO CROSS  
THE CASCADES, BUT A CHANCE OF LIGHT RAIN AND SHOWERS WILL BE  
CONFINED TO THE CASCADES CREST REGION. TEMPERATURES WILL BE IN THE  
MID 40S TO MID 50S TODAY THEN WARM MONDAY AND TUESDAY TO THE MID TO  
UPPER 50S IN THE COLUMBIA BASIN AND IN THE MID 40S TO MID 50S  
ELSEWHERE. PERRY  
 
LONG TERM...TUESDAY NIGHT THROUGH SUNDAY NIGHT...THE LATEST GFS  
MODEL RUN IS MORE IN LINE NOW WITH THE ECMWF AND CANADIAN MODELS FOR  
THE EXTENDED PERIOD...ESPECIALLY THIS COMING MID WEEK. THE MAIN  
CONCERN DURING THE EXTENDED PERIOD WILL BE A COUPLE OF WEATHER  
SYSTEMS BRINGING MORE RAIN TO THE CWA. WHILE THESE WILL MOSTLY BE  
JUST SPRING TIME RAIN EVENTS WITH LITTLE HAZARDOUS IMPACTS IT MAY  
CAUSE RIVERS AND STREAMS TO RISE AGAIN. HOWEVER AT THIS TIME RIVERS  
ARE NOT EXPECTED TO REACH FLOOD STAGE ANYMORE. THERE ARE A FEW THAT  
WILL BE AT BANKFULL WHICH WILL BE COVERED WITH RIVER STATEMENTS.  
TUESDAY NIGHT AND WEDNESDAY A WEATHER SYSTEM WILL MOVE INTO THE  
REGION WITH A PERIOD OF RAIN FOLLOWED BY MAINLY MOUNTAIN RAIN  
SHOWERS BEHIND THE SYSTEM BY WEDNESDAY AFTERNOON, CAUSED BY UPSLOPE.  
SNOW LEVELS WILL BE QUITE HIGH SO THERE WILL BE NO CONCERN WITH  
WINTER WEATHER AT THIS TIME. CONDITIONS WILL DRY OUT BY FRIDAY AND  
THEN IT WILL STAY MOSTLY DRY UNTIL NEXT SUNDAY NIGHT. HOWEVER THAT  
FAR OUT THE MODELS DO NOT AGREE WELL WITH EACH OTHER ANYMORE, AND  
THEREFORE ONLY MADE MINOR CHANGES TO THE PREVIOUS FORECAST UNTIL THE  
FORECAST BECOMES MORE CERTAIN. IT MAY BE BREEZY AT TIMES...  
ESPECIALLY ON THE RIDGE TOPS AND OPEN GRASSY TERRAIN. TEMPERATURES  
WILL BE NEAR NORMAL THROUGH THE EXTENDED PERIOD. 88  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 53 40 55 38 / 60 80 40 10  
ALW 56 43 57 43 / 60 70 40 20  
PSC 54 42 59 41 / 60 60 20 10  
YKM 55 38 61 38 / 70 60 20 10  
HRI 53 41 57 39 / 60 60 20 10  
ELN 48 35 51 36 / 70 60 20 10  
RDM 55 35 52 31 / 70 70 30 10  
LGD 56 39 53 35 / 50 80 60 20  
GCD 56 38 53 33 / 60 90 50 10  
DLS 53 42 56 43 / 70 70 20 10  
 

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

 
 

 
 
91/77/77  
 
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