859  
FXUS66 KPDT 232159  
AFDPDT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PENDLETON OR  
256 PM PDT THU MAR 23 2017  
   
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
 
A MID/UPPER LEVEL  
RIDGE OF HIGH PRESSURE CONTINUES MOVING EASTWARD. THE WESTERN FLANK  
OF THE RIDGE IS NOW OVER THE FORECAST AREA THUS ALLOWING FLOW ALOFT  
TO BACK TO SOUTHWEST, WHICH WILL ALLOW TRANSPORT OF MOISTURE AHEAD  
OF A COLD FRONT NOW APPROACHING THE COAST. CLOUDS WILL INCREASE  
TONIGHT WITH CLOUD BASES LOWERING. RAIN PRECEDING THE COLD FRONT  
WILL MOVE INTO CENTRAL AND NORTH CENTRAL OREGON, THE EASTERN  
COLUMBIA GORGE, THE EAST SLOPES OF THE WASHINGTON CASCADES AND THE  
KITTITAS VALLEY THIS EVENING. SNOW LEVELS TONIGHT WILL BE 3000-4000  
FEET ALONG THE EAST SLOPES OF THE WASHINGTON CASCADES AND 4000-5000  
FEET ALONG THE EAST SLOPES OF THE OREGON CASCADES AS WELL AS IN THE  
EASTERN MOUNTAINS OF OREGON AND THE BLUE MOUNTAINS OF SE WASHINGTON.  
THE COLD FRONT WILL BEGIN ITS MARCH THROUGH THE FORECAST FRIDAY  
MORNING IN THE WESTERN SECTIONS OF THE CWA. THE COLD FRONT WILL THEN  
MOVE ACROSS THE EASTERN SECTIONS OF THE FORECAST AREA FRIDAY  
AFTERNOON. AS SUCH WIDESPREAD RAIN WILL OCCUR WITH THE FRONT. THE  
FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS ARE LIKELY TO GET 0.30-  
0.50 INCHES OF RAIN BY FRONTAL PASSAGE LATE IN THE AFTERNOON.  
FRIDAY NIGHT THE MID/UPPER LEVEL TROUGH MOVES EAST AND REACHES THE  
CASCADES AND THEN MOVES ACROSS THE REGION ON SATURDAY PROVIDING SOME  
DYNAMIC LIFT COMBINED WITH OROGRAPHIC LIFT OVER THE MOUNTAINS FOR  
RAIN AND SNOW SHOWERS LIKELY IN THE BLUE MOUNTAINS AND THE WALLOWA  
MOUNTAINS WITH SNOW LEVELS 3500-4000 FEET. SATURDAY NIGHT A  
MID/UPPER LEVEL RIDGE OF HIGH PRESSURE MOVES OVER THE INTERIOR  
PACIFIC NORTHWEST FOR DRY CONDITIONS. POLAN  
   
LONG TERM...SUNDAY THROUGH THURSDAY
 
TWO MAJOR WEATHER SYSTEMS  
WILL IMPACT THE FORECAST AREA DURING THE EXTENDED. THE FIRST WILL  
ARRIVE ON SUNDAY AND LINGER INTO MONDAY. THIS SYSTEM COMES OFF THE  
PACIFIC OCEAN IN A WESTERLY FLOW AS AN UPPER LEVEL TROUGH BUT THEN  
DEVELOPS A CLOSED LOW THAT DIVES INTO CALIFORNIA AND EVENTUALLY THE  
DESERT SOUTHWEST. THIS WILL WEAKEN THE SYSTEM AS IT MOVES INLAND BUT  
STILL THE SYSTEM WILL SPREAD PRECIPITATION ACROSS THE FORECAST AREA  
WITH SNOW LEVELS 3500 TO 5000 FEET.  
 
THE NEXT SYSTEM ARRIVES ON WEDNESDAY AS ANOTHER UPPER LEVEL TROUGH  
PUSHES A COLD FRONT THROUGH THE REGION. SNOW LEVELS WILL BEGIN  
AROUND 5000 FEET AND THEN LOWER TO AROUND 4000 FEET ON THURSDAY AS  
PRECIPITATION TURNS TO SHOWERS AND DECREASES.  
 

 
   
AVIATION...00Z TAFS
 
VFR CONDITIONS WILL PREVAIL OVER THE  
NEXT 24 HOURS BUT EXPECTING A WEATHER SYSTEM WILL MOVE IN TONIGHT  
WITH INCREASING CLOUDS AND SHOWERS FROM THE WEST. THIS MAY RESULT IN  
BRIEF PERIODS OF MVFR IN LOWER CIGS AND VISIBILITY LATE NIGHT AND  
EARLY FRIDAY.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
PDT 40 53 39 54 / 60 90 40 20  
ALW 43 53 42 56 / 60 90 40 30  
PSC 43 55 41 59 / 50 80 10 10  
YKM 41 57 36 59 / 50 60 10 10  
HRI 41 55 40 57 / 60 80 10 10  
ELN 36 50 33 52 / 70 70 10 10  
RDM 39 54 33 52 / 60 50 10 10  
LGD 39 52 37 54 / 50 80 60 40  
GCD 39 52 35 54 / 60 80 50 40  
DLS 43 55 41 57 / 60 80 10 20  
 

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

 
 

 
 
99/91/91  
 
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