842  
FXUS66 KSEW 202222  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
222 PM PST THU FEB 20 2020  
   
SYNOPSIS
 
DRY CONDITIONS WILL PERSIST INTO FRIDAY. A WEAK FRONT  
MAY BRING A FEW LIGHT SHOWERS ON SATURDAY, WITH A MORE ROBUST  
SYSTEM EXPECTED FOR SUNDAY. THIS SYSTEM WILL BRING LOWLAND RAIN  
AND MOUNTAIN SNOW TO THE AREA, WHICH WILL LINGER INTO MONDAY. DRY  
CONDITIONS RETURN FOR TUESDAY AND LAST THROUGH MID-WEEK.  
 

 
   
SHORT TERM /TONIGHT THROUGH SUNDAY/
 
HIGH PRESSURE AND OFFSHORE  
FLOW CONTINUES ACROSS WESTERN WA TODAY FOR DRY AND MILD WEATHER.  
SKIES ARE MOSTLY CLEAR THIS AFTERNOON WITH TEMPERATURES IN THE  
50S. TEMPERATURES WILL BE CHILLY OVERNIGHT UNDER CLEAR SKIES AND  
LIGHT WINDS. EXPECT LOWS IN THE 20S TO LOWER 30S ONCE AGAIN.  
 
THE RIDGE WILL EXITS EAST ON FRIDAY WHILE THE FLOW ALOFT BECOMES  
MORE WESTERLY OR ZONAL. A WEAK SYSTEM MOVING INTO B.C. WILL  
SPREAD HIGH CLOUDS INTO WESTERN WA. OTHERWISE, WE'LL SEE ONE MORE  
DRY AND MILD DAY ACROSS THE REGION.  
 
RAIN RETURNS LATE FRIDAY NIGHT INTO SATURDAY AS A WEAK FRONTAL  
SYSTEM CLIPS WESTERN WA. OVERALL, PRECIPITATION AMOUNTS LOOK LIGHT  
AND MOST AREAS WILL SEE LESS THAN 0.10" THROUGH THE PERIOD.  
 
A STRONGER AND WETTER PACIFIC FRONTAL SYSTEM IS SLATED FOR SUNDAY.  
THIS SYSTEM WILL BRING MORE RAIN, GUSTY WINDS AND POSSIBLY HEAVY  
MOUNTAIN SNOW TO THE AREA. SNOW LEVELS WILL REMAIN LOW, AROUND  
3000 FT, WITH ACCUMULATING SNOW EXPECTED AT THE HIGHER PASSES  
(LIKE STEVENS AND WHITE PASS). SNOQUALMIE PASS MAY SEE A RAIN/SNOW  
MIX. WINDS WILL BE GUSTY (OUT OF THE S/SW) AS THE COLD FRONT  
MOVES THROUGH THE INTERIOR SUNDAY AFTERNOON - GUSTS TO 40 MPH  
POSSIBLE. SHOWERS WILL MOSTLY IMPACT THE CASCADES SUNDAY NIGHT  
UNDER POST-FRONTAL ONSHORE FLOW. WILL LIKELY SEE A CONVERGENCE  
ZONE DEVELOP WHICH MAY BRING MORE HEAVY SNOW TO STEVENS PASS. 33  
   
LONG TERM /MONDAY THROUGH THURSDAY/
 
SHOWERS WILL LINGER INTO  
MONDAY AS ONSHORE FLOW CONTINUES. AN UPPER LEVEL RIDGE WILL BUILD  
INLAND ON TUESDAY FOR A BREAK IN THE PATTERN. THE RIDGE MAY  
FLATTEN OVER THE PAC NW ON WEDNESDAY AS A WEAK FRONT CLIPS THE  
REGION. HIGH PRESSURE WILL REBUILD LATE IN THE WEEK, PUTTING US  
BACK IN A RELATIVELY QUIET PERIOD OF WEATHER. 33  
 

 
   
AVIATION
 
VFR CONDITIONS WITH GENERALLY LIGHT AND VARIABLE WINDS  
AT NEARLY ALL TAF SITES. HQM CONTINUES TO HAVE EAST-SOUTHEASTERLY  
PREVAILING WINDS AROUND 10 KNOTS, WITH THE LATEST METAR REPORTING  
3SM DUE TO HAZE AT THIS HOUR. OTHERWISE, FOG IS EXPECTED TO DEVELOP  
AT AND AROUND OLM OVERNIGHT.  
 
KSEA...VFR CONDITIONS WITH WINDS CURRENTLY OUT OF THE NW AT 7KTS.  
WINDS ARE EXPECTED TO WEAKEN AND SHIFT BACK TO AN EASTERLY DIRECTION  
ENE TO ESE OVERNIGHT BEFORE BECOMING SOUTHERLY AFTER DAYBREAK.  
SPEEDS BELOW 7KTS EXPECTED. INCREASING HIGH CLOUDS AOA 25K FT  
FRIDAY.  
 
PULLIN  
 

 
   
MARINE
 
LIGHT OFFSHORE FLOW WILL CONTINUE THROUGH FRIDAY MORNING  
BEFORE GIVING WAY TO LIGHT ONSHORE FLOW DURING THE DAY. A WEAKENING  
FRONT WILL MOVE THROUGH THE AREA SATURDAY, WITH A SECOND FRONT  
MOVING THROUGH THE AREA SUNDAY INTO SUNDAY NIGHT. THE SECOND FRONT  
WILL YIELD INCREASING WINDS AND SEAS, WITH THE POTENTIAL FOR STRONG  
WINDS SPREADING FROM THE NEARSHORE WATERS INTO THE STRAIT OF JUAN DE  
FUCA ON SUNDAY.  
 
PULLIN  
 

 
   
HYDROLOGY
 
RIVER FLOODING IS NOT EXPECTED OVER THE NEXT 7 DAYS.  
 

 
   
SEW WATCHES/WARNINGS/ADVISORIES
 
 
WA...NONE.  
PZ...NONE.  

 
 

 
 
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