856  
FXUS66 KSEW 232231  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
330 PM PDT THU MAR 23 2017  
   
SYNOPSIS
 
RAIN WILL SPREAD INTO THE INTERIOR THIS EVENING AS A  
FRONT MOVES ONSHORE. AN UPPER TROUGH WILL BRING SHOWERS FRIDAY.  
SHOWERS WILL DECREASE SATURDAY AS THE TROUGH SHIFTS INLAND.  
ADDITIONAL FRONTS WILL REACH THE AREA SUNDAY AND AROUND WEDNESDAY.  
 

 
   
SHORT TERM
 
RAIN ON THE COAST IS QUITE APPARENT IN RADAR, AND HAS  
BEEN SHOWING UP IN SURFACE OBS AS WELL. VISIBLE SATELLITE IMAGERY  
STILL SHOWS SOME CLEAR BITS OVER INLAND AREAS, BUT CLOUDS WILL BE  
INCREASING PRESENTLY. THE FRONT WILL MOVE ONSHORE THIS EVENING  
BRINGING RAIN TO ALL AREAS, WITH DECREASING SHOWERS BEHIND THE FRONT  
LATER TONIGHT. THE MOUNTAINS WILL GET SNOW--SOUTHERLY FLOW ALOFT  
FAVORS THE VOLCANOES BUT NOT THE PASSES, SO HAVE ISSUED A WINTER  
WEATHER ADVISORY MAINLY FOR THE VOLCANOES ABOVE ABOUT 4000 FEET LATE  
TONIGHT THROUGH FRIDAY MORNING. THERE WILL ALSO BE SOME BREEZY TO  
WINDY CONDITIONS COAST AND NORTH INTERIOR.  
 
AN UPPER TROUGH WILL MOVE OVER THE AREA ON FRIDAY GIVING SHOWERS.  
A SHORTWAVE IN THE FLOW WILL ENHANCE SHOWERS IN THE AFTERNOON.  
MODELS HAVE CONTINUED TO SHOW NEGATIVE LIFTED INDICES SPREADING FROM  
OFFSHORE FRIDAY MORNING TO INLAND AREAS FRIDAY AFTERNOON AND  
EVENING. HAVE INTRODUCED A SLIGHT CHANCE OF THUNDERSTORMS INTO THE  
FORECAST FOR FRIDAY AFTERNOON AND EVENING.  
 
THE UPPER TROUGH WILL SLOWLY SHIFT INLAND FRIDAY NIGHT AND SATURDAY.  
THERE WILL BE ENOUGH LINGERING INSTABILITY FOR A CONTINUED CHANCE OF  
SHOWERS BUT THE TREND SHOULD BE TOWARD DRYING ON SATURDAY AND  
ESPECIALLY SATURDAY NIGHT. SUNDAY WILL BEGIN DRY BUT ANOTHER SYSTEM  
WILL REACH THE COAST IN THE AFTERNOON AND PROBABLY SPREAD RAIN OVER  
THE WHOLE AREA SUNDAY EVENING. HIGH TEMPERATURES FRIDAY THROUGH  
SUNDAY WILL BE A FEW DEGREES BELOW NORMAL. BURKE  
   
LONG TERM
 
MONDAY WILL BE SHOWERY AS AN UPPER TROUGH PASSES.  
TUESDAY NOW LOOKS WETTER IN THE MODELS AND HAVE BOOSTED POPS,  
ESPECIALLY ON THE COAST AND IN THE MOUNTAINS. WEDNESDAY STILL  
APPEARS TO BE A DAY WHEN A FRONT BRINGS RAIN. THURSDAY WILL BE  
SHOWERY AT FIRST BUT COULD SEE SIGNIFICANT DRYING LATER IN THE DAY.  
TEMPERATURES WILL BE CLOSE TO NORMAL THROUGH THE PERIOD. BURKE  
 

 
   
AVIATION
 
STRONG SOUTHWEST FLOW ALOFT THROUGH FRIDAY MORNING AS A  
TROUGH MOVES INTO THE PACIFIC NORTHWEST. MODERATE WEST-SOUTHWEST  
FLOW ALOFT BY FRIDAY AFTERNOON. AIR MASS GENERALLY MOIST AND STABLE.  
A SURFACE FRONT WILL REACH THE COAST BY AROUND MIDNIGHT AND  
DISSIPATE AS IT SLOWLY MOVES THROUGH PUGET SOUND FRIDAY MORNING.  
RAIN DEVELOPING OVER MOST OF WRN WA BY EARLY THIS EVENING, BECOMING  
SHOWERS BEHIND A FRONT FRIDAY. MAINLY VFR CIGS, HOWEVER BRIEF  
PERIODS OF MVFR CIGS/VIS POSSIBLE WITH STEADY RAIN AHEAD OF THE  
FRONT LATER TONIGHT.  
 
KSEA...SOUTHEAST WIND 8-13 KT, BECOMING SOUTH-SOUTHWEST 10-16 KT  
GUSTS TO 28 KT FRIDAY. VFR CIGS AROUND 7-8K FT LOWERING RAPIDLY TO  
AROUND 4K FT AS STEADY RAIN DEVELOPS AROUND 02Z.  
 

 
   
MARINE
 
SOUTHEAST GALES UP TO 40 KT OVER THE COASTAL WATERS THIS  
EVENING, SWITCHING TO SOUTH OR SOUTHWESTERLY LATE TONIGHT AND  
GRADUALLY EASING BEHIND A FRONT. GALE FORCE WINDS OVER THE EAST  
ENTRANCE TO THE STRAIT AND NORTH INLAND WATERS WILL BE MORE BRIEF  
TONIGHT. SMALL CRAFT WINDS DEVELOPING THIS EVENING ALL OTHER WATERS  
INCLUDING PUGET SOUND. AS GALES EASE LATE TONIGHT, SMALL CRAFT  
STRENGTH WINDS WILL LINGER IN MOST WATERS FRIDAY IN POST FRONTAL  
ONSHORE FLOW.  
 
HIGHER PRESSURE BUILDS OVER THE WATERS FRIDAY NIGHT THROUGH  
SATURDAY. ANOTHER LOW WILL AFFECT THE WATERS LATE SUNDAY INTO  
MONDAY.  
 

 
   
HYDROLOGY
 
RIVER FLOODING IS UNLIKELY OVER THE NEXT 7 DAYS.  
 

 
   
SEW WATCHES/WARNINGS/ADVISORIES
 
 
WA...WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 AM PDT  
FRIDAY FOR CASCADES OF PIERCE AND LEWIS COUNTIES-CASCADES  
OF WHATCOM AND SKAGIT COUNTIES.  
 
PZ...SMALL CRAFT ADVISORY FROM 3 AM TO 5 PM PDT FRIDAY FOR COASTAL  
WATERS FROM CAPE FLATTERY TO JAMES ISLAND 10 TO 60 NM-  
COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-  
COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE 10 TO  
60 NM-COASTAL WATERS FROM JAMES ISLAND TO POINT GRENVILLE  
OUT 10 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE  
SHOALWATER 10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE  
TO CAPE SHOALWATER OUT 10 NM-EAST ENTRANCE U.S. WATERS  
STRAIT OF JUAN DE FUCA-NORTHERN INLAND WATERS INCLUDING THE  
SAN JUAN ISLANDS.  
 
GALE WARNING UNTIL 3 AM PDT FRIDAY FOR COASTAL WATERS FROM CAPE  
FLATTERY TO JAMES ISLAND 10 TO 60 NM-COASTAL WATERS FROM  
CAPE FLATTERY TO JAMES ISLAND OUT 10 NM-COASTAL WATERS FROM  
JAMES ISLAND TO POINT GRENVILLE 10 TO 60 NM-COASTAL WATERS  
FROM JAMES ISLAND TO POINT GRENVILLE OUT 10 NM-COASTAL  
WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM-  
COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER OUT  
10 NM-EAST ENTRANCE U.S. WATERS STRAIT OF JUAN DE FUCA-  
NORTHERN INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.  
 
SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 11 PM PDT FRIDAY FOR  
GRAYS HARBOR BAR.  
 
SMALL CRAFT ADVISORY UNTIL 5 PM PDT FRIDAY FOR ADMIRALTY INLET-  
PUGET SOUND AND HOOD CANAL-WEST ENTRANCE U.S. WATERS STRAIT  
OF JUAN DE FUCA.  
 
SMALL CRAFT ADVISORY UNTIL 6 AM PDT FRIDAY FOR CENTRAL U.S.  
WATERS STRAIT OF JUAN DE FUCA.  
 

 
 

 
 
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