611  
FXUS66 KSEW 230333  
AFDSEW  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SEATTLE WA  
733 PM PST TUE JAN 22 2019  
   
UPDATE /TONIGHT/
 
AS OF 5PM PST, SNOWFALL RATES AT PARADISE  
RANGER STATION HAD INCREASED TO 2 INCHES PER HOUR WITH 11 INCHES  
FALLEN TODAY. A COMBINATION OF SHORT RANGE MODELS INCLUDING THE  
HRRR, SREF, RAP, AND NAM SHOW INTENSE PRECIPITATION CONTINUING  
UNTIL THE FRONTAL SYSTEM NOW MOVING THROUGH THE COASTAL WATERS  
PUSHES INLAND. THEREFORE, THE WINTER WEATHER ADVISORY FOR THE  
CASCADES OF PIERCE AND LEWIS COUNTIES WAS UPGRADED TO A WARNING  
FOR UP TO ANOTHER FOOT OF SNOW POSSIBLE BY MIDNIGHT TONIGHT.  
DESPITE SNOW LEVELS RISING, EASTERLY FLOW THROUGH THE PASSES IS  
KEEPING PRECIPITATION AT SNOQUALMIE AND STEVENS PASSES IN THE FORM  
OF SNOW THIS EVENING, SO WILL LET THE WARNING CONTINUE THERE AND  
POINTS NORTHWARD AS WELL.  
 
HEAVY RAINFALL IS FALLING IN THE SKOKOMISH RIVER BASIN IN MASON  
COUNTY AND THE RIVER IS BEGINNING TO RESPOND. IT REMAINS POSSIBLE  
THAT THE RIVER WILL BRIEFLY REACH FLOOD STAGE EARLY WEDNESDAY  
MORNING, SO WILL MAINTAIN THE FLOOD WATCH AND WILL ISSUE A WARNING  
OVERNIGHT IF FLOODING APPEARS IMMINENT.  
 
THE REMAINDER OF THE FORECAST APPEARS TO BE IN GOOD SHAPE THIS  
EVENING, SO UPDATES TO THE AVIATION AND MARINE SECTIONS FOLLOW,  
AND THE PREVIOUS FORECAST DISCUSSION FOLLOWS THOSE SEGMENTS. ALBRECHT  
 

 
   
AVIATION
 
A WARM FRONT IS LIFTING NORTHEASTWARD THROUGH THE  
CENTRAL PORTIONS OF THE THE AREA THIS EVENING AND A TRAILING COLD  
FRONT IS OVER THE COASTAL WATERS AT 7 PM PST. THE COLD FRONT WILL  
SWEEP INLAND OVERNIGHT. AN ASSOCIATED WEAKENING SURFACE LOW NEAR  
50N 130W WILL SLIDE ESE THROUGH THE NORTHERN INTERIOR OF WESTERN  
WASHINGTON WEDNESDAY MORNING. WESTERLY FLOW ALOFT WILL BECOME MORE  
NORTHWESTERLY ON WEDNESDAY. AT THE SURFACE, BRIEF POST-FRONTAL  
ONSHORE FLOW WILL RAPIDLY EASE ON WEDNESDAY AS WEAK HIGH PRESSURE  
MOVES OVER THE AREA. THE AIR MASS IS MOIST AND STABLE.  
 
THE PASSING WARM FRONT AND INCOMING COLD FRONT IS PRODUCING  
WIDESPREAD MVFR AND AREAS OF IFR CONDITIONS ACROSS THE AREA.  
STEADY RAINFALL WILL CHANGE TO SHOWERS WITH CONDITIONS IMPROVING  
SLIGHTLY BEHIND THE COLD FRONT LATE TONIGHT OR EARLY WEDNESDAY.  
BUT RATHER WIDESPREAD IFR CONDITIONS ARE EXPECTED TO REDEVELOP  
LATER WEDNESDAY MORNING AS WEAK HIGH PRESSURE MOVES INTO THE AREA  
AND THE AIR MASS REMAINS MOIST AND STABLE. ALBRECHT  
 
KSEA...LOW MVFR TO IFR CONDITIONS TONIGHT MAY IMPROVE FOR A FEW  
HOURS LATE TONIGHT INTO EARLY WED, BUT IFR CONDITIONS IN LOW CIGS  
ARE EXPECTED TO DOMINATE LATE WED MORNING THROUGH WED NIGHT. S  
WIND 15G25 KT THIS EVENING WILL EASE OVERNIGHT THEN BECOMING LIGHT  
AND VARIABLE WED MORNING THROUGH WED NIGHT. ALBRECHT  
 

 
   
MARINE
 
A WARM FRONT IS LIFTING NORTHWARD THROUGH THE INLAND  
WATERS THIS EVENING. A COLD FRONT OVER THE COASTAL WATERS WILL  
SWEEP INLAND AFTER MIDNIGHT TONIGHT. A WEAKENING LOW NEAR 50N 130W  
WILL FILL AS IT MOVES ESE THROUGH THE NORTHERN INLAND WATERS WED  
MORNING. GALE CONDITIONS CONTINUE ACROSS THE SOUTHERN THIRD OF THE  
COASTAL WATERS WHILE SMALL CRAFT ADVISORY CONDITIONS ARE OCCURRING  
ELSEWHERE. POST FRONTAL ONSHORE FLOW WILL KEEP SMALL CRAFT  
ADVISORY CONDITIONS ARE EXPECTED TO RAPIDLY DECREASE WED MORNING.  
 
HIGH PRESSURE WILL BUILD INTO THE WATERS ON WED WITH WINDS ALL  
AREAS EASING. HOWEVER, SMALL CRAFT ADVISORY CONDITIONS FOR  
HAZARDOUS SEAS OVER 10 FT WILL CONTINUE THROUGH WEDNESDAY EVENING  
AND POSSIBLY A BIT LONGER. HENCE THE SMALL CRAFT ADVISORIES FOR  
THE COAST AND THE WEST ENTRANCE TO THE STRAIT WERE STRETCHED OUT  
INTO WED NIGHT.  
 
HIGH PRESSURE IS EXPECTED THU THROUGH SAT ACROSS THE AREA. THEN  
OFFSHORE FLOW MAY INCREASE ON SUN AS HIGH PRESSURE BUILDS INTO THE  
INTERIOR OF BRITISH COLUMBIA.  
 
COASTAL FLOOD ADVISORIES REMAIN IN EFFECT FOR THE SHORELINES  
ALONG THE INLAND WATERS FROM POINT ROBERTS TO THE SOUTH END OF  
PUGET SOUND AND HOOD CANAL AROUND THE WEDNESDAY MORNING HIGH TIDE.  
TIDES ARE NEAR THE HIGHEST VALUES FOR THE YEAR AND WILL BE  
ACCOMPANIED BY RELATIVELY LOW PRESSURE AND LINGERING LONGER-PERIOD  
ANOMALIES. ANY SALT-WATER FLOODING THAT OCCURS IS EXPECTED TO BE  
BRIEF AND MINOR. ALBRECHT  
 

 
   
PREV DISCUSSION
 
/ISSUED 312 PM PST TUE JAN 22 2019/  
 
SYNOPSIS...A FRONTAL SYSTEM PRECIPITATION WILL DRIVE RAIN,  
MOUNTAIN SNOW, AND BREEZY CONDITIONS OVER PARTS OF THE AREA THIS  
EVENING INTO WEDNESDAY MORNING. DRIER, BENIGN WEATHER WILL RETURN  
THURSDAY AND CONTINUE INTO THE WEEKEND. A COUPLE OF WEAK WEATHER  
SYSTEMS MAY BRUSH THE REGION THURSDAY NIGHT AND AGAIN SUNDAY FOR A  
CHANCE OF SHOWERS MAINLY OVER THE NORTH.  
 
SHORT TERM /TONIGHT THROUGH FRIDAY/...PRECIPITATION HAS SPREAD  
THROUGH THE ARE THIS AFTERNOON, WITH SNOW FALLING ABOVE 3000 TO  
4000 FEET IN THE MOUNTAINS. EXPECT PRECIPITATION TO PICK UP THIS  
EVENING AS THE COLD FRONT MOVES INLAND. THIS WILL ALSO BOOST SNOWFALL  
THE CASCADES THROUGH THE EVENING HOURS, WHERE A WINTER STORM  
WARNING IS IN EFFECT FOR THE CASCADES FROM WHATCOM COUNTY  
SOUTHWARD THROUGH KING COUNTY THROUGH, AND WINTER WEATHER  
ADVISORY IS IN EFFECT FOR THE CASCADES IN PIERCE AND LEWIS  
COUNTIES. IN ADDITION, EXPECT WINDY CONDITIONS ALONG THE COAST  
INTO THIS EVENING AND BREEZY TO LOCALLY WINDY OVER THE INTERIOR AS  
THE FRONT WORKS ONSHORE. WINDS ARE EXPECTED TO REMAIN SUB-  
ADVISORY WITH LITTLE OR NO IMPACTS ANTICIPATED AT THIS TIME.  
PRECIPITATION WILL TRANSITION TO SHOWERS WEDNESDAY, WITH SNOW LEVELS  
HOLDING AROUND 4000 TO 4500 FEET.  
 
AN UPPER LEVEL RIDGE THAT HAS BEEN BUILDING OVER THE EASTERN PACIFIC  
WILL BEGIN TO SHIFT SLOWLY ONSHORE WEDNESDAY EVENING. THIS SHIFT IN  
THE LARGE SCALE PATTERN WILL SET UP A DRY NORTHWESTERLY TO NORTH  
FLOW OVER WASHINGTON THURSDAY AND FRIDAY. MODELS HAVE BEEN PRETTY  
CONSISTENTLY SHOWING A WEAK SYSTEM RIDING UP AND OVER THE RIDGE AND  
INTO WESTERN WASHINGTON THURSDAY NIGHT INTO FRIDAY MORNING. THIS  
CONTINUES TO LOOK VERY WEAK AND WILL LIKELY RESULT IN LITTLE MORE  
THAN SOME LIGHT SHOWERS FOR PARTS OF THE AREA. IN GENERAL IT LOOKS  
LIKE THE BIGGEST WEATHER IMPACT TO THE AREA WILL BE PATCHY MORNING  
FOG IN THE FAVORED AREAS.  
 
LONG TERM /SATURDAY THROUGH TUESDAY/...THE OFFSHORE UPPER RIDGE  
WILL WILL BUILD FURTHER AND FULLY SHIFT ONSHORE SATURDAY. IT  
CONTINUES TO TREND TOWARDS A PLEASANT START TO THE WEEKEND WITH SOME  
MORNING FOG FOLLOWED BY SUNSHINE AND ABOVE AVERAGE TEMPERATURES. THE  
UPPER RIDGE SHIFTS OFFSHORE LATE IN THE WEEKEND, WHICH MAY ALLOW A  
WEAK SYSTEM TO CLIP THE AREA FROM THE NORTHWEST SUNDAY AFTERNOON OR  
EVENING. MODELS HAVE BEEN TRENDING WEAKER WITH THIS, SO THE DRY  
WEATHER MAY IN FACT EXTEND FULLY THROUGH THE WEEKEND. WITH THE UPPER  
LEVEL RIDGE FIRMLY ANCHORED OVER THE EASTERN PACIFIC INTO EARLY NEXT  
WEEK, IT CONTINUES TO LOOK GENERALLY DRY AND BENIGN INTO THE EARLY  
PART OF NEXT WEEK.  
 
AVIATION...A WARM FRONT WILL MOVE INLAND THIS EVENING. A  
TRAILING COLD FRONT WILL MOVE ONSHORE TONIGHT. AN ASSOCIATED  
WEAKENING SURFACE LOW MOVING EAST ACROSS THE NORTHERN INTERIOR  
TONIGHT. WESTERLY FLOW ALOFT WILL BECOME NORTHWESTERLY ON WEDNESDAY.  
AT THE SURFACE, ONSHORE FLOW WILL RAPIDLY EASE ON WEDNESDAY AS WEAK  
HIGH PRESSURE MOVES OVER THE AREA. THE AIR MASS IS MOIST AND STABLE.  
 
WIDESPREAD LOW CLOUDS AND OCCASIONAL REDUCED VISIBILITIES IN RAIN  
WILL PREVAIL TONIGHT AS A COLD FRONT PUSHES INLAND. THE RAIN WILL  
CHANGE TO SHOWERS WEDNESDAY MORNING BUT THE LOW LEVELS WILL REMAIN  
MOIST FOR CONTINUED LOW CLOUDS.  
 
KSEA...IT LOOKS QUITE SOUPY WITH LOTS OF LOW CLOUDS AND REDUCED  
VISIBILITIES TONIGHT AND WEDNESDAY. SOUTH WIND 5-10 KNOTS WILL  
INCREASE TO 12-18 KNOTS TONIGHT AND BECOME GUSTY THEN EASE AGAIN ON  
WEDNESDAY. SCHNEIDER  
 
MARINE...A WARM FRONT WILL MOVE INLAND THIS EVENING. A TRAILING  
COLD FRONT AND AN ASSOCIATED FILLING LOW WILL MOVE INLAND ACROSS THE  
NORTHERN PART OF THE AREA TONIGHT. MOST AREAS WILL HAVE SMALL CRAFT  
ADVISORY STRENGTH WINDS TONIGHT WITH MARGINAL GALES POSSIBLE OVER  
THE SOUTHERN COASTAL WATERS THIS EVENING.  
 
ONSHORE FLOW WILL RAPIDLY EASE ON WEDNESDAY. WEAK HIGH PRESSURE WILL  
MOVE OVER THE AREA ON THURSDAY AND LINGER IN THE VICINITY THROUGH  
SATURDAY FOR A PERIOD OF RELATIVELY LIGHT WINDS. OFFSHORE FLOW WILL  
DEVELOP ON SUNDAY AS HIGH PRESSURE BUILDS INTO BRITISH COLUMBIA.  
 
A COASTAL FLOOD ADVISORY IS IN EFFECT FOR THE CENTRAL COAST FOR  
MINOR TIDAL OVERFLOW AROUND THE TIME OF HIGH TIDES EARLY THIS  
AFTERNOON. A SECOND ROUND OF MINOR TIDAL OVERFLOW IS POSSIBLE FOR  
THE INLAND WATERS WEDNESDAY MORNING DUE TO HIGH ASTRONOMICAL TIDES  
AND TIDAL ANOMALIES DUE TO RELATIVELY LOW ATMOSPHERIC PRESSURE.  
SCHNEIDER  
 
HYDROLOGY...THE SKOKOMISH RIVER, AND RIVERS FLOWING OFF THE NORTH  
CASCADES WILL SEE SHARP RISES TONIGHT DUE TO A PERIOD OF HEAVY RAIN.  
ONE HALF TO ONE INCH OF RAIN HAS ALREADY FALLEN OVER THE OLYMPICS.  
THIS SYSTEM WILL PUSH THROUGH RELATIVELY QUICKLY, BUT WITH SNOW  
LEVELS ABOVE 5000 FEET, THERE MAY STILL BE UP TO 3-4 INCHES STORM  
TOTAL RAINFALL OVER THE OLYMPICS. THIS WILL DRIVE THE SKOKOMISH  
RIVER UP TO NEAR OR ABOVE FLOOD STAGE. RIVERS WILL RECEDE ON  
WEDNESDAY AND THIS SHOULD BE THE LAST FLOOD THREAT FOR THE NEXT 7  
DAYS. NO OTHER RIVER FLOODING IS EXPECTED FOR WESTERN WASHINGTON  
DURING THIS TIME.  
JBB  
 

 
   
SEW WATCHES/WARNINGS/ADVISORIES
 
 
WA...COASTAL FLOOD ADVISORY FROM 5 AM TO 10 AM PST WEDNESDAY FOR  
ADMIRALTY INLET AREA-BREMERTON AND VICINITY-EVERETT AND  
VICINITY-HOOD CANAL AREA-SAN JUAN COUNTY-SEATTLE AND  
VICINITY-SOUTHWEST INTERIOR-TACOMA AREA-WESTERN SKAGIT  
COUNTY-WESTERN WHATCOM COUNTY.  
 
WINTER STORM WARNING UNTIL MIDNIGHT PST TONIGHT FOR CASCADES OF  
PIERCE AND LEWIS COUNTIES-CASCADES OF SNOHOMISH AND KING  
COUNTIES-CASCADES OF WHATCOM AND SKAGIT COUNTIES.  
 
FLOOD WATCH FROM MIDNIGHT PST TONIGHT THROUGH WEDNESDAY  
AFTERNOON FOR HOOD CANAL AREA-LOWER CHEHALIS VALLEY AREA-  
OLYMPICS.  
 
PZ...SMALL CRAFT ADVISORY FOR ROUGH BAR UNTIL 9 PM PST WEDNESDAY FOR  
GRAYS HARBOR BAR.  
 
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 3 AM PST THURSDAY  
FOR COASTAL WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER  
10 TO 60 NM-COASTAL WATERS FROM POINT GRENVILLE TO CAPE  
SHOALWATER OUT 10 NM.  
 
GALE WARNING UNTIL MIDNIGHT PST TONIGHT FOR COASTAL WATERS FROM  
POINT GRENVILLE TO CAPE SHOALWATER 10 TO 60 NM-COASTAL  
WATERS FROM POINT GRENVILLE TO CAPE SHOALWATER OUT 10 NM.  
 
SMALL CRAFT ADVISORY UNTIL 3 AM PST THURSDAY 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.  
 
SMALL CRAFT ADVISORY UNTIL 9 AM PST WEDNESDAY FOR EAST ENTRANCE  
U.S. WATERS STRAIT OF JUAN DE FUCA.  
 
SMALL CRAFT ADVISORY UNTIL 6 AM PST WEDNESDAY FOR NORTHERN  
INLAND WATERS INCLUDING THE SAN JUAN ISLANDS.  
 
SMALL CRAFT ADVISORY UNTIL 9 PM PST WEDNESDAY FOR WEST ENTRANCE  
U.S. WATERS STRAIT OF JUAN DE FUCA.  
 
SMALL CRAFT ADVISORY FROM 2 AM TO 9 AM PST WEDNESDAY FOR CENTRAL  
U.S. WATERS STRAIT OF JUAN DE FUCA.  
 
SMALL CRAFT ADVISORY UNTIL MIDNIGHT PST TONIGHT FOR ADMIRALTY  
INLET.  
 
SMALL CRAFT ADVISORY UNTIL NOON PST WEDNESDAY FOR PUGET SOUND  
AND HOOD CANAL.  
 

 
 

 
 
WWW.WEATHER.GOV/SEATTLE  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab WA Page Main Text Page