638
FXUS66 KSEW 191023
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
323 AM PDT WED AUG 19 2026
SYNOPSIS
WEAK UPPER LEVEL RIDGE WITH LIGHT ONSHORE FLOW IN THE LOWER
LEVELS THROUGH THURSDAY. UPPER LEVEL LOW APPROACHING FROM THE
SOUTHWEST FRIDAY WILL MOVE INTO THE COASTAL WATERS SATURDAY.
SHOWER CHANCES INCREASING FRIDAY NIGHT INTO SATURDAY WITH
THUNDERSTORMS POSSIBLE. LOW MOVES BY TO THE NORTH SATURDAY
NIGHT. UPPER LEVEL RIDGE REBUILDING SUNDAY AND MONDAY WILL MOVE
EAST TUESDAY AS AN UPPER LEVEL TROUGH DEVELOPS OFF THE COAST.
SHORT TERM /TODAY THROUGH FRIDAY/
SATELLITE IMAGERY SHOWS LOW CLOUDS ALONG THE COAST HAVE ALREADY
MOVED THROUGH THE LOWER CHEHALIS VALLEY AND DOWN THE STRAIT OF
JUAN DE FUCA TO THE PUGET SOUND AT 3 AM/10Z. JUST SOME HIGH
CLOUDS OVER THE REMAINDER OF THE AREA. TEMPERATURES WERE IN THE
50S AND LOWER 60S.
STRATUS A LITTLE FURTHER EAST THIS MORNING VERSUS THE LAST
COUPLE OF MORNINGS AND WILL MOVE EAST OF PUGET SOUND AROUND
SUNRISE. LIKE THE OTHER MORNINGS THE LAYER IS SHALLOW WITH TOP
REPORTS AROUND 1000 FEET MSL. WITH THE LAYER BEING SO SHALLOW
LOCATIONS IN THE LOWLANDS FROM SNOHOMISH COUNTY SOUTHWARD WILL
SEE SOME PATCHY FOG THROUGH MID MORNING. LAYER RETREATING BACK
TO THE COAST LATE MORNING/MIDDAY WITH AFTERNOON SUNSHINE FOR THE
INTERIOR. CLOUDS HANGING RIGHT ALONG THE COASTLINE IN THE
AFTERNOON. HIGHS INLAND IN THE 70S AND LOWER 80S, ALONG THE
COAST IN THE MID AND UPPER 60S.
NOT MUCH CHANGE IN THE PATTERN OVERNIGHT INTO THURSDAY. LOW
LEVEL ONSHORE FLOW A TOUCH WEAKER MAKING IT HARDER FOR THE
STRATUS TO GET EAST OF PUGET SOUND FOR VERY LONG THURSDAY
MORNING. SLIGHTLY SHALLOWER MARINE LAYER COMBINED WITH SLIGHT
WARMING ALOFT ADDING A COUPLE OF DEGREES TO THE HIGHS. LOWS IN
THE 50S. HIGHS IN THE MID 70S TO MID 80S INLAND AND NEAR 70
COAST.
PATTERN STARTS TO CHANGE THURSDAY NIGHT INTO FRIDAY. UPPER LEVEL
LOW WELL OFFSHORE APPROACHING THE AREA. UPPER LEVEL FLOW
BECOMING SOUTHERLY SENDING MIDDLE AND HIGH LEVEL CLOUDS INTO
WESTERN WASHINGTON. INCREASING LOW LEVEL ONSHORE FLOW FRIDAY
AFTERNOON LOOKS TO BE TOO LATE TO MAKE MUCH OF A DIFFERENCE IN
THE TEMPERATURES. LOWS AGAIN IN THE 50S. HIGHS FRIDAY IN THE
70S AND LOWER 80S INTERIOR AND MID TO UPPER 60S COAST. FELTON
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
EXTENDED MODELS IN MUCH BETTER AGREEMENT IN THE 00Z RUN. UPPER
LEVEL LOW CONTINUING TO APPROACH WESTERN WASHINGTON WITH THE
LOW OVER THE COASTAL WATERS FRIDAY NIGHT. SYSTEM SPINNING OUT OF
THE LOW MOVING THROUGH LATE FRIDAY NIGHT INTO SATURDAY MORNING
WITH SCATTERED SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS. LOW
CONTINUING TO SLOWLY MOVE NORTHEAST SATURDAY NIGHT AND SUNDAY
WITH THE SHOWER CHANCES CONFINED TO THE NORTHERN PORTIONS
SUNDAY. UPPER LEVEL RIDGE REBUILDING LATER SUNDAY INTO MONDAY.
THE RIDGE WILL SHIFT EAST TUESDAY WITH AN UPPER LEVEL TROUGH
DEVELOPING OFF THE COAST.
HIGHS SATURDAY MUCH BELOW NORMAL, IN THE 60S AND LOWER 70S. A
LITTLE WARMER SUNDAY BUT STILL BELOW NORMAL, LOWER 60S TO MID
70S. HIGHS WARMING BACK TO NORMAL, IN THE 70S INTERIOR AND MID
TO UPPER 60S COAST MONDAY AND TUESDAY. LOWS IN THE 50S THROUGH
THE PERIOD. FELTON
AVIATION
LIGHT SOUTHWESTERLY FLOW ALOFT WITH WEAK LOW LEVEL ONSHORE FLOW
THROUGH THURSDAY. LIFR CEILINGS WITH VISIBILITIES DOWN TO A MILE
OR LESS ABOVE ABOUT 400 FEET THIS MORNING. CEILINGS OVER THE
INTERIOR LIFTING TO IFR MID TO LATE MORNING WITH JUST SCATTERED
CLOUDS BY 19-20Z. ALONG THE COAST CEILINGS LIFTING TO MVFR IN
THE AFTERNOON.
STRATUS SLOWLY MOVING BACK INLAND OVERNIGHT GETTING JUST EAST OF
PUGET SOUND 12Z-15Z.
KSEA...LEADING EDGE OF THE STRATUS DECK 10-15 MILES TO THE
SOUTHWEST AT 10Z. STRATUS REACHING THE TERMINAL 13Z-14Z WITH
LIFR CEILINGS AND VISIBILITY DROPPING TO AS LOW AS A MILE.
IMPROVING TREND BEGINNING AROUND 17Z WITH NO VISIBILITY
RESTRICTIONS AND IFR CEILINGS BY 18Z. CLOUDS DISSIPATING BY 19Z.
SOUTHWEST WIND 4 TO 8 KNOTS BECOMING NORTHWESTERLY AROUND 02Z.
FELTON
MARINE
BROAD SURFACE HIGH PRESSURE OVER THE WATERS WILL WEAKEN FRIDAY.
A WEAK SURFACE LOW WILL MOVE INTO THE COASTAL WATERS SATURDAY
THEN DISSIPATE SATURDAY NIGHT. HIGH PRESSURE WILL REBUILD OVER
THE WATERS SUNDAY.
SMALL CRAFT ADVISORY WINDS IN THE CENTRAL STRAIT FRIDAY NIGHT
OTHERWISE WINDS REMAINING BELOW 20 KNOTS THROUGH THE PERIOD.
SEAS 3 TO 5 FEET FOR THE MOST PART THROUGH THE WEEKEND. FELTON
FIRE WEATHER
LOW LEVEL ONSHORE FLOW CREATING GOOD HUMIDITY RECOVERIES
OVERNIGHT INTO THE EARLY MORNING HOURS WILL KEEP FIRE WEATHER
CONCERNS AT A MINIMUM THROUGH THURSDAY.
SYSTEM MOVING THROUGH THE REGION FRIDAY NIGHT INTO SATURDAY
WILL ELEVATE FIRE WEATHER CONCERNS. THIS SYSTEM COULD PRODUCE
THUNDERSTORMS MAINLY OVER THE OLYMPICS AND CASCADES. ANY
THUNDERSTORMS THAT DEVELOP MAY BE CAPABLE OF PRODUCING LOCALLY
WETTING RAINS ALONGSIDE GUSTY AND ERRATIC OUTFLOW WINDS AND
ABUNDANT LIGHTNING.
FIRE WEATHER CONCERNS DECREASE SUNDAY WITH THE SYSTEM TO THE
NORTH AND HIGH PRESSURE BUILDING INTO THE AREA. LOW LEVEL
ONSHORE FLOW SUNDAY THROUGH TUESDAY WITH MORNING STRATUS AND
AFTERNOON SUN, NEAR NORMAL TEMPERATURES, AND GENERALLY CALM
WINDS. FELTON
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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