233
FXUS66 KSEW 021020
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
320 AM PDT SAT MAY 2 2026
SYNOPSIS
WEAK UPPER LEVEL LOW OFF THE OREGON COAST MOVING SOUTH THROUGH
TONIGHT. UPPER LEVEL RIDGE BUILDING INTO THE BRITISH COLUMBIA
COAST SUNDAY WILL SAG SOUTH OVER WESTERN WASHINGTON BY TUESDAY.
THE RIDGE WILL WEAKEN WEDNESDAY, REBUILD THURSDAY, THEN START TO
SLIDE EAST FRIDAY. LIGHT FLOW IN THE LOWER LEVELS TURNING
OFFSHORE TONIGHT AND SUNDAY. LOW LEVEL FLOW TURNING ONSHORE
SUNDAY NIGHT INTO MONDAY. LOW LEVEL FLOW REMAINING LIGHT ONSHORE
THROUGH NEXT WEEK.
SHORT TERM /TODAY THROUGH MONDAY/
SATELLITE IMAGERY SHOWS BROAD WEAK UPPER LEVEL LOW OFF THE
OREGON COAST. MIDDLE AND HIGH LEVEL CLOUDS MOVING OVER WESTERN
WASHINGTON WITH SOUTHERLY FLOW ALOFT. STRATUS ALONG THE COAST
LAST NIGHT HAS SPREAD AS FAR INLAND AS SHELTON AT 3 AM/10Z.
TEMPERATURES WERE IN THE MID 40S TO MID 50S.
UPPER LEVEL LOW DRIFTING SOUTH TODAY AND TONIGHT WITH THE
SOUTHERLY FLOW ALOFT GETTING CUT OFF LATE THIS AFTERNOON. THIS
WILL STOP THE FLOW OF MIDDLE AND HIGH LEVEL CLOUDS OVER WESTERN
WASHINGTON. LIGHT FLOW IN THE LOWER LEVELS WILL PREVENT THE
STRATUS FROM EXPANDING MUCH FARTHER EASTWARD BUT THE AIR MASS IS
PRETTY MOIST OVER THE INTERIOR, DEW POINTS NEAR 50, SO WE COULD
SEE SOME SHALLOW STRATUS FORM IN PLACE OVER THE CENTRAL PUGET
SOUND AROUND SUNRISE. THE STRATUS WILL DISSIPATE LATER THIS
MORNING. WITH PLENTY OF SUNSHINE IN THE AFTERNOON HIGHS WARMING
INTO THE MID 60S TO MID 70S.
LOW LEVEL FLOW TURNING OFFSHORE TONIGHT INTO SUNDAY. TEMPERATURES
ALOFT CONTINUE TO WARM WITH 850 MB TEMPS PEAKING AROUND PLUS
16C SUNDAY AFTERNOON. SUNDAY WILL BE THE WARMEST DAY OF THE YEAR
SO FAR WITH HIGHS IN THE MID 70S TO MID 80S. RECORD HIGHS ARE
PROBABLE. OFFSHORE FLOW KICKING IN OVERNIGHT WILL KEEP SUNDAY
MORNING LOWS IN THE UPPER 40S TO MID 50S.
LOW LEVEL FLOW TURNING WEAKLY ONSHORE SUNDAY NIGHT WITH THE LOW
LEVEL ONSHORE FLOW INCREASING MONDAY. STRATUS DEVELOPING ALONG
THE COAST MONDAY WITH SIGNIFICANT COOLING, HIGHS BACK INTO THE
MID 60S. FOR THE INTERIOR THE MARINE LAYER WILL BE SHALLOW AND
HAVE A HARD TIME GETTING EAST OF THE PUGET SOUND IN THE
AFTERNOON AS IT GETS ERODED BY THE WARM AIR MASS OVER THE
INTERIOR. TEMPERATURES ALOFT COOLING SLIGHTLY. THIS COMBINED
WITH THE WEAK ONSHORE FLOW KNOCKING A COUPLE OF DEGREES OFF THE
HIGHS MONDAY COMPARED TO SUNDAY. STILL A VERY WARM DAY. HIGHS
IN THE 70S AND LOWER 80S.
THE HEATRISK FOR THE MOST PART REMAINS IN THE MINOR CATEGORY
SUNDAY AND MONDAY DUE TO THE TEMPERATURES COOLING OFF NICELY IN
THE OVERNIGHT HOURS. FELTON
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
UPPER LEVEL RIDGE AXIS DROPPING DOWN FROM THE NORTH OVER
WESTERN WASHINGTON MONDAY NIGHT INTO TUESDAY. LOW LEVEL ONSHORE
FLOW INCREASING MONDAY NIGHT WITH STRATUS GETTING EAST OF PUGET
SOUND TUESDAY MORNING. COOLER TUESDAY OVER THE INTERIOR WITH
HIGHS IN THE UPPER 60S TO MID 70S. COAST REMAINING IN THE MID
60S.
UPPER LEVEL RIDGE OVER THE AREA WEAKENING WEDNESDAY, REBUILDING
THURSDAY THEN STARTS TO MOVE EAST FRIDAY. LOW LEVEL FLOW
REMAINING LIGHT ONSHORE. RELATIVELY WARM AIR ALOFT COMBINED WITH
ONLY A SHALLOW MARINE LAYER OVER THE INTERIOR IN THE LATE NIGHT
AND MORNING HOURS WILL KEEP DAYTIME HIGHS ABOVE NORMAL THROUGH
THE WEEK. A LITTLE COOLING FRIDAY AS THE RIDGE STARTS TO EXIT
THE AREA. HIGHS WEDNESDAY AND THURSDAY IN THE 60S AND LOWER 70S,
FRIDAY IN THE 60S. LOWS IN THE 40S.
AVIATION
AN UPPER LEVEL LOW DIGGING SOUTHWARD ALONG THE OREGON COAST
WILL PRODUCE LIGHT SOUTHWEST FLOW ALOFT TODAY. AN UPPER LEVEL
RIDGE WILL BEGIN TO REBUILD INTO THE REGION TONIGHT WITH THE
FLOW ALOFT SWITCHING TO LIGHT NORTHEASTERLY. LIGHT LOW LEVEL
ONSHORE FLOW WILL TURN NORTHERLY THIS AFTERNOON. RESIDUAL HIGH
AND MID LEVEL MOISTURE WILL THIN WITH TIME TODAY. COASTAL
STRATUS AND ASSOCIATED MVFR/IFR CEILINGS WILL EXTEND INLAND AS
FAR AS KITSAP COUNTY THIS MORNING BEFORE LIFTING AND SCATTERING
OUT.
KSEA...VFR WITH MID AND HIGH LEVEL CLOUDS GRADUALLY THINNING AND
CLEARING TOWARD AFTERNOON. SURFACE WIND LIGHT AND VARIABLE EARLY
WILL BECOME NORTHERLY AND INCREASE TO 9 TO 13 KNOTS THIS
AFTERNOON.
27
MARINE
THERMALLY INDUCED LOW PRESSURE WILL EXPAND NORTHWARD ALONG THE
COAST TODAY INTO SUNDAY WITH LIGHT NORTHERLY OR WEAK OFFSHORE
FLOW DEVELOPING. THE THERMAL TROUGH WILL SHIFT INTO THE INTERIOR ON
MONDAY ALLOWING ONSHORE FLOW TO RESUME AND INCREASE TOWARD THE
MIDDLE OF NEXT WEEK. WESTERLIES IN THE CENTRAL AND EAST STRAIT WILL
LIKELY APPROACH GALE FORCE MONDAY NIGHT OR TUESDAY.
27
HYDROLOGY
NO RIVER FLOODING IN THE NEXT 7 DAYS.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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