717
FXUS66 KSEW 170312
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
812 PM PDT THU JUL 16 2026
SYNOPSIS
CONDITIONS ARE FAVORED TO TREND DRIER OVER THE
WEEKEND WITH NEAR-SEASONAL TEMPERATURES. HIGH PRESSURE THEN
BUILDS OVER THE AREA NEXT WEEK, BRINGING CONTINUED DRY WEATHER
AND WELL-ABOVE AVERAGE TEMPERATURES ALONG WITH MODERATE
HEATRISK.
SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/
AN UPPER LOW
(OFFSHORE) WILL CONTINUE TO SHIFT NORTH TONIGHT WITH SHOWERS AND
THUNDERSTORMS ENDING. MOST OF THE ACTIVITY IS IN THE NORTHERN
INTERIOR WITH ISOLATED CELLS IN THE NORTHERN CASCADES. THE
THUNDERSTORM THREAT HAS ENDED IN THE OLYMPICS AND THE RED FLAG
WARNING WAS ENDED EARLY. 33
PREVIOUS DISCUSSION...SHOWERS AND THUNDERSTORMS ARE PERSISTING
BUT MAINLY ALONG THE WESTERN HALF OF THE CWA (OLYMPIC PENINSULA
AND ISLAND COUNTY). THIS ACTIVITY WILL PERSIST BEFORE
DECREASING IN COVERAGE INTO THE EVENING. FOR TONIGHT, DRIER
WEATHER IS EXPECTED AS THE UPPER- LOW RESPONSIBLE FOR
THUNDERSTORMS LIFTS NORTH INTO BC. MINIMUM TEMPERATURES WILL
FALL INTO THE LOWER TO MID 50S.
BAGGY TROUGHING IN THE 500 MB LEVELS FRIDAY AND SATURDAY AS THE
AFOREMENTIONED UPPER-LOW CONTINUES TO TRACK WELL INTO BC AND
ALBERTA. CAN'T RULE OUT LINGERING SHOWERS (15-30% POPS),
PRIMARILY OVER THE OLYMPICS AND NORTH CASCADES ON FRIDAY BUT
CONDITIONS ARE FAVORED TO TREND DRIER, ESPECIALLY INTO SATURDAY.
HIGH TEMPERATURES WILL BE RIGHT AROUND SEASONAL AVERAGES WITH
HIGHS IN THE LOWER 70S TO NEAR 80 F AND OVERNIGHT LOWS IN THE
50S. DAYTIME HIGHS ALONG THE COAST WILL BE ABOUT 10 DEGREES
COOLER - IN THE 60S.
LONG TERM /SUNDAY THROUGH THURSDAY/
GUIDANCE HAS THE UPPER-
LEVEL PATTERN INTO EARLY NEXT WEEK FEATURING THE RETURN OF HIGH
PRESSURE ACROSS THE REGION. A SHARP WARM-UP IN TEMPERATURE IS
EXPECTED AS HIGHS TOP OUT 7-10 DEGREES ABOVE AVERAGE FOR MONDAY
AND TUESDAY. WIDESPREAD MODERATE HEATRISK IS FAVORED DURING THIS
TIME. THERE'S DISAGREEMENT IN GUIDANCE REGARDING THE EVOLUTION
OF THE PATTERN MIDWEEK ONWARD. GFS AND CANADIAN ENSEMBLES ARE
HINTING AT UPPER-LEVEL RIDGING PERSISTING ACROSS THE PNW WITH
UPPER- TROUGHING OFFSHORE. THE ECMWF RESEMBLES ARE SIMILAR IN
RIDGING OVER THE PNW BUT ALSO OVER THE OFFSHORE WATERS OF THE NE
PAC, DISSIMILAR THAN ITS GFS AND CANADIAN COUNTERPARTS.
NONETHELESS, WELL-ABOVE AVERAGE TEMPERATURES ARE FAVORED IN THE
LONG-TERM FORECAST WITH NO MAJOR SIGNAL FOR PRECIPITATION.
AVIATION
GENERALLY LOW END VFR TO MVFR THIS EVENING AS
SHOWERS AND THUNDERSTORM ACTIVITY TAPER OFF ACROSS THE REGION.
LOW END VFR TO MVFR CEILINGS ARE FAVORED TO CONTINUE OVERNIGHT
INTO FRIDAY MORNING, WITH LOCALIZED AREAS OF IFR/LIFR ALONG THE
PACIFIC COAST AND OVER THE KITSAP PENINSULA. SOUTHWEST WINDS
WILL CONTINUE THROUGH THE TAF PERIOD FOR MOST AREAS AROUND 5-10
KT.
KSEA...CEILINGS ARE FAVORED TO BOUNCE BETWEEN LOW END VFR AND MVFR
THROUGH EARLY FRIDAY MORNING AS SHOWERS WRAP UP OVER THE TERMINAL.
CHANCES FOR IFR CEILINGS INCREASE BETWEEN 12Z-18Z FRIDAY MORNING,
BUT CONFIDENCE IS LOW. SOUTHWEST WINDS AROUND 5-10 KT WILL CONTINUE
THROUGH THE FORECAST PERIOD.
HPR/15
MARINE
THUNDERSTORMS WILL CONTINUE TO TAPER OFF OVER THE
COASTAL WATERS AND PORTIONS OF THE INTERIOR WATERS THIS EVENING
AS A LOW PRESSURE SYSTEM MOVES OVER THE AREA. A WESTERLY PUSH OF
WINDS THROUGH THE STRAIT OF JUAN DE FUCA WILL FOLLOW TONIGHT
INTO FRIDAY, WHERE A SMALL CRAFT ADVISORY IS IN EFFECT. HIGH
PRESSURE WILL REBUILD OFF THE COAST THIS WEEKEND, WITH DAILY
ONSHORE PUSHES CONTINUING. SATURDAY AFTERNOON AND EVENING LOOKS
LIKE THE NEXT BEST CHANCE OF WINDS EXCEEDING 20 KT IN THE
STRAIT.
SEAS TO DROP TO 4-6 FT TONIGHT, WITH THEM BUILDING TO 6-8 FT NEXT
WEEK AND POTENTIALLY 9 FT IN A FEW AREAS WITH PERIODS AT 8-9 SECONDS.
HPR/15
FIRE WEATHER
THE RED FLAG WARNING FOR THE OLYMPICS HAS ENDED
AS THE THUNDERSTORM THREAT REMAINS NORTH AND EAST OF THE AREA.
FIRE WEATHER CONCERNS WILL LINGER THROUGH THE REMAINDER OF THE
FORECAST PERIOD AS A HOTTER AND DRIER PATTERN RETURNS QUICKLY
OVER WESTERN WASHINGTON, ESPECIALLY INTO EARLY NEXT WEEK. THIS
HAS THE POTENTIAL FOR INCREASING FIRE ACTIVITY FROM ANY NEW
LIGHTNING STARTS FROM TODAY'S CONVECTION.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR CENTRAL
U.S. WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S.
WATERS STRAIT OF JUAN DE FUCA.
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