803
FXUS66 KSEW 140437
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
937 PM PDT MON JUL 13 2026
UPDATE
SATELLITE IMAGERY SHOWS SOME HIGH CLOUDS OVER THE
NORTH COAST OTHERWISE CLEAR SKIES ACROSS WESTERN WASHINGTON THIS
EVENING. NORTHERLY LOW LEVEL FLOW GOING LIGHT OVERNIGHT BUT THE
MARINE LAYER HAS BEEN DISSIPATED BY A COUPLE OF DAYS OF SUNSHINE
SO NOT EXPECTING MUCH IN THE WAY OF STRATUS IN THE MORNING EVEN
ON THE COAST. 500 MB HEIGHTS RISING A LITTLE TOMORROW PEAKING IN
THE MID 580 DMS. WITH SOUTHWESTERLY FLOW ALOFT COULD SEE SOME
HIGH CLOUDS AT TIMES THE NEXT COUPLE OF DAYS. WARMER TUESDAY AND
WEDNESDAY WITH HIGHS IN THE MID 70S TO MID 80S OVER THE INTERIOR
AND LOWER TO MID 70S COAST. FIRST LOOK AT 00Z MODELS STILL
INDICATING THE POSSIBILITY OF CONVECTION THURSDAY. CURRENT
FORECAST ON TRACK. NO UPDATE THIS EVENING. PREVIOUS DISCUSSION
FOLLOWS WITH UPDATED AVIATION SECTION. FELTON
SYNOPSIS
HIGH PRESSURE ALOFT WILL REBUILD ACROSS THE REGION
INTO WEDNESDAY FOR WARM AND DRIER CONDITIONS. AN AREA OF LOW
PRESSURE MAY BRING A THREAT OF SHOWERS AND THUNDERSTORMS AROUND
THURSDAY BEFORE HIGH PRESSURE REGAINS CONTROL OVER THE WEEKEND
FOR A RETURN OF DRY CONDITIONS AND WELL ABOVE NORMAL
TEMPERATURES.
SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/
MOSTLY CLEAR
CONDITIONS THIS AFTERNOON ACROSS WESTERN WASHINGTON WITH
LOCALIZED STRATUS ALONG THE COAST. HIGH PRESSURE WILL CONTINUE
TO BUILD OVER THE REGION AS AN AREA OF LOW PRESSURE DIVES
SOUTHWARDS WELL OFFSHORE. DRY, WARM CONDITIONS CONTINUE FOR THE
MAJORITY OF THE AREA THROUGH WEDNESDAY. TEMPERATURES WILL WARM
INTO THE 80S FOR MUCH OF THE INTERIOR TUESDAY INTO WEDNESDAY,
RESULTING IN CONTINUED MINOR HEATRISK AND AREAS OF MODERATE
HEATRISK. ALTHOUGH POPS REMAIN VERY LOW ON WEDNESDAY AFTERNOON,
WILL NEED TO MONITOR THE THREAT FOR CONVECTION OVER THE
CASCADES WITH INCREASING INSTABILITY. OTHERWISE, HAZE ALOFT WILL
BE AROUND INTO MIDWEEK WITH CONTINUED SOUTHERLY FLOW.
LONG TERM /THURSDAY THROUGH MONDAY/
UNCERTAINTY INCREASES IN
ENSEMBLES FOR THURSDAY INTO FRIDAY AS THE UPPER LOW LOCATED
OFFSHORE MEANDERS CLOSER TO THE PACIFIC NORTHWEST. HOWEVER,
THERE HAS BEEN AN UPTICK IN POPS FOR THE THURSDAY PERIOD ON THE
NBM. LOOKING AT CLUSTER ANALYSIS, ECMWF/CMC ENSEMBLES GENERALLY
BRING THE UPPER LOW TRACK CLOSER TO W WA BY THURSDAY, WITH THE
GEFS MAINTAINING MORE OF AN OFFSHORE SOLUTION (MORE RIDGING OVER
W WA). DEPENDENT ON THE TRACK, THERE IS A THREAT FOR SHOWERS AND
THUNDERSTORMS DURING THIS PERIOD WITH MORE S/SE FLOW ALOFT.
GIVEN THE POTENTIAL IN ELEVATED INSTABILITY, CONVECTION COULD
OCCUR DURING THE OVERNIGHT AND MORNING PERIODS AS WELL, FROM
LATE WEDNESDAY NIGHT INTO EARLY FRIDAY. THIS WILL NEED TO BE
MONITORED CLOSELY AS THIS WOULD POSE A FIRE WEATHER CONCERN, AS
WELL AS IMPACT ANY OUTDOOR EVENTS.
UPPER LEVEL RIDGING IS THEN EXPECTED TO BUILD NEXT WEEKEND INTO
EARLY NEXT WEEK, RESULTING IN THE RETURN OF DRY CONDITIONS AND
WARMING TEMPERATURES. THE THREAT FOR MODERATE HEATRISK INCREASES
EARLY NEXT WEEK, WITH WIDESPREAD PROBABILITIES OF 50% OR GREATER
FOR MODERATE HEATRISK.
AVIATION
SOUTHWESTERLY FLOW ALOFT CONTINUES INTO TUESDAY AS HIGH
PRESSURE REMAINS OVER THE REGION WITH A AREA OF LOW PRESSURE
OFFSHORE. VFR CONDITIONS AT ALL AREA TERMINALS WILL CONTINUE
INTO THE OVERNIGHT HOURS AS CONDITIONS REMAIN STABLE. WINDS
GENERALLY FROM THE NW TO NE THIS EVENING AROUND 8 TO 12 KNOTS
AND WILL DECREASE OVERNIGHT, TURNING MORE VARIABLE INTO TUESDAY
MORNING.
KSEA...VFR CONDITIONS THROUGHOUT THE FORECAST PERIOD. N/NE WINDS
THIS EVENING TO AROUND 5 TO 10 KNOTS. WINDS WILL DECREASE INTO THE
OVERNIGHT HOURS, AND WILL REMAIN N/NE WITH SPEEDS AROUND 3 TO 6
KNOTS.
MAZURKIEWICZ/15
MARINE
SURFACE HIGH PRESSURE WILL REMAIN OVER THE COASTAL
WATERS THROUGHOUT THE NEXT COUPLE OF DAYS. DIURNALLY DRIVEN
WESTERLY PUSHES DOWN THE STRAIT OF JUAN DE FUCA WILL CONTINUE,
WITH A SMALL CRAFT ADVISORY OUT FOR THIS EVENINGS PUSH. THE
COASTAL WATERS MAY SEE A FEW WIND GUSTS UP TO 20 KTS ON THURSDAY
AND FRIDAY AS A LOW PRESSURE SYSTEM TRACKS THROUGH THE WATERS,
BUT CONFIDENCE IS LOW AT THIS TIME.
COASTAL SEAS REMAIN AT 4 TO 6 FEET THROUGH MIDWEEK, WITH SEAS
SLIGHTLY INCREASING TO 7 TO 8 FEET WITH PERIODS OF 6 TO 8
SECONDS.
MAZURKIEWICZ
FIRE WEATHER
WARMING TEMPERATURES ARE ON TRACK THROUGH THE MIDDLE
OF THE WEEK, WITH MINIMUM RELATIVE HUMIDITY VALUES DIPPING INTO THE
UPPER 20 TO LOW 30 PERCENT RANGE THROUGHOUT WESTERN WASHINGTON. A
BIT OF A CHANGE IS POSSIBLE BY MIDWEEK AS THUNDERSTORMS GET
REINTRODUCED INTO THE FORECAST FOR THURSDAY. WHILE THIS FORECAST IS
STILL HIGHLY VARIABLE, THE POTENTIAL FOR NEW IGNITIONS ON DRY FUELS
DUE TO LIGHTNING STRIKES IS OF NOTABLE CONCERN. LESS IS KNOWN ABOUT
EXACT RAIN AMOUNTS AND WHETHER THESE STORMS WILL CONTAIN WETTING
RAINS, BUT THESE DETAILS WILL BECOME MORE AVAILABLE OVER THE NEXT
FEW FORECAST CYCLES. IT'S IMPORTANT TO NOTE THAT EVEN IF
THUNDERSTORMS DO NOT OCCUR, ELEVATED FIRE WEATHER CONDITIONS ARE
LIKELY TO PERSIST DUE TO THE WARMER AND DRIER WEATHER THAT IS
FORECAST TO CONTINUE WELL INTO THE WEEKEND.
21
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PDT TUESDAY FOR CENTRAL U.S.
WATERS STRAIT OF JUAN DE FUCA-EAST ENTRANCE U.S. WATERS
STRAIT OF JUAN DE FUCA.
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