617
FXUS66 KSEW 141038
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT TUE JUL 14 2026
SYNOPSIS
HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION INTO WEDNESDAY FOR
CONTINUED 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 /TODAY THROUGH THURSDAY/
LATEST SATELLITE IMAGERY SHOWS SOME HIGH CLOUDS OVER THE NW CORNER
OF THE CWA THIS EARLY MORNING WITH SWERLY FLOW ALOFT PREVENTING
THOSE CLOUDS MAKING ANY SIGNIFICANT EASTWARD PROGRESS. ANOTHER BAND
OF HIGH CLOUDS PRESENT OVER THE SOUTHERN AND CENTRAL CASCADES, WITH
THE REMAINDER OF THE AREA UNDER MOSTLY CLEAR SKIES.
AN UPPER LEVEL RIDGE CENTERED OVER THE ROCKIES WILL REMAIN THE
DOMINANT FACTOR IN THE WEATHER OVER W WA TODAY AND AGAIN WEDNESDAY,
KEEPING WARM AND DRY CONDITIONS IN PLACE. HIGH TEMPS IN THE LOWER TO
MID 80S WILL PRESENT GENERALLY PERSISTENT MINOR HEATRISK FOR MUCH OF
THE AREA. THE EXCEPTION TO THIS WILL BE ALONG THE I-5 CORRIDOR
BETWEEN SEATTLE AND TACOMA, WHERE PROBABILITIES FOR MODERATE
HEATRISK WILL VARY BETWEEN 50-80 PCT BOTH DAYS, WHICH COULD IMPACT
THOSE MORE SENSITIVE TO HEAT-RELATED ISSUES.
AN UPPER LEVEL LOW SETTING UP OVER THE COASTAL WATERS WEDNESDAY WILL
BEGIN TO MOVE INLAND VERY LATE WEDNESDAY NIGHT AND THURSDAY MORNING.
AFTER A SHAKY START, MODELS SEEM TO BE GELLING ON A SOLUTION
BRINGING FAIRLY WIDESPREAD RAINFALL TO THE AREA. THE PROSPECT FOR
CONVECTION CONTINUES TO BE MONITORED, WITH PROBABILITY OF THUNDER
DATA GENERALLY IN THE 15-25 PCT AT THIS TIME. LATEST STABILITY
ANALYSIS SUGGESTS FOCUS FOR THUNDER BEING LINKED MAINLY WITH THE
HIGHER TERRAIN, BUT A LITTLE SPILLOVER INTO VALLEYS CANNOT BE RULED
OUT. THIS ASPECT HAS BEEN THE HARDEST ONE FOR MODELS TO AGREE UPON
UP TO THIS POINT, BUT CONFIDENCE HAS UPPED JUST ENOUGH TO ALLOW FOR
SLIGHT CHANCE/ISOLATED TYPE WORDING TO MAKE ITS WAY INTO THE
FORECAST FOR THURSDAY AFTERNOON AND EVENING. THUNDER OR NO, THIS
SYSTEM WILL TAKE THE EDGE OFF OF DAYTIME HIGHS THURSDAY, WITH MOST
LOWLAND LOCATIONS RANGING FROM THE MID 70S TO AROUND 80.
18
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
DETERMINISTIC MODELS SHOWING AGREEMENT WITH THE UPPER LOW TRACKING
NORTH-NORTHEASTWARD THURSDAY NIGHT AND TAKING ITS MOISTURE WITH IT,
TAPERING POPS OFF FROM SOUTH TO NORTH THROUGHOUT THE NIGHT. FRIDAY
BRINGS A RETURN TO DRY CONDITIONS BUT LINGERING CLOUDS AND MOISTURE
WILL KEEP TEMPS STATIC IN THE MID 70S TO AROUND 80 FOR THE AREA.
BUILDING UPPER LEVEL HIGH PRESSURE OVER THE PACIFIC WILL BRING A
RETURN TO DRY CONDITIONS AND WARMING TEMPERATURES TO W WA STARTING
ON SATURDAY AS DAYTIME HIGHS CLIMB FROM THE UPPER 70S TO LOWER 80S
TO LOWER TO MID 80 ON SUNDAY AND THE MID 80S TO AROUND 90 ON MONDAY.
FOR THE LATER TWO-THIRDS OF THIS TIME FRAME, MORE WIDESPREAD
MODERATE HEATRISK SEEMS INCREASINGLY PROBABLE...WITH PERHAPS EVEN
SOME AREAS SEEING PROBABILITIES FOR MAJOR HEATRISK ON MONDAY. THAT
BEING OUT IN THE DAY 7 RANGE HOWEVER, THERE IS CERTAINLY A DEGREE OF
UNCERTAINTY THAT COMES ALONG WITH THAT DATA AND WILL LIKELY SEE
UPDATES.
18
AVIATION
SOUTHWESTERLY FLOW ALOFT BETWEEN OFFSHORE LOW PRESSURE AND INLAND
HIGH PRESSURE CONTINUES. WIDESPREAD VFR CONDITIONS EXPECTED ACROSS
THE AIRSPACE, ASIDE FROM LOW MARINE STRATUS AT COASTAL TERMINALS
YIELDING RESTRICTED CIGS IN THE OVERNIGHT AND EARLY MORNING HOURS.
CIGS WILL IMPROVE AS CLOUDS MIX OUT AND SKIES CLEAR THROUGH THE
MORNING, WITH 50% CHANCES TO RETURN TO VFR BY 17Z TUE AT KHQM.
DIURNAL WEST TO NORTHWEST WINDS RISE TO 8-12 KT ALONG THE COAST AND
5-10 NEAR GAPS IN COASTAL TERRAIN INCLUDING NEAR KOLM. VARIABLE
WINDS ALONG THE CENTRAL PUGET SOUND WILL RISE TO 4-8 KT GENERALLY
OUT OF THE NORTH TO NORTHWEST BEFORE EASING AFTER 06Z WED.
KSEA...VFR CONDITIONS BENEATH LARGELY CLEAR SKIES EXPECTED THROUGH
THE PERIOD. DIURNAL WINDS WILL RISE TO 4-8 KT OUT OF THE NORTHWEST,
EASING BELOW 3-4 KT IN THE EVENING, AFTER 06Z WED.
PICARD
MARINE
NORTHWESTERLY FLOW CONTINUES OVER THE COASTAL WATERS AS
WEAK SURFACE LOW PRESSURE LINGERS WELL OFFSHORE WHILE SEAS CONTINUE
AT 3-6 FT WITH A DOMINANT W/NW SWELL AT 7-8 SECONDS. INTERMITTENT
GUSTS TO 20 KT ARE MOST LIKELY THURSDAY AFTERNOON BEYOND 40 NM.
DIURNAL WESTERLY PUSHES DOWN THE STRAIT OF JUAN DE FUCA WILL ALSO
CONTINUE, THOUGH WINDS SHOULD REMAIN BELOW CONDITIONS HAZARDOUS TO
SMALL CRAFT. THE WEAK SURFACE LOW WILL MEANDER NEAR THE COAST LATE
IN THE WEEK, SHIFTING SURFACE WINDS OUT OF THE SOUTH TO SOUTHWEST,
BEFORE TURNING AGAIN OUT OF THE NORTHWEST WITH GUSTS REACHING 15-20
KT LATE FRIDAY. SEAS MAY BUILD SLIGHTLY TO 5-8 FT AS WINDS PEAK NEAR
THESE SHIFTS IN DIRECTION, HOWEVER UNCERTAINTY IN THE POSITION OF
THE WEAK LOW YIELDS LOWER FORECAST CONFIDENCE. A MORE TYPICAL SUMMER
PATTERN WITH DIURNAL NORTH TO NORTHWEST WINDS REACHING 10-15 KT
BEYOND 30 NM RETURNS THIS WEEKEND INTO EARLY NEXT WEEK.
PICARD
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 SHOWERS AND POSSIBLY
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.
21/18
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...NONE.
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