002
FXUS66 KSEW 130917
AFDSEW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
217 AM PDT MON JUL 13 2026
SYNOPSIS
HIGH PRESSURE ALOFT WILL REBUILD ACROSS THE REGION INTO TUESDAY
FOR WARM AND DRIER CONDITIONS. AN AREA OF LOW PRESSURE MAY BRING
A THREAT OF SHOWERS AND THUNDERSTORMS AROUND MIDWEEK BEFORE HIGH
PRESSURE REGAINS CONTROL TOWARD THE WEEKEND FOR A RETURN OF DRY
CONDITIONS AND WELL ABOVE NORMAL TEMPERATURES.
SHORT TERM /TODAY THROUGH WEDNESDAY/
MOSTLY CLEAR CONDITIONS PREVAIL ACROSS WESTERN WASHINGTON EARLY
THIS MORNING. HIGH PRESSURE ALOFT WILL CONTINUE TO BUILD OVER
THE REGION TODAY AS AN AREA OF LOW PRESSURE DIGS SOUTHWARD
OFFSHORE. THE WARMING TREND CONTINUES INTO TUESDAY AS THE RIDGE
CONTINUES TO STRENGTHEN OVER THE AREA WITH THE OFFSHORE TROUGH
BECOMING CUT-OFF. HIGH TEMPERATURES WILL GET INTO THE 80S FOR
INTERIOR AREAS...ESPECIALLY SEATTLE SOUTHWARD...WITH PORTIONS OF
THE SEATTLE-TACOMA AREA GETTING INTO LIKELY MODERATE HEATRISK.
WARM TEMPERATURES FOR INTERIOR AREAS CONTINUE INTO WEDNESDAY
WITH THE RIDGE IN PLACE FOR CONTINUED LIKELY MODERATE HEATRISK
FOR A LARGE SWATH OF THE SEATTLE-TACOMA CORRIDOR.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
UNCERTAINTY IN THE FORECAST BECOMES A SIGNIFICANT FACTOR BY
THURSDAY AS MODELS CONTINUE TO STRUGGLE WITH THE PATH OF THE
CUT-OFF LOW OFFSHORE. A SIGNIFICANT PORTION OF THE ENSEMBLES,
ESPECIALLY THE SUITE OF ECMWF SOLUTIONS, SUGGEST A CONTINUED
THREAT OF SHOWERS AND/OR THUNDERSTORMS ON THURSDAY COUPLED WITH
A BRIEF COOL DOWN. NEGATIVELY TILTED LOWS SUCH AS THIS OFTEN
HAVE A WAY OF INITIATING ELEVATED INSTABILITY WITH NO DEFERENCE
TO THE TIME OF DAY. THIS WILL CONTINUE TO POSE A FIRE WEATHER
CONCERN AND NEED TO BE MONITORED CLOSELY.
ONCE THIS SYSTEM EXITS THE AREA, MODELS REMAIN PRETTY LOCKED IN
WITH STRONG UPPER RIDGING FOR AN EXTENDED PERIOD OF WELL ABOVE
NORMAL TEMPERATURES AND DRY CONDITIONS FOR THE WEEKEND AND
BEYOND.
27
AVIATION
SOUTHWESTERLY FLOW ALOFT WILL PERSIST INTO TUESDAY. SURFACE WINDS
GENERALLY LIGHT AND VARIABLE ALTHOUGH SOME TERMINALS REPORTING
NORTHERLY WINDS 4-8 KTS. BY THIS AFTERNOON, MOST TERMINALS SHOULD BE
REPORTING SIMILAR DIRECTION AND SPEED...WITH SOME VARIANCES TO THE
NORTHEAST OR NORTHWEST.
SOME HIGH CLOUDS IN PLACE OVER W WA THIS EARLY MORNING WITH VAST
SWATHS OF CLEAR SKIES. MARINE STRATUS THAT HAD BEEN EXPECTED TO
DEVELOP ALONG THE COAST AND THE STRAIT HAS YET TO DEVELOP, WHICH
SHOULD THIS TREND CONTINUE WOULD NECESSITATE ALTERATIONS TO HQM, CLM
AND PWT FOR THE 12Z PACKAGE. OTHERWISE, VFR CONDITIONS ARE EXPECTED
FOR REMAINING TERMINALS THROUGHOUT THE FORECAST PERIOD, WITH THE
AFOREMENTIONED TERMINALS EXPECTED TO BE VFR BY LATE MORNING.
KSEA...VFR THROUGHOUT THE PERIOD. NORTHERLY WINDS RUNNING A LITTLE
HOTTER THAN ADVERTISED ABOVE, 5-10 KTS, AND LIKELY TO REMAIN THAT
WAY INTO THE AFTERNOON BEFORE A SLIGHT SHIFT TO THE NW BY 22Z.
RETURNING NORTHERLY WITH SPEEDS EASING SLIGHTLY TO 4-8 KTS THIS
EVENING AND OVERNIGHT.
18
MARINE
SURFACE HIGH PRESSURE OVER AREA WATERS THROUGHOUT THE NEXT FEW DAYS.
DIURNAL WESTERLY WINDS THROUGH THE STRAIT OF JUAN DE FUCA WILL BE
THE MAIN THEME. SPEEDS FOR THE MOST PART LOOK TO REMAIN BELOW SCA
CRITERIA, WITH TONIGHT BEING THE EXCEPTION WHERE SPEEDS LOOK TO RUN
15-25 KTS. AS SUCH, A SMALL CRAFT ADVISORY HAS BEEN ISSUED STARTING
LATE THIS AFTERNOON AND RUNNING INTO TONIGHT. COASTAL WATERS MAY
ALSO SEE WIND GUSTS APPROACH 20 KT TOWARDS THE END OF THE WEEK ON
THURSDAY AND FRIDAY WITH ANOTHER LOW SYSTEM TRACKING THROUGH THE
WATERS.
SEAS FOR THE MAJORITY OF THE FORECAST WILL REMAIN AT 4-6 FT, WITH
THE SYSTEM THURSDAY/FRIDAY INCREASING SEAS TO 7-8 FT WITH PERIODS
AROUND 6-8 SECONDS.
41/18
FIRE WEATHER
WARMING TEMPERATURES THIS WEEK WILL INCREASE THE FIRE WEATHER
RISKS GOING INTO THE WEEKEND. A POTENTIAL CUT-OFF LOW PRESSURE
SYSTEM ARRIVING AROUND MIDWEEK REMAINS A CONCERN FOR CONVECTION
AND ASSOCIATED RISKS OF LIGHTNING STRIKES WITH FUELS NOW
RUNNING QUITE DRY.
SEW WATCHES/WARNINGS/ADVISORIES
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 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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