Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 101635
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
933 AM PDT THU JUL 10 2014

.SYNOPSIS...STABLE WEST FLOW ALOFT WILL REMAIN OVER SOUTHWEST
WASHINGTON AND NORTHWEST OREGON TODAY. MOIST AND UNSTABLE SOUTH FLOW
ALOFT SPREADS INTO THE AREA BEGINNING LATE TONIGHT AND CONTINUING
THROUGH FRIDAY NIGHT. THIS BRINGS THE THREAT OF THUNDERSTORMS TO THE
CASCADES AND POSSIBLY AS FAR WEST AS THE COAST RANGE BY FRIDAY
EVENING. AN UPPER LOW OFF THE NORTH CALIFORNIA COAST SATURDAY IS
EXPECTED TO MOVE NORTH TO NORTHEAST AND INLAND INTO EXTREME SW OREGON
BY LATE SUNDAY FOR ANOTHER THREAT OF THUNDERSTORMS. WELL-ABOVE NORMAL
DAYTIME TEMPERATURES CAN BE EXPECTED FRIDAY THROUGH AT LEAST EARLY
NEXT WEEK.

&&

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...MARINE STRATUS COVERAGE
BASICALLY THE SAME AS 24 HOURS AGO. INLAND INTRUSION EAST OF
INTERSTATE 5 INTO NW CLACKAMAS COUNTY TO NEAR KUAO. LARGE-SCALE WATER
VAPOR IMAGERY SHOWS DRY WLY FLOW OVER THE FORECAST AREA AS A DEEP
UPPER TROUGH TRACKS EAST ACROSS CANADA. BAGGY TROUGH OFF THE
CALIFORNIA COAST WITH TWO CIRCULATION CENTERS PRESENT. ONE NEAR 35N
128W AND THE SECOND AT 36N 138W. THE FIRST ONE WILL BE THE PLAYER FOR
FRIDAY AFTERNOON AND FRIDAY NIGHT.

TODAY WILL BE A PLEASANT DAY OVERALL. 00Z THU KSLE SOUNDING SHOWED AN
850 MB TEMP OF 16.8C...WHILE THE 12Z THU RUN CAME IN AT 17.2C. GFS
AND ECMWF FORECAST 18C FOR 00Z FRI. THUS...SHOULD REALIZE ABOUT 2-4
DEGREES WARMING INLAND COMPARED TO YESTERDAY. DEW POINTS TODAY WILL
REMAIN IN THE UPPER 40S TO MID 50S.

NO CHANGES TO THE FRI FORECAST THIS MORNING. SOUTH FLOW SPREADS INTO
SRN OREGON AS EARLY AS THIS EVENING...BUT CONTINUES TO SPREAD N
OVERNIGHT AND FRI. LATEST NAM SHOWS A CIRCULATION CENTER W OF KACV BY
15Z FRI THEN SLOWLY DRIFTS IT NWD DURING THE DAY. NAM CONTINUES TO BE
THE MORE ROBUST MODEL REGARDING CONVECTIVE POTENTIAL. GFS NOT SO
MUCH. NAEFS PRECIPITABLE WATER FOR KPDX FRI EVENING IS ABOVE THE 97TH
PERCENTILE FOR THIS TIME OF YEAR. NAMM MODEL SOUNDING FOR KPDX SHOWS
AROUND 0.50 INCHES PWAT EARLY FRI AFTERNOON...BUT JUMPS TO NEARLY AN
INCH BY LATE FRI EVENING. SE-S DIFFLUENT FLOW ALOFT IS A FAVORABLE
THUNDERSTORM PATTERN. CAVEATS INCLUDE WHETHER A TRIGGER MECHANISM
EXISTS...AMOUNT OF MOISTURE AND IF THERE IS ANY ADDITIONAL LIFT
PROVIDED BY AN UPPER LEVEL JET. WILL KEEP THE THUNDERSTORM THREAT AS
IS...IN THE OREGON CASCADE ZONES AND WILLAMETTE VALLEY 00Z-06Z SAT
THEN CONFINE IT TO THE CASCADES 06Z-12Z SAT AS MID-LEVEL LAPSE RATES
DIMINISH WITH THE EXTENSIVE CLOUD SHIELD.

SATURDAY LOOKS TO BE AN IN-BETWEEN DAY AS A TRANSITORY 500 MB RIDGE
MOVES OVER THE AREA IN THE WAKE OF THE FRI NIGHT SHORT-WAVE. MODEL
SOUNDINGS FOR SAT AFTERNOON...PARTICULARLY THE GFS...ARE QUITE
DRY...LIKELY INDICATING DECENT SUBSIDENCE BEHIND THE DEPARTING
SYSTEM. MAIN ISSUE SATURDAY WILL BE THE RISING 850 MB TEMPS...
CLIMBING TO AROUND 22C OVER KPDX. THIS WILL BE THE START OF A
MULTI-DAY HOT SPELL. WILL LIKELY ISSUE AN SPS THIS AFTERNOON COVERING
THIS EVENT. WEISHAAR

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS.
MAIN EVENT WILL BE THE CONTINUED HOT AND HUMID CONDITIONS. BY SUN
THE UPPER RIDGE AXIS SHIFTS TO WRN IDAHO AS AN UPPER LOW OFF THE N
CALIFORNIA COAST FINALLY WORKS ITS WAY NORTH AND EAST. GFS AND ECMWF
HAVE BEEN HANDLING THIS FEATURE DIFFERENTLY THE PAST COUPLE OF DAYS.
BY 00Z MON THE GFS MAINTAINS A CLOSED LOW CIRCULATION OFF THE N CAL
COAST WHILE THE ECMWF HAS AN OPEN TROUGH. THE GFS APPEARS TO GENERATE
MORE DYNAMICS SUN NIGHT AS THE SHORT-WAVE LIFTS NORTHEAST. SHOULD THE
ECMWF VERIFY...THERE WOULD BE MUCH LESS OF A CONVECTIVE THREAT.
SEVERAL FACTORS TO CONSIDER REGARDING THUNDERSTORM
POTENTIAL...INCLUDING TIMING AND POSITIONING OF THE TROUGH. EITHER
WAY...IT WILL REMAIN HOT AND HUMID SUNDAY. 500 MB HEIGHTS REBOUND
EARLY NEXT WEEK FOR CONTINUED UNSEASONALLY HOT CONDITIONS. MUCH
LARGER MODEL DIFFERENCES CROP UP TUE AND BEYOND...WITH THE ECMWF
HOLDING FIRM WITH THE MONSTER RIDGE. WEISHAAR &&

.AVIATION...MARINE INVERSION AROUND 2500-3000 FEET THIS MORNING
WITH MVFR STRATUS ALONG THE COAST AND INTO THE COAST RANGE.
STRATUS MOVED INLAND DOWN THE COLUMBIA INTO SOUTHWEST WASHINGTON
AND GOT AS FAR AS AURORA IN THE N WILLAMETTE VALLEY. STRATUS AND
MVFR CIGS WILL DISSIPATE INLAND FROM THE SOUTH BETWEEN 18-19Z.
MVFR CIGS SHOULD BREAK UP AROUND 19Z ALONG THE CENTRAL OREGON
COAST BUT WILL LIKELY PERSIST ALONG THE NORTH OREGON COAST THROUGHTHE
DAY WITH SOME BREAKS AND BECOMING VFR AFT AROUND 22Z. EXPECT MVFR
CIGS AND POSSIBLE IFR ALONG THE COAST AFTER 04Z IN THE N THIS
EVENING. AREAS OF IFR CIGS AND VISIBILITY LIKELY ALONG THE
CENTRAL OREGON COAST AFT 09Z AS THE INVERSION LOWERS UNDER THE
INFLUENCE OF INCREASING HIGH PRESSURE ALOFT. SCHNEIDER

KPDX AND APPROACHES...MVFR CIGS THROUGH ABOUT 18Z...THEN VFR
THROUGH FRIDAY MORNING. SCHNEIDER

&&

.MARINE...HIGH PRES WILL REMAIN OVER THE NW PAC THROUGH THE
WEEKEND...KEEPING WINDS FROM THE N TO NW. THERE WERE A FEW GUSTS
ABOVE 21 KTS THIS MORNING IN THE CENTRAL OREGON COASTAL WATERS BUT
MODELS INDICATE THEY SHOULD WINDS WILL REMAIN BELOW SMALL CRAFT
CRITERIA TODAY. HOWEVER...WILL HAVE TO WATCH FOR SOME GUSTS THIS
AFTERNOON AND THE THERMAL GRADIENT INCREASES. WINDS WILL BE
LIGHTER OVER THE NEXT COUPLE OF DAYS AS THE UPPER RIDGE MOVES
INLAND AND AN UPPER LEVEL DISTURBANCE APPROACHES FROM THE
SOUTHWEST.

SEAS ARE RUNNING AROUND 9 TO 10 FEET ACROSS THE WATERS WITH ABOUT
A 9 SECOND PERIOD. THESE ARE MOSTLY WIND DRIVEN SEAS AS NOTED BY
THE FACT THAT THE PERIOD IS LESS THAN OR EQUAL TO THE WAVE HEIGHT
AND WILL PRODUCE ROUGH CONDITIONS. THE ENP MODEL INDICATES THE
SEAS WILL DIMINISH SOME THIS AFTERNOON AND SHOULD BE JUST BELOW
SMALL CRAFT CRITERIA LATER THIS AFTERNOON. SEAS WILL CONTINUE TO
DECREASE AS WINDS DECREASE OVER THE NEXT COUPLE OF DAYS.

THE COLUMBIA BAR WILL BE JUST BELOW CRITERIA FOR A SMALL CRAFT
ADVISORY WITH THE EBB THIS AFTERNOON BUT BECOME ROUGH DURING THE
STRONG EBB CURRENT TONIGHT. SCHNEIDER

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 2 PM PDT THIS
     AFTERNOON FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 2 AM TO
     7 AM PDT FRIDAY.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...    HTTP://WEATHER.GOV/PORTLAND

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON
FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS
COMMONLY REFERRED TO AS THE FORECAST AREA.


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