Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 110959
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
258 AM PDT FRI JUL 11 2014

.SYNOPSIS...MOIST AND UNSTABLE SOUTH FLOW ALOFT WILL SPREAD INTO THE
AREA TODAY AND TONIGHT. THIS BRINGS THE THREAT OF THUNDERSTORMS TO
THE CASCADES AND POSSIBLY AS FAR WEST AS THE COAST RANGE BY LATER
THIS EVENING. AN UPPER LOW OFF THE NORTH CALIFORNIA COAST SATURDAY IS
EXPECTED TO MOVE NORTH TO NORTHEAST AND INLAND INTO EXTREME SW OREGON
SUNDAY FOR ANOTHER THREAT OF THUNDERSTORMS...EXTENDING FROM THE COAST
RANGE...THE VALLEY AND TO THE CASCADES. WELL-ABOVE NORMAL DAYTIME
TEMPERATURES CAN BE EXPECTED FRIDAY THROUGH THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...TODAY THROUGH SUNDAY...FOG PRODUCT SATELLITE IMAGERY
SHOWS MARINE STRATUS BANKED ALONG THE COAST AND STARTING TO PUSH
ALONG THE COLUMBIA RIVER AND INTO COASTAL GAPS EARLY THIS MORNING...
BUT THE MARINE PUSH WILL BE LIMITED TODAY DUE TO WEAK ONSHORE
PRESSURE GRADIENTS.  ALSO STARTING TO SEE MID/HIGH CLOUDS LIFTING
NORTH OVER SW OREGON ASSOCIATED WITH A DISTURBANCE CENTERED ALONG THE
FAR NORTHERN BORDERS OF CALIFORNIA AND NEVADA.

NOW ONTO THE MAIN FORECAST CONCERN: THREAT FOR CONVECTION LATER TODAY
AND INTO TONIGHT AS SOUTHERLY FLOW ALOFT INCREASES. THE 06Z NAM IS
SHOWING MUCH OF THE MOISTURE POTENTIAL JUST CLIPPING THE LANE COUNTY
CASCADES AND POSSIBLY A LITTLE FURTHER NORTH BY EARLY THIS
AFTERNOON...BEFORE SPREADING FURTHER NORTH AND INLAND BY THIS
EVENING. THE 06Z GFS IS SHOWING THE MAIN NEGATIVE LIFTED INDEX VALUES
A LITTLE SOUTH OF THE CWA BY THIS AFTERNOON AND EVENING...SO KEPT THE
THREAT FOR THUNDERSTORMS ACROSS THE WILLAMETTE VALLEY AS THE
DISTURBANCE LIFTS NORTH SINCE CANNOT DISCOUNT THE FACT THAT
THUNDERSTORMS MAY DRIFT OFF THE CASCADES AND INTO THE VALLEY. ASIDE
FROM TODAY AND SATURDAY...MAIN CHANGES FOR THE MORNING PACKAGE LIE IN
THE THUNDERSTORM THREAT FOR SUNDAY...

SATURDAY LOOKS TO BE AN IN-BETWEEN DAY AS A TRANSITORY 500 MB RIDGE
MOVES OVER THE AREA IN THE WAKE OF TONIGHTS SHORT-WAVE. MODEL
SOUNDINGS FOR SAT AFTERNOON...PARTICULARLY THE GFS...ARE SOMEWHAT
DRY...POSSIBLY INDICATING DECENT SUBSIDENCE BEHIND THE DEPARTING
SYSTEM...BUT MORE LIKELY THAT THE AIR MASS WILL BE SO WARM AND CAN
HOLD MUCH MORE MOISTURE THAN AN AIR MASS UNDER SEASONAL CONDITIONS.
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. KEPT ANY THUNDERSTORM MENTION SAT TO THE CASCADES WHERE
MID-LEVEL LAPSE RATES CLOSE TO 8C/KM ARE FORECAST BY THE GFS MODEL
SOUNDING.

SUNDAY IS LOOKING TO BE THE MORE INTERESTING DAY. ANOTHER ROUND OF
MOIST SOUTH FLOW ALOFT BEGINS TO SPREAD INTO SWRN OREGON AS EARLY AS
SAT EVENING. BY 12Z SUN THE NAM BRINGS THE AFOREMENTIONED SECOND LOW
CENTER TO 41N 129W. THE 12Z GFS IS A BIT MORE N WITH IT...BUT AT THE
SAME LONGITUDE. NAM ALSO A 70-80 KT JET SEGMENT ROUNDING THE BASE OF
THE TROUGH INTO SWRN OREGON BY 18Z SUN AND GENERATES AN AREA OF QPF
OVER THE SRN HALF OF THE FORECAST AREA. THIS HAS THE POTENTIAL TO BE
A MAJOR THUNDERSTORM EVENT FOR THE CWA. THE SPC CONVECTIVE OUTLOOK
FOR SUNDAY HIGHLIGHTS WESTERN OREGON FOR THUNDERSTORM POTENTIAL. HAVE
ADDED A THREAT FOR GUSTY WINDS AND SMALL HAIL OVER THE CASCADES FOR
SUNDAY AFTERNOON AND EVENING. THERE IS ABOUT 20-40 KTS OF 0-6 KM BULK
SHEAR PARTICULARLY OVER THE LANE COUNTY CASCADES WHICH WOULD HELP
SPUR ON HAIL POTENTIAL. BOUNDARY LAYER WINDS ARE ALSO SHOWING WINDS
AROUND 25-30 KT CLIPPING OUR SE CORNER OF THE FORECAST AREA.
WEISHAAR/27

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. SUNDAY NIGHT
THROUGH THURSDAY...MAIN EMPHASIS WILL BE ON THE UNSEASONABLY HOT
CONDITIONS THROUGH MUCH OF THE PERIOD. MODEL 850 MB TEMPS IN THE 22C-
25C RANGE MON-WED. MEX GUIDANCE SPITS OUT 100 FOR KPDX MON...PUSHING
QUITE CLOSE TO RECORD TERRITORY. IT WILL ALSO BE RATHER HUMID WITH
HIGH DEW POINTS...RESULTING IN UNCOMFORTABLE NIGHTTIME PERIODS. HOT
SPELLS BEYOND 3-4 DAYS ARE RARE. WILL BE ISSUING AN SPS FOR THIS
EVENT. 12Z ECMWF SHOWING SIGNS THAT IT MAY NOT BE AS HOT AS
PREVIOUSLY THOUGHT...BUT THE RUN IS DIFFERENT FROM ITS PREVIOUS
VERSION. THERE MAY BE SLIGHT RELIEF IN THE TUE-WED TIME FRAME...BUT
MAX TEMPS WILL REMAIN SEVERAL DEGREES ABOVE NORMAL. WEISHAAR

&&

.AVIATION...IFR CONDITIONS ALONG THE COAST THIS MORNING WITH SOLID
LOW STRATUS ALONG THE COAST AND INTO THE WEST SLOPES OF THE COAST
RANGE. CONDITIONS AT THE COAST WILL LIKELY BECOME VFR FOR A FEW
HOURS THOUGH THE LOW CLOUDS BANK MAY NOT CLEAR VERY FAR OFF THE
COAST. EXPECT IFR CONDITIONS TO REFORM ALONG THE COAST TONIGHT.
INLAND CONDITIONS WILL STAY MOSTLY VFR. WE WILL PROBABLY SEE LOW
END MVFR CIGS NEAR KKLS IN THE NEXT HOUR OR TWO...BUT IT WILL BE
CLOSE WHETHER IT MAKES KPDX OR NOT. SOUTHERLY FLOW ALOFT WILL
BRING SOME HIGH LEVEL MOISTURE INTO THE AREA FOR A CHANCE OF
THUNDERSTORMS OVER THE CASCADES THIS AFTERNOON...AND NORTHWARD
ACROSS A GREATER AREA TONIGHT.

KPDX AND APPROACHES...VFR TODAY AND TONIGHT. THERE MAY BE SOME
PATCHY STRATUS AROUND 1200 FEET FOR AN HOUR OR TWO AFTER SUNRISE.
THERE IS A SLIGHT CHANCE OF A SHOWER OR THUNDERSTORM LATER
TONIGHT. PT
&&

.MARINE...HIGH PRES WILL REMAIN OVER THE NE PAC THROUGH THE
WEEKEND...KEEPING WINDS FROM THE N TO NW. THE GRADIENTS WILL BE
WEAKER TODAY AND SATURDAY FOR WEAKER WINDS THAN THE LAST COUPLE OF
DAYS. THE MODELS INDICATE THE NORTH TO NORTHWEST WINDS WILL THEN
STRENGTHEN SUNDAY AND POSSIBLY REACH SMALL CRAFT ADVISORY
LEVELS...THEN REMAIN BRISK INTO THE MIDDLE OF NEXT WEEK.

SEAS HAVE BEEN SLOW TO FALL OVERNIGHT...AND ARE STILL RUNNING
AROUND 7 FT EARLY THIS MORNING...1 TO 2 FT ABOVE THE WAVE MODELS.
PERIODS ARE IN THE 9 SECOND RANGE SO SEAS WILL STILL BE A LITTLE
STEEP. SEAS WILL CONTINUE TO DECREASE TODAY AND FRIDAY...BOTTOMING
OUT AROUND 3 OR 4 FT SATURDAY. SEAS WILL LIKELY BUILD AGAIN IN
THE INCREASING NORTHWEST WINDS LATER SUNDAY AND MONDAY.

WILL CONTINUE THE SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR
EARLY THIS MORNING DUE TO THE VERY STRONG EBB AND WITH BACKGROUND
SEAS RUNNING 1 TO 2 FT ABOVE THE MODELS. ANOTHER VERY STRONG EBB
IS EXPECTED AROUND DAYBREAK SATURDAY AND IT WILL BE CLOSE WHETHER
THIS ONE WILL MEET SMALL CRAFT ADVISORY THRESHOLDS AS BACKGROUND
SEAS WILL BE FALLING. PT
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 7 AM PDT
     THIS MORNING.

&&

$$

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.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.