Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 221115
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
415 AM PDT TUE JUL 22 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL BRING AN INCREASING THREAT
OF SHOWERS TO THE AREA TUESDAY AND ESPECIALLY WEDNESDAY. A FEW
THUNDERSTORMS WILL BE POSSIBLE OVER THE CASCADES MAINLY LATE THIS
AFTERNOON AND FOR THIS EVENING. WEDNESDAY WILL LIKELY BE THE COOLEST
DAY OF THE WEEK...HOWEVER...THUNDER WILL BE POSSIBLE WITH ANY OF THE
HEAVIER SHOWERS AS THE UPPER LOW CROSSES OVERHEAD. DRIER AND MORE
SUMMER-LIKE TEMPERATURES ARE EXPECTED TO ARRIVE LATE IN THE WORK WEEK
AND CONTINUE INTO THE WEEKEND.

&&

.SHORT TERM...TODAY THROUGH THURSDAY...AN UPPER TROUGH CONTINUES TO
SLOWLY EXPAND SOUTH WITH A PARENT CLOSED LOW REMAINING CENTERED JUST
OFF HAIDA GWAII BRITISH COLUMBIA. THE FLOW PATTERN IS BECOMING MORE
COMPLEX OFF TO OUR SOUTHWEST AS SHORTWAVE ENERGY HAS DETACHED FROM
THE SOUTH END OF THE CLOSED LOW BUT IS SHOWING SIGNS OF ITSELF
DEVELOPING INTO A CLOSED LOW. THIS A NOTABLE DEPARTURE FROM WHAT
MODELS INDICATE AND HAS POTENTIAL TO DISRUPT THE FORECAST FOR THE
NEXT DAY OR SO. IF THIS SOUTHERLY WAVE CONTINUES TO DIG SOUTH AND
CLOSE OFF...THEN IT BECOMES LESS LIKELY FOR THE PARENT UPPER LOW TO
DIGS SOUTH. ASSUMING THAT HAPPENS...THEN OUR AREA DOES NOT SEE QUITE
THE SAME CONVECTIVE THREATS AS HAVE BEEN INDICATED OVER THE LAST
SEVERAL DAYS. DECIDED TO CONTINUE THE BULK OF THE FORECAST AS IS
WITH THE EXPANDING LARGER SCALE TROUGH ALSO SENDING A DRY CLOSED LOW
UP TOWARD THE NORTHERN CALIFORNIA COAST. IN ALL...MODELS ARE NOT
PICKING UP ON THE COMPLEX EVOLUTION AND THIS AS SIGNIFICANTLY
DECREASED CONFIDENCE...EVEN IN THE MOST IMMEDIATE SHORT-TERM. IT
STILL APPEARS AFTERNOON CONVECTION IS THE ON THE DOCKET FOR THE
CASCADES MOVING FROM SOUTH TO NORTH THROUGH THE LATE AFTERNOON INTO
THE EVENING. BUT WHAT HAPPENS BETWEEN NOW AND THEN REMAINS SOMEWHAT
IN DOUBT. THE CURRENT BAROCLINIC BAND IS FILLING IN AS WE SPEAK AND
HAS PRODUCED LIGHT ACCUMULATIONS EVEN DOWN TO THE VALLEY FLOOR.
FINALLY HAD TO GIVE UP ON THE DYNAMICALLY CHANGING SCENARIO AND PUT
THE PACKAGE OUT, BUT WITH FULL EXPECTATIONS OF AN UPDATE TO BE
RELEASED OVER THE NEXT FEW HOURS.

FOLLOWING THE ASSUMPTION OF MODELS HAVING A GOOD HANDLE...FAIRLY
STRONG CAPE THROUGH THE HAIL GROWTH ZONE PLUS SOME DECENT SHEAR
COULD MAKE FOR A STRONGER STORM OR TWO LATER TODAY. MIGHT SEE SOME
1/2 INCH HAIL ALONG THE CASCADES BUT WILL STILL NEED TO HAVE THE
RIGHT COMBINATION. THAT EXACT LOCATION CANNOT BE DETERMINED THIS FAR
IN ADVANCE BUT IT SEEMS LIKE THE BEST CHANCE WILL BE FOR THE CENTRAL
CASCADES VERSUS AREAS FURTHER NORTH.

THE UPPER LOW IS STILL PROGGED TO SLOWLY PUSH SOUTHEAST AND CROSS
THE AREA BUT MODELS CONTINUE TO HAVE DIFFERING OPINIONS FOR THE
EXACT TRACK AND RAIN IMPACTS. ODDLY...BOTH THE NAM AND GFS SHOW
MOST OF THE INCOMING PRECIP LATER TONIGHT AND WEDNESDAY AS
STRATIFORM IN NATURE. BY LOOKING AT THE CONVECTIVE PRECIP OUTPUT IS
APPEARS THE CONVECTIVE PARAMETERIZATION SCHEMES ARE FIRING VERY
LITTLE EXCEPT FOR ALONG THE IMMEDIATE CREST AND EAST OF THE
CASCADES. GIVEN THE UNCERTAINTY COVERING THE NEXT 24 HOURS...OPTED
TO NOT MAKE CHANGES THEREAFTER...HOPING ALL BECOMES CLEARER WITH
TIME. WE CURRENTLY HAVE RATHER DECENT POPS AND QPF FORECAST BUT
WOULD NOT BE SURPRISED TO SEE DRAMATIC CHANGES IN THE NATURE AND
PLACEMENT OF HEAVIER RAIN OVER THE NEXT COUPLE SHIFTS. ALL
TOLD...THURSDAY STILL LOOKS TO BRING THE TAIL END OF RAIN WITH THIS
SYSTEM BUT RAPID RIDGING IS NO LONGER A GIVEN PER THE 00Z GFS AND
ECMWF RUNS. THURSDAY STILL APPEARS TO BE DRY BUT WE MAY NOT SEE AS
MUCH OF A WARM UP AS WAS PREVIOUSLY EXPECTED. /JBONK

.LONG TERM...NO CHANGES...PREVIOUS DISCUSSION FOLLOWS. AN UPPER-
LEVEL RIDGE IS FORECAST TO BUILD BACK IN OVER THE PACIFIC NORTHWEST
BRINGING HIGH PRESSURE OVER OUR AREA.  SOUTHWESTERLY WINDS AND
GENERALLY SUNNY SKIES WILL CAUSE TEMPERATURES TO INCREASE BY EARLY
THIS WEEKEND. TEMPERATURES ARE FORECAST TO GET BACK INTO THE MID 80S
BY FRIDAY AND POSSIBLY REACH THE LOW 90S IN SOME AREAS INLAND AS
EARLY AS SATURDAY. -MCCOY

&&

.AVIATION...VFR CONDITIONS WITH HIGH CIGS 7-10K FT. -RA MAKING ITS
WAY NE THROUGH THE VALLEY AND INTO THE PDX AREA AND WILL CONTINUE TO
BE POSSIBLE THROUGH THE FORECAST PERIOD. HOWEVER...CIGS WILL REMAIN
HIGH AND ANY RAIN AT THE TERMINALS WILL BE LIGHT.

KPDX AND APPROACHES...VFR CONDITIONS NEXT 24 HOURS WITH BKN TO OVC
HIGH CLOUDS. OCCASIONAL -RA POSSIBLE.

&&

.MARINE...QUIET CONDITIONS OVER THE WATERS CONTINUE AS THE SURFACE
GRADIENT REMAINS WEAK...KEEPING WINDS AOB 10 KT. SEAS ON THE
DECREASE TODAY TO ABOUT 3 FT BEFORE COMING BACK UP SLIGHTLY
WEDNESDAY TO 4-5 FT WITH CONTINUED SMALL W-NW SWELL.

A WEAK LOW PRESSURE SYSTEM WILL PASS THROUGH THE WATERS TUE INTO
WED...BUT WITH LITTLE IMPACT AS WINDS SHOULD REMAIN AROUND 15 KT OR
LESS. LATER THIS WEEK...HIGH PRESSURE REDEVELOPS OVER THE NE PAC AS
THERMAL LOW PRESSURE BUILDS OVER N CALIFORNIA...BRINGING A RETURN TO
GUSTY N WINDS AND STEEP WIND DRIVEN SEAS FRI THROUGH THE WEEKEND.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WA...NONE.
PZ...NONE.

&&

$$


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.
COMMONLY REFERRED TO AS THE FORECAST AREA.


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