000
FXUS66 KPQR 171556
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
855 AM PDT MON JUN 17 2013

.SYNOPSIS...AN UPPER LEVEL LOW WILL GRADUALLY MOVE TOWARDS THE
PACIFIC NORTHWEST COAST TODAY...INCREASING CLOUD COVER AND SHOWERS
THROUGH TONIGHT. THE LOW WILL MAKE ITS MAIN PUSH ONSHORE TUESDAY AND
TUESDAY NIGHT WITH A GOOD INCREASE IN SHOWERS...THEN LINGER OVER
WESTERN OREGON WEDNESDAY FOR CONTINUED UNSETTLED WEATHER. WE WILL
LIKELY SEE SOME INSTABILITY AT TIMES WITH THIS LOW FOR AN OCCASIONAL
THUNDERSTORM. THE MAIN ENERGY WITH THE LOW WILL MOVE EAST DURING THE
LATTER PART OF THE WEEK...BUT WEAKER LOW PRESSURE ALOFT WILL MAINTAIN
ONSHORE FLOW TO KEEP NIGHT AND MORNING CLOUDS AROUND...BUT WITH A
DECREASING CHANCE OF SHOWERS.

&&

.SHORT TERM...SOME MID-HIGH LEVEL INSTABILITY IS APPARENT THIS
MORNING...AS THERE ARE PLENTY OF ALTOCUMULUS AND CIRROCUMULUS CLOUDS
OVER THE FORECAST AREA EAST OF INTERSTATE 5. AT THIS EARLY HOUR THERE
ARE ALREADY SOME SMALL SFC-BASED CUMULUS DEVELOPING OVER THE LANE
COUNTY CASCADES. THERE IS SOME WEAK DIFFLUENCE ALOFT...THOUGH THE
BEST DIFFLUENCE REMAINS OVER WASHINGTON.

ALL THIS IS ASSOCIATED WITH A PERSISTENT UPPER LEVEL LOW OFF THE PAC
NW COAST. A WEAK SHORTWAVE IS ROUNDING THE BASE OF THIS LOW AND WILL
SKIRT THE COAST THIS AFTERNOON...POSSIBLY PROVIDING A LITTLE EXTRA
LIFT FOR CONVECTION TO DEVELOP. THUS IT APPEARS THERE IS A GOOD
CHANCE WE WILL SEE ISOLATED THUNDER THIS AFTERNOON AND EVENING. THE
BEST CHANCES WILL BE IN THE NORTH OREGON COAST RANGE...THE WILLAPA
HILLS...AND OUR CASCADES ZONES...WHERE THERE IS THE BEST CHANCE FOR
SFC-BASED INSTABILITY TO COUPLE WITH THE INSTABILITY ALOFT. FLOW
ALOFT IS S-SW...SO THE BEST CHANCE FOR THE VALLEYS WILL BE FROM TSTMS
WHICH DEVELOP OVER THE EAST SLOPES OF THE COAST RANGE...POSSIBLY
DRIFTING OVER THE VALLEY AFTER THEY DEVELOP. AT THIS POINT...KEPT THE
CHANCES FOR THE VALLEY NORTH OF SALEM...WHERE THERE IS THE BETTER
DIFFLUENCE ALOFT. REMAINDER OF DISCUSSION FOR TUESDAY AND BEYOND
REMAINS VALID...NO CHANGES WERE MADE.  WEAGLE

TUESDAY WILL SEE ANOTHER DECENT THREAT FOR CONVECTION AS UPPER LEVEL
FLOW TURNS A LITTLE MORE SOUTH-SOUTHEASTERLY...BRINGING THE THREAT
FOR THUNDERSTORMS OVER THE VALLEY. AS THE LOW MOVES ONSHORE LATE
TUESDAY NIGHT AND WEDNESDAY...EXPECT INCREASING SHOWERS. YET ANOTHER
CHANCE FOR THUNDERSTORMS OVER THE NE PORTION OF THE CWA IS EXPECTED
WEDNESDAY AFTERNOON...BUT NOW ITS NOT LOOKING QUITE AS PROMISING AS
PREVIOUS DAYS. WILL KEEP THE THREAT IN THE FORECAST RIGHT NOW GIVEN
THE VERY UNSETTLED ENVIRONMENT AS THE MAIN COLD POOL MOVES ACROSS THE
PACIFIC NORTHWEST.

THE LOW PUSHES INTO SOUTHEAST WASHINGTON LATE WEDNESDAY NIGHT AND
THURSDAY...BUT EXPECT SHOWERS TO CONTINUE TO WRAP AROUND THE LOW.
EXPECT THE BULK OF THE SHOWERS TO IMPACT THE NORTHERN FORECAST
ZONES...GRADUALLY DECREASING OVER THE SOUTHERN ZONES BY THURSDAY
AFTERNOON.

EXPECT BELOW NORMAL TEMPERATURES THROUGH MUCH OF THE SHORT TERM
PERIOD AS UNSETTLED WEATHER REMAINS ACROSS THE REGION. /27

.LONG TERM...THURSDAY NIGHT THROUGH SUNDAY...THE UPPER LEVEL LOW THAT
BROUGHT COOL AND UNSETTLED WEATHER ACROSS THE REGION DURING THE FIRST
HALF OF THE WEEK WILL REACH THE CANADIAN BORDER LATE THURSDAY INTO
FRIDAY. EXPECT ONLY A SLIGHT CHANCE OF SHOWERS IN NORTHERN ZONES OF
THE CWA AND INTO WASHINGTON STATE THROUGH LATE FRIDAY. MUCH OF THE
REGION LOOKS TO BE DRY SATURDAY AS A WEAK RIDGE BUILDS IN.
UNCERTAINTY INCREASES ON SUNDAY AS THE MODELS ARE ADVERTISING A
LARGE TROUGH SETTING UP OVER THE EASTERN PACIFIC...LIKELY BRINGING
ANOTHER ROUND OF WET WEATHER TO THE REGION LATE SUNDAY. BURGESS/27

&&

.AVIATION...VARIABLE MID AND HIGH CLOUDS CONTINUE STREAMING OVER
THE REGION ON S TO SW FLOW ALOFT. POCKETS OF MARINE STRATUS ALONG
THE COAST...BUT SHOULD DISSIPATE BY 18Z. WITH UPPER LOW OFFSHORE
TODAY AND TONIGHT...WILL SEE VARIABLE AMOUNTS OF MID AND HIGH
CLOUDS ROTATING FROM THE PAC INTO THE REGION. GENERAL TREND WILL
BE LOWERING CIGS AND INCREASING CHANCE OF SHOWERS LATER TODAY AND
TONIGHT. WILL HAVE CONTINUED THREAT OF ISOLATED THUNDERSTORMS OVER
THE CASCADES...AND MAYBE COAST RANGE LATE TODAY INTO THIS EVENING.

KPDX AND APPROACHES...VFR CONDITIONS THROUGH THIS EVENING. WILL
HAVE INCREASING 4500 TO 6000 FT CIGS LATER TODAY AND THIS EVENING
DUE TO INCREASING CONVECTION OVER THE MOUNTAINS. BETWEEN 22Z AND
06Z...ISOLATED THUNDERSTORMS POSSIBLE OVER COAST RANGE...BUT MUCH
BETTER POTENTIAL OVER THE CASCADES.  ROCKEY.

&&

.MARINE...A BROAD AREA OF LOW PRES WILL CONTINUE TO SLOWLY TRACK
TOWARDS THE COAST THROUGH WED. WINDS GENERALLY 15 KT OR LESS...
BUT MAY HAVE SOME GUST UP TO 20 KT AT TIMES. WITH SHOWERS AROUND
TODAY AND TUE...THERE IS DECENT POTENTIAL FOR BRIEF STRONGER
GUSTS...BUT WILL NOT PUT IN FORECAST AT THIS TIME.

SWELL CONTINUES TO BE MIXED...WITH PRIMARY SWELL FROM THE W AND A
SECONDARY SWELL FROM THE S. OVERALL...COMBINED SEAS RUNNING 3 TO 4
FT TODAY...BUT AS W SWELL INCREASES TONIGHT AND TUE...INFLUENCE OF
S SWELL WILL DECREASE.

WEAK HIGH PRES WILL BUILD AGAIN OVER THE NE PAC LATER THIS WEEK
WITH A RETURN OF N TO NW WINDS...BUT STILL MOSTLY 20 KT OR LESS.
ROCKEY.

&&

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

&&

$$

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

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.