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000
FXUS66 KPQR 132205
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
300 PM PDT MON MAY 13 2013

.SYNOPSIS...A LOW PRESSURE MOVING INTO WESTERN WASHINGTON WILL BRING
ISOLATED THUNDERSTORMS TO SOUTHWEST WASHINGTON AND SHOWERS TO THE
REST OF THE AREA TODAY...PARTICULARLY ACROSS THE MOUNTAINS. WEAK HIGH
PRESSURE SHOULD RESULT IN A DRY TUESDAY ACROSS MOST OF THE AREA.
EXPECT SOME LIGHT SHOWERS WEDNESDAY AND THURSDAY AS A WEAK LOW
PRESSURE MOVES INTO THE REGION. ADDITIONAL WEAK LOW PRESSURE SYSTEMS
WILL KEEP TEMPERATURES NEAR NORMAL WITH SOME LIGHT SHOWERS POSSIBLE
OVER THE WEEKEND.

&&

.SHORT TERM...A LOOP OF VISIBLE SATELLITE IMAGERY SHOWS AN UPPER
LEVEL LOW PRESSURE MOVING NORTHEASTWARD INTO THE OLYMPIC PENINSULA. A
LOOSE LINE OF CONVECTION HAS DEVELOPED ALONG THE LEADING EDGE OF A
MID LEVEL VORT MAX SWINGING NORTHEASTWARD UNDERNEATH THE
AFOREMENTIONED UPPER LEVEL LOW PRESSURE. INSTABILITY GENERALLY
REMAINS DEEPEST OVER WASHINGTON SO LIGHTNING HAS BEEN PRIMARILY
CONFINED TO THE VERY NORTHERN PORTION OF OUR CWA. WITH THAT SAID...A
STRIKE DID OCCUR NEAR WOODLAND WASHINGTON AND A SPOTTER REPORTED
HEARING THUNDER IN SE PDX. SOME ADDITIONAL CONVECTION WILL LIKELY
FIRE BEHIND THIS INITIAL LINE AS THE LOWER ATMOSPHERE DESTABILIZES
ONCE AGAIN UNDER MORE SUNSHINE. AS A RESULT...ANOTHER ROUND OR TWO OF
INTENSE SHOWERS AND ISOLATED THUNDERSTORMS WILL BE
POSSIBLE...PARTICULARLY ACROSS OUR FAR NORTHERN ZONES. EXPECT SHOWER
ACTIVITY TO QUICKLY WIND DOWN THIS EVENING AS THE ATMOSPHERE
STABILIZES.

SHORTWAVE RIDGING SHOULD RESULT IN A DRY DAY ACROSS THE CWA ON
TUESDAY WITH NEAR NORMAL TEMPERATURES EXPECTED.

MODELS THEN LOOSELY AGREE A WEAK SHORTWAVE TROUGH WILL CREEP TOWARDS
THE OREGON COAST MIDWEEK. UNDER WEAK ISENTROPIC LIFT...THE GFS BRINGS
THE FIRST RAIN FROM THIS SYSTEM INTO THE AREA BY TUESDAY NIGHT. THE
NAM AND EC GENERALLY HOLD OFF ON PRECIPITATION ACROSS THE AREA UNTIL
WEDNESDAY. I TRENDED THE FORECAST TOWARDS A BLEND OF THE MODELS
TUESDAY NIGHT INTO WEDNESDAY. NONETHELESS...ALL MODELS GENERALLY
AGREE PRECIPITATION ODDS WILL BE HIGHEST ACROSS OUR NORTHWESTERN
ZONES AND LOWEST ACROSS OUR SOUTHEASTERN ZONES.

A REINFORCING SHORTWAVE TROUGH APPEARS AS THOUGH IT WILL TRY TO DIG
SOUTH OF OUR AREA THURSDAY. HOWEVER...A WEAK SURFACE LOW PRESSURE
SKIRTING OUR SOUTHERN WATERS MAY ENHANCE RAIN CHANCES ACROSS OUR
SOUTHERN ZONES THURSDAY. IN ADDITION...ENOUGH INSTABILITY AND ONSHORE
FLOW SHOULD RESULT IN A THREAT FOR SHOWERS AREA WIDE THURSDAY.
HOWEVER...I KEPT POPS GENERALLY IN THE CHANCE RANGE AT THIS POINT AS
CONFIDENCE IN DETAILS REMAINS LOW. /NEUMAN

.LONG TERM...THE LONG TERM PERIOD BEGINS THU EVENING WITH AN UPPER
LEVEL TROUGH EXITING THE PACIFIC NORTHWEST REGION AND GENERALLY
ZONAL FLOW ALOFT PUSHING INTO THE NORTHWEST THROUGH SUNDAY MORNING.
INCOMING SHORTWAVES EMBEDDED IN THE UPPER FLOW WILL BRING A CHANCE
FOR SHOWERS OR LIGHT RAIN FRIDAY...SATURDAY AND POSSIBLY AGAIN ON
SUNDAY.  SHOWERS TAPER OFF AND MODELS SHOW A WEAK RIDGE BUILDING
OVER THE WEST COAST AND FLOW TURNING TO OFFSHORE AT THE SURFACE. IF
THIS HAPPENS...WARMER TEMPERATURES AND CLEAR SKIES RETURN AT LEAST
TEMPORARILY EARLY NEXT WEEK. KWELSON


&&

.AVIATION...POST-FRONTAL SHOWERS WILL PERSIST THIS AFTERNOON AND
EARLY EVENING...WITH THUNDERSTORMS ACCOMPANYING SOME OF THESE
SHOWERS. GUSTY WINDS WILL IMPACT MOST OF THE REGION THIS AFTERNOON
WITH ERRATIC AND POSSIBLY STRONGER GUSTS WITH THE THUNDERSTORMS.
MOSTLY
VFR CONDITIONS INLAND THIS AFTERNOON...WITH TEMPORARY SPOTTY MVFR
CIGS. MVFR CONDITIONS FOR THE COAST...EXCEPT IFR STILL LINGERING
IN PARTS OF THE CENTRAL OREGON COAST. EXPECT ONLY A BRIEF PERIOD
OF VFR FOR THE COAST LATER THIS EVENING BEFORE MARINE STRATUS/FOG
WITH LOW CIGS RETURNS LATE TONIGHT. CLOUDY BUT VFR CIGS WILL
CONTINUE INLAND THROUGH TUESDAY MORNING.

KPDX AND APPROACHES...SHOWERS WITH A MIX OF VFR AND MVFR THIS
AFTERNOON AND EARLY EVENING. CONVECTION POSSIBLE AND GUSTY WINDS
EXPECTED BEFORE 02Z. VFR CIGS SHOULD PERSIST TONIGHT INTO TUE
MORNING.

&&

.MARINE...GUSTY SOUTH WINDS IN THE WATERS WILL CONTINUE THIS
EVENING. THE WINDS SHOULD EASE IN THE SOUTHERN WATERS BEFORE THE
NORTHERN WATERS AND HAVE SPLIT AND ALTERED THE TIMING OF THE SMALL
CRAFT ADVISORIES. A S-SW SWELL IS BUILDING AND SEAS WILL PEAK AROUND
8 FEET TONIGHT. THE WINDS WILL DRAMATICALLY DECREASE TONIGHT AND
LIGHT
W-SW WINDS WILL PERSIST THROUGH TUES MORNING. THERE WILL BE A BRIEF
BURST OF LIGHT NW WINDS TUE AFTERNOON. ANOTHER WEAK FRONT WILL
MOVE ACROSS THE WATERS WED...BUT WINDS SHOULD REMAIN BELOW 25 KT.
A SMALL WEST SWELL WILL DOMINATE THE WATERS MOST OF THE WEEK.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 9 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60
     NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT THIS AFTERNOON FOR

     COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 6 AM TO
     9 AM PDT TUESDAY.

&&

$$

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.