000
FXUS66 KPQR 161547
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
847 AM PDT SUN JUN 16 2013

.SYNOPSIS...AN UPPER LEVEL LOW WILL REMAIN OFF THE COAST THROUGH
MONDAY...WITH A FEW SHOWERS AT TIMES OR POSSIBLY EVEN A THUNDERSTORM
MAINLY OVER THE HIGHER CASCADES. THE LOW WILL MOVE CLOSER TO THE
COAST ON MONDAY...THEN MAKE A SIGNIFICANT MOVE INTO SOUTHWEST
WASHINGTON AND NORTHWEST OREGON MONDAY NIGHT AND TUESDAY FOR AN
INCREASE IN SHOWERS. THE MAIN LOW CENTER WILL MOVE ONSHORE LATE
TUESDAY AND TUESDAY NIGHT KEEPING A COOL SHOWERY AIR MASS OVER THE
REGION. THE MAIN ENERGY WITH THE LOW WILL MOVE EAST DURING THE
LATTER PART OF THE WEEK...BUT WEAKER...BROADER LOW PRESSURE ALOFT
WILL MAINTAIN ONSHORE FLOW AND NIGHT AND MORNING CLOUDS AROUND...
WITH A DECREASING CHANCE OF SHOWERS.
&&

.SHORT TERM...MARINE AIR MASS BROUGHT CLOUDS INTO THE INLAND VALLEYS
OVERNIGHT...MOST WIDESPREAD ON THE E SIDE OF THE VALLEY AND INTO THE
CASCADE FOOTHILLS. THIS WILL COOL TEMPS A FEW DEGREES TODAY. WATER
VAPOR IMAGERY SHOWED A SHORTWAVE APPROACHING THE S OREGON COAST THIS
MORNING...LIFTING NE. S TO SW FLOW ALOFT WILL PROVIDE MARGINAL MID
LEVEL INSTABILITY AHEAD OF THE SHORT WAVE...SO WILL BUMP UP POPS
ALONG THE CASCADE CREST TO CHANCE CATEGORY FOR THIS AFTERNOON AND
EVENING.

REMAINDER OF SHORT TERM DISCUSSION FOLLOWS...
THE UPPER LEVEL LOW BEGINS TO SWIFTLY MOVE TOWARDS THE REGION LATE
TONIGHT INTO EARLY MONDAY MORNING...INCREASING ONSHORE FLOW AND
ALLOWING MORE LOW STRATUS TO PUSH FURTHER INLAND THROUGH THE COASTAL
GAPS MONDAY MORNING. SHOWERS SPREAD INLAND MONDAY AS A STRONGER
SHORTWAVE WRAPS AROUND THE PARENT LOW.

THE BEST THREAT FOR ANY CONVECTION FOR THE REGION DOES NOT ARRIVE
UNTIL TUESDAY. MODELS ARE IN GOOD AGREEMENT BRINGING THE CENTER OF
THE LOW INTO CENTRAL OREGON BY TUESDAY...BRINGING THE MAIN COLD POOL
ONSHORE. THIS SHOULD INITIATE A DECENT THREAT FOR THUNDERSTORMS
ACROSS THE CASCADES. UPPER LEVEL FLOW TURNS MORE S-SE LATE TUESDAY...
ALLOWING ANY THUNDERSTORMS OVER THE CASCADES TO DRIFT ACROSS THE
VALLEY. LIFTED INDICES NEAR -1/-2 ARE POSSIBLE AGAIN FOR WEDNESDAY
AFTERNOON AND EVENING AS THE CENTER OF THE LOW STATIONS ITSELF RIGHT
OVER THE FORECAST AREA. /27

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS.
THE UPPER LOW SLOWLY PUSHES ACROSS THE FORECAST AREA WEDNESDAY
NIGHT...GRADUALLY SHIFTING EAST OF THE REGION BY THURSDAY. POPS WILL
ALSO GRADUALLY DISSIPATE INTO THURSDAY...WITH SOME WRAP AROUND
ENERGY KEEPING A SLIGHT CHANCE FOR SHOWERS ACROSS THE REGION INTO
THURSDAY NIGHT. THE POTENTIAL FOR DRIER WEATHER IMPROVES LATE IN THE
WEEK AS THE LOW MOVES E AND WEAK RIDGING FOLLOWS. EXPECT COOLER THAN
NORMAL TEMPS TO ACCOMPANY THE UPPER LOW...SIMILAR TO THIS PAST
WEEK...THEN TEMPS WARMING AGAIN AT THE END OF THE WEEK.
&&

.AVIATION...PLENTY OF MVFR MARINE STRATUS ALONG THE COAST...AND
INLAND ALONG THE COLUMBIA RIVER INTO THE WILLAMETTE VALLEY. TOPS
2500 TO 3000 FEET...SO WILL TAKE SEVERAL HOURS TO BURN
OUT...ALTHOUGH COASTAL STRATUS LIKELY TO REMAIN MOST OF THE DAY DUE
TO ONSHORE FLOW. INLAND WILL IMPROVE WITH VARIABLE MID/HIGH CLOUDS
AFTER 18Z. OTHER CONCERN WILL BE SOME CUMULUS BUILDUPS AGAIN TODAY
OVER THE MTNS...WITH ISOLATED TO SCATTERED THUNDERSTORMS OVER THE
CASCADES AGAIN BETWEEN 20Z AND 04Z TODAY. MOST AREAS REMAIN VFR THIS
EVENING. MARINE STRATUS WILL RETURN TONIGHT...MOSTLY IN SAME AREAS
AS SUN AM.

KPDX AND APPROACHES...MVFR STRATUS OVER OPS AREA THIS AM... BUT
SHOULD BREAK UP BETWEEN 18Z AND 19Z...THEN VFR CONDITIONS. BETWEEN
21Z AND 04Z...WATCH FOR CUMULUS BUILDUPS AND PERHAPS A THUNDERSTORM
OVER THE CASCADES IN THE EASTERN APPROACHES.              ROCKEY.
&&

.MARINE...NOT MUCH CHANGE. LOW PRES NOW PUSHING INTO THE REGION
WILL MAINTAIN RATHER LIGHT PRES GRADIENTS. WINDS REMAIN 15 KT OR
LESS. DO HAVE MIXED SWELL SET...WITH PRIMARY SWELL FROM W AT 2 TO
3 FT...BUT ALSO HAVE S SWELL ABOUT THE SAME. OVERALL SEAS RUNNING
AT 3 TO 4 FT FOR NEXT SEVERAL DAYS.

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

&&

.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.