000
FXUS66 KPQR 290943
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
242 AM PDT THU JUL 29 2010

.SYNOPSIS...A WEAK UPPER TROUGH OVER THE EASTERN PACIFIC WILL KEEP A
MARINE LAYER ALONG THE COAST RESULTING IN LOW CLOUDS ALONG THE COAST
WITH MARINE AIR SEEPING A BIT FARTHER INLAND EACH DAY IN ONSHORE
FLOW. WEAK WEATHER DISTURBANCES MAY BRING ISOLATED AFTERNOON AND
EVENING THUNDERSTORMS TO THE CASCADES AT TIMES.

&&

.SHORT TERM...MARINE STRATUS SLOW TO PUSH INLAND ALONG THE COLUMBIA
RIVER SO A LITTLE MORE PESSIMISTIC ABOUT LONGEVITY OF INLAND COVERAGE
THIS MORNING. AFTER CLOUDS BURN OFF...PLENTY OF SUN IN THE  INTERIOR
BY MIDDAY. THE UPPER FLOW WILL AGAIN BECOME MORE SOUTHWESTERLY ON
THURSDAY. THIS COUPLED WITH WEAKER FORCING AND WEAK UPPER RIDGING
ALOFT SHOULD ALLOW THE CHANCES FOR TSTMS TO DECREASE ON THURSDAY.

AN UPPER LEVEL TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC
TODAY AND FRI WILL SLOWLY PUSH ONSHORE SATURDAY. THIS TROUGH WILL
SERVE TO DEEPEN THE STRATUS LAYER FOR THE REMAINDER OF THE WEEK.
EXPECT THE MARINE STRATUS TO PERSIST ALONG THE COAST AND SPREAD A
LITTLE FURTHER INLAND EACH DAY. AS THE STRATUS LAYER THICKENS...THE
POSSIBILITY OF DRIZZLE WILL INCREASE EACH DAY.

DAILY HIGH TEMPERATURES WILL BE A FEW DEGREES COOLER EACH DAY...WITH
INLAND TEMPERATURES IN THE MID 70S BY SATURDAY AS THE UPPER LEVEL
FLOW BECOMES MORE CONSOLIDATED...PUSHING THE STRONGER DYNAMICS AND
COOLER AIR ASSOCIATED WITH THE UPPER LEVEL TROUGH INLAND.


.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...THE LONG TERM
PORTION OF THE FORECAST WILL MAINLY BE CHARACTERIZED BY AN UPPER
LEVEL TROUGHING PATTERN. THE INITIAL TROUGH AXIS APPROACHING AND
EVENTUALLY MOVING ASHORE THIS WEEKEND WILL ALLOW FOR CONTINUED
ONSHORE FLOW FOR SUNDAY. MARINE CLOUDS SHOULD PERSIST THROUGHOUT THE
DAY ALONG THE COAST AND WELL INTO THE AFTERNOON FOR MANY INLAND
LOCATIONS. THIS WILL KEEP TEMPERATURES RELATIVELY COOL. WITH THIS
MARINE INFLUENCE...COASTAL AREAS COULD EXPERIENCE A PERIOD OF
DRIZZLE...MAINLY IN THE MORNING. THE INITIAL TROUGH WILL PUSH OFF TO
THE EAST EARLY NEXT WEEK...BUT A SERIES OF SHORTWAVES WILL ROTATE IN
BEHIND...KEEPING THE GENERAL TROUGHING PATTERN THROUGH MUCH OF THE
WEEK. THE MODELS ARE INDICATING THAT THE ONSHORE MARINE INFLUENCE
MAY WEAKEN BY TUESDAY...AS WE SHIFT FROM A WESTERLY TO MORE OF A
NORTHERLY FLOW REGIME. THIS SHOULD ALLOW TEMPERATURES TO RECOVER TO
NEAR OR ABOVE SEASONAL BY THE MIDDLE OF NEXT WEEK. JFP


&&

.AVIATION...UPPER TROUGH OFFSHORE IS KEEPING THE MARINE LAYER IN
PLACE OVER WESTERN OREGON. MARINE INVERSION IS ABOUT 2K FT DP WITH
MOSTLY IFR CIGS ALONG THE COAST AND INTO THE COAST RANGE THIS
MORNING. SOME STRATUS HAS PUSHED INLAND ALONG THE COLUMBIA RIVER TO
ABOUT KKLS AT 08Z. WITH CONTINUED ONSHORE GRADIENTS EXPECT STRATUS
TO MOVE DOWN THE COLUMBIA AND SHOULD REACH KPDX AROUND 12-13Z WITH
MVFR CIGS. THE SOUTHERN AND CENTRAL WILLAMETTE VALLEY SHOULD BE
MOSTLY VFR SKC TODAY. GRADIENTS WILL REMAIN ABOUT THE SAME TONIGHT
AND EXPECT LOW CLOUDS WILL GIVE IFR AND LIFR CIGS TO COAST TONIGHT
AND FRIDAY MORNING.

KPDX AND APPROACHES...VFR. MVFR CIGS...POSSIBLE IFR CIGS DEVELOPING
AROUND 12Z FOR ABOUT 4 HOURS BEFORE DISSIPATING.

&&

.MARINE...HIGH PRESSURE WILL REMAIN OFFSHORE WITH THERMAL LOW
PRESSURE OVER EASTERN WASHINGTON FOR THE REMAINDER OF THE WEEK. A
WEAK UPPER LEVEL TROUGH WILL LINGER OFFSHORE...KEEPING NW
WINDS/SEAS LIGHT TO MODERATE THROUGH FRIDAY.

&&

.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.

Weather information courtesy of NOAA and AviationWeather.gov

© Willamette Aviation Service, LLC