Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 031622
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
922 AM PDT THU SEP  3 2015

.SYNOPSIS...AN UPPER LOW WILL REMAIN CENTERED IN SOUTHWEST B.C.
TODAY...MAINTAINING COOL ONSHORE FLOW AND A CHANCE OF SHOWERS AND A
SLIGHT CHANCE OF THUNDERSTORMS. THE LOW WILL BEGIN ITS MOVE SOUTH
TONIGHT AND CONTINUE MOVING SOUTH FRIDAY AS ENERGY ON THE WEST SIDE
OF THE LOW DIGS SOUTH. THE LOW WILL BE OVER WESTERN OREGON ON
FRIDAY...AND THIS SHOULD LEAD TO MORE CHANCES OF SHOWERS OR
THUNDERSTORMS IN THE AFTERNOON AND EVENING HOURS. THE LOW WILL MOVE
EAST SATURDAY FOR IMPROVING WEATHER. A WEAK SYSTEM PASSING BY TO OUR
NORTH SUNDAY INTO MONDAY MAY BRING A SLIGHT CHANCE OF SHOWERS NEAR
THE COAST AND LOCALLY IN THE NORTH INTERIOR. DRIER AND WARMER WEATHER
MAY RETURN FOR THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...THE UPPER LEVEL LOW CENTERED OVER SOUTHERN BRITISH
COLUMBIA THIS MORNING IS SPINNING A WEAK SHORTWAVE ONSHORE. THIS IS
TRIGGERING SOME DECENT SHOWER ACTIVITY JUST OFF THE COAST. THERE HAS
BEEN A GOOD AMOUNT OF LIGHTNING OBSERVED ALONG THE NORTH AND CENTRAL
WASHINGTON COAST OVER THE PAST SEVERAL HOURS WHERE THE COLDER AIR
ALOFT IS LOCATED. TEMPS ALOFT ARE NOT QUITE AS COOL OVER OUR FCST
AREA TODAY...WHICH LIMITS INSTABILITY SOMEWHAT. HOWEVER...STILL THINK
WE WILL SEE SOME ISOLATED THUNDERSTORMS ALONG THE COAST AS THE
SHOWERS SPREAD INLAND LATER THIS MORNING...WITH THE POTENTIAL
SPREADING INTO THE INTERIOR DURING THE AFTERNOON AND EARLY EVENING.
THE BEST CHANCES WILL BE FURTHER NORTH OVER SW WASHINGTON AND FAR NW
OREGON. ANY THUNDERSTORMS THAT DO FORM SHOULD BE SHORT LIVED WITH THE
MAIN ASSOCIATED THREAT BEING BRIEF HEAVY DOWNPOURS.

THE LOW MOVES SOUTH ALONG THE COAST TONIGHT AND FRIDAY AS SOME ENERGY
DIGS SOUTH ON THE WEST SIDE OF THE LOW. THE MAIN INSTABILITY AND
SHOWERS TONIGHT AND FRIDAY MORNING WILL BE OVER THE COASTAL WATERS.

THE LOW WILL BE OVER WESTERN OREGON ON FRIDAY AFTERNOON AND
EVENING...WITH NORTHERLY FLOW OVER THE COAST RANGE AND SOUTHERLY FLOW
OVER THE CASCADES AND CENTRAL OREGON. THE MODELS INDICATE THAT WE
SHOULD SEE SOME SHOWERS AND POSSIBLY A FEW THUNDERSTORMS DEVELOP OVER
THE CASCADES FRIDAY AFTERNOON AND EVENING...AND POSSIBLY ALSO OVER
THE COAST RANGE. WE MIGHT SEE A FEW DRIFT OUT INTO THE VALLEYS AS
WELL...BUT THE BEST CHANCE LOOKS TO BE OVER THE HIGHER TERRAIN.

THE LOW MOVES OFF TO THE EAST SATURDAY WITH IMPROVING WEATHER ACROSS
OUR FORECAST AREA. A FEW SHOWERS MIGHT LINGER OVER THE HIGHER
CASCADES EARLY SATURDAY...BUT THE REMAINDER OF THE DAY SHOULD SEE
MORE SUNSHINE AND WARMER TEMPS. PYLE/TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
SATURDAY NIGHT THROUGH WEDNESDAY. CONFIDENCE AGAIN SOMEWHAT BELOW
AVERAGE FOR THE START OF NEXT WEEK WITH MODEL GUIDANCE EXHIBITING
NOTABLE RUN TO RUN VARIABILITY. THE OVERALL PATTERN WILL HAVE THE THE
LONGWAVE TROUGH WELL INTO EASTERN OREGON BY SATURDAY NIGHT. A FEW
WEAK UPPER TROUGHS PASS TO THE NORTH OF THE AREA WHICH MAY PROVIDE
FOR SOME LIGHT SHOWERS AT TIMES SUNDAY OR MONDAY... PRIMARILY FOR THE
N OREGON COAST AND SW WASHINGTON. ANOTHER UPPER TROUGH MAY BRING SOME
MORE WIDESPREAD SHOWERS AND SLIGHT COOLING TO THE AREA ON TUESDAY.
OVERALL...WITH ONLY WEAKER DISTURBANCES PASSING NEAR THE
AREA...HEIGHTS GRADUALLY WILL RISE TO SUPPORT TEMPERATURES CLOSER TO
SEASONAL NORMALS AND GENERALLY EXPECT DRIER AND WARMER AGAIN FOR THE
MIDDLE OF THE WEEK AND TRENDED THE FORECAST FOR WEDNESDAY IN THIS
DIRECTION IN LINE WITH THE 12Z ECMWF SOLUTION. CULLEN

&&

.AVIATION...A SHOWERY UNSTABLE AIR MASS REMAINS OVER THE REGION
THROUGH FRIDAY. LINGERING POCKETS OF LOWER CIGS WILL DISSIPATE
OVER THE NEXT SEVERAL HOURS. OTHERWISE...EXPECT MOSTLY VFR
CONDITIONS THE NEXT 24 HOURS. THERE IS A SLIGHT CHANCE FOR
THUNDERSTORMS BETWEEN 18-03Z. MVFR CIGS POSSIBLE EARLY FRIDAY
MORNING ACROSS THE INTERIOR AS STRATUS BACK BUILDS OFF THE
CASCADES...BUT CONFIDENCE IS LOW.

KPDX AND APPROACHES...VFR THE NEXT 24 HOURS. WILL SEE SHOWER
ACTIVITY INCREASE THIS AFTERNOON/EVENING...WITH THUNDERSTORMS
POSSIBLE BETWEEN 20-03Z. A BRIEF PERIOD OF MVFR CIGS POSSIBLE
AFTER 12Z FRIDAY...BUT CONFIDENCE IS LOW. /64

&&

.MARINE...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...LOW PRESSURE
ALOFT AND SURFACE HIGH PRESSURE OVER THE NORTHEAST PACIFIC WILL
KEEP WINDS DOWN AND ALLOW SEAS TO SUBSIDE THROUGH THE FIRST HALF
OF THE WEEKEND. A DYING FRONT WILL TURN WINDS SOUTHERLY ON
SUNDAY...BUT AT THIS POINT THE FRONT APPEARS WEAK ENOUGH TO BRING
FEW APPRECIABLE IMPACTS TO OUR WATERS. HIGH PRESSURE WILL THEN
RETURN TO THE NORTHEAST PACIFIC. STRENGTHENING THERMAL LOW
PRESSURE OVER NORTHERN CALIFORNIA SHOULD ALLOW OUR MORE TYPICAL
SUMMER-LIKE GUSTY NORTHERLY WIND PATTERN TO RETURN EARLY NEXT
WEEK. AT WHICH TIME...EXPECT SEAS TO BECOME MORE WIND
DOMINATED...ESPECIALLY ACROSS THE CENTRAL OREGON WATERS. /NEUMAN

&&

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

&&

$$

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
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.


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