Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 040956
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
255 AM PDT FRI SEP  4 2015

.SYNOPSIS...A BROAD UPPER LEVEL LOW WILL MOVE SOUTH ACROSS WESTERN
WASHINGTON AND WESTERN OREGON TODAY...PRODUCING CONTINUED CHANCES FOR
SHOWERS AND ISOLATED THUNDERSTORMS...ESPECIALLY THIS AFTERNOON AND
EVENING. THE WEATHER WILL IMPROVE SATURDAY AS THE UPPER LOW FINALLY
BEGINS TO SLIDE EAST THOUGH SOME SHOWERS MAY LINGER IN THE HIGHER
CASCADES UNTIL LATER IN THE DAY SATURDAY. ANOTHER LOW IS THEN
EXPECTED TO MOVE INTO THE PACIFIC NORTHWEST FROM THE NORTHWEST...
WITH SOME PRECIPITATION POSSIBLE LATE SATURDAY NIGHT INTO SUNDAY
NIGHT MAINLY ACROSS SOUTHWEST WASHINGTON AND FAR NORTHWEST OREGON.
WARMER AND DRIER WEATHER IS EXPECTED TO RETURN FOR MUCH OF THE COMING
WEEK.
&&

.SHORT TERM...AN UPPER LOW CONTINUES TO BE THE DOMINANT FEATURE
AFFECTING THE WEATHER OVER THE PACIFIC NORTHWEST THIS MORNING. SOME
ENERGY IS MOVING SOUTH THROUGH THE COASTAL WATERS ON THE WEST SIDE OF
THE LOW...AND NATIONAL WEATHER SERVICE DOPPLER RADAR SHOWS SOME
DECENT SHOWERS OVER THE COASTAL WATERS. CANNOT RULE OUT THUNDER WITH
THESE THIS MORNING. INLAND IS LOOKING DRY EARLY THIS MORNING. AREAS
OF CLEARING OVERNIGHT IS LEADING TO SOME AREAS OF LOW CLOUDS AND
LOCAL FOG DEVELOPING DUE TO COOLING OVERNIGHT FROM DECENT RADIATIONAL
CONDITIONS. TEMPS IN MANY AREAS THIS MORNING WILL FALL INTO THE 40S.
SOME MOISTURE AND ENERGY IS TRYING TO SWING ONSHORE ACROSS THE
SOUTHERN PART OF OUR AREA AND WOULD NOT BE SURPRISED TO SEE A SHOWER
OR TWO TRY TO FORM DOWN SOUTH THIS MORNING.

THE UPPER LOW IS FORECAST TO MOVE SOUTH TODAY ACROSS WESTERN
WASHINGTON AND WESTERN OREGON...AND BE PRETTY MUCH OVERHEAD OVER OUR
FORECAST AREA THIS AFTERNOON. THE MODELS SHOW SHOWERS INCREASING WITH
THE DAYTIME HEATING IN THE AFTERNOON AS INSTABILITY BUILDS IN CONCERT
WITH THE COLD POOL ALOFT FROM THE LOW. THE GREATEST CHANCE OF SHOWERS
AND THUNDERSTORMS WILL BE OVER THE CASCADES AND THE COASTAL MOUNTAINS
THIS AFTERNOON AND EVENING...BUT SOME OF THESE SHOULD DRIFT OUT OVER
THE VALLEYS AS WELL.

THE LOW LINGERS SOME TONIGHT BEFORE MOVING TO THE EAST ON SATURDAY.
THE MODELS INDICATE SOME SHOWERS MAY LINGER TONIGHT AND A GOOD PART
OF SATURDAY NEAR THE CASCADE CREST DUE TO THE PROXIMITY OF THE LOW.
THE REMAINDER OF THE FORECAST AREA MAY SEE SOME LOCAL MORNING FOG OR
LOW CLOUDS UNDER ANOTHER COOL START TO THE DAY BEFORE WARMING UP
CLOSE TO 70 OR THE LOW 70S IN THE AFTERNOON UNDER INCREASING
SUNSHINE.

THE IMPROVING WEATHER WILL BE SHORT LIVED AS ANOTHER SYSTEM DROPS IN
FROM THE NORTHWEST LATE SATURDAY NIGHT AND SUNDAY. THE MODELS
INDICATE THE MAIN CHANCE OF RAIN WILL BE IN THE NORTH HALF OF OUR
FORECAST AREA...CATCHING MOST OF THE COAST BUT MAINLY AFFECTING
INLAND AREAS FROM ABOUT PORTLAND NORTHWARD. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
SUNDAY NIGHT THROUGH THURSDAY. A SHORTWAVE DISTURBANCE WILL BRING A
THREAT FOR SHOWERS AND INCREASING CLOUDS LATE SUNDAY INTO EARLY
MONDAY MORNING AS AN UPPER LEVEL TROUGH DRIFTS OVER THE PACIFIC
NORTHWEST. 12Z EXTENDED MODELS HAVE BEEN SHOWING NOTABLE RUN TO RUN
VARIABILITY...BUT HINT AT BRIEF UPPER LEVEL RIDGING LATE TUESDAY...
BEFORE THE UPPER LEVEL FLOW BECOMES MORE ZONAL BY WEDNESDAY.
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. /27
&&

.AVIATION...A STABILIZING LOWER ATMOSPHERE...LIGHT WINDS AND PLENTY
OF LOW LEVEL MOISTURE ARE ALLOWING IFR TO LOW END MVFR CONDITIONS TO
DEVELOP ACROSS THE NORTHERN WILLAMETTE VALLEY AND COAST. SOME HIGH
CLOUDS OVER THE SOUTH AND CENTRAL WILLAMETTE VALLEY ARE DELAYING
DEVELOPMENT IN THIS REGION...BUT DETERIORATIONS STILL SEEM
PROBABLE...JUST MORE TOWARDS 12Z TO 15Z FRIDAY. EXPECT MOST
RESTRICTIONS TO IMPROVE BY 18Z FRIDAY. ANOTHER ROUND OF SCATTERED
SHOWERS AND VERY ISOLATED THUNDERSTORMS WILL POP UP BETWEEN 18Z
FRIDAY AND 03Z SATURDAY BEFORE SKIES CLEAR ONCE AGAIN. THIS MAY LEAD
TO ANOTHER NIGHT OF DETERIORATIONS AT MANY TAF SITES AS WE APPROACH
12Z SATURDAY.

KPDX AND APPROACHES...A STABILIZING LOWER ATMOSPHERE...LIGHT WINDS
AND PLENTY OF MOISTURE WILL PRODUCE IFR TO LOW END MVFR CONDITIONS
THROUGH APPROXIMATELY 18Z FRIDAY. A FEW SHOWERS IN THE AREA WILL GIVE
WAY TO CLEARING SKIES FRIDAY EVENING WITH A POSSIBILITY OF IFR TO LOW
END MVFR CONDITIONS RETURN AFTER 09Z SATURDAY. /NEUMAN
&&

.MARINE...LOW PRESSURE ALOFT WILL BRING SCATTERED SHOWERS AND A
SLIGHT CHANCE OF THUNDERSTORMS TO THE WATERS TODAY. INCREASING LOW
PRESSURE INLAND WILL ALSO ALLOW NORTHERLY WINDS TO INCREASE THIS
AFTERNOON...BUT GUSTS SHOULD GENERALLY REMAIN NEAR 20 KT. A WEAK
FRONT DROPPING SOUTHEASTWARD ACROSS THE WATERS ON SUNDAY SHOULD BRING
FEW APPRECIABLE IMPACTS. THERMAL LOW PRESSURE DEVELOPING OVER
NORTHERN CALIFORNIA NEXT WEEK SHOULD BRING A RETURN TO A SUMMER-LIKE
GUSTY NORTHERLY WIND PATTERN TO THE WATERS. THIS WILL BE MOST
PREVALENT ACROSS THE CENTRAL OREGON WATERS...ESPECIALLY DURING THE
AFTERNOON AND EVENING HOURS. SEAS WILL LIKELY BECOME A BIT MORE WIND
DOMINATED DURING THIS PERIOD AS WELL. /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.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.