Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 041615
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
916 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...UPPER LEVEL TROUGH WAS SEEN IN WATER VAPOR LOOP THIS
MORNING JUST INLAND OF THE COAST OVER WA AND OREGON. SHOWER ACTIVITY
THIS MORNING WAS MAINLY RELEGATED TO AREAS OFF THE COAST. AS DAYIME
WARMING KICKS IN THOUGH...EXPECT SHOWERS TO POP UP INLAND AS WELL.
WITH THE COLD POOL ALOFT OVERHEAD FORECAST MODEL SOUNDINGS SUGGEST A
THREAT FOR THUNDER THIS AFTERNOON MOST ANYWHERE...ALTHOUGH WILL
RETAIN BEST POPS OVER MOUNTAINS. COOL POOL WILL ALSO BRING ANOTHER
DAY OF TEMPS WELL BELOW SEASONAL NORMALS.

REMAINDER OF SHORT TERM DISCUSSION FOLLOWS. 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 STABLE LOWER ATMOSPHERE...LIGHT WINDS AND PLENTY OF
LOW LEVEL MOISTURE WILL KEEP A MIXTURE OF IFR TO MVFR STRATUS OVER
THE NORTH COAST AND INTERIOR VALLEY THROUGH THE MORNING. EXPECT
MOST RESTRICTIONS TO IMPROVE BY 18Z WITH VFR AND SCATTERED CU
THROUGH THIS EVENING. ANOTHER ROUND OF SCATTERED SHOWERS AND VERY
ISOLATED THUNDERSTORMS POSSIBLE BETWEEN 18-03Z. SKIES CLEAR
OVERNIGHT WHICH SHOULD ALLOW WIDESPREAD IFR TO MVFR STATUS TO
REDEVELOP OVER MUCH OF THE REGION AFTER 09Z.

KPDX AND APPROACHES...A STABLE LOWER ATMOSPHERE...LIGHT WINDS AND
PLENTY OF MOISTURE WILL KEEP IFR TO MVFR CONDITIONS THROUGH
APPROXIMATELY 18Z. A FEW SHOWERS IN THE AREA WILL GIVE WAY TO
CLEARING SKIES THIS EVENING...WITH A POSSIBILITY OF IFR TO MVFR
CONDITIONS RETURN AFTER 09Z SATURDAY. /64/NEUMAN

&&

.MARINE...NO SIGNIFICANT CHANGES. PREVIOUS DISCUSSION FOLLOWS...
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.


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