Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 182158
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
256 PM PDT SAT APR 18 2015

.SYNOPSIS...SUNNY AND WARM WEATHER IS EXPECTED THROUGH MONDAY AS HIGH
PRESSURE DOMINATES THE PACIFIC NORTHWEST. TEMPERATURES WILL WARM UP A
BIT EACH DAY...LIKELY REACHING 80 DEGREES FOR SOME INLAND AREAS BY
MONDAY. COASTAL AREAS WILL BE COOLER...BUT SHOULD STILL SEE PLENTY OF
SUNSHINE THIS WEEKEND. AN UPPER TROUGH MAY BRING A FEW SHOWERS AS
EARLY AS TUESDAY...WITH UNSETTLED WEATHER AND COOLER TEMPERATURES
EXPECTED FOR THE REST OF THE WEEK.

&&

.SHORT TERM...TONIGHT THROUGH TUESDAY...YET ANOTHER WARM AND SUNNY
SPRING DAY IS UNDERWAY THIS AFTERNOON AS HIGH PRESSURE CONTINUES TO
DOMINATE THE PACIFIC NORTHWEST. TEMPERATURES SHOULD PEAK IN THE MID
70S FOR MOST OF OUR INLAND VALLEYS THIS AFTERNOON. THE COAST IS
GETTING IN ON THE SUNSHINE AS WELL...THOUGH BRISK N-NW WINDS ARE
KEEPING TEMPERATURES COOLER. THERMAL LOW PRESSURE OVER CALIFORNIA IS
BEGINNING TO EXTEND NORTHWARD ALONG THE OREGON COAST...DRIVING THOSE
NORTHERLY WINDS. LIGHT OFFSHORE WINDS SHOULD DEVELOP OVERNIGHT AS
INLAND AREAS COOL...WITH ONLY SOME VERY PATCHY FOG EXPECTED IN THE
MOST SHELTERED VALLEY LOCATIONS.

LOOKS LIKE A GOOD BET THAT AT LEAST A COUPLE INLAND LOCATIONS WILL
SEE THEIR FIRST 80 DEGREE READINGS OF THE YEAR SUNDAY AND/OR MONDAY
AS 850 MB TEMPS REACH +12 TO +14 DEG C WITH NEAR FULL SUNSHINE.
COASTAL AREAS WILL STAY COOLER...THOUGH THEY COULD GET A DECENT JUMP
IN TEMPS EARLY IN THE DAY DUE TO THE WEAK MORNING LAND BREEZE.
STRATUS MAY RETURN ALONG THE COAST MONDAY AS THERMAL LOW PRESSURE
SHIFTS INLAND...RESULTING IN A COOLDOWN ALONG THE COAST.

THE MARINE LAYER AND ASSOCIATED STRATUS WILL CONTINUE TO DEEPEN
MONDAY NIGHT...PUSHING INLAND ON ONSHORE FLOW LATER IN THE NIGHT AND
TUE MORNING. 12Z/18Z NAM SUGGEST A SOUTHWESTERLY MARINE PUSH MON
NIGHT/TUE MORNING...WHICH SEEMS REASONABLE CONSIDERING SW FLOW ALOFT
AND THE THERMAL LOW CROSSING THE CASCADES INTO THE COLUMBIA BASIN.
THIS SHOULD RESULT IN A SIGNIFICANT COOLDOWN TUESDAY...BRINGING TEMPS
CLOSER TO APRIL NORMALS. SOME AREAS OF DRIZZLE MAY DEVELOP IN THE
STRATUS ALONG THE COAST AND IN THE HILLS. MODEL QPF ALSO SEEMS TO
INDICATE THE DEEP MARINE LAYER PRODUCING A COUPLE SHOWERS TUE
AFTERNOON AS THE BOUNDARY LAYER MIXES AND TURNS OVER. THE MARINE
LAYER SHOULD SEVERELY LIMIT THE POTENTIAL FOR DEEP CONVECTION ACROSS
SW WASHINGTON AND NW OREGON EXCEPT RIGHT ALONG THE CASCADE CREST...
WHERE SURFACE PARCELS WILL START ABOVE THE MARINE INVERSION. DECIDED
TO CARRY A SLIGHT CHANCE OF THUNDER RIGHT ALONG THE CREST TUESDAY
AFTERNOON AS A RESULT.WEAGLE

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...UNSETTLED WEATHER
EXPECTED INTO THE WEEKEND AS A LONGWAVE TROUGH REMAINS SITUATED OVER
THE NORTHERN PACIFIC AND MULTIPLE SHORTWAVES DEVELOP OFF THE PARENT
TROUGH. AS THE FIRST OF THESE WAVES MOVES THROUGH THE AREA ON
WEDNESDAY...EXPECT SHOWERS THROUGH THE DAY. WHEN THIS FRONT MOVES
OFF TO THE EAST...THERE COULD BE A DRY PERIOD WEDNESDAY NIGHT
THROUGH MIDDAY THURSDAY AS HIGH PRESSURE BRIEFLY BUILDS AHEAD OF THE
NEXT FRONT FORECAST TO MOVE THROUGH THURSDAY NIGHT INTO FRIDAY.
HAVE LEFT ENOUGH POPS FOR A SLIGHT CHANCE DURING THE DAY THURSDAY AS
THERE IS SOME UNCERTAINTY ON THE TIMING OF THESE FRONTAL SYSTEMS
MOVING THROUGH. THE NEXT FRONT WILL BRING ANOTHER ROUND OF SHOWERS
FOR THURSDAY NIGHT THROUGH SATURDAY...WITH EVEN MORE UNCERTAINTY ON
THE TIMING OF THIS FRONT MOVING THROUGH. -MCCOY

&&

.AVIATION...HIGH PRES WITH DRY STABLE FLOW ALOFT WILL ALLOW
WIDESPREAD VFR CONDITIONS TO REMAIN IN CONTROL FOR THE NEXT 24 HRS.
BREEZY NORTHERLY WINDS WILL CONTINUE TO IMPACT THE REGION DURING THE
AFTERNOON AND EVENING HOURS...PARTICULARLY ALONG THE COAST. THERE
IS A SLIGHT CHANCE THAT THE COASTAL TAF SITES MAY SEE BRIEF PATCHY
FOG EARLY SUN MORNING...BUT THINK THERE WILL BE ENOUGH NE FLOW
OVERNIGHT TO PREVENT THIS.

KPDX AND APPROACHES...VFR CONTINUE THROUGH 00Z SUN IN DRY NORTHERLY
FLOW.  PYLE

&&

.MARINE...HIGH PRES REMAINS OVER THE NE PAC THROUGH MON...WHICH IN
COMBINATION WITH THERMAL LOW PRES OVER N CALIF AND SW OREGON WILL
KEEP BREEZY NORTHERLY WINDS OVER THE COASTAL WATERS. THE STRONGEST
WINDS WILL BE OVER THE CENTRAL OREGON WATERS SOUTH OF CASCADE
HEAD...WHERE WINDS OF 25 TO 30 KT WILL CONTINUE. WINDS WILL BE
LIGHTER NORTH OF CASCADE HEAD...CLOSER TO 20 TO 25 KT. THE WINDS
WILL BE STRONGEST DURING THE AFTERNOON AND EVENING HOURS...THEN
DIMINISH SOMEWHAT OVERNIGHT.

SEAS CONTINUE TO RUN ABOUT 8 TO 10 FT THIS AFTERNOON WITH A
COMBINATION OF NORTHWESTERLY SWELL AND LOCALLY GENERATED WIND
WAVES. EXPECT SEAS TO GRADUALLY DIMINISH SUN AND MON AS THE SWELL
LESSENS SOMEWHAT.

THE NEXT FRONT WILL MOVE THROUGH THE WATERS ON TUE. THEN THE LONGER
RANGE SHOWS HIGH PRES OVER THE NE PAC STRENGTHENING DURING THE
MIDDLE OF NEXT WEEK..WITH NW WINDS GUSTING 20 TO 30 KT AT TIMES.
ALSO EXPECT INCREASING NW SWELL TO PUSH SEAS BACK INTO THE LOW TO
MID TEENS STARTING WED. PYLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL NOON PDT SUNDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 8 PM
     PDT THIS EVENING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 4 AM TO
     8 AM PDT SUNDAY.

&&

$$

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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