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 192157
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
257 PM PDT SUN APR 19 2015

.SYNOPSIS...HIGH PRESSURE CONTINUES TO PROVIDE UNSEASONABLY WARM AND
SUNNY WEATHER TO THE PACIFIC NORTHWEST TODAY...WITH MONDAY EXPECTED
TO BE VERY SIMILAR INLAND. THERMAL LOW PRESSURE WILL SHIFT INLAND
MONDAY...ALLOWING A DEEPER MARINE LAYER TO DEVELOP ALONG THE COAST BY
LATE AFTERNOON. THIS WILL BEGIN A SIGNIFICANT COOLDOWN FOR TUESDAY AS
A DEEP MARINE LAYER PUSHES ONSHORE AHEAD OF AN INCOMING COLD FRONT.
AN UPPER LEVEL TROUGH WILL THEN LINGER THROUGH THE END OF THE
WEEK...KEEPING TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL WITH A
CHANCE OF SHOWERS AT TIMES.

&&

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...VISIBLE SATELLITE IMAGERY
SHOWS CLEAR SKIES YET AGAIN...EXCEPT FOR SOME SLIGHT FILTERING OF THE
SUNSHINE BY SMOKE FROM FIRES IN SOUTHERN SIBERIA LAST WEEK. AS
EXPECTED...IT IS APPEARING THAT SMOKE IS HAVING LITTLE TO NO IMPACT
ON TEMPERATURES TODAY. AS THE SUN ANGLE INCREASED...THE LOSS OF
INSOLATION AS DETECTED BY RAWS STATIONS DECREASED FROM 20-30 PERCENT
LOSS THIS MORNING TO ONLY A 5-10 PERCENT LOSS THIS AFTERNOON. AS A
RESULT TEMPS ARE GENERALLY 0-3 DEG F WARMER THAN THEY WERE YESTERDAY
AT THIS TIME...AND A COUPLE 80 DEGREE READINGS STILL LOOK POSSIBLE
FOR THE INLAND VALLEYS. IF NOT...THERE WILL BE PLENTY OF UPPER 70S.

FOG AND LOW CLOUDS WILL BE MINIMAL AGAIN TONIGHT THOUGH A PATCH OF
COASTAL STRATUS IS DEVELOPING ALONG THE WA COAST. THIS MAY SPREAD
SOME FOG INTO ASTORIA LATER TONIGHT...AND SOME PATCHY RADIATIONAL FOG
MAY DEVELOP AGAIN IN THE NEHALEM RIVER VALLEY AS WELL AS SOME OF THE
COASTAL VALLEYS.

NESDIS ANALYSTS BELIEVE THE SMOKE WILL BE LESS APPARENT MONDAY...
STAYING TO OUR NORTH AS THE UPPER RIDGE AXIS MOVES INTO THE PAC NW.
THEREFORE EXPECT PLENTY OF SUNSHINE AGAIN MONDAY FOR THE INLAND
AREAS. MODELS SHOW 500 MB HEIGHTS DECREASING A BIT MONDAY...BUT TEMPS
REMAIN ABOUT THE SAME AT 850 MB. WITH THE THERMAL TROUGH
OVERHEAD...PLENTY OF SUNSHINE...AND EVEN A LITTLE DOWNSLOPING OFF THE
COAST RANGE AS THE BEGINNINGS OF A SEABREEZE DEVELOP...EXPECT TEMPS
WILL REACH THE LOWER 80S FOR MANY INLAND SITES MONDAY. TEMPS IN
CORVALLIS AND EUGENE MAY BE CAPPED IN THE MID-UPPER 70S AS ONSHORE
FLOW BEGINS TO PUSH THROUGH THE COASTAL VALLEYS BY LATE AFTERNOON.

LOW CLOUDS SHOULD BEGIN DEVELOPING ALONG THE COAST BY LATE MONDAY
AFTERNOON...THEN PUSH INLAND OVERNIGHT MON NIGHT AHEAD OF AN INCOMING
UPPER TROUGH AND ASSOCIATED COLD FRONT. NAM CROSS SECTIONS SHOW A
DEEP MARINE LAYER PUSHING IN MONDAY NIGHT AND EARLY TUE... WITH THE
POTENTIAL FOR ISOLATED SHOWERS TUE AFTERNOON AS THE MARINE LAYER
MIXES/TURNS OVER. TEMPS WILL BE 10-15 DEGREES COOLER TUESDAY DUE TO
THE DEEP ONSHORE FLOW AND MARINE INFLUENCE. THE DEEP MARINE LAYER
WILL KEEP ANY SHOWERS SHALLOW EXCEPT ALONG THE CASCADE CREST WHICH
MAY REMAIN ABOVE THE MARINE INVERSION...WHERE SOME WARMER SURFACE
PARCELS MAY BE MORE BUOYANT FOR DEEPER SHOWERS AND ISOLATED
THUNDERSTORMS. A SIMILAR SITUATION IS EXPECTED WEDNESDAY...WITH A
DEEP MARINE LAYER...BUT PERHAPS A LITTLE MORE OF A TRIGGER FOR
SHOWERS AS THE UPPER TROUGH AXIS DRAGS ACROSS THE PAC NW. ONCE TEMPS
COOL DOWN TUESDAY...EXPECT NEAR TO SLIGHTLY BELOW NORMAL TEMPS TO
PERSIST FOR SEVERAL DAYS.  WEAGLE

.LONG TERM...WEDNESDAY NIGHT THROUGH SATURDAY...MODELS ARE HAVING A
HARD TIME WITH THE DETAILS OF WHAT IS LEFT BEHIND AS THE INCOMING
UPPER TROUGH FALLS APART OVER THE PACIFIC NORTHWEST MIDDLE TO LATE
THIS UPCOMING WEEK. IT APPEARS THERE WILL BE ENOUGH OF A WEAKNESS IN
500 MB HEIGHTS AND JUST ENOUGH COOL AIR ALOFT TO MAKE IT DIFFICULT TO
COMPLETELY RULE OUT SHOWERS ANYTIME BETWEEN WED-FRI. 12Z GEM/EC SHOW
A COLD FRONT HOLDING TOGETHER ENOUGH TO BRING A MORE ORGANIZED CHANCE
OF SHOWERS TO OUR NORTHERN ZONES THU NIGHT/FRI. HOWEVER THE 12Z GFS
HAS THIS SYSTEM FALLING APART BEFORE MOVING ONSHORE. RAIN CHANCES
INCREASE NEXT WEEKEND AS MODELS AGREE ON A STRONGER FRONTAL SYSTEM
MOVING ONSHORE...PERHAPS WITH A WEAK TO MODEST ATMOSPHERIC RIVER.
CONFIDENCE IS HIGH ONE THING...AFTER THIS MONDAY THE NEAR- RECORD
WARMTH WILL BE HISTORY AND TEMPS WILL BE MUCH CLOSER TO LATE APRIL
NORMALS.  WEAGLE

&&

.AVIATION...WIDESPREAD VFR CONDITIONS TO CONTINUE TODAY AND
TONIGHT WITH DRY NORTHERLY FLOW. BREEZY WINDS ALONG THE COAST WILL
CONTINUE INTO THIS EVENING...BUT WILL THEN SUBSIDE OVERNIGHT.
PATCHY FOG MAY AGAIN AFFECT THE COASTAL TAF SITES BETWEEN 10Z AND
15Z MON.

KPDX AND APPROACHES...CLEAR AND DRY UNDER HIGH PRES. NO WEATHER
IMPACTS EXPECTED THROUGH MON. BREEZY NW FLOW THROUGH THE AFTERNOON
AND EVENING WILL SUBSIDE OVERNIGHT. PYLE


&&

.MARINE...GUSTY 20 TO 25 KT NORTHERLY WINDS WILL CONTINUE OVER THE
COASTAL WATERS INTO EARLY MON. THE WINDS WILL BEGIN TO SUBSIDE
DURING THE DAY MON AS A WEAK FRONT APPROACHES...WHICH WILL WEAKEN
THE HIGH PRES THAT HAS BEEN ANCHORED OVER THE NE PAC FOR THE PAST
SEVERAL DAYS. THE FRONT WILL MOVE THROUGH ON TUE AND SHOULD NOT
CAUSE MUCH IN THE WAY OF MARINE CONCERNS. THE NE PAC HIGH
STRENGTHENS AGAIN MIDWEEK BEHIND THE FRONT...WHICH WILL CAUSE THE
GUSTY SMALL CRAFT ADVISORY NORTHERLY WINDS TO RETURN FOR TUE
NIGHT AND WED. THE WINDS WEAKEN AGAIN ON THU AS ANOTHER WEAK FRONT
MOVES THROUGH THE WATERS.

SEAS WILL REMAIN AROUND 6 TO 8 FT THROUGH TUE. THEY WILL REMAIN
FAIRLY CHOPPY THROUGH TONIGHT DUE TO WIND WAVES BEING GENERATED BY
THE GUSTY NORTHERLY FLOW. THE INCREASING WINDS TUE NIGHT AND WED
WILL LIKELY PUSH THE SEAS BACK UP AROUND 10 FT FOR A BRIEF PERIOD
BEFORE THEY DROP BACK DOWN ON THU. PYLE

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT MONDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 AM TO
     8 AM PDT MONDAY.

&&

$$

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.