Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 020354
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
855 PM PDT MON JUN 1 2015

.SYNOPSIS...WEAK LOW CENTERS WILL CONTINUE TO ROTATE THROUGH A
COMPLEXT UPPER LEVEL LOW PRES SYSTEM OVER THE PACIFIC NW FOR THE
NEXT FEW DAYS. WITH A MOIST ONSHORE FLOW THIS WILL KEEP TEMPS COOL
WITH A THREAT OF SHOWERS IN THE FORECAST THROUGH MID WEEK. A STRONG
UPPER LEVEL RIDGE OF HIGH PRESSURE IS EXPECTED TO BUILD OVER THE
PACIFIC NORTHWEST LATER THIS WEEK AND THROUGH THE WEEKEND...
POSSIBLY BRINGING THE WARMEST TEMPERATURES SO FAR THIS YEAR.

&&

.SHORT TERM...INITIAL LOW CENTER IN THE LARGER UPPER TROUGH WAS SEEN
IN WATER VAPOR PICTURES THIS EVENING LIFTING N INTO THE S PUGET
SOUND AREA. ANOTHER VORT MAX MOVING E WAS SEEN OFF THE COAST NEAR
43N 130W. AS A LOW LEVEL ONSHORE FLOW CONTINUES OVERNIGHT WITH DEEP
MOISTURE REMAINING IN PLACE...EXPECT SCATTERED SHOWERS TO CONTINUE.
WITH DEW POINTS IN THE LOW TO MID 50S AND PLENTY OF CLOUDS...TEMPS
WILL BE MILD OVERNIGHT.

REMAINDER OF SHORT TERM DISCUSSION UNCHANGED...18Z NAM CONTINUES TO
SHOW ONSHORE GRADIENTS UPWARDS OF +10 MB TUE AFTERNOON...WHICH
SHOULD RESULT IN EXTENSIVE LOW CLOUDINESS TUESDAY AS WELL. THIS
SHOULD HOLD TEMPS IN THE LOWER TO MID 60S EVEN FOR THE INLAND
VALLEYS. CONTINUED CYCLONIC FLOW SHOULD PROMOTE MORE SHOWER ACTIVITY
THROUGH TUESDAY...SO KEPT POPS HIGH AS A RESULT. NAM/GFS CONTINUE TO
STRENGTHEN THE CAP ABOVE 600-500 MB...SO IT WILL BE DIFFICULT FOR
SHOWERS TO HAVE TOPS MUCH ABOVE 15 KFT ACROSS OUR DISTRICT TUESDAY.
THEREFORE IT APPEARS THUNDER IS UNLIKELY TUE AFTERNOON ON OUR SIDE
OF THE CREST...AS IT WILL BE A TALL ORDER TO WARM SURFACE PARCELS
SUFFICIENTLY TO BREAK THIS CAP.

WITH LITTLE FORCING IT APPEARS SHOWERS SHOULD BE DIURNALLY DRIVEN FOR
THE MOST PART TUESDAY...AND SHOWERS SHOULD DECREASE AFTER SUNSET.
FLOW REMAINS CYCLONIC AND THERE IS ENOUGH MOISTURE AND LOW-LEVEL
INSTABILITY TO KEEP SOME POPS IN WEDNESDAY...ESPECIALLY IN THE
AFTERNOON AND NORTH OF SALEM. WITH PLENTY OF CLOUDS AND 850 MB TEMPS
REMAINING NEAR +5 DEG C IT APPEARS HIGHS WED WILL ALSO FALL SHORT OF
EARLY JUNE NORMALS. HOWEVER...MODELS ARE SUGGESTING DEVELOPMENTS WILL
BEGIN TO OCCUR WEDNESDAY WHICH WILL START A TRANSITION TOWARD MUCH
WARMER WEATHER LATER IN THE WEEK THROUGH THE WEEKEND.

WHILE THERE REMAINS SOME UNCERTAINTY...MODELS ARE SHOWING IMPRESSIVE
AGREEMENT ON A SIGNIFICANT WARM SPELL DEVELOPING BY THE WEEKEND. THIS
STARTS WITH THE SHEARING OFF OF A SHORTWAVE APPROACHING THE PAC NW
WEDNESDAY...THEN THE FORMATION OF A CUTOFF LOW NEAR CALIFORNIA
THURSDAY. THIS SHOULD TURN THE FLOW MORE NORTHERLY...POSSIBLY
NORTHEASTERLY...CONSIDERABLY DRYING OUT THE BOUNDARY LAYER BY
THURSDAY AFTERNOON. ANY MORNING CLOUDS THURSDAY ARE EXPECTED TO CLEAR
OUT EXCEPT PERHAPS ALONG THE WA COAST. DECIDED TO LEAVE A SLIGHT
CHANCE OF THUNDER IN THE LANE COUNTY CASCADES THU AFTERNOON...TO
MATCH OUR NEIGHBORS JUST IN CASE THE UPPER LOW CUTS OFF A BIT FURTHER
NORTH THAN THE 12Z GFS/ECMWF SUGGEST. HOWEVER THURSDAY SHOULD BE THE
FIRST REAL SUNNY DAY THIS WEEK...AND PROBABLY THE FIRST OF SEVERAL AS
WE HEAD INTO WHAT COULD BE A SIGNIFICANT WARM SPELL.  WEAGLE

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS. THURSDAY NIGHT
THROUGH MONDAY...12Z GFS AND ECMWF BOTH SHOW THE DEEP UPPER LEVEL
TROUGH GETTING PINCHED OFF AND BECOMING A CUT-OFF LOW OVER NORTHERN
CALIFORNIA LATE THURSDAY. AS THIS CUT-OFF LOW DIGS FURTHER SOUTH
INTO CALIFORNIA...AN UPPER LEVEL RIDGE DEVELOPS OVER THE EAST
PACIFIC...ATTEMPTING TO SET UP A REX BLOCK OVER WESTERN CONUS FRIDAY
AND THROUGH THE WEEKEND. EXPECT GUSTY NORTHERLY WINDS ALONG THE
COAST...PERIODS OF MORNING CLOUDS FOR COASTAL LOCATIONS AND ALONG
THE LOWER COLUMBIA RIVER...AND TEMPERATURES LIKELY WARMING WELL
ABOVE AVERAGE TOWARDS THE WEEKEND. MODELS ARE SHOWING 850 MB
TEMPERATURES HOVERING AT OR JUST ABOVE 20 DEG CELSIUS FOR SATURDAY
AND SUNDAY...WHICH WOULD ALLOW SURFACE TEMPERATURES TO FLIRT AT OR
JUST ABOVE 90 DEG FAHRENHEIT. /27

&&

.AVIATION...COASTAL SITES SHOULD CONTINUE TO HAVE MVFR/IFR CIGS
OVERNIGHT...WITH MVFR VIS POSSIBLY DROPPING TO IFR WITH RAIN
SHOWERS. CIGS SHOULD REMAIN PRIMARILY MVFR/IFR THROUGH TOMORROW
MORNING WITH CONTINUED ONSHORE FLOW. INLAND LOW HAS MOVED OFF TO
THE NORTHEAST PUTTING THE AREA BACK UNDER WESTERLY/NORTHWESTERLY
FLOW. INLAND CIGS HAVE IMPROVED TO MOSTLY VFR. ANOTHER BAND OF
SHOWERS IS MOVING NORTHWARD CURRENTLY JUST NORTH OF SALEM WHICH
COULD DROP CIGS DOWN TO MVFR OVER THE NEXT COUPLE HOURS AT KPDX
AND KTTD. BEHIND THIS BAND...IMPROVEMENT BACK TO PRIMARILY VFR IS
EXPECTED AS CIGS RISE BACK ABOVE FL030. EARLY TUESDAY...ANOTHER
TROUGH MOVES ONSHORE FROM THE WEST BRINGING MORE SHOWERS STARTING
AROUND 13-16Z AT INLAND SITES. WITH SHOWERS...EXPECT CIGS TO DROP
BACK DOWN TO MVFR. REDUCED VIS POSSIBLE WITH HEAVIER SHOWERS.
MODELS SHOW CIGS STARTING TO LIFT INLAND AROUND 18-21Z...BUT
THINKING THAT CIGS MAY BOUNCE BETWEEN VFR/MVFR FOR A FEW HOURS
BEFORE IMPROVING TO PRIMARILY VFR BY 21-00Z.

KPDX AND APPROACHES...CIGS CURRENTLY VFR MAY DROP TO MVFR OVER THE
NEXT HOUR OR TWO AS ANOTHER BAND OF SHOWERS MOVES NORTHWARD OVER
THE TERMINAL. AFTER AROUND 05Z...CIGS SHOULD IMPROVE BACK TO VFR
FOR THE REST OF THE EVENING. AROUND 12Z TUES CIGS MAY DROP BACK
DOWN TO MVFR AS MORE SHOWERS MOVE THROUGH...IMPROVING BACK TO
PRIMARILY VFR BY AROUND 18Z. -MCCOY

&&

.MARINE...WINDS TO REMAIN FAIRLY BENIGN THROUGH TOMORROW OUT OF
THE SOUTH...SHIFTING TO THE NORTHWEST EARLY WEDNESDAY AS HIGH
PRESSURE BUILDS OVER THE WATERS. SEAS THROUGH THIS TIME SHOULD
REMAIN AROUND 3-4 FT. SEAS START TO BUILD ON WEDNESDAY AS WINDS
START TO INCREASE OUT OF THE NORTHWEST...WITH HIGH PRESSURE
BUILDING OVER THE WATERS. MODELS ARE SUGGESTING THAT WINDS MAY GET
UP ABOVE 20 KTS BY THURSDAY AFTERNOON/EVENING...WITH SEAS BUILDING
TO AROUND 6 TO 7 FT. A SMALL CRAFT ADVISORY FOR WINDS MAY BE
NEEDED THURSDAY AFTERNOON THROUGH THE WEEKEND...ESPECIALLY OVER
THE CENTRAL OR WATERS AS WINDS ARE FORECAST TO STAY ABOVE 20 KT.
DURING THIS PERIOD THERE MAY BE SHORT BREAKS DURING THE MORNING
HOURS WITH WEAKER WINDS...BEFORE WINDS RAMP BACK UP DURING THE
AFTERNOON HOURS. GUSTS UP TO 25 TO 30 KTS WILL BE POSSIBLE DURING
THE AFTERNOON HOURS...ESPECIALLY OVER THE CENTRAL OR WATERS.
-MCCOY


&&

.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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