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 062207
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
306 PM PDT MON JUL  6 2015

.SYNOPSIS...HOT WEATHER WILL CONTINUE OVER MOST OF THE REGION THROUGH
MIDWEEK AS A STRONG RIDGE OF HIGH PRESSURE ALOFT REMAINS OVER THE
AREA. THE EXCEPTION IS THE COASTAL REGION WHERE COOLER MARINE AIR
WILL HUG THE COASTLINE THE NEXT SEVERAL DAYS. AN UPPER LOW OFF
CALIFORNIA MAY DRIFT FAR ENOUGH NORTH THIS WEEK TO BRING
THUNDERSTORMS ALONG THE CASCADE CREST IN LANE COUNTY. RELIEF FROM THE
HEAT WILL COME LATER THIS WEEK AS THE UPPER RIDGE BREAKS DOWN ENOUGH
TO ALLOW STRONGER ONSHORE FLOW.

&&

.SHORT TERM...TUESDAY THROUGH THURSDAY. NOT A LOT OF CHANGE IN THE
WEATHER PATTERN THE NEXT COUPLE DAYS. THE STRETCH OF HOT WEATHER WILL
CONTINUE THROUGH MID-WEEK...THEN A CHANGE IN THE WEATHER PATTERN
TOWARD THE END OF THE WEEK WILL BRING TEMPERATURES BACK TO NEAR
SEASONAL NORMALS.

850 MB TEMPS REMAIN NEAR +18 TO 20 DEG C THROUGH WED FOR CONTINUED
WARM WEATHER WITH INLAND TEMPS NEAR 90F. THE LONGEST CONTINUED
STRETCH OF 90 PLUS DEGREE DAYS FOR THE PORTLAND AREA IS 10
DAYS...WHICH OCCURRED JUL 25-AUG 3 2009. THIS RECORD LOOKS LIKE IT
WILL BE TIED AND POSSIBLY BROKEN THIS WEEK. TODAY WILL BE THE 8TH
CONSECUTIVE DAY OF 90 PLUS DEGREES IN PORTLAND WITH 2 OR 3 MORE 90
DEGREE DAYS EXPECTED THIS WEEK.

THERE IS POTENTIAL FOR THUNDER IN THE OREGON CASCADES THE NEXT FEW
DAYS.  SATELLITE IMAGERY AT 2PM SHOWS CUMULUS BUILDING ALONG THE
CASCADE CREST. THERE WILL LIKELY BE MORE INSTABILITY ALONG THE
CASCADE CREST EACH DAY...WITH THURSDAY AFTERNOON/EVENING BEING THE
MOST FAVORABLE DAY FOR THUNDERSTORM ACTIVITY THIS WEEK. TW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...THURSDAY
THROUGH SUNDAY...FINALLY AN END IS IN SIGHT TO THIS HISTORIC HEAT
WAVE...AS THE BLOCKING PATTERN WHICH HAS KEPT US UNDER ANOMALOUSLY
HIGH 500 MB HEIGHTS BREAKS DOWN. THE HIGH 500 MB HEIGHTS HAVE KEPT
THE MARINE LAYER SHALLOW...ROBBING ONSHORE FLOW OF ITS COOLING
INFLUENCE BEFORE IT REACHES THE INLAND VALLEYS. THE MOST IMPORTANT
CHANGE EXPECTED DURING THE EXTENDED FORECAST PERIOD WILL LIKELY BE
THE SLOW LOWERING OF OVERALL 500 MB HEIGHTS OVER THE WESTERN UNITED
STATES AND THE NE PACIFIC...AS THE CA CUTOFF LOW OPENS UP MIDWEEK
AND THE MEAN UPPER RIDGE POSITION SLOWLY SHIFTS EASTWARD INTO THE
GREAT PLAINS. AS OVERALL HEIGHTS LOWER...EXPECT THE MARINE LAYER TO
BECOME DEEPER...THUS BECOMING MORE EFFECTIVE IN COOLING THE INTERIOR
GIVEN ONSHORE FLOW.

THERMAL LOW PRESSURE WILL LIKELY LINGER OVER THE WILLAMETTE VALLEY
THURSDAY...ALLOWING ONE MORE FAIRLY HOT DAY...THOUGH THE OVERALL AIR
MASS WILL BE COOLING AS 500 MB HEIGHTS LOWER. THU NIGHT APPEARS TO BE
THE BIG COOL DOWN AS THE THERMAL TROUGH MOVES INTO ERN WA AND
ENCOURAGES A STRONG SW PUSH OF MARINE AIR TO PUSH INTO THE DISTRICT.
THIS WILL AT LEAST PUSH TEMPERATURES CLOSER TO NORMAL WITH NIGHT AND
MORNING LOW CLOUDS EXTENDING INLAND BY THE WEEKEND...HOWEVER MODELS
DIVERGE ON WHETHER OR NOT AN INCOMING UPPER TROUGH CAN REMAIN STRONG
ENOUGH TO PRODUCE SHOWERS. DECIDED TO KEEP POPS VERY LOW...AS MODELS
HAVE A TENDENCY TO BE TOO AGGRESSIVE IN PUSHING THESE PACIFIC SYSTEMS
ONSHORE AFTER BEING UNDER A STRONG UPPER RIDGE. A MORE FAVORED
SOLUTION FOR THE WEEKEND IS THE 00Z ECMWF SOLUTION...WHICH LEAVES THE
UPPER TROUGH AXIS OFFSHORE AND SOUTHERLY FLOW OVER THE FORECAST AREA
KEEPING TEMPS CLOSE TO NORMAL RATHER THAN GOING BELOW NORMAL.
THEREFORE WE CONTINUE TO BE ON THE CONSERVATIVE SIDE OF GUIDANCE IN
THE MAGNITUDE OF COOLING EXPECTED WITH THIS PATTERN CHANGE.  WEAGLE

&&

.AVIATION...VFR CONDITIONS INLAND. SOME AREAS OF MVFR CIGS WILL
CONTINUE ALONG THE COAST LATE THIS AFTERNOON WITH LOCAL IFR
CIGS ALONG THE CENTRAL OREGON COAST. EXPECT IFR CONDITIONS TO
BECOME WIDESPREAD ALONG THE OREGON AND WASHINGTON COAST. AREAS OF
LIFR CONDITIONS EXPECTED ON THE CENTRAL OREGON COAST 05Z-15Z. STRATUS
WILL LIKELY SPREAD INLAND TO KKLS 11Z-15Z. THERE IS A POSSIBILITY
THAT PATCHY STRATUS WILL DEVELOP AROUND KPDX 12-15Z. INSTABILITY
OVER THE CENTRAL CASCADES WILL RESULT IN ISOLATED THUNDERSTORMS
THROUGH 04Z OVER CASCADES IN LANE COUNTY. ISOLATED THUNDERSTORMS
WILL DEVELOP AGAIN TOMORROW 21Z-04Z UNDER INFLUENCE OF LOW TO OFF
OF CALIFORNIA AND INCREASING MOISTURE FROM THE SOUTH.  SCHNEIDER

KPDX AND APPROACHES...VFR WILL CONTINUE THROUGH MONDAY TUESDAY.
MVFR CIGS POSSIBLE NEAR KKLS AFT 11Z AND THERE COULD BE SOME
PATCHY STRATUS AROUND KPDX 13-15Z TUESDAY. SCHNEIDER

&&

.MARINE...SURFACE GRADIENTS ARE NOT TOO STRONG SO WINDS ARE
GENERALLY 10 KTS OVER MOST OF THE WATERS. HOWEVER THERE IS SOME
MIXING WHICH IS ALLOWING GUSTY SURFACE WINDS RIGHT ALONG THE
IMMEDIATE COASTLINE WITH A FEW GUSTS TO 20KT UNTIL SUNSET. AS THE
OFFSHORE HIGH BUILDS IN  TOMORROW WINDS WILL SHIFT FROM SOUTHWEST
TO NORTHWEST REMAINING FAIRLY LIGHT. SHORT PERIOD WIND DRIVE SWELL
OF AROUND 2 FT IS COMBINED WITH A 2 TO 3 FT SOUTHWEST SWELL OVER
THE WATERS OVER THE NEXT FEW DAYS. FRESH SWELL WEAKENS AND IT
LOOKS LIKE THE DOMINANT SWELL WILL BECOME THE SOUTHWEST SWELL ON
TUESDAY. SCHNEIDER

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HEAT ADVISORY UNTIL MIDNIGHT PDT WEDNESDAY NIGHT FOR CENTRAL
     COLUMBIA RIVER GORGE-CENTRAL WILLAMETTE VALLEY-GREATER
     PORTLAND METRO AREA-NORTHERN OREGON CASCADE FOOTHILLS-SOUTH
     WILLAMETTE VALLEY-UPPER HOOD RIVER VALLEY-WESTERN COLUMBIA
     RIVER GORGE.

WA...HEAT ADVISORY UNTIL MIDNIGHT PDT WEDNESDAY NIGHT FOR CENTRAL
     COLUMBIA RIVER GORGE-GREATER VANCOUVER AREA-WESTERN
     COLUMBIA RIVER GORGE.

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.