Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 121715 AAA
AFDPQR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1015 AM PDT SAT JUL 12 2014

UPDATED TO ADD FIRE WEATHER SECTION

.SYNOPSIS...MOIST AND UNSTABLE SOUTH FLOW ALOFT WILL CONTINUE
TODAY WITH A THREAT OF THUNDERSTORMS TO THE CASCADES THIS AFTERNOON
AND EVENING. AN UPPER LOW OFF THE NORTH CALIFORNIA COAST
WILL APPROACH OREGON TONIGHT AND SUNDAY AND BRING A GREATER THREAT
FOR THUNDERSTORMS OVERNIGHT TONIGHT AND CONTINUING THROUGH SUNDAY.
INLAND TEMPERATURES WILL REMAIN WELL-ABOVE NORMAL THROUGH LATE NEXT
WEEK. SUNDAY...THOUGH STILL WARM...COULD PROVE TO BE AN EXCEPTION
GIVEN SHADING FROM CONVECTIVE CLOUDS AND CONVECTIVE DEBRIS CLOUDS.

&&

.UPDATE...HAD A BUSY UPDATE CYCLE THIS MORNING AS WE WANTED TO BRING
CONCERN FOR OVERNIGHT CONVECTION INTO THE MIX. THE NEGATIVELY TILTED
UPPER LEVEL TROUGH SLATED TO BRING TOMORROWS EXCITEMENT LOOKS LIKE
IT WILL ACT OVERNIGHT TONIGHT ON AN INCREASING SATURATED LAYER
CENTERED AROUND 650 MB. LIFT AHEAD OF THE ASSOCIATED TROPOPAUSE FOLD
APPEARS TO BE ENOUGH TO PUSH PARCELS THROUGH A PHASE CHANGE AND RISE
UNABATED TO A HEIGHT IN EXCESS OF 30 KFT. BEST LIFT APPEARS TO STAY
OFF THE NORTH OREGON/SOUTH WASHINGTON COAST BUT FELT THIS WAS FAR
TOO CLOSE FOR COMFORT AND DECIDED TO BRING THE THUNDER THREAT INLAND
STARTING WITH THE EARLY MORNING HOURS ALONG A FLORENCE/EUGENE LINE
AND PERHAPS REACHING AS FAR NORTH AS A SALEM/TILLAMOOK LINE NO LATER
THAN SUNRISE. AREAS FURTHER NORTH SUCH AS PORTLAND METRO/ASTORIA AND
THE GORGE WILL SEE CONVECTION POTENTIAL FOR THE FIRST FEW HOURS
AFTER SUNRISE WHILE THE AFOREMENTIONED AREAS WILL LIKELY SEE A BREAK
IN THE ACTION AHEAD OF THE MAIN CONVECTIVE EVENT SUNDAY AFTERNOON.
INLAND CELLS OVERNIGHT WILL BE ON THE WEAKER SIDE WITH THE BEST
FORCING FOR MORE ACTIVE CELLS LIKELY REMAINING OFFSHORE THROUGH
EARLY DAYLIGHT HOURS. CONDITIONS WILL BRIEFLY STABILIZE ALOFT BEHIND
THE EARLY ACTION BUT THERE WILL BE PLENTY OF TIME AHEAD OF THE
TROUGH AXIS TO CHARGE THE LOWER ATMOSPHERE FOR THE STRONGER DYNAMICS
TO CROSS SUNDAY AFTERNOON. THE BEST THREAT FOR THE SURFACE BASED
CONVECTION STILL APPEARS TO BE CLOSER TO AND OVER THE CASCADES BUT
WILL CONTINUE TO ASSESS THE WESTERN EXTENT AS THE DETAILS EVOLVE.
THE PRIMARY THREAT FROM THE THUNDERSTORMS WILL BE FOR GUSTY WINDS
AND AS YOU GO FARTHER NORTH POTENTIAL FOR SOME LARGER HAIL.


THE EARLY CONVECTION AND POTENTIAL INLAND MARINE PUSH SIMILAR TO
TODAY...CREATED QUITE THE DILEMMA FOR SUNDAYS TEMPERATURES. IT
APPEARS WE WILL START OUT WITH A MARINE INTRUSION SOMEWHAT SIMILAR
TO TODAY BUT OF GREATER CONSEQUENCE WILL BE THE EARLY CONVECTIVE
CLOUDS AND DEBRIS CLOUDS BLOCKING INITIAL HEATING. AT THE SAME
TIME...THESE COOLER TEMPERATURES HAVE POTENTIAL TO INHIBIT THE
STRENGTH OF THE SURFACE BASED CONVECTION AWAY FROM THE CASCADES AND
FOOTHILLS. THE SOMEWHAT COOLER TEMPERATURES CERTAINLY PLACE THE NEED
FOR A HEAT ADVISORY IN DOUBT BUT ANY MARINE LAYER INTRUSION OR
EVAPORATIVE EFFECTS FROM RAIN WILL ONLY REINFORCE DEW POINTS AND
CONTINUE TO INHIBIT OVERNIGHT RELIEF TONIGHT AND MORE SO INTO SUNDAY
NIGHT. WILL LEAVE THE ADVISORY IN PLACE FOR THE TIME BEING AS THE
RIDGE STRENGTHENS BEHIND SUNDAYS EPISODE WITH WARM TO HOT CONDITIONS
EXTENDING INTO EARLY NEXT WEEK. /JBONK

&&

.PREV DISC... /ISSUED 320 AM PDT SAT JUL 12 2014/

SHORT TERM...A BAND OF UPPER CLOUDS AND MID-LEVEL INSTABILITY
WRAPPING AROUND AN UPPER LOW OFFSHORE...CURRENTLY CENTERED NEAR 41N
132W IS MOVING OVER SW WASHINGTON AND THE EXTREME NW OREGON EARLY
THIS MORNING. THESE CLOUDS ARE QUICKLY MOVING NW AND SHOULD CLEAR BY
THIS AFTERNOON. THE FOG-PRODUCT SATELLITE IMAGERY SHOWS LOW CLOUDS
ALONG THE COAST AND COVERING MOST OF THE CENTRAL OREGON COAST RANGE.
THE HIGHER CLOUDS TO THE NORTH ARE BLOCKING THE THE SATELLITE VIEW OF
LOWER CLOUDS...BUT SURFACE OBSERVATIONS SUGGEST THAT THE STRATUS IS
MOVING INLAND THROUGH THE LOWER COLUMBIA VALLEY AND MAY REACH INTO
PARTS OF THE NORTHERN WILLAMETTE VALLEY LATER THIS MORNING. THE LOW
CLOUDS SHOULD CLEAR INLAND THIS AFTERNOON...BUT HANG ON NEAR THE
IMMEDIATE COAST...ESPECIALLY ALONG THE CENTRAL OREGON COAST MOST OF
THE DAY.

AN UPPER RIDGE WILL BUILD OVER THE PACIFIC NW TODAY AND INCREASED
SUBSIDENCE HELPING TO WARM THE LOWER LEVELS. THE COASTAL CLOUDS
COMBINED WITH ONSHORE FLOW WILL LIMIT WARMING FOR THE COAST...BUT
MODELS ARE FORECASTING 850MB TEMPERATURES NEAR 20C INLAND...RESULTING
IN DAYTIME HIGHS INLAND PEAKING IN THE LOW TO MID 90S. MID-LEVEL
MOISTURE ASSOCIATED WITH THE UPPER LOW OFFSHORE WILL CONTINUE TO
STREAM OVER THE AREA...AND PROVIDE ANOTHER OPPORTUNITY FOR
THUNDERSTORMS THIS AFTERNOON WITH THE GREATEST THREAT OVER THE
CASCADES.

THE UPPER LOW WILL APPROACH THE OREGON COAST TONIGHT AND MOVE OVER
THE PORTLAND FORECAST AREA SUNDAY...PROVIDING A BETTER CHANCE FOR
THUNDERSTORMS. THIS WAVE WILL BE SUPPORTED BY A 60-80 KT 300 MB JET
STREAK OVER SWRN OREGON...WHICH IS A FAVORABLE POSITION FOR ADDITIONAL
CONVECTIVE SUPPORT. ALL IN ALL...MODELS ARE SHOWING SEVERAL
INGREDIENTS COMING TOGETHER FOR A CLASSIC PAC NW THUNDERSTORM EVENT.
THUNDERSTORM ACTIVITY COULD BEGIN EARLY SUNDAY MORNING AND PERSIST
THROUGH SUNDAY NIGHT INTO MONDAY MORNING. CLOUDS FROM THESE STORMS
MAY REDUCE THE AFTERNOON TEMPERATURES SOMEWHAT...BUT WITH MODELED
850MB TEMPERATURES AROUND 18C THINK THE INLAND TEMPERATURES WILL
STILL PEAK IN THE UPPER 80S TO LOWER 90S.

EXPECT A DEEPER MARINE PUSH SUNDAY NIGHT AND MONDAY AS THE TROUGH
PUSHES INLAND. HIGH PRESSURE WILL BUILD IN ITS WAKE AND PUSH THE
GREATEST THREAT FOR CONVECTION EAST OF THE CASCADES. 850 TEMPS WARM
CONSIDERABLY MONDAY AND TUESDAY WITH A 1000-500 MB THICKNESS RIDGE
NEAR THE OREGON COAST RANGE...AND EXPECT VERY HOT WEATHER WITH
TEMPERATURES PEAKING IN THE MID TO UPPER 90S. TJ

LONG TERM...AN UPPER RIDGE WILL MAINTAIN HOT WEATHER THROUGH WED.
MODELS HINT AT THE POSSIBILITY OF A LITTLE MARINE AIR SEEPAGE
BEGINNING WEDNESDAY...BUT MORE SO ON THURSDAY. DO NOT AGREE WITH THE
GFS SOLUTION OF HAVING A DEEP UPPER LOW SWING THROUGH LATE IN THE
WEEK. 12Z ECMWF KEEPS THE AREA IN NWLY FLOW ALOFT AND ONSHORE
LOW-LEVEL FLOW...KEEPING DAYTIME TEMPERATURES SLIGHTLY ABOVE AVERAGE.
A PRIMARY CONCERN WILL BE THE HIGH DEW POINTS...RESULTING IN
UNCOMFORTABLE NIGHTTIME PERIODS. WEISHAAR

&&

.AVIATION...STRATUS ABOUT 2000 FEET DEEP THIS MORNING UP AGAINST
THE COAST RANGE AND DOWN THE COLUMBIA TO KELSO AND IN THE SOUTH
VALLEY GAP TO EUGENE. INLAND AREAS WILL REMAIN VFR. STRATUS WILL
BURN BACK TO THE COASTAL AREAS BUT REMAIN IFR AND LIFR THROUGHOUT
THE DAY A FEW AREAS MAY LIFT TO CIGS AROUND 1200 FEET 20-22Z.
THERE IS A SLIGHT CHANCE OF THUNDERSTORMS DEVELOPING THIS
AFTERNOON MAINLY OVER THE CASCADES. TOMORROW A DISTURBANCE MOVING
INTO THE AREA FROM THE SOUTHWEST WILL INCREASE THE THUNDERSTORM
THREAT. SCHNEIDER

KPDX AND APPROACHES...VFR NEXT 24 HRS. SCHNEIDER

&&

.MARINE...HIGH PRES WILL REMAIN OVER THE NE PAC THROUGH THE
WEEKEND...KEEPING WINDS FROM THE N TO NW. THE GRADIENTS WILL
CONTINUE TO BE WEAK FOR LIGHTER WINDS THROUGH SUNDAY MORNING. THE
OFFSHORE HIGH AND THE INLAND THERMAL LOW WILL STRENGTHEN SUNDAY
FOR INCREASING NORTHWEST WINDS BY AFTERNOON AND LIKELY REACH SMALL
CRAFT ADVISORY LEVELS...THEN REMAIN BRISK INTO THE MIDDLE OF NEXT
WEEK.

SEAS WILL REMAIN LOW TODAY WITH THE LIGHTER WINDS ACROSS THE E
PACIFIC WATERS. BY THIS AFTERNOON THE NORTHWEST FRESH SWELL
ABATES UNDER LIGHT WINDS. NOAA WAVE MODEL INDICATES WE WILL START
TO SEE A LONG PERIOD WEST SWELL OF 2 TO 3 FT THIS AFTERNOON. ALL
IN ALL THE SEAS WILL REMAIN BELOW 5 FT UNTIL THE NORTHWESTERLY
WINDS INCREASE SUNDAY AFTERNOON.

EVEN THOUGH THERE IS RELATIVELY LIGHT INCOMING SWELL...THE
COMBINATION OF A VERY STRONG EBB SUNDAY MORNING AND A QUICK RAMP
UP FROM 3 FT TO NEAR 7 FT SEAS NEAR THE BAR DURING THE EBB HAS
PROMPTED ISSUANCE OF A SMALL CRAFT ADVISORY FOR SUNDAY MORNING.
MARINERS SHOULD USE CAUTION WHEN CROSSING THE BARS DURING THIS
VERY STRONG EBB. SCHNEIDER

&&

.FIRE WEATHER...A COMPLICATED FORECAST THE NEXT FEW DAYS WITH THE
COMBINATION OF INSTABILITY...HEAT...AND MOISTURE AT VARIOUS LEVELS.
FIRST OFF...THE MARINE LAYER DEEPENED A BIT MORE THAN ANTICIPATED
OVERNIGHT...ALLOWING LOW CLOUDS AND COOL ONSHORE FLOW TO PUSH FURTHER
INTO THE COASTAL VALLEYS THIS MORNING. HOWEVER THERE IS LITTLE
EVIDENCE OF THIS EAST OF THE COAST RANGE...WHERE TEMPERATURES ARE
WARMING UP QUICKLY AND EXPECTED TO REACH THE 90S IN MANY AREAS.
WITH THE HEAT ACROSS THE INLAND AREAS...A THERMAL TROUGH WILL LINGER
OVER THE WILLAMETTE VALLEY AND CASCADE CREST...LEADING TO MID-LEVEL
HAINES 5 OR 6 CONDITIONS TODAY. THE INSTABILITY MAY ALSO BE ENOUGH
TO TRIGGER A STRAY THUNDERSTORM OR TWO OVER THE CASCADE CREST THIS
AFTERNOON. HOWEVER THE MORE SIGNIFICANT AND WIDESPREAD THUNDERSTORM
THREAT WILL COME LATER TONIGHT AND SUNDAY AS AN UPPER LEVEL
DISTURBANCE OFF THE NORTHERN CALIFORNIA COAST LIFTS NORTHEAST TOWARD
THE PACIFIC NORTHWEST COAST. THIS SYSTEM WILL PULL IN SOME TROPICAL
MOISTURE...LEADING TO THE POTENTIAL FOR ELEVATED THUNDERSTORMS LATE
TONIGHT AND EARLY SUNDAY. THESE INITIAL THUNDERSTORMS MAY HAVE
LIMITED PRECIPITATION AT FIRST...BUT CHANCES FOR WETTING RAINS WILL
INCREASE AS THE AIR MASS MOISTENS UP SUNDAY. A SECOND ROUND OF
SURFACE-BASED THUNDERSTORMS IS POSSIBLE SUNDAY AFTERNOON...AND WOULD
TEND TO BE WETTER PRODUCING LOCALLY HEAVY RAIN.

THIS SYSTEM WILL LIKELY PULL THE THERMAL TROUGH EAST OF THE CASCADES
FOR NEXT WEEK...WITH THE HOTTEST WEATHER FOCUSING OVER THE MID
COLUMBIA BASIN. THIS WILL INDUCE GENERAL ONSHORE FLOW...HOWEVER THE
AIR MASS WILL STILL BE HOT ENOUGH EAST OF THE COAST RANGE FOR
TEMPERATURES TO REMAIN WELL ABOVE NORMAL WELL INTO NEXT WEEK.  WEAGLE

&&


.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HEAT ADVISORY UNTIL 2 PM PDT TUESDAY FOR CASCADE FOOTHILLS IN
     LANE COUNTY-CASCADES IN LANE COUNTY-CENTRAL COAST RANGE OF
     WESTERN OREGON-CENTRAL COLUMBIA RIVER GORGE-CENTRAL
     WILLAMETTE VALLEY-COAST RANGE OF NORTHWEST OREGON-GREATER
     PORTLAND METRO AREA-LOWER COLUMBIA-NORTHERN OREGON CASCADE
     FOOTHILLS-NORTHERN OREGON CASCADES-SOUTH WILLAMETTE VALLEY-
     UPPER HOOD RIVER VALLEY-WESTERN COLUMBIA RIVER GORGE.

WA...HEAT ADVISORY UNTIL 2 PM PDT TUESDAY FOR CENTRAL COLUMBIA RIVER
     GORGE-GREATER VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY-
     SOUTH WASHINGTON CASCADE FOOTHILLS-SOUTH WASHINGTON
     CASCADES-WESTERN COLUMBIA RIVER GORGE-WILLAPA HILLS.

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

&&

$$

MORE WEATHER INFORMATION ONLINE AT... HTTP://WEATHER.GOV/PORTLAND

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
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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