Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 031530
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
830 AM PDT FRI JUL 3 2015

.SYNOPSIS...LITTLE CHANGE IN THE OVERALL WEATHER PATTERN IS EXPECTED
THROUGHOUT THIS HOLIDAY WEEKEND...WITH A STRONG UPPER LEVEL RIDGE
RESULTING IN PERSISTENT INLAND HEAT. THE RIDGE IS KEEPING THE MARINE
LAYER SHALLOW...WITH ITS COOLING INFLUENCE GENERALLY LIMITED TO THE
COAST AND ADJACENT COASTAL VALLEYS. INLAND VALLEYS REMAIN WELL ABOVE
NORMAL WITH TEMPERATURES IN THE 90S THROUGH AT LEAST SUNDAY...
POSSIBLY LONGER. AN UPPER LEVEL LOW CUTTING OFF NEAR THE CENTRAL
CALIFORNIA COAST MAY SPIN SOME MOISTURE UP TOWARD THE LANE COUNTY
CASCADES...BUT THE BEST CHANCE OF THUNDER WILL BE SOUTH TOWARD THE
OR/CA BORDER. SOME COOLING IS POSSIBLE LATER NEXT WEEK AS THE UPPER
RIDGE LOOSENS ITS GRIP...BUT WELL ABOVE NORMAL TEMPERATURES APPEAR
LIKELY THROUGH AT LEAST THE MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...NOT A WHOLE LOT HAS CHANGED IN THE PAST 24 HOURS...SO
TODAY NOT LIKELY TO DIFFER MUCH FROM THU. ONSHORE FLOW WAS A BIT
STRONGER THIS MORNING WHICH ALLOWED MARINE CLOUDS TO PUSH A LITTLE
FURTHER UP THE LOWER COLUMBIA PAST KLS. A COMBINATION OF A BIT
STRONGER ONSHORE FLOW AND A LITTLE WEAKENING OF THE RIDGE ALOFT MAY
TAKE A COUPLE DEGREES OFF THE HIGH TEMPS TODAY.

REMAINDER OF SHORT TERM DISCUSSION UNCHANGED...THROUGH SUNDAY...HOT
WEATHER CONTINUES FOR ALL BUT THE COAST OF SOUTHWEST WASHINGTON AND
NORTHWEST OREGON AS A STRONG AND SPRAWLING UPPER LEVEL RIDGE EXTENDS
FROM TEXAS THROUGH OREGON AND INTO NE PACIFIC. THIS RIDGE WILL
LIKELY KEEP THE MARINE LAYER TOO SHALLOW FOR ANY APPRECIABLE COOLING
IN THE INLAND VALLEYS...AT LEAST THROUGH SUNDAY AND PROBABLY LONGER.

MODEL 850 MB TEMPS REMAIN IN THE +20 TO +22 DEG C RANGE...YIELDING
TEMPS WELL INTO THE 90S FOR THE INLAND VALLEYS GIVEN FULL DAYTIME
SUNSHINE THROUGH SUNDAY. SFC PRESSURE GRADIENTS REMAIN ONSHORE...
KEEPING THE COAST AND ADJACENT COASTAL VALLEYS MUCH COOLER WITH AREAS
OF NIGHT AND MORNING LOW CLOUDS CLEARING EACH AFTERNOON FRI/SAT.

A COLD FRONT MOVING ACROSS WESTERN CANADA SAT/SAT NIGHT WILL LIKELY
BE TOO FAR NORTH AND EAST TO HAVE MUCH OF AN IMPACT ON THE MARINE
LAYER. IN FACT...HIGH PRESSURE BUILDING INTO INTERIOR BC MAY SHOVE
PART OF THE THERMAL LOW OFFSHORE...WEAKENING ONSHORE PRESSURE
GRADIENTS AND CAUSING SUNDAY TO BE NEARLY AS HOT AS YESTERDAY.
PUSHING THE THERMAL LOW OFFSHORE MAY INVITE A SOUTHERLY WIND
REVERSAL/SURGE TO PUSH UP THE COAST...BUT AT THIS POINT IT APPEARS
DOUBTFUL THE RESULTING SURGE OF MARINE AIR WILL BE DEEP ENOUGH TO
HAVE A LARGE IMPACT ON INLAND TEMPS. IF IT DOES...THE BEST CHANCE FOR
A COOLDOWN MONDAY WOULD BE NEAR EUGENE. THE HEAT ADVISORY REMAINS IN
PLACE FOR MOST INLAND AREAS THROUGH SUNDAY...WILL HOLD ON TO THAT
THOUGH IT MAY NEED TO BE EXTENDED INTO THE NIGHT HOURS AS RELIEF WILL
BE SLOW TO COME INLAND.

WILL ALSO NEED TO WATCH AN UPPER LOW FORMING OFF THE CALIFORNIA
COAST...WHICH IS EXPECTED TO REMAIN NEARLY STATIONARY THE NEXT FEW
DAYS. THIS SYSTEM MAY TRIGGER AFTERNOON AND EVENING THUNDER AS FAR
NORTH AS THE SOUTH OREGON CASCADES THIS WEEKEND...WITH SOME DEBRIS
CLOUDINESS CLIPPING LANE COUNTY. UNLESS THE UPPER LOW WOBBLES A
LITTLE FURTHER NORTH THAN PRESENTLY EXPECTED...INSTABILITY WILL BE
LACKING FOR THUNDER IN OUR CASCADES THIS WEEKEND. KEPT MENTION OF
THUNDER OUT OF THE FORECAST THROUGH SUNDAY.  WEAGLE

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
SUNDAY NIGHT THROUGH THURSDAY...THE EXTENDED PERIOD BEGINS WITH HIGH
AMPLITUDE 500 MB REX BLOCK OVER THE EASTERN PACIFIC AND OR/WA IN WEAK
TROUGH OR COL SEPARATING SWRN U.S. RIDGE AND ERN PACIFIC/GULF OF AK
RIDGE. DESPITE THE WEAK TROUGHINESS...AMS REMAINS WARM WITH ABOVE
AVERAGE HEIGHTS AND NLY LOW LEVEL FLOW. LITTLE CHANGE OCCURS IN
OVERALL PATTERN INTO TUESDAY. BY WEDNESDAY...BLOCK BEGINS TO BREAK
DOWN WITH RIDGING TO THE NORTH AND PACIFIC CUTOFF MAKING SLOW EWD
PROGRESS TOWARD CNTRL CA CSTLN. DETERMINISTIC MODELS AND GEFS MEMBERS
IN GOOD AGREEMENT THROUGH TUESDAY...WITH DIFFERENCES THEREAFTER
MAINLY IN AMPLITUDE OF RIDGING OVER OR/WA/WRN CANADA AND POSITION OF
ERN PACIFIC CUTOFF. DESPITE THE INCREASING UNCERTAINTY MID
WEEK...WARM TEMPERATURES NEARLY CERTAIN /10-12 DEG ABOVE NORMAL/ BUT
INFLUENCE OF ERN PACIFIC CUTOFF PROVIDES A CHANCE OF INLAND/MOUNTAIN
THUNDERSTORMS TUESDAY-THURSDAY. BRIGHT

&&

.AVIATION...STABLE WESTERLY FLOW CONTINUES ALOFT. EXPECT WIDESPREAD
VFR TO REMAIN IN CONTROL FOR THE INLAND TAF SITES OVER THE NEXT 24
HRS. IFR MARINE STRATUS FORMED AT THE COAST OVERNIGHT AND PUSHED
UP THE COLUMBIA RIVER AS FAR AS KELSO. THE COASTAL STRATUS APPEARS
TO BE A BIT THICKER THAN YESTERDAY...SO EXPECT A SLOWER
BURNOFF...LIKELY BETWEEN 18Z AND 20Z. SIMILAR TO THE PAST FEW
DAYS...BREEZY NORTHWESTERLY WINDS TO DEVELOP DURING THE LATE
AFTERNOON AND EARLY EVENING. STRATUS SHOULD RETURN TO THE COAST
THIS EVENING.

KPDX AND APPROACHES...VFR WILL PERSIST FOR THE NEXT 24 HOURS.
BREEZY NORTHWESTERLY WINDS TO DEVELOP DURING THE LATE AFTERNOON
AND EARLY EVENING. PYLE

&&

.MARINE...HIGH PRES OVER THE NE PAC AND THERMAL LOW PRES INLAND
WILL CONTINUE TO PRODUCE BREEZY NORTHERLY WINDS OVER THE COASTAL
WATERS INTO THE WEEKEND. THE BEST WINDS ARE FURTHER
OFFSHORE...WHERE A SMALL CRAFT ADVISORY REMAINS IN EFFECT. WINDS
ARE LIGHTER NEAR SHORE...BUT EXPECT THEM TO PICK UP LATER
THIS AFTERNOON...WITH GUSTS OF 20 TO 25 KT LIKELY. THE THERMAL
LOW PRES WILL MOVE WESTWARD THIS WEEKEND...WEAKENING THE PRES
GRADIENT OVER THE WATERS. THIS SHOULD ALLOW WINDS ACROSS ALL
WATERS TO DROP BELOW 20 KT LATE IN THE WEEKEND AND INTO NEXT WEEK.
THE FCST MODELS ARE INDICATING THAT A SOUTHERLY WIND REVERSAL WILL
OCCUR LATE SUN.

EXPECT PERIODS OF STEEP AND CHOPPY SEAS OVER THE OUTER WATERS TO
CONTINUE INTO THIS WEEKEND WITH COMBINED SEAS OF 7 TO 8 FT AND A
DOMINATE PERIOD AROUND 8 SECONDS. STRONG WINDS OFF OF VANCOUVER
ISLAND WILL PRODUCE A BUILDING NW SWELL THIS WEEKEND THAT COULD
PUSH SEAS TO NEAR 10 FT. SEAS WILL SUBSIDE EARLY NEXT WEEK TO
AROUND 4 TO 5 FT.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...     HEAT ADVISORY UNTIL 6 PM PDT SUNDAY FOR CASCADE FOOTHILLS IN
     LANE COUNTY-CENTRAL COAST RANGE OF WESTERN OREGON-CENTRAL
     COLUMBIA RIVER GORGE-CENTRAL WILLAMETTE VALLEY-GREATER
     PORTLAND METRO AREA-LOWER COLUMBIA-NORTHERN OREGON CASCADE
     FOOTHILLS-SOUTH WILLAMETTE VALLEY-UPPER HOOD RIVER VALLEY-
     WESTERN COLUMBIA RIVER GORGE.

WA...HEAT ADVISORY UNTIL 6 PM PDT SUNDAY FOR CENTRAL COLUMBIA RIVER
     GORGE-GREATER VANCOUVER AREA-I-5 CORRIDOR IN COWLITZ COUNTY-
     SOUTH WASHINGTON CASCADE FOOTHILLS-WESTERN COLUMBIA RIVER
     GORGE.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 7 AM PDT SATURDAY FOR
     WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM 10
     TO 60 NM-WATERS FROM CASCADE HEAD TO FLORENCE OR FROM 10 TO
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 7 AM PDT SATURDAY
     FOR WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM
     10 TO 60 NM-WATERS FROM CASCADE HEAD TO FLORENCE OR FROM 10
     TO 60 NM.

&&

$$

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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