Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 302153 RRA
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PDT THU JUL 30 2015

.SYNOPSIS...STRONG UPPER LEVEL HIGH PRESSURE WILL KEEP VERY HOT
WEATHER IN PLACE THROUGH FRIDAY. TEMPERATURES WILL BEGIN TO COOL
SLIGHTLY ON SATURDAY...BUT WILL REMAIN WELL ABOVE NORMAL. A GRADUAL
COOLING TREND WILL THEN OCCUR AS THE RIDGING MOVES EASTWARD AND AN
UPPER LEVEL TROUGH APPROACHES FROM THE NORTH. CONDITIONS WILL RETURN
TO NEAR NORMAL FOR THE SECOND HALF OF NEXT WEEK AS THE UPPER TROUGH
MOVES ONSHORE. MONSOONAL MOISTURE FROM THE SOUTH WILL BRING A SLIGHT
CHANCE OF THUNDERSTORMS NEAR THE OREGON CASCADE CREST STARTING OVER
THE WEEKEND...WITH THE THREAT CONTINUING THROUGH MUCH OF NEXT WEEK.


&&

.SHORT TERM...TONIGHT THROUGH SUNDAY SUNDAY NIGHT...
VERY HOT AND DRY WEATHER WILL PERSIST THROUGH FRI AS A STRONG UPPER
LEVEL RIDGE REMAINS FIRMLY ENTRENCHED FROM THE DESERT SW UP THROUGH
THE PAC NW. SUBSIDENCE ASSOCIATED WITH THE RIDGE HAS DRIVEN 850 MB
TEMPS INTO THE 23 TO 25 C RANGE TODAY...WHICH IS BASICALLY RIGHT AT
THE CLIMATOLOGICALLY MAXIMUM VALUES RECORDED FOR THIS DATE. AS
EXPECTED...IT APPEARS THAT MOST OF THE INTERIOR LOWLANDS ARE HEADED
TOWARD HIGH TEMPS IN THE TRIPLE DIGITS THIS AFTERNOON. IT SEEMS LIKE
A VERY GOOD BET THAT MANY LOCATIONS WILL SEE THEIR HOTTEST TEMPS
SINCE AUG 2012. IN FACT...IT IS HIGHLY POSSIBLE THAT SOME SPOTS WILL
SEE THE WARMEST TEMPS SINCE JULY OF 2009. OVERNIGHT LOWS WILL NOT
PROVIDE MUCH RELIEF FOR THOSE WITHOUT AIR CONDITIONING...LIKELY ONLY
DROPPING INTO THE MID 60S OVER THE LOWLANDS. LOWS OVER THE COAST
RANGE AND CASCADE FOOTHILLS WILL BE EVEN WARMER DUE TO THE PRESENCE
OF A THERMAL BELT CAUSED BY THE STRONG LOW LEVEL SUBSIDENCE.

THE THERMAL TROUGH THAT IS DRAPED RIGHT OVER THE WILLAMETTE VALLEY
AND ADJACENT FOOTHILLS THIS AFTERNOON SHOULD DRIFT BACK TOWARD THE
COAST OVERNIGHT INTO FRI MORNING...THEN MOVE INLAND AGAIN DURING THE
DAY TOMORROW AS THE INTERIOR HEATS UP. EXPECT FRI WILL BE A NEAR
REPEAT OF TODAY.  THE FCST MODELS ARE INDICATING THAT A LITTLE BETTER
ONSHORE GRADIENT MAY BE GENERATED TOMORROW AFTERNOON IN RESPONSE TO
THE TROUGH MOVING INLAND. IT IS POSSIBLE THAT THIS MAY MODERATE TEMPS
OVER THE NORTHERN INTERIOR BY A COUPLE OF DEGREES...BUT IN GENERAL
EXPECT TEMPS TO BE PRETTY SIMILAR TO WHAT WE ARE SEEING TODAY. AN
EXCESSIVE HEAT WARNING REMAINS IN EFFECT FOR MOST OF THE INTERIOR
LOWLANDS THROUGH FRI NIGHT...AND A HEAT ADVISORY IS IN EFFECT FOR THE
COAST RANGE...CASCADE FOOTHILLS...AND THE LOWER COLUMBIA REGION.

THE UPPER LEVEL RIDGE WILL WEAKEN SLIGHTLY OVER THE PAC NW ON SAT.
MORE IMPORTANTLY...IT APPEARS THAT THE THERMAL TROUGH WILL MOVE EAST
OF THE CASCADES DURING THE DAY. THIS WILL BRING BETTER ONSHORE
FLOW AND LOWER TEMPS BY SEVERAL DEGREES...ALTHOUGH THEY WILL STILL BE
WELL ABOVE NORMAL. THE RIDGE WEAKENS FURTHER SUN AS UPPER LEVEL LOW
PRES BEGINS TO DIG SOUTH ALONG THE BRITISH COLUMBIA COAST. THIS WILL
CONTINUE THE GRADUALY COOLING TREND WITH INLAND HIGHS LIKELY IN THE
LOW TO MID 90S.

THE FCST MODELS ALSO CONTINUE TO INDICATE THAT SOME MONSOONAL
MOISTURE WILL MOVE IN FROM THE SOUTH OVER THE WEEKEND...BRINGING THE
POTENTIAL FOR SOME ISOLATED THUNDERSTORMS IN THE OREGON CASCADES.
THERE ARE NO OBVIOUS TRIGGERS FOR THE CONVECTION AT THIS TIME...BUT
THE FCST MODEL SOUNDINGS ARE SHOWING SOME MID LEVEL
INSTABILITY...ALBEIT NOT THAT IMPRESSIVE. IT WILL BE DIFFICULT TO
PINPOINT TIME PERIODS WHEN THUNDER WILL BE MORE PROBABLE UNTIL WE GET
CLOSER TO THE EVENT. PYLE

&&

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...AN UPPER LEVEL TROUGH
WILL SLOWLY DIG SOUTH ALONG THE PAC NW COAST THROUGH EARLY NEXT WEEK.
THIS WILL RESULT IN A RETURN TO A MORE TYPICAL NORTHWEST FLOW
PATTERN...WITH INCREASING ONSHORE FLOW AND MARINE INFLUENCE AND
GRADUALLY COOLING TEMPS. THE TROUGH IS MODELED TO MOVE ONSHORE DURING
THE SECOND HALF OF THE WEEK...AND SHOULD BRING TEMPS BACK TO NEAR OR
EVEN BELOW AVERAGE TEMPERATURES. THERE WILL ALSO BE CONTINUED CHANCES
FOR ISOLATED CASCADE THUNDERSTORMS FOR MUCH OF NEXT WEEK. PYLE

&&

.AVIATION...VFR CONDITIONS EXPECTED TO CONTINUE THROUGHOUT NW OREGON
AND SW WA THROUGH FRIDAY.

KPDX AND APPROACHES...VFR CONDITIONS FOR THE NEXT 24 HRS.

&&

.MARINE...SEAS HAVE REMAINED AT 5 TO 6 FT AND JUST BELOW THE SQUARE
SEA 7 FOOT CRITERIA. SPECTRAL GUIDANCE INDICATES THIS SHOULD REMAIN
THE CASE FOR AT LEAST THE NEXT 24 HOURS SO DECIDED TO CANCEL THE
HAZARDOUS SEAS ADVISORY FOR THE CENTRAL WATERS UN TIL WE GET
CLOSER TO THE NEXT EVENT FRIDAY EVENING AT THE EARLIEST. WINDS HAVE
BEEN MUCH LIGHTER ACROSS THE SO FAR TODAY BUT WILL INCREASE OVER
THE NEXT FEW HOURS THOUGH REMAIN A BIT MARGINAL FOR THE SMALL
CRAFT WIND ADVISORY CRITERIA. RAPIDSCAT AND ASCAT SATELLITE
DERIVED WINDS DO INDICATE SUSTAINED WINDS IN THE 15 TO 20 KT RANGE
ARE OCCURRING ACROSS THE OUTER WATERS SO WILL CONTINUE THE
ADVISORY FOR WINDS AS PLANNED.

NO BROAD CHANGES IN THE PRESSURE PATTERN THROUGH THE WEEKEND.
THIS WILL KEEP N TO NW WINDS BLOWING OVER THE WATERS THROUGH THE
WEEKEND...WITH A CLIMATOLOGICAL TENDENCY TO STRENGTHEN IN THE LATE
AFTERNOON AND OVERNIGHT HOURS AND WEAKEN IN THE MORNING HOURS EACH
DAY. EXPECT TO SEE WINDS GUSTING INTO SMALL CRAFT RANGE OFF AND ON
THROUGH THE WEEKEND.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...EXCESSIVE HEAT WARNING UNTIL 9 PM PDT FRIDAY FOR CENTRAL
     COLUMBIA RIVER GORGE-CENTRAL WILLAMETTE VALLEY-GREATER
     PORTLAND METRO AREA-SOUTH WILLAMETTE VALLEY-UPPER HOOD
     RIVER VALLEY-WESTERN COLUMBIA RIVER GORGE.

     RED FLAG WARNING UNTIL 11 PM PDT FRIDAY FOR CENTRAL OREGON
     CASCADE FOOTHILLS-EAST SLOPES OF THE CENTRAL OREGON COAST
     RANGE-MT. HOOD NATIONAL FOREST WEST OF CASCADE CREST-NORTH
     OREGON CASCADE FOOTHILLS-NORTH OREGON COAST RANGE-
     WILLAMETTE NATIONAL FOREST-WILLAMETTE VALLEY.

     HEAT ADVISORY UNTIL 9 PM PDT FRIDAY FOR CASCADE FOOTHILLS IN
     LANE COUNTY-CENTRAL COAST RANGE OF WESTERN OREGON-COAST
     RANGE OF NORTHWEST OREGON-LOWER COLUMBIA-NORTHERN OREGON
     CASCADE FOOTHILLS.

WA...EXCESSIVE HEAT WARNING UNTIL 9 PM PDT FRIDAY FOR CENTRAL
     COLUMBIA RIVER GORGE-GREATER VANCOUVER AREA-WESTERN
     COLUMBIA RIVER GORGE.

     RED FLAG WARNING UNTIL 11 PM PDT FRIDAY FOR CLARK COUNTY
     LOWLANDS-EAST WILLAPA HILLS-EXTREME SOUTH WASHINGTON
     CASCADES AND FOOTHILLS.

     HEAT ADVISORY UNTIL 9 PM PDT FRIDAY FOR I-5 CORRIDOR IN COWLITZ
     COUNTY.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 3 AM PDT FRIDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 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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