Excessive Heat in Oregon, August 18 to 19, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
200 PM PDT TUE AUG 18 2015

.SYNOPSIS...A VERY STRONG UPPER LEVEL RIDGE REMAINS ANCHORED OVER THE
NORTHEAST PACIFIC...AND EXTENDS INTO THE PACIFIC NORTHWEST WITH
NORTHWEST FLOW ALOFT. THIS HAS INDUCED A SURFACE THERMAL TROUGH OVER
WESTERN WASHINGTON AND OREGON AND ALONG THE COAST FOR HOT WEATHER
INLAND TODAY AND WEDNESDAY AND AT THE COAST MAINLY TODAY. LIGHT
OFFSHORE FLOW WILL RESULT IN AREAS OF SMOKE AND HAZE FROM NEARBY
FIRES. THE LOW LEVEL FLOW WILL TURN ONSHORE ALONG THE COAST WEDNESDAY
AFTERNOON AND INLAND BY WEDNESDAY EVENING AS A WEAK DISTURBANCE
APPROACHES AND MOVES THROUGH AND INCREASES THE ONSHORE FLOW THROUGH
THURSDAY. A SECOND TRAILING AND STRONGER UPPER TROUGH WILL APPROACH
THE PACIFIC NORTHWEST THURSDAY NIGHT AND MOVE THROUGH THE REGION
FRIDAY FOR EVEN A SMALL CHANCE AT A FEW SHOWERS IN THE NORTH PART OF
THE FORECAST AREA. DRY AND WARMER WEATHER WILL RETURN THIS WEEKEND AS
A WEAKER UPPER LEVEL RIDGE MOVES OVER THE PACIFIC NORTHWEST. SOME
MODERATION IS POSSIBLE AGAIN BY THE MIDDLE OF NEXT WEEK AS ANOTHER
UPPER TROUGH BEGINS TO SET UP OVER THE NORTHEAST PACIFIC.
&&

.SHORT TERM...TONIGHT THROUGH FRIDAY...A STRONG UPPER LEVEL RIDGE
REMAINS ANCHORED OVER THE NORTHEAST PACIFIC WITH NORTHWEST FLOW ALOFT
INTO THE PACIFIC NORTHWEST ON THE EASTERN FLANK OF THE UPPER RIDGE.
THIS HAS INDUCED A SURFACE THERMAL TROUGH OVER WESTERN WASHINGTON AND
WESTERN OREGON WITH LIGHT OFFSHORE FLOW. THIS HAS ALL COMBINED FOR A
HOT DAY ACROSS SOUTHWEST WASHINGTON AND NORTHWEST OREGON TODAY...WITH
70S AND 80S AT THE COAST AND GENERALLY 90S TO AROUND 100 INLAND. SO
FAR TEMPS THIS AFTERNOON ARE RUNNING 5 TO 7 DEGREES ABOVE THOSE
YESTERDAY. WILL STAY WITH THE EXCESSIVE HEAT WARNING FOR TODAY FOR
THE WILLAMETTE VALLEY AND THE PORTLAND AND VANCOUVER METRO
AREAS...WITH A HEAT ADVISORY FOR MOST OF THE REMAINDER OF THE INLAND
AREAS TODAY. WILL STAY WITH A HEAT ADVISORY EAST OF THE COASTAL
MOUNTAINS FOR WEDNESDAY. WILL CONTINUE THE RED FLAG WARNING AS IS
THROUGH WEDNESDAY AS WELL.

WEDNESDAY WILL START OUT AS ANOTHER VERY WARM DAY WITH THE THERMAL
TROUGH NEAR THE COAST. THIS WILL KEEP THE AREA CLEAR AND DRY EXCEPT
FOR THE AREAS OF SMOKE AND HAZE. THE NORTHWEST FLOW ALOFT INCREASES
THROUGH THE DAY AS A SYSTEM CURRENTLY ALONG THE NORTH B.C. COAST
APPROACHES. WE SHOULD START TO SEE MARINE CLOUDS MOVE INTO THE
COASTAL WATERS ON WEDNESDAY...AND POSSIBLY REACH THE COAST LATER IN
THE AFTERNOON. THE COAST WILL START OUT WARM BUT THEN THE SEA BREEZE
WILL CAP TEMPS WEDNESDAY BELOW THOSE OF TODAY.

THERE IS ALSO A SOUTHERLY STRATUS SURGE MOVING ONTO THE SOUTH OREGON
COAST FROM CALIFORNIA THIS AFTERNOON THAT THE MODELS INDICATE WILL
REACH THE NEWPORT AREA AROUND WEDNESDAY MORNING...BRINGING COOLING TO
THAT AREA AS WELL.

INLAND ON WEDNESDAY WILL LIKELY STILL BE HOT...PERHAPS NOT QUITE AS
HOT AS TODAY BUT CLOSE. THE COAST RANGE AND PERHAPS AROUND KELSO WILL
START TO SEE ENOUGH ONSHORE BREEZES IN THE AFTERNOON TO KEEP THEM
BELOW HEAT ADVISORY THRESHOLDS...BUT INLAND MAY NOT SEE ENOUGH
ONSHORE BREEZES UNTIL WEDNESDAY EVENING.

THE ONSHORE FLOW WILL INCREASE IN EARNEST ACROSS THE FORECAST AREA
WEDNESDAY NIGHT AS THE WEAK SYSTEM ALONG THE NORTH B.C. COAST REACHES
OUR AREA IN A MUCH WEAKENED FORM. WE MAY SEE A WEAK BOUNDARY PRODUCE
SOME DRIZZLE ALONG THE COAST WEDNESDAY NIGHT AND THURSDAY MORNING.
SHOULD SEE AMPLE LOW CLOUDS SPREAD INLAND...AND COVER MOST OF THE
NORTH VALLEY AREAS THURSDAY MORNING...BUT PROBABLY HAVE A HARDER TIME
REACHING THE SOUTH VALLEY THOUGH. TEMPS WILL BE MUCH COOLER INLAND
THURSDAY...DOWN A GOOD 20 DEGREES OR MORE MOST AREAS. ALSO LOOK FOR
INCREASING GUSTY WEST WINDS THROUGH THE GORGE AS WELL.

A TRAILING RATHER SIGNIFICANT UPPER TROUGH WILL REINFORCE THE ONSHORE
FLOW FOR THURSDAY NIGHT AND FRIDAY. THE MAIN PART OF THE UPPER TROUGH
WILL TRACK THROUGH SOUTHERN B.C. AND NORTHERN WASHINGTON...BUT ENOUGH
OF THE TROUGH WILL EXTEND TOWARD OREGON FOR MORE CLOUDS...PERHAPS A
FEW SHOWERS IN OUR NORTHERN AND COASTAL FORECAST ZONES...AND EVEN
SOME BREEZY CONDITIONS IN THE HIGHER CASCADES. TOLLESON

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...THE MODELS AGREE WITH A
WEAK UPPER RIDGE MOVING INTO THE PACIFIC NORTHWEST THIS WEEKEND FOR
WARMER AND DRY CONDITIONS RETURNING AS A SURFACE THERMAL TROUGH
BUILDS BACK OVER WESTERN OREGON. AN UPPER TROUGH BEGINS TO SLOWLY
DEVELOP IN THE NORTHEAST PACIFIC EARLY NEXT WEEK AND SLOWLY SAG SOUTH
OFF THE COAST. THIS WILL TURN THE FLOW ALOFT MORE
SOUTHWESTERLY...GRADUALLY INCREASE THE ONSHORE FLOW AND BRING A NIGHT
AND MORNING LOW CLOUD REGIME TO THE AREA. THE MODELS ARE VARYING ON
HOW MUCH THE UPPER TROUGH MAY SAG SOUTH IN THE MIDDLE OF NEXT
WEEK...AND THIS WILL ULTIMATELY AFFECT HOW MUCH COOLING WE SEE AND IF
ANY PRECIPITATION IS POSSIBLE. THE WESTERN PACIFIC IS QUITE ACTIVE
ALONG THE ITCZ AND THERE IS QUITE A BIT OF TROPICAL ACTIVITY
OCCURRING THAT WILL LIKELY BE ABSORBED INTO THE WESTERLIES. THIS WILL
PROBABLY AFFECT OUR WEATHER EVENTUALLY...THOUGH MODEL SOLUTIONS COULD
BE A BIT UNSTABLE AT LONGER RANGES FOR A WHILE. TOLLESON
&&

.AVIATION...VFR CONDITIONS CONTINUE NEXT 24 HOURS. SKIES WILL REMAIN
GENERALLY CLOUD FREE BUT HAZY CONDITIONS FROM COAST RANGE EASTWARD
WILL CONTINUE DUE TO SMOKE FROM NEARBY WILDFIRES. HOWEVER...DO NOT
EXPECT RESTRICTIONS TO VSBYS. GUSTY N WINDS PROBABLE ALONG THE COAST
THIS AFTERNOON AND EVENING. THERE IS A SOUTHERLY WIND REVERSAL AND
COINCIDENT LIFR MARINE STRATUS LAYER MAKING ITS WAY UP THE COAST...
MOVING INTO OREGON JUST IN THE PAST COUPLE OF HOURS. THERE IS SOME
INDICATION THAT THIS PUSH WILL MAKE IT AS FAR NORTH AS ABOUT NEWPORT
BUT CONFIDENCE IS LOW AT THIS POINT. AT ITS CURRENT PACE...THE
STRATUS AND WIND REVERSAL COULD MAKE IT TO NEWPORT AS EARLY AS THIS
EVENING IF IT MAKES IT THAT FAR NORTH.

KPDX AND APPROACHES...VFR THE NEXT 24 HOURS UNDER CLOUD FREE SKIES.
HOWEVER...HAZY CONDITIONS CONTINUE TUE DUE TO SMOKE FROM NEARBY
FIRES. BOWEN/CULLEN
&&

.MARINE...AS DURING THE PAST COUPLE OF DAYS...WINDS ARE SLOW TO PICK
UP TODAY WITH BUOY 50 STILL REPORTING JUST 14 KT SUSTAINED. WINDS
WILL PICK UP OVER THE NEXT FEW HOURS THOUGH...AND REMAIN ELEVATED
THROUGH THE OVERNIGHT HOURS AGAIN. EXTENDED THE SMALL CRAFT ADVISORY
FOR WINDS FOR THE OFFSHORE WATERS THROUGH TOMORROW NIGHT AS IT LOOK
LIKE MORNING BREAK IN WINDS WILL NOT BE TOO SIGNIFICANT. THERMAL LOW
PRESSURE WILL WEAKEN SOME TOMORROW...LIMITING NEARSHORE WINDS
SOMEWHAT...SO HAVE KEPT THOSE ZONES SEPARATE AND ISSUED A SEPARATE
SMALL CRAFT ADVISORY FOR WINDS THERE FOR A SHORTER PERIOD OF TIME
TOMORROW.

SEAS REMAIN IN THE 6 TO 7 FT RANGE BUT THE DOMINANT WAVE PERIOD HAS
INCREASED TO 8 SECONDS AND SHOULD GET TO AROUND 9 SECONDS DURING
LATER TODAY AS FRESH SWELL COMES IN FROM THE NORTHWEST. STILL THINK A
SMALL CRAFT ADVISORY WILL NOT BE WARRANTED FOR THE NEXT 24
HOURS...BUT SEAS WILL REMAIN STEEP AT AROUND 7 FT AT 8 TO 9 SECONDS.

SWELL CONTINUES TO BUILD TOMORROW AND MAY BE EVEN A BIT HIGHER THAN
MODELS ARE CURRENTLY SHOWING WITH STRONG NW WINDS OFF VANCOUVER
ISLAND PUSHING SWELL ENERGY OUR WAY. COULD SEE SOME 10 FT SEAS OR 9
FT AT 9 SECONDS TOMORROW NIGHT BUT WILL WAIT TO ISSUE A SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS DUE TO LOW CONFIDENCE AT THIS POINT.

WINDS DECREASE SOME ON THURSDAY BELOW 20 KT AND MAY SEE A PERIOD
WHERE WE DO NOT NEED A SMALL CRAFT ADVISORY FOR WINDS. HOWEVER LOW
PRESSURE BUILDS OVER VANCOUVER ISLAND FRIDAY AND INCREASES THE
GRADIENT ONCE AGAIN. FOR NOW IT LOOKS LIKE THERMAL LOW PRESSURE
RETURNS DURING THE WEEKEND TAKING US RIGHT BACK INTO THE PATTERN WE
ARE CURRENTLY SEEING WITH INCREASING WINDS IN THE LATE AFTERNOON AND
EVENING HOURS. SEAS WILL REMAIN CHOPPY AND ABOVE 6 FEET THROUGH MUCH
OF THE WEEK. BOWEN/CULLEN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...RED FLAG WARNING UNTIL 6 PM PDT WEDNESDAY 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-WILLAMETTE NATIONAL FOREST-
     WILLAMETTE VALLEY.

     HEAT ADVISORY UNTIL 6 PM PDT WEDNESDAY FOR CASCADE FOOTHILLS IN
     LANE COUNTY-CENTRAL COLUMBIA RIVER GORGE-NORTHERN OREGON
     CASCADE FOOTHILLS-UPPER HOOD RIVER VALLEY-WESTERN COLUMBIA
     RIVER GORGE.

     EXCESSIVE HEAT WARNING UNTIL 9 PM PDT THIS EVENING FOR CENTRAL
     WILLAMETTE VALLEY-GREATER PORTLAND METRO AREA-SOUTH
     WILLAMETTE VALLEY.

     HEAT ADVISORY FROM 9 PM THIS EVENING TO 6 PM PDT WEDNESDAY FOR
     CENTRAL WILLAMETTE VALLEY-GREATER PORTLAND METRO AREA-SOUTH
     WILLAMETTE VALLEY.

     HEAT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR CENTRAL COAST
     RANGE OF WESTERN OREGON-COAST RANGE OF NORTHWEST OREGON-
     LOWER COLUMBIA.

WA...HEAT ADVISORY UNTIL 6 PM PDT WEDNESDAY FOR CENTRAL COLUMBIA
     RIVER GORGE-WESTERN COLUMBIA RIVER GORGE.

     EXCESSIVE HEAT WARNING UNTIL 9 PM PDT THIS EVENING FOR GREATER
     VANCOUVER AREA.

     HEAT ADVISORY FROM 9 PM THIS EVENING TO 6 PM PDT WEDNESDAY FOR
     GREATER VANCOUVER AREA.

     HEAT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR I-5 CORRIDOR IN
     COWLITZ COUNTY-SOUTH WASHINGTON CASCADE FOOTHILLS.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 AM PDT THURSDAY 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 WINDS FROM 1 PM WEDNESDAY TO MIDNIGHT
     PDT WEDNESDAY NIGHT FOR COASTAL WATERS FROM CAPE SHOALWATER
     WA TO CASCADE HEAD OR OUT 10 NM-COASTAL WATERS FROM CASCADE
     HEAD TO FLORENCE OR OUT 10 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CASCADE HEAD TO FLORENCE OR OUT 10 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.