Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 012228
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
327 PM PDT SAT AUG  1 2015

.SYNOPSIS...A NEGATIVELY TILTED UPPER LEVEL RIDGE WITH 500 MB HEIGHTS
AROUND 590 DM WILL CONTINUE OVER SOUTHWEST WASHINGTON AND NORTHWEST
OREGON THIS AFTERNOON. AN UPPER LEVEL LOW OFF THE CALIFORNIA COAST
WILL STEER SOME MONSOONAL MOISTURE FROM THE DESERT SOUTHWEST INTO
WESTERN OREGON THIS AFTERNOON THROUGH SUNDAY INTO MONDAY. THIS WILL
BRING AN INCREASING THREAT OF THUNDERSTORMS TO THE OREGON CASCADES
INITIALLY...WITH SOME DEBRIS MOISTURE POSSIBLE WEST OF THE CASCADES
LATER TONIGHT THROUGH SUNDAY INTO MONDAY. THIS COMBINED WITH A SLOWLY
DEVELOPING MARINE LAYER ALONG THE COAST THAT WILL EVENTUALLY PUSH THE
THERMAL TROUGH EAST OF THE CASCADES ON SUNDAY WILL BRING GRADUAL
COOLING TO THE AREA AFTER TODAY. AN UPPER LEVEL TROUGH WILL SWING IN
FROM THE NORTHWEST IN THE MIDDLE OF NEXT WEEK FOR MORE COOLING AND
POSSIBLY EVEN SOME COASTAL DRIZZLE.
&&

.SHORT TERM...THE SYNOPTIC SCALE SET UP THIS AFTERNOON CONTINUES TO
HAVE A POSITIVELY TILTED UPPER RIDGE OVER THE WESTERN U.S. WITH 590
DM 500MB HEIGHTS INTO NORTHWEST OREGON AND SOUTHWEST WASHINGTON.
THERE IS A SHALLOW MARINE LAYER ALONG THE COAST WITH NORTHERLY LOW
LEVEL FLOW ALONG THE COAST. AN UPPER LOW IS OFF THE CALIFORNIA COAST
WITH A SOUTHEASTERLY STEERING FLOW SPREADING MONSOONAL THUNDERSTORM
MOISTURE NORTHWARD ALONG THE SIERRAS TOWARD WESTERN OREGON...WITH
SOME LIGHTNING NEAR MEDFORD THIS MORNING. THERE IS SOME SOUTHERLY LOW
LEVEL WINDS ALONG THE SOUTH OREGON COAST WITH DEEPER STRATUS
THERE...BUT THE MODELS INDICATED THESE WINDS WILL HAVE TROUBLE
REACHING OUR COAST VERY SOON DESPITE THE FAVORABLE WIND FLOW ALOFT.

WE ARE SEEING ANOTHER HOT DAY TODAY...WITH 850 MB TEMPS AROUND 23 DEG
C TODAY...SIMILAR TO THOSE FRIDAY. WE ARE SEEING A BIT OF THE
CONVECTIVE CLOUD TO OUR SOUTH SPREADING INTO LANE COUNTY. WE ARE
RUNNING A COUPLE OF DEGREES BEHIND FRIDAY AT THIS TIME...BUT STILL
SHOULD GET WELL UP INTO THE 90S AND POSSIBLE TOUCH 100 AT A FEW
SPOTS. REGARDING THE THUNDERSTORM DEBRIS MOVING NORTHWARD...THE
MODELS ALL SAY THE MAIN CHANCE OF INSTABILITY THIS AFTERNOON AND
EVENING WILL BE IN THE CASCADES AND HAVE CONTINUED THAT IDEA FOR NOW
BUT IT WILL BARE WATCHING.

CONVECTIVE DEBRIS CONTINUES TO SPREAD NORTH LATE TONIGHT AND THROUGH
THE DAY SUNDAY AND SUNDAY NIGHT...SO NEARLY THE ENTIRE FORECAST AREA
WILL SEE MORE CLOUDS SUNDAY INTO MONDAY THAN WE HAVE SEEN SINCE LAST
WEEKEND. QUESTION CONTINUES TO BE WHERE THE THUNDERSTORMS WILL BE
LOCATED. THE MODELS SEEM PRETTY CERTAIN THAT THEY WILL SPREAD FARTHER
NORTH THROUGH THE OREGON CASCADES ON SUNDAY...BUT FEEL THAT THERE IS
A CHANCE TOWARD THE COAST RANGE ON SUNDAY. MADE SOME ADJUSTMENTS TO
THE MORNING FORECAST ALONG THOSE LINES AND WILL STAY WITH THAT IDEA
IN THE AFTERNOON PACKAGE.

THE MODELS SHOW A SHORT WAVE CURRENTLY IN SOUTHERN NEVADA SPREADING
NORTH THROUGH WESTERN OREGON AND INTO SOUTHWEST WASHINGTON SUNDAY
NIGHT INTO MONDAY MORNING...LIKELY MODULATED BY CONVECTIVE ACTIVITY
ON SUNDAY. THIS WILL LIKELY SPREAD THUNDERSTORMS INTO THE SOUTH
WASHINGTON CASCADES. THIS COULD BE A BETTER TRIGGER FOR SOME
CONVECTION IN THE VALLEYS AS WELL AND CLOSE TO THE COAST RANGE.

THE MODELS SHOW THE THERMAL TROUGH EXTENDING BACK OVER THE WESTERN
VALLEY AGAIN THIS AFTERNOON...BUT MOVING EAST OF THE CASCADES ON
SUNDAY AS ONSHORE FLOW BEGINS TO INCREASE. AFTER POSSIBLY FLIRTING
WITH 100 AGAIN IN MANY INLAND AREAS AGAIN THIS AFTERNOON...TEMPS
INLAND WILL PROBABLY FALL INTO 90 TO 95 RANGE ON SUNDAY. THE ONSHORE
FLOW WILL CONTINUE TO INCREASE INTO MONDAY WITH POSSIBLY SOME MARINE
CLOUDS REACHING PORTLAND AND EUGENE. THIS MAY BE ENOUGH TO KEEP
INLAND TEMPS NOT MUCH ABOVE 90..IF THAT.

THUNDER AFTER MONDAY MORNING WILL BECOME MORE CONFINED TO THE HIGHER
CASCADES AND IN THE SOUTH AS THE UPPER FLOW STARTS TO TURN MORE
SOUTHWESTERLY MONDAY AFTERNOON AND EVENING.

THE MODELS INDICATE A BIT BETTER MARINE INTRUSION INLAND ON TUESDAY
MORNING AND WENT WITH MORE MORNING CLOUDS IN THE NORTH VALLEY THEN.
TEMPS WILL BE IN THE LOWER TO MID 80S IN THE NORTH VALLEY AND MID TO
UPPER 80S IN THE SOUTH VALLEY. THE BEST CHANCE OF ANY THUNDER ON
TUESDAY AFTERNOON WILL BE THE CENTRAL OREGON CASCADES...BUT LIGHT
SOUTHWEST FLOW ALOFT MAKES THAT NOT CERTAIN EITHER. TOLLESON

.LONG TERM...THE GENERAL TREND IN THE EXTENDED PERIOD WILL BE
TOWARDS COOLER WEATHER. MODELS CONTINUE TO SHOW AN UPPER LEVEL
TROUGH BRUSHING BY THE REGION LATE TUESDAY...BUT KEEPS MOST OF THE
ENERGY TO OUR NORTH. WILL KEEP A SLIGHT CHANCE OF THUNDERSTORMS OVER
THE LANE COUNTY CASCADES FOR LATE TUESDAY DUE TO SOME LINGERING
INSTABILITY. TEMPERATURES RETURN TOWARDS SEASONAL NORMALS BY
WEDNESDAY...BUT WILL INCREASE SLIGHTLY FOR THE LATTER HALF OF THE
WEEK AS A WEAK UPPER LEVEL RIDGE BUILDS INTO THE PACIFIC NORTHWEST.
MODELS DIVERGE SIGNIFICANTLY AS WE GO INTO NEXT WEEKEND. AS
SUCH...HAVE USED A BROAD BRUSH APPROACH FOR NEXT WEEKEND AND
INTRODUCED A SLIGHT CHANCE OF SHOWERS OVER THE SOUTH WASHINGTON
CASCADES AND A SLIGHT CHANCE OF THUNDERSTORMS FOR THE OREGON
CASCADES. /64
&&

.AVIATION...VFR INLAND. A RIBBON OF STRATUS CONTINUES TO HUG THE
COASTLINE AND IS SHOWING SIGNS OF MOVING ONSHORE AFTER BURNED OFF THE
IMMEDIATE COASTLINE EARLIER. STILL FEEL THERE IS A MODERATE OR BETTER
CHANCE OF IT RETURNING INLAND THIS EVENING WITH IMPACTS LIKELY
LIMITED TO KAST AND KONP ONCE AGAIN TONIGHT. CONVECTION DEBRIS CLOUDS
FROM EARLIER ARE REMAINING HIGH LEVEL WITH RADAR INDICATING SOME
VIRGA FROM THEM. NEW CONVECTION IS DEVELOPING OVER THE SISKIYOUS AND
THE SOUTH CASCADES WITH FURTHER DEVELOPMENT EXPECTED TO OCCUR OVER
THE CENTRAL CASCADES THIS AFTERNOON AND EVENING. BETTER CHANCE FOR
IMPACTS TO THE TAF TERMINALS WILL HAPPEN OVERNIGHT FROM ADDITIONAL
DEBRIS DRIFTING NORTH BRINGING ALTO CUMULUS AND SOME LIGHT SHOWER
POTENTIAL. DEEPER CONVECTION BECOMES POSSIBLE CLOSER TOWARD 03/00Z
FOR INLAND AREAS INCLUDING KEUG AND NORTH THROUGH KSLE.

KPDX AND APPROACHES...VFR CONDITIONS ALTHOUGH DENSER MID-LEVEL
POCKETS OF WILDFIRE SMOKE WILL CONTINUE DRIFTING NORTH ACROSS THE
LONGER RANGE EASTERN APPROACHES THROUGH 02/02Z. /JBONK
&&

.MARINE...NO SIGNIFICANT CHANGE IN THE LARGE SCALE PRESSURE PATTERN.
WILL CONTINUE TO SEE NORTHERLY COMPONENT WINDS OVER THE WATERS WITH
VARYING DEGREES OF STRENGTH FOR THE NEXT SEVERAL DAYS. CURRENT SET OF
WINDS WILL KEEP AFTERNOON AND EVENING GUSTS 20 TO 25 KTS ACROSS THE
FULL SET OF WATERS. THE INNER WATER SPEEDS WILL DROP OFF AROUND
SUNSET WHILE THE OUTER WATERS CONTINUE PAST MIDNIGHT. AN ADDITIONAL
SET OF GUSTY WINDS WILL DEVELOP SUNDAY AFTERNOON AND EVENING BEFORE
EASING BELOW CRITERIA FOR THE FIRST PART OF NEXT WEEK. HAVE SPLIT THE
ADVISORY FOR WINDS TO BETTER REFLECT EXPECTED CONDITIONS AND ALSO FOR
WHAT REALITY HAS BROUGHT THE PAST 48 HOUR.

THIS LONGER TIME FRAME OF PERSISTENT NORTHERLY WINDS IS PRODUCING
CHOPPY SEAS AND HAVE BEEN HOVERING AROUND THE 7 FT SQUARE SEA MINIMUM
CRITERIA. REALITY IS SHOWING SEAS ABOUT A FOOT BELOW WW3 GUIDANCE SO
HAVE DECIDED TO NOT ISSUE AN ADVISORY FOR HAZARDOUS SEAS AT THIS TIME
BUT STILL FEEL LIKE WE ARE WALKING A FINE LINE. OTHERWISE /JBONK
&&

.FIRE WEATHER...RED FLAG WARNING REMAINS IN EFFECT THROUGH 05Z FOR
MID AND HIGH-LEVEL HAINES 5-6. MOST UNSTABLE CONDITIONS WILL BE OVER
THE NORTH ZONES...NORTH OF A LINE FROM AROUND BENTON COUNTY EAST TO
MT. JEFFERSON. MID AND HIGH-LEVEL MOISTURE FILTERING INTO THE SOUTH
ZONES WILL LIKELY PRODUCE HIGH-LEVEL HAINES 4 VALUES...HELPING TO
REDUCE POTENTIAL COLUMN VERTICAL DEVELOPMENT. ONE OTHER NEAR-TERM
CONCERN IS LIGHTNING IN THE FAR SE PART OF THE AREA. AT 22Z A FEW
STRIKES NOTED ALONG THE CASCADE CREST NEAR WILLAMETTE PASS. FEEL ANY
CONVECTION THIS EVENING SHOULD BE LIMITED TO ZONE 608 AND PERHAPS
THE EAST HALF OF ZONE 606. CONVECTIVE THREAT SPREADS NORTH AND WEST
SUNDAY AS SOUTH FLOW ALOFT FURTHER NORTH AND 500 MB RIDGE AXIS
GRADUALLY SHIFTS NORTH AS WELL. HAVE SPREAD MENTION OF THUNDERSTORMS
TO THE S WA CASCADES SUN EVENING THROUGH MON MORNING. WILL NEED TO
CONSIDER POTENTIAL HIGHLIGHTS FOR SUN...BUT FOR NOW FEEL LIKE
COVERAGE WILL NOT BE ENOUGH FOR RED FLAG. ALSO...ANY STORMS THAT
DEVELOP OVER THE S HALF OF THE AREA SUNDAY WILL TEND TO BECOME
WETTER DUE TO THE LONGER-DURATION MOIST SOUTH FLOW. CONVECTIVE
THREAT GETS PUSHED EAST OF THE CASCADES MON NIGHT AND TUE...WITH ANY
THREAT TUE NEAR THE CREST OF ZONE 608. WEISHAAR
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...EXCESSIVE HEAT WARNING UNTIL 9 PM PDT THIS EVENING 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 10 PM PDT THIS EVENING 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 THIS EVENING FOR CASCADE FOOTHILLS
     IN LANE COUNTY-CENTRAL COAST RANGE OF WESTERN OREGON-
     NORTHERN OREGON CASCADE FOOTHILLS.

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

     RED FLAG WARNING UNTIL 10 PM PDT THIS EVENING FOR CLARK COUNTY
     LOWLANDS-EAST WILLAPA HILLS-EXTREME SOUTH WASHINGTON
     CASCADES AND FOOTHILLS.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM PDT SUNDAY FOR
     WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR FROM 10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 3 PM SUNDAY TO MIDNIGHT PDT
     SUNDAY NIGHT FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA 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.



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