866
FXUS66 KPQR 202307
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
306 PM PST THU FEB 20 2020
SYNOPSIS
VARYING DEGREES OF HIGH PRESSURE OVER THE PACIFIC
NORTHWEST WILL BRING COOL NIGHTS, MILD DAYS, AND MAINLY DRY WEATHER
THROUGH NEXT WEEK. THE MAIN EXCEPTION TO THIS WILL BE ON SUNDAY INTO
MONDAY WHEN A STORM SYSTEM WILL BRING THE RETURN OF VALLEY RAIN AND
MOUNTAIN SNOW.
SHORT TERM...TONIGHT THROUGH SUNDAY
WATER VAPOR SATELLITE IMAGERY
CONTINUES TO SHOW A CLOSED UPPER LEVEL LOW DROPPING SOUTHWARD OFF THE
CALIFORNIA COAST, WITH SHORTWAVE RIDGING OVER THE PACIFIC NORTHWEST.
ASIDE FROM SOME MID AND HIGH CLOUDS STREAMING OVER THE REGION THIS
AFTERNOON CONDITIONS REMAIN RATHER MILD. EXPECT THESE CONDITIONS TO
GENERALLY CONTINUE THROUGH SATURDAY. THE EXCEPTION TO THIS WILL BE
THE INCREASE OF MARINE CLOUDS ALONG THE COAST STARTING FRIDAY AS
ONSHORE FLOW TAKES OVER AHEAD OF AN INCOMING SHORTWAVE DISTURBANCE.
GUIDANCE CONTINUES TO SHOW A WEAK FRONT BRUSHING BY THE FAR NORTHERN
PORTIONS OF THE FORECAST AREA ON SATURDAY WHICH COULD BRING SOME
LIGHT RAIN TO AREAS NORTH OF THE COLUMBIA RIVER. A MUCH STRONGER
FRONT LOOKS TO THEN MOVE ACROSS THE FORECAST AREA LATE SATURDAY INTO
SUNDAY. THIS FRONT WILL BRING THE RETURN OF WIDESPREAD VALLEY RAIN
AND MOUNTAIN SNOW ON SUNDAY, WITH SNOW LEVELS LOWERING BELOW CASCADES
PASSES. THERE IS STILL SOME UNCERTAINTY WITH QPF AND SNOW AMOUNTS
OVER THE WEEKEND, BUT BASED ON THE LATEST GUIDANCE IT STILL LOOKS
LIKE ADVISORY LEVEL SNOW IS POSSIBLE OVER THE NORTH OREGON AND SOUTH
WASHINGTON CASCADES. /64/NEUMAN
LONG TERM...SUNDAY NIGHT THROUGH WEDNESDAY
MODELS AND THEIR
ENSEMBLES ARE IN GOOD AGREEMENT THE SHORTWAVE TROUGH IMPACTING THE
PACIFIC NORTHWEST ON SUNDAY WILL SLIDE EASTWARD AND BE REPLACED BY
SHORTWAVE RIDGING. THIS WILL RESULT IN DECREASING SHOWERS AND CLOUDS
ACROSS THE AREA SUNDAY NIGHT INTO MONDAY. THERE IS STRONG CONSENSUS
THE PACIFIC NORTHWEST WILL THEN BE UNDER THE INFLUENCE OF A SHORTWAVE
RIDGE FOR MUCH OF NEXT WEEK. THIS WILL BRING COOL NIGHTS, HIGH
TEMPERATURES NEAR AVERAGE AND MAINLY DRY WEATHER. VARIOUS OPERATIONAL
AND ENSEMBLE MEMBERS DO SUGGEST A SHORTWAVE TROUGH WILL TRY TO SLIDE
INTO THE RIDGE TOWARDS THE MIDDLE OF NEXT WEEK AND POTENTIALLY BRING
LIGHT PRECIPITATION TO THE AREA. HOWEVER, THERE'S VERY LITTLE
CONSENSUS ON HOW THIS MIGHT TAKE SHAPE AND WHEN EXACTLY IT WILL OCCUR
AMONG MODEL AND ENSEMBLE GUIDANCE. AS A RESULT, THE NBM SLIGHT CHANCE
POPS TOWARDS THE END OF THE LONG TERM FORECAST SEEM REASONABLE GIVEN
THE PATTERN AND UNCERTAINTY. /NEUMAN
AVIATION
HIGH PRESSURE PERSISTS CREATING VFR CONDITIONS THROUGH
FRI. GUSTY EAST WINDS CONTINUE THROUGH THE GORGE AND COAST RANGE
THROUGH 00Z FRI WHEN THE PRESSURE GRADIENT WEAKENS. WINDS WILL
GENERALLY BECOME LIGHT AND VARIABLE THROUGH THE VALLEY AFTER 08Z FRI.
SLIGHT CHANCE OF PATCHY FOG AROUND SUNRISE AT 13Z FRI, BUT WITH A DRY
BOUNDARY LAYER, CHANCES ARE LOW. IF IT DOES FORM, IT WOULD BE NEAR
KEUG AND OTHER FOG PRONE AREAS.
KPDX AND APPROACHES...VFR CONDITIONS WITH GUSTY EAST WINDS. STRONG
EAST WINDS AROUND 2000 FT AGL WILL PERSIST THROUGH 06Z FRI. POTENTIAL
FOR SOME PATCHY FOG AROUND THE AIRPORT IN THE EARLY MORNING FRI, BUT
UNLIKELY DUE TO WINDS THROUGH THE EVENING. NOT INCLUDED IN TAF.
-MUESSLE
MARINE
HIGH PRESSURE REMAINS OVER THE AREA WITH A WESTERLY SWELL
THROUGH SAT MORNING. SEAS AROUND 5 FT WILL PERSIST THROUGH SAT
EVENING WITH WINDS GENERALLY CALM. SAT NIGHT, A 990 MB LOW OFF THE
ALASKA PENINSULA WILL MOVE SOUTH TOWARDS THE CONUS PACIFIC NORTHWEST.
WHILE THE LOW WILL STAY NORTH OF THE AREA OVER THE AK-PEN, WINDS AND
SEAS ARE EXPECTED TO RAMP UP.
THE MAIN PORTION OF THIS SYSTEM WILL MOVE OVER THE WATERS SUN
AFTERNOON. WITH A STRONG GRADIENT, SMALL CRAFT LEVEL WINDS WITH
STRONG SOUTHERLY GUSTS UP TO 30 KT ARE LIKELY. SEAS WILL ALSO BUILD
TO NEAR 10 FT SAT AFTERNOON, RISING TO NEAR 16 FT SUN AFTERNOON. WITH
THIS SYSTEM, THERE IS STILL QUITE A BIT OF UNCERTAINTY DUE TO MODEL
DIFFERENCES WITH THE INTENSITY OF THE LOW (HOW DEEP IT IS), AND WHERE
IT WILL TRACK. IN ANY CASE, A MORE ACTIVE PATTERN IS EXPECTED THIS
WEEKEND. BY MON NIGHT, CONDITIONS SHOULD SETTLE AND WEAK HIGH
PRESSURE WILL DEVELOP OVER THE PACIFIC CREATING CALM CONDITIONS ONCE
AGAIN. -MUESSLE
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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 NM OFFSHORE. THIS AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
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