192
FXUS66 KPQR 180413
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
920 PM PDT SAT OCT 17 2026
SYNOPSIS
LARGELY DRY WEATHER EXPECTED THROUGH MIDWEEK WHILE
TEMPERATURES REMAIN NEAR TO ABOVE AVERAGE FOR MID-OCTOBER. CHANCES
FOR RAIN AND COOLER TEMPERATURES RAMP UP LATE IN THE WORK WEEK.
SHORT TERM...NOW THROUGH MONDAY NIGHT
A BAND OF MID TO HIGH LEVEL
CLOUD COVER WILL PUSH EAST OF THE REGION LATER THIS EVENING. BETWEEN
THIS, DECREASING WINDS OVERNIGHT AND AND DEWPOINTS CURRENTLY
HOVERING IN THE LOW TO MID 40S IN SOME LOCATIONS, WE SHOULD SEE SOME
OF OUR COLDER VALLEY LOCATIONS, PARTICULARLY ACROSS THE NORTH OREGON
COAST RANGE AND VALLEYS OF SOUTHWESTERN WASHINGTON, DROP INTO THE
MID TO UPPER 30S TOWARDS DAYBREAK. AS A RESULT, OPTED TO EXPAND THE
FROST ADVISORY TO COVER THE THREAT FOR SURFACES REACHING FREEZING IN
SOME OF THESE TYPICALLY COLDER SPOTS. HIGHER DEWPOINTS AND MORE
PERSISTENT WIND IN THE WILLAMETTE VALLEY SHOULD MAKE IT DIFFICULT
FOR TEMPERATURES TO DROP INTO THE MID TO UPPER 30S AND ALLOW
TEMPERATURES NEAR THE GROUND TO REACH FREEZING FOR ALL BUT THE
COLDEST SPOTS.
ON MONDAY, THERE IS GOOD CONSENSUS THAT AN UPPER-LEVEL TROUGH
APPROACHING THE COAST WILL ELONGATE AND PINCH OFF INTO A CLOSED
UPPER LOW WHICH WILL TRACK SOUTH TOWARD CALIFORNIA. AS THE
TROUGH AND ITS ASSOCIATED SURFACE LOW MAKE THEIR CLOSEST
APPROACH, CHANCES FOR RAIN WILL LARGELY REMAIN OFFSHORE, WITH
COASTAL AND COAST RANGE COMMUNITIES SEEING ONLY 5-15% CHANCES
FOR RAIN. RAINFALL AMOUNTS ARE NOT EXPECTED TO BE SIGNIFICANT.
REINFORCING COOL AIR ALOFT WITHIN THE TROUGH WILL CONTINUE TO
PUSH TEMPERATURES DOWNWARD, WITH NEAR-NORMAL HIGHS EXPECTED ON
MONDAY. MONDAY NIGHT WILL BRING MORE WIDESPREAD CHANCES FOR
OVERNIGHT LOWS IN THE 30S FOR MANY VALLEYS AWAY FROM THE CORE URBAN
CENTERS.
LONG TERM...TUESDAY THROUGH SATURDAY
WHILE THE UPPER LOW
DRIFTS SOUTHWARD OVER CALIFORNIA, HEIGHTS ALOFT REBOUND LOCALLY
AS TRANSIENT UPPER-LEVEL RIDGING DEVELOPS OVERHEAD. THIS WILL
MAINTAIN DRY CONDITIONS THROUGH MIDWEEK AND SUPPORT A WARMING
TREND WITH TEMPERATURES RETURNING TO THE LOW 70S INLAND BY
WEDNESDAY. OVERNIGHT LOWS LOOK TO REMAIN SEASONABLE, YIELDING
NIGHTLY CHANCES FOR FROST WITHIN INLAND VALLEYS.
THROUGH THE LATTER HALF OF THE WORKWEEK, THERE REMAINS DECENT
CONSENSUS AMONG LONG-RANGE ENSEMBLES THAT TROUGHING WILL
REDEVELOP OVER THE GULF OF ALASKA BUT WITH UNCERTAINTY IN ITS
LOCATION AND AMPLITUDE. THE PATTERN NONETHELESS SUPPORTS
MODEST CHANCES FOR RAIN FOR THURSDAY AND FRIDAY, AS WELL AS
FAVORING A RETURN TO SEASONABLE TEMPERATURES EACH DAY. NIGHTLY
CHANCES FOR FROST CONTINUE WITHIN INLAND VALLEYS. -36
AVIATION...THROUGH 06Z MONDAY
BREEZY NORTHERLY WINDS AT MANY TAF
SITES SHOULD CONTINUE TO DIMINISH OVERNIGHT. AS A BAND OF MID-HIGH
LEVEL CLOUDS CURRENTLY OVER THE REGION MOVES EAST OF THE AREA
BETWEEN 06-08Z, VALLEYS SHOULD BEGIN TO COOL OFF MORE EFFICIENTLY
WITH SOME PATCHY FOG AND LOW CLOUDS DEVELOPING IN MORE WIND
SHELTERED VALLEYS. THE PROBABILITY FOR IFR CONDITIONS TO DEVELOP BY
DAYBREAK IS HIGHEST AT KEUG WITH A 25-30% CHANCE AT ANY GIVEN HOUR
IN THE 13-17Z SUNDAY TIMEFRAME. THE PROBABILITIES ARE CLOSER TO 20%
FOR OTHER INLAND TAF SITES. WHATEVER FOG AND LOW CLOUDS DO DEVELOP
OVERNIGHT SHOULD LIFT AND SCATTER OUT RATHER QUICKLY ON SUNDAY, MOST
LIKELY IN THE 17-20Z SUNDAY TIMEFRAME.
KPDX AND APPROACHES...EXPECT MAINLY VFR CONDITIONS THROUGH 06Z
MONDAY. HOWEVER, CLEARING SKIES, DECREASING WINDS AND CURRENT
DEWPOINTS IN THE MID 40S WILL LEAD TO A THREAT OF SOME PATCHY FOG
AND LOW CLOUDS TRYING TO DEVELOP LATER TONIGHT IN THE VICINITY OF
THE AIRPORT. HOWEVER, THERE IS ONLY A 15-20% CHANCE AT ANY GIVEN
HOUR FOR IFR CONDITIONS AT THE TERMINAL BETWEEN 13-17Z SUNDAY SO
WILL KEEP THE TAF VFR FOR THE TIME BEING.
MARINE
NORTHERLY FLOW CONTINUES THROUGH THE WEEKEND. IN
ADDITION, NORTHERLY WIND GUSTS OF 20-25 KT ARE BEGINNING TO OCCUR AT
BUOY 50 AND ARE EXPECTED TO PERSIST FOR SEVERAL HOURS SO A SMALL
CRAFT ADVISORY WAS ISSUED FOR THE WATERS OFF THE CENTRAL COAST OF
OREGON. A BUILDING MID-PERIOD WEST-NORTHWESTERLY SWELL WILL PUSH
SEAS TO 8-9 FT AT 11-12 SECONDS TONIGHT THROUGH SUNDAY.
CHANCES FOR SEAS HIGHER THAN 10 FT ARE ONLY ~10% BEYOND 30 NM NORTH
OF CAPE LOOKOUT. THIS SWELL WILL ALSO CONTINUE TO POSE A MODERATE
RISK FOR SNEAKER WAVES ALONG THE COAST; CAUTION SHOULD BE USED BY
THOSE IN OR NEAR THE WATER ALONG BEACHES THROUGH THIS WEEKEND.
ANOTHER WEATHER SYSTEM DROPPING SOUTHWARD OFF THE COAST MONDAY INTO
TUESDAY WILL GENERATE ANOTHER SWELL THAT PUSH INTO THE REGION. THERE
IS A 50% CHANCE FOR SEAS TO PUSH TO 10 FT ACROSS THE WATERS,
PARTICULARLY BEYOND 20 NM TUESDAY. IN ADDITION, THERE IS A >75%
CHANCE FOR WIND GUSTS TO CLIMB INTO THE 21-25 KT RANGE TUESDAY.
WINDS AND SEAS APPEAR TO TREND DOWNWARD MIDWEEK WITH MORE ACTIVE
WEATHER LATE IN THE WORK WEEK.
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY FROM 3 AM TO 9 AM PDT SUNDAY FOR ORZ104-105.
FROST ADVISORY UNTIL 9 AM PDT SUNDAY FOR ORZ121.
WA...FROST ADVISORY FROM 3 AM TO 9 AM PDT SUNDAY FOR WAZ205-208.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT SUNDAY FOR PZZ253-273.
WWW.WEATHER.GOV/PORTLAND
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