658
FXUS66 KPQR 210521 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1021 PM PDT MON APR 20 2026
..UPDATED AVIATION DISCUSSION
SYNOPSIS
LIGHT SHOWERS WILL CONTINUE TO STREAM INTO THE
REGION FROM THE SOUTH AS AN THE UPPER LEVEL LOW SHIFTS
EASTWARD. THE BEST SIGNAL FOR THE COOLEST AND MOST UNSETTLED
STRETCH REMAINS TUESDAY INTO WEDNESDAY AS UPPER LEVEL LOW MOVES
FURTHER INLAND. BEYOND THAT, GUIDANCE SUPPORTS A RETURN OF DRY
AND WARMER WEATHER BEGINNING THURSDAY AND CONTINUING INTO THE
WEEKEND AS HIGH PRESSURE REBUILDS.
DISCUSSION...NOW THROUGH MONDAY
HIGH AND MID LEVEL CLOUDS
ALONG WITH LIGHT SHOWER CONTINUE TO STREAM INTO THE REGION
FROM THE SOUTH AS AN UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES
TO SLOWLY MOVING EAST/SOUTHEAST TOWARDS THE OR/CA BORDER. THIS
LOW WILL BE THE DOMINANT SYNOPTIC FEATURE THROUGH AT LEAST THE
MIDDLE OF THE WEEK. AS THIS LOW CONTINUES TO TREK
EAST/SOUTHEAST, IT WILL BRING WIDESPREAD CLOUD COVER ALONG WITH
INCREASING POPS, WITH LOW QPF VALUES ACROSS THE CWA THROUGH
LATE WEDNESDAY. AS THE LATTER PART OF THE WEEK APPROACHES AND
THE AFOREMENTIONED LOW PUSHES FURTHER INTO THE GREAT BASIN,
WEAK HIGH PRESSURE WILL BUILD IN BEHIND THE LOW AND WILL BRING
ABOUT A WARMING AND DRYING TREND THAT WILL PERSIST THROUGH THE
WEEKEND AND INTO THE START OF NEXT WEEK.
TONIGHT THROUGH WEDNESDAY NIGHT, AN UPPER LEVEL LOW WILL BRING
INCREASING CLOUD COVER, GENERALLY COOLER TEMPERATURES AS WELL AS
AS A MODERATE/HIGH POPS AND A LOW QPF PATTERN. BROKEN CLOUD
COVER THROUGH THIS EVENING AND TOMORROW WILL RESULT IN A 10-20%
CHANCE FOR THUNDERSTORMS, WITH THE HIGHEST PROBABILITY FOR
THUNDERSTORMS ALONG THE CASCADES. DAYTIME HIGHS ON TUESDAY AND
WEDNESDAY WILL BE IN THE MID 50S TO MID 60S, WITH WEDNESDAY
SHAPING UP TO BE THE COOLEST DAY THIS WEEK. OVERNIGHT LOWS
DURING THIS TIME FRAME WILL ALSO BE IN THE LOW 40S TO LOW 50S.
PRECIPITATION TOTALS THROUGH TONIGHT WILL RANGE AROUND
0.05-0.25 INCHES WITH THE HIGHEST TOTALS EXPECTED ALONG THE
COAST RANGE. TUESDAY AND WEDNESDAY, PRECIPITATION TOTALS LOOK
TO BE FAIRLY SIMILAR WITH 24 HOUR TOTALS FOR MOST AREAS BETWEEN
0.10-0.50 INCHES, WITH THE HIGHEST ACCUMULATIONS EXPECTED WITHIN
THE CASCADES. IT SHOULD BE NOTED THAT IF A THUNDERSTORM DOES
DEVELOP, THEN TOTAL PRECIPITATION WILL LIKELY BE HIGHER.
THURSDAY THROUGH SUNDAY, CONDITIONS TREND DRIER AND WARMER
AS HIGH PRESSURE RETURNS TO THE PAC NW. DAYTIME HIGHS ARE
EXPECTED TO WARM BACK INTO THE 60S ON THURSDAY AND FURTHER
WARMING INTO THE UPPER 60S AND MID 70S BY FRIDAY WITH THOSE
DAYTIME HIGHS PERSISTING THROUGH THE WEEKEND AND LIKELY
(60-80%) INTO THE START OF NEXT WEEK. OVERNIGHT LOWS IN THE
DURING THIS TIME FRAME WILL BE IN THE LOW 40S TO LOW 50S.
LOOKING TOWARDS THE START OF NEXT WEEK, A PATTERN CHANGE LOOKS
TO OCCUR AS THE RIDGE LOOKS TO BREAK DOWN. HOWEVER, UNCERTAINTY
IS VERY HIGH WITH THE WPC 500 MB CLUSTER MULTI-MODEL ENSEMBLE
KEEPING VERY WEAK AND BROAD TROUGHING OVER THE WESTERN PART OF
CONUS. THIS GENERALLY SUPPORTS A SLIGHT COOLING TREND WITH A
VERY LOW CHANCE OF LIGHT PRECIPITATION. /42
AVIATION
SATELLITE IMAGERY AS OF LATE MONDAY EVENING DEPICTS
SHOWERS ACROSS NORTHWEST OREGON AS A WEAK FRONT ASSOCIATED WITH A
LOW PRESSURE SYSTEM OFFSHORE LIFTS NORTHWARD OVER THE AREA. EXPECT
CIGS TO FALL TO LOW-END VFR, BEFORE TRENDING PREDOMINATELY MVFR
AFTER 09-12Z TUE. GUIDANCE SUGGESTS A 60-80% CHANCE FOR MVFR CIGS OR
LOWER AT ANY GIVEN HOUR BETWEEN 12-18Z TUE FOR ALL TERMINALS.
AFTER 18-21Z TUE, THE SYSTEM WEAKENS FURTHER AND CIGS BEGIN TO
GRADUALLY IMPROVE TO A MIX OF MVFR/VFR CIGS. AFTER 21Z TUE-00Z WED,
CIGS WITHIN THE WILLAMETTE VALLEY IMPROVE TO PREDOMINATELY VFR.
EXPECT WEST-SOUTHWEST WINDS ACROSS THE REGION UNDER 10 KT THROUGH
TUESDAY MORNING, TURNING SLIGHTLY MORE WEST-NORTHWESTERLY IN THE
AFTERNOON.
KPDX AND APPROACHES...VFR CONDITIONS WITH SHOWERS UNTIL AROUND 10-
12Z TUE. AFTER 12Z TUE, CIGS DROP TO MVFR WITH THE LOWEST CIGS (1-2
KFT) BETWEEN 12-21Z TUE. CIGS IMPROVE TO HIGH-END MVFR AFTER 21Z
TUE, THEN VFR AFTER 00-03Z WED. SOUTHWESTERLY WINDS AROUND 5 KT
THROUGH 18Z TUE, TURNING MORE NORTHWESTERLY IN THE AFTERNOON.
-10
MARINE
BENIGN CONDITIONS CONTINUE TODAY INTO TUESDAY. BUOY
OBSERVATIONS FROM MONDAY AFTERNOON SHOWED SEAS HOVERING AROUND 6
TO 7 FT WITH LIGHT SOUTHWEST TO WEST WINDS. SCATTERED LIGHT RAIN
SHOWERS AND SPRINKLES ARE ALSO OCCURRING OVER THE COASTAL WATERS
MONDAY AFTERNOON WITH A WEAK FRONTAL PASSAGE.
AN UPPER LEVEL LOW OFF THE COAST WILL SUPPORT ADDITIONAL SHOWERS
MONDAY NIGHT THROUGH TUESDAY NIGHT AS THE CENTER OF THE LOW NEARS
THE COAST, WITH SEAS LIKELY STAYING UNDER 8 FT AND WINDS STAYING
UNDER 15 KT. BY EARLY WEDNESDAY MORNING, A NORTHWEST SWELL WILL
PUSH SEAS UP TO 7 TO 8 FT. SEAS AND WINDS BOTH INCREASE MORE
CONSIDERABLY WEDNESDAY AFTERNOON AND EVENING WITH ANOTHER FRONTAL
PASSAGE. EXPECT SEAS TO PEAK BETWEEN 10 AND 12 FT BY WEDNESDAY
EVENING WITH WEST TO WEST-NORTHWEST WINDS AROUND 10 TO 15 KT WITH
GUSTS UP TO 20-25 KT WEDNESDAY AFTERNOON AND EVENING. THERE IS A
50-80% CHANCE SEAS PEAK ABOVE 10 FEET BEYOND 10 NM OFFSHORE AND A
30-50% CHANCE FOR SEAS ABOVE 12 FEET OVER THE NORTHERN OUTER
WATERS BEYOND 30 NM OFFSHORE. SEAS ARE EXPECTED TO PEAK CLOSER TO
9-10 FT OVER THE INNER WATERS. WINDS DECREASE WEDNESDAY NIGHT
BEHIND THE FRONTAL PASSAGE, HOWEVER SEAS WILL REMAIN ELEVATED
UNTIL SIGNIFICANT WAVE HEIGHTS FALL BELOW 10 FT SOMETIME THURSDAY
AFTERNOON OR EVENING.
A VERY STRONG EBB CURRENT WILL OCCUR DURING THE TUESDAY MORNING
EBB CYCLE, PUSHING SEAS UP TO 6 FT WITH STEEP EBB CHOP. HAVE
DECIDED NOT TO ISSUE A SMALL CRAFT ADVISORY FOR THIS EBB CYCLE AS
THIS IS SLIGHTLY BELOW CRITERIA THRESHOLDS. -23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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