661
FXUS66 KPQR 042217
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
317 PM PDT THU JUN 4 2026
SYNOPSIS
DRY AND WARM WEATHER THIS AFTERNOON. A DEEPER
TROUGH SHIFTS SOUTHWARD INTO THE REGION FRIDAY TO SATURDAY
INCREASING ONSHORE FLOW AND RETURNING CHANCES FOR
PRECIPITATION. SLIGHT CHANCES FOR THUNDERSTORMS FRIDAY AND
SATURDAY AFTERNOON. DRIER WEATHER RETURNS SUNDAY BEFORE ANOTHER
TROUGH RETURNS CHANCES FOR PRECIPITATION EARLY TO MID NEXT WEEK.
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
SATELLITE IMAGERY
AS OF EARLY THURSDAY AFTERNOON DEPICTS DECREASING CLOUDS WITH
MOSTLY SUNNY SKIES AS DRY WESTERLY FLOW SETS UP OVER THE REGION.
ONSHORE FLOW IS ALSO INCREASING - WHILE WINDS ARE GENERALLY
LIGHT THROUGHOUT MOST AREAS, INCREASING KTTD-KDLS PRESSURE
GRADIENTS OF +2.5 TO +3.5 WILL LEAD TO BREEZY WESTERLY WINDS
WITH GUSTS UP TO 30 MPH THROUGH THE CENTRAL COLUMBIA RIVER
GORGE AND UPPER HOOD RIVER VALLEY THIS AFTERNOON AND EVENING.
THE OVERALL FORECAST ON FRIDAY AND SATURDAY HAS REMAINED
UNCHANGED AND MODELS ARE IN GOOD AGREEMENT IN THE SYNOPTIC
PATTERN. ON FRIDAY, A COOLER AND WETTER PATTERN RETURNS AS A
DEEPER TROUGH DROPS APPROACHES THE PACIFIC NORTHWEST FROM THE
GULF OF ALASKA. AS THIS UPPER TROUGH MOVES IN, IT WILL PUSH A
WEAK FRONT INTO NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THIS
WILL RETURN CHANCES FOR PRECIPITATION OVER SOUTHWEST WASHINGTON
AND THE NORTH OREGON COAST, COAST RANGE, AND CASCADES, WHILE
MOST INTERIOR VALLEYS REMAIN DRY. GIVEN THE SHOWERY NATURE OF
THIS SYSTEM, RAINFALL AMOUNTS WILL VARY ACROSS THE AREA AND THE
HIGHEST AMOUNTS WILL ULTIMATELY DEPEND ON WHERE SHOWERS SET-UP.
OVERALL, SHOWERS WILL BE NON-IMPACTFUL. IN ADDITION, THERE IS A
10-15% CHANCE FOR ISOLATED THUNDERSTORMS ACROSS SOUTHWEST
WASHINGTON FRIDAY AFTERNOON DUE TO INCREASING INSTABILITY FROM
COLD AIR ALOFT ALONG WITH SUFFICIENT LIFT FROM THE TROUGH.
ON SATURDAY, THE AFOREMENTIONED UPPER TROUGH WILL MOVE SOUTH AND
INLAND OVER THE PACIFIC NORTHWEST, BRINGING MORE WIDESPREAD
CHANCES FOR RAIN ACROSS NORTHWEST OREGON AND SOUTHWEST
WASHINGTON. AT THE SAME TIME, COOLING TEMPERATURES ALOFT WILL
FURTHER INCREASE INSTABILITY WITH CAPE VALUES AS HIGH AS 150-200
J/KG. THIS PLUS HIGHER 500 MB VORTICITY WILL LEAD TO A 15-25%
CHANCE FOR THUNDERSTORMS SATURDAY, MAINLY FROM PACIFIC CITY AND
SALEM NORTHWARD WITH THE HIGHEST CHANCES (20-25%) ACROSS
SOUTHWEST WASHINGTON. THE HIGHEST THREAT FOR THUNDERSTORMS
APPEARS TO BE IN THE LATE MORNING TO AFTERNOON (11 AM-5 PM
SATURDAY) WHEN INSTABILITY IS THE GREATEST. ANY PASSING
THUNDERSTORMS FRIDAY AND SATURDAY AFTERNOON MAY PRODUCE
LIGHTNING, BRIEF HEAVY RAIN, ERRATIC WINDS, AND/OR SMALL HAIL.
ONSHORE FLOW WILL ALSO INCREASE FRIDAY TO SATURDAY AS THIS UPPER
TROUGH MOVES IN. WEST-SOUTHWESTERLY WINDS WON'T BE TOO IMPACTFUL
ACROSS MOST AREAS WITH GUSTS UP TO 20 MPH ALONG THE I-5
CORRIDOR, HOWEVER, TYPICAL BREEZY SPOTS DURING ONSHORE FLOW LIKE
THE CENTRAL GORGE AND UPPER HOOD RIVER VALLEY COULD GUST UP TO
35 MPH. THERE IS ALSO A 20-30% CHANCE FOR ISOLATED WIND GUSTS OF
40-45 MPH THROUGH THESE AREAS AS WELL, WITH HIGHER CHANCES
(30-50%) FOR HIGHER TERRAIN AND EXPOSED RIDGETOPS. IF THE LOW
SHIFTS ANY FURTHER NORTH, THESE WINDS WOULD END UP WEAKER. -10
LONG TERM...SUNDAY THROUGH WEDNESDAY
FOR THOSE WITH SUNDAY
PLANS, DRIER WEATHER BRIEFLY RETURNS ON SUNDAY AS A SHORTWAVE
RIDGE PASSES OVER THE PACIFIC NORTHWEST. BY MONDAY, THE VAST
MAJORITY OF ENSEMBLE MEMBERS ARE SHOWING BROAD TROUGHING AND
BELOW-AVERAGE 500 MB HEIGHTS RETURNING TO THE AREA. WHILE THIS
WOULD RETURN WIDESPREAD CHANCES FOR PRECIPITATION AND COOLER
TEMPERATURES, THERE STILL REMAINS UNCERTAINTY ON THE EXACT
MAGNITUDE AND TRACK OF THIS TROUGH.
UNCERTAINTY FOLLOWS ON TUESDAY TO WEDNESDAY WITH EXACTLY HOW
THIS TROUGH PROGRESSES THROUGH THE AREA, BUT MOST ENSEMBLE
MEMBERS (65%) KEEPS SOME SORT OF TROUGHING MOVING THROUGH THE
PACIFIC NORTHWEST, MAINTAINING A COOLER AND WETTER PATTERN.
HOWEVER, THE OTHER 35% OF ENSEMBLE MEMBERS SHOW THE TROUGH
EITHER SWINGING SOUTHWARD INTO CALIFORNIA OR THE TROUGH EXITING
EASTWARD WITH HIGH PRESSURE RE-BUILDING. IF THIS WERE TO OCCUR,
THEN WE'D END UP DRIER. BY WEDNESDAY, THERE IS GREATER
UNCERTAINTY AS ENSEMBLE GUIDANCE IS HALF AND HALF ON WHETHER OR
NOT TROUGHING LINGERING OVERHEAD OR EXITS THE AREA. IT APPEARS
MODELS ARE MOST UNCERTAIN WITH THE EXACT TIMING/DURATION OF THIS
TROUGH. EITHER WAY, ANY PRECIPITATION THAT FALLS WILL LIKELY BE
LIGHT AND NON-IMPACTFUL. CHANCES FOR EXCEEDING 1 INCH OF LIQUID
PRECIPITATION IN 48 HOURS BETWEEN 5 AM TUESDAY TO 5 AM THURSDAY
ARE ONLY 15-20% WEST OF THE CASCADES, AND AROUND 35-45% ACROSS
THE CASCADES. -10
AVIATION
LIGHT NORTH TO NORTHWEST WINDS AROUND 5-10 KT WILL
CONTINUE THROUGH 06Z FRIDAY AS ONSHORE FLOW CONTINUES. SATELLITE
AND SURFACE WEATHER OBSERVATIONS AT 21Z THURSDAY SHOWED MOSTLY
CLEAR SKIES FROM KONP TO KSLE TO KEUG, WITH SCATTERED CLOUDS
NORTH OF KSLE WITH CEILINGS ABOVE 4000 FT.
A BROKEN OR OVERCAST VFR CLOUD DECK WILL LIKELY REDEVELOP AROUND
AND AFTER 06Z FRIDAY ALONG THE CASCADE FOOTHILLS AND WILLAMETTE
VALLEY WITH CEILINGS MOST LIKELY STAYING ABOVE 4000 FT. PERIODS
OF MVFR CEILINGS ARE MOST LIKELY TO OCCUR ALONG THE COAST
BETWEEN 06-18Z FRIDAY. THIS IS ALSO WHEN A WEAK FRONT WILL BEGIN
MOVING INLAND FROM THE COASTAL WATERS, WHICH WILL BRING
SCATTERED LIGHT RAIN SHOWERS TO THE COAST BY APPROXIMATELY 12Z
FRIDAY. THIS FRONT WILL ALSO BRING A SHIFT TO SOUTHWESTERLY
SURFACE WINDS BY 18Z FRIDAY.
KPDX AND APPROACHES...VFR CEILINGS ARE EXPECTED TO CONTINUE
THROUGH 00Z SATURDAY ALONG WITH DRY CONDITIONS. NORTHWEST WINDS
WILL CONTINUE AROUND 5-10 KT THROUGH THIS EVENING, WITH GUSTS AS
HIGH AS 15-18 KT TOWARDS 01-02Z FRIDAY. WINDS BECOME LIGHT AND
VARIABLE AGAIN TONIGHT. -23
MARINE
LOOKING AT FAIRLY BENIGN CONDITIONS OVER THE NEXT
SEVERAL DAYS DESPITE A SERIES OF FRONTAL SYSTEMS MOVING THROUGH.
WESTERLY FLOW WILL CONTINUE THROUGH SATURDAY. SEAS ARE EXPECTED
TO REMAIN AROUND 5 TO 6 FT AS A WESTERLY SWELL PERSISTS. SEAS
THEN BUILD TO 6-8 FT AT 11 TO 12 SECONDS LATE TONIGHT INTO
FRIDAY MORNING AS A WEAK FRONTAL BOUNDARY APPROACHES THE WATERS.
THIS FRONT WILL ALSO BRING INCREASING SOUTHWESTERLY TO WESTERLY
WINDS WITH GUSTS UP TO 15-20 KT. THERE IS LESS THAN A 5-10%
CHANCE OF WIND GUSTS OF 25 KT OR GREATER.
A SECONDARY FRONT ARRIVES ON SATURDAY, BRINGING A SHIFT TO
NORTHWEST WINDS IN THE AFTERNOON. WIND SPEEDS ARE NOT EXPECTED
TO INCREASE MUCH WITH THIS FRONTAL PASSAGE, AS THERE IS LESS
THAN A 15-30% CHANCE OF SMALL CRAFT ADVISORY WIND GUSTS. THE
TIME PERIOD WITH HIGHEST WIND SPEEDS WILL LIKELY OCCUR ON MONDAY
AS A STRONGER SYSTEM MOVES OVER THE WATERS, BRINGING SOUTH
WINDS UP TO 20-25 KT AND SEAS APPROACHING 8-9 FT. -23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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