881
FXUS66 KPQR 050535 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1035 PM PDT THU JUN 4 2026
UPDATED AVIATION DISCUSSION.
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...NOW 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
VFR CONDITIONS CONTINUE WITH MID LEVEL CLOUDS
DEVELOPING ALONG INCREASING SOUTHWESTERLY FLOW. A TROUGH OVER THE
GULF OF ALASKA IS DRIFTING SOUTHEAST TOWARD THE AREA, SUPPORTING
INCREASING MOISTURE AND CLOUD COVER. A CLOUD DECK AROUND 5-6 KFT
HAS DEVELOPED OVER THE CASCADE FOOTHILLS AND INTO PORTIONS OF THE
WILLAMETTE VALLEY. PERIODS OF MVFR CEILINGS ARE MOST LIKELY TO
OCCUR ALONG THE COAST BETWEEN 12Z AND 18Z. 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.
SOUTHWESTERLY WINDS TURN MORE WESTERLY FRIDAY AFTERNOON BUT
MAINTAIN SPEEDS BETWEEN 5-10 KT.
KPDX AND APPROACHES...VFR CEILINGS ARE EXPECTED TO CONTINUE
THROUGH 06Z SATURDAY ALONG WITH DRY CONDITIONS. NORTHWEST WINDS
SHIFT SOUTHERLY AFTER 12Z THEN MORE WESTERLY AFTER 0Z SATURDAY.
LIGHT AND VARIABLE OVERNIGHT THEN INCREASING TO 8-11 KT AFTER 18Z.
-19
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
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