360
FXUS66 KPQR 271812 AAA
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1111 AM PDT WED MAY 27 2026
UPDATED AVIATION DISCUSSION
SYNOPSIS
A DEPARTING UPPER LOW WILL ALLOW WARMER AND DRIER
WEATHER TO BUILD IN TODAY AS HIGH PRESSURE REBUILDS. WRAP-AROUND
MOISTURE THEN RETURNS MID TO LATE WEEK, BRINGING INCREASING
SHOWER AND THUNDERSTORM CHANCES THURSDAY AFTERNOON AND EVENING,
FOCUSED MAINLY OVER THE CASCADES AND THE UPPER HOOD RIVER
VALLEY. COOLER TEMPERATURES RETURN FRIDAY, FOLLOWED BY A DRIER
WEEKEND. EARLY NEXT WEEK REMAINS UNCERTAIN WITH A WIDE SPREAD IN
POTENTIAL AFTERNOON TEMPERATURES.
DISCUSSION... TODAY THROUGH TUESDAY
EARLY THIS MORNING, THE BROAD
UPPER LOW THAT PRODUCED YESTERDAY’S SCATTERED SHOWERS IS SLIDING
FARTHER SOUTH INTO THE GREAT BASIN. IN ITS WAKE, 500MB HEIGHTS RISE
OVER THE PACIFIC NORTHWEST AND THE LOWLANDS SHOULD TREND WARMER AND
DRIER THROUGH THE DAY.
BY THIS AFTERNOON AND EVENING, ATTENTION SHIFTS BACK TO THE
CASCADES AS WRAP-AROUND MOISTURE CURLS NORTHWARD OUT OF THE
SOUTHEAST. THE BEST SIGNAL FOR CONVECTION TODAY REMAINS OVER THE
LANE COUNTY CASCADES, WHERE A 10-20% CHANCE OF THUNDERSTORMS
PERSISTS ALONG WITH A 30-60% CHANCE OF SHOWERS. ELSEWHERE WEST
OF THE CASCADES, MOST LOCATIONS REMAIN DRY AND WARM, WITH MID TO
HIGH CLOUDS OVERHEAD AT TIMES.
THURSDAY HAS TRENDED MORE ACTIVE AND IS THE PRIMARY DAY TO
WATCH FOR CONVECTIVE IMPACTS. STRENGTHENING EASTERLY FLOW ALOFT
PULLS IN SUBSTANTIAL MOISTURE (MODEL SOUNDINGS SUGGEST PWAT
VALUES UP TO AROUND 1.25 INCHES), WHICH MAINLY INCREASES RAIN
EFFICIENCY AND THE POTENTIAL FOR HEAVIER DOWNPOURS IN ANY
SHOWERS/STORMS THAT DEVELOP. CURRENT FORECAST FAVORS A 15-35%
CHANCE OF THUNDERSTORMS ACROSS THE CASCADES AND UPPER HOOD RIVER
VALLEY, WITH THE HIGHEST ODDS OVER THE LANE COUNTY CASCADES.
GUIDANCE ALSO SUGGESTS SOME SHOWER POTENTIAL EXPANDING WEST
INTO THE I-5 CORRIDOR, ESPECIALLY LATER IN THE DAY.
THE INGREDIENTS FOR A FEW STRONGER STORMS, SOME POTENTIALLY
SEVERE, APPEAR TO OVERLAP THURSDAY BETWEEN ROUGHLY 11 AM AND 10
PM. JOINT PROBABILITIES FOR CAPE EXCEEDING 1000 J/KG AND 0-6 KM
BULK SHEAR OVER 30 KT (A COMBINATION SUPPORTIVE OF ORGANIZED
CONVECTION) RUN ON THE ORDER OF 40-80% ACROSS PORTIONS OF THE
CASCADES, WITH THE STRONGEST OVERLAP FAVORED IN THE SOUTH
WASHINGTON AND NORTH OREGON CASCADES. MODEL SOUNDINGS BROADLY
SUPPORT AROUND 1000-1500 J/KG OF CAPE WITH 30-40 KT OF BULK
SHEAR. SPC ALSO HIGHLIGHTS A MARGINAL RISK IN THE CASCADES AND
UPPER HOOD RIVER VALLEY. IF THUNDERSTORMS DO INITIATE OVER THE
CASCADES, A FEW CELLS MAY BE CAPABLE OF DRIFTING WEST INTO THE
FOOTHILLS AND THE WILLAMETTE VALLEY, INCLUDING THE
PORTLAND/VANCOUVER METRO LATER IN THE AFTERNOON/EVENING, THOUGH
CONFIDENCE IN WESTWARD STORM EXTENT REMAINS LOWER THAN OVER THE
HIGHER TERRAIN.
THE MAIN HAZARDS WITH ANY STRONGER STORM THAT DEVELOPS WILL BE BRIEF
HEAVY RAINFALL COULD LEAD TO LOCALIZED PONDING IN POOR-DRAINAGE/URBAN
AREAS, ALONG WITH HAIL RANGING ANYWHERE IN SIZE FROM PEAS TO THE
SIZE OF QUARTERS, AND GUSTY OUTFLOW WINDS THAT COULD APPROACH
40-60 MPH IN ISOLATED INSTANCES. THE REFS ENSEMBLE MEAN
SUPPORTS ABOUT 0.25 INCH PER HOUR RAINFALL RATES THROUGH
THURSDAY AFTERNOON/EVENING ACROSS THE VALLEYS, WITH SOME MEMBERS
SUGGESTING LOCALIZED BURSTS NEAR 0.50 INCH PER HOUR. A SMALL
SUBSET (ROUGHLY 5-10%) HINTS AT VERY INTENSE 1-2 INCH PER HOUR
RATES, THOUGH THIS APPEARS TO BE AN UNREALISTIC OUTLIER SIGNAL
AT THIS TIME. STORM MOTION IS CURRENTLY PROJECTED NEAR 20 KT,
FAST ENOUGH TO LIMIT DURATION OVER ANY ONE SPOT, BUT NOT FAST
ENOUGH TO REMOVE THE THREAT OF BRIEF HEAVIER DOWNPOURS IF STORMS
TRAIN OR REPEATEDLY DEVELOP OVER THE SAME AREA.
WARMTH CONTINUES TODAY INTO THURSDAY FOR THE VALLEYS AS THE
RIDGE REASSERTS ITSELF, THOUGH EXACT HIGHS WILL DEPEND ON CLOUD
AND SHOWER COVERAGE, ESPECIALLY THURSDAY IF CONVECTION BECOMES
MORE WIDESPREAD. CURRENT GUIDANCE STILL SUPPORTS HIGHS RUNNING
5-10 DEGREES ABOVE NORMAL, WITH THE PORTLAND/VANCOUVER METRO
HAVING A 60-80% CHANCE OF EXCEEDING 80 TODAY AND 80-90%
THURSDAY. OTHER INTERIOR VALLEYS CARRY A 30-60% CHANCE OF
EXCEEDING 80 BOTH DAYS.
FRIDAY BRINGS A TURN BACK TOWARD COOLER TEMPERATURES AS ANOTHER
TROUGH APPROACHES FROM THE NORTHEAST PACIFIC. SHOWER CHANCES
LINGER FRIDAY (ESPECIALLY NEAR THE CASCADES) BEFORE A DRIER
WEEKEND DEVELOPS. LOOKING INTO EARLY NEXT WEEK, ENSEMBLE SPREAD
REMAINS LARGE, WITH MONDAY HIGHS IN THE PORTLAND AREA STILL
RANGING FROM THE LOW 70S TO THE LOW 90S ON MONDAY AND UPPER 70S
TO UPPER 90S ON TUESDAY DEPENDING ON RIDGE PLACEMENT. CURRENT
GUIDANCE SUPPORTS A 15-30% CHANCE OF 90+ IN THE GREATER
PORTLAND/VANCOUVER METRO MONDAY AND A 35-50% ON TUESDAY, WITH
ABOUT 5-15% ELSEWHERE ACROSS THE WILLAMETTE VALLEY, SOUTHWEST
WASHINGTON LOWLANDS, AND THE UPPER HOOD RIVER VALLEY ON MONDAY
AND 20-35% ON TUESDAY.~12
AVIATION
NORTHEAST FLOW ALOFT TODAY AS AN UPPER LEVEL LOW
SPINS OVER CENTRAL CALIFORNIA. EXPECT PREDOMINATELY VFR CONDITIONS
INLAND AS RESIDUAL STRATUS CONTINUES TO SCATTER OUT THIS MORNING.
LOW-END MVFR MARINE STRATUS ALONG THE COAST IS LIKELY TO PERSIST
THROUGH AT LEAST 21Z THIS AFTERNOON, WITH AROUND A 50-70% CHANCE
OF IMPROVING TO VFR AFTERWARDS AT COASTAL TERMINALS AS STRATUS
MOVES OFFSHORE. CHANCES FOR MVFR TO IFR STRATUS RETURNING TO THE
COAST INCREASES BY 05-07Z THURSDAY. NORTH TO NORTHWESTERLY SURFACE
WINDS INCREASE THIS AFTERNOON WITH GUSTS UP TO 20-25 KT.
KPDX AND APPROACHES...VFR CONDITIONS WITH FEW HIGH CLOUDS EXPECTED
THROUGH TONIGHT. CHANCES FOR MVFR STRATUS RETURN TO AROUND 20-30%
BETWEEN 14-18Z THU. NORTHWEST WINDS EXPECTED TO INCREASE TO AROUND
10-12 KT WITH GUSTS UP TO 20 KT LATER THIS AFTERNOON. /DH
MARINE
WESTERLY SWELL CONTINUES TO MOVE THROUGH THE WATERS BUT
THE PEAK WAVE HEIGHTS SUBSIDED EARLIER THIS MORNING. SEAS ARE
GENERALLY BELOW 15 FT AND WILL CONTINUE TO DROP CLOSER TO 10 FT
OVERNIGHT. WINDS FROM THE NORTHWEST AT AROUND 10 KT. SMALL CRAFT
ADVISORIES REMAIN IN EFFECT FOR ALL ZONES DUE TO STEEP SEAS. HAVE
EXTENDED THE SMALL CRAFT UNTIL 1 AM AS AREA BUOYS ARE STILL
SHOWING CONDITIONS HOVERING RIGHT ON THE EDGE OF 10 FT. WINDS
THOUGH ARE BEGINNING TO EASE WHICH WILL AID IN LOWERING SEAS. THE
SMALL CRAFT FOR THE INNER WATERS HAS BEEN EXTENDED TO 1 AM AS AND
THE OUTER WATERS EXTENDED THROUGH 5 PM WEDNESDAY FOR STEEP SEAS
AND WIND GUSTS UP TO 25 KT. ANOTHER NORTHWESTERLY SWELL IS
EXPECTED TO MOVE INTO THE WATER ON THURSDAY, STEEPENING SEAS
ACROSS ALL MARINE ZONES AGAIN. CONDITIONS ARE BORDERLINE FOR
HAZARDOUS SEAS WARNING OR A SMALL CRAFT ADVISORY AT THIS TIME.
-27/19
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT THURSDAY FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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X.COM/NWSPORTLAND
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