295
FXUS66 KPQR 241049
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
349 AM PDT WED JUN 24 2026
SYNOPSIS
TODAY WILL BE THE LAST DAY OF ABNORMALLY WARM
TEMPERATURES. CONDITIONS REMAIN DRY WHILE ONSHORE FLOW
INCREASES. A SIGNIFICANT WEATHER PATTERN CHANGE IS ON TRACK
BEGINNING THURSDAY AS A FRONTAL SYSTEM SWINGS THROUGH AND
RETURNS WIDESPREAD CHANCES FOR RAIN BEGINNING THURSDAY NIGHT AND
THROUGH THE WEEKEND. THERE IS ALSO A 10-25% CHANCE FOR
THUNDERSTORMS FRIDAY AFTERNOON AND SATURDAY AFTERNOON.
CONDITIONS TREND DRIER AND SLIGHTLY WARMER SUNDAY THROUGH EARLY
NEXT WEEK, BUT WE'LL MAINTAIN SLIGHT CHANCES FOR LIGHT RAIN
SHOWERS ACROSS THE COAST RANGE AND CASCADES.
DISCUSSION...TODAY THROUGH TUESDAY
SATELLITE IMAGERY AS OF
EARLY WEDNESDAY MORNING DEPICTS WIDESPREAD MARINE STRATUS ALONG
THE COAST AND MOSTLY CLEAR SKIES INLAND. AS DAYTIME HEATING
PROGRESSES TODAY, WE'LL SEE INCREASED MIXING AND SOME STRATUS
BREAK-OUT ALONG THE COAST BY LATE MORNING. GUIDANCE IS
OPTIMISTIC FOR STRATUS BREAKING OUT ALONG THE ENTIRE COAST,
HOWEVER, BASED ON THE PERSISTENT PATTERN AND OBSERVATIONS FROM
THE LAST FEW DAYS, TRENDS FAVOR THE NORTH OREGON COAST CLEARING
OUT AFTER 17-18Z WED WHILE STRATUS KEEPS HOLD ALONG THE CENTRAL
OREGON COAST. WHETHER STRATUS BREAKS OUT OR NOT TODAY, THERE IS
HIGH CONFIDENCE THAT MARINE STRATUS WILL FILL BACK IN LATER THIS
EVENING.
TODAY IS THE FINAL DAY OF VERY WARM AND DRY CONDITIONS AS THE
UPPER-LEVEL RIDGE THAT BROUGHT THE HEAT THE LAST COUPLE DAYS IS
BREAKING DOWN AND SHIFTING EASTWARD. MODEL GUIDANCE CONTINUES TO
SHOW A WEAK UPPER-LEVEL TROUGH PASSING THROUGH THE REGION
TODAY, HOWEVER, IT'S NOT EXPECTED TO BRING ANY SHOWER ACTIVITY
WEST OF THE CASCADE CREST-LINE GIVEN THE LINGERING DRY AIRMASS
OVER OUR AREA. EVEN THOUGH WE'RE EXPECTED TO STAY DRY, THIS
TROUGH WILL BRING INCREASED ONSHORE FLOW AND AFTERNOON HIGH
TEMPERATURES A FEW DEGREES COOLER THAN THE LAST COUPLE DAYS -
UPPER 80S TO LOW 90S ACROSS INTERIOR VALLEYS. AS A RESULT, THERE
REMAINS WIDESPREAD MODERATE HEATRISK ACROSS THE WILLAMETTE
VALLEY, SW WASHINGTON LOWLANDS, AND COLUMBIA RIVER GORGE. THIS
LEVEL OF HEAT WILL AFFECT THOSE WHO ARE SENSITIVE TO HEAT,
ESPECIALLY THOSE WITHOUT ADEQUATE COOLING OR HYDRATION. MAKE
SURE TO STAY HYDRATED, WEAR LIGHT-COLORED AND LOOSE-FITTED
CLOTHING, WEAR SUN PROTECTION, TAKING FREQUENT BREAKS FROM THE
HEAT, AND LIMIT STRENUOUS OUTDOOR ACTIVITIES DURING THE HOTTEST
PART OF THE DAY.
A LARGE-SCALE PATTERN CHANGE TO COOLER AND WETTER CONDITIONS
REMAINS ON TRACK FOR THURSDAY NIGHT THROUGH THE WEEKEND AS
ENSEMBLE AND DETERMINISTIC GUIDANCE IS IN EXCELLENT AGREEMENT
OF AN UPPER-LEVEL LOW PRESSURE SYSTEM PROGRESSING INTO THE
PACIFIC NORTHWEST FROM THE GULF OF ALASKA. MOST ENSEMBLE MEMBERS
HAVE RAINFALL VIA A COLD-FRONTAL BOUNDARY REACHING THE COAST BY
LATE THURSDAY AFTERNOON/EVENING AND THEN SPREADING INTO THE I-5
CORRIDOR BY LATE THURSDAY NIGHT INTO FRIDAY MORNING. WE'LL
REMAIN IN THIS COOLER AND WET PATTERN THROUGH AT LEAST SATURDAY,
BUT AT LEAST TOTAL RAIN AMOUNTS AT THIS TIME APPEAR BENEFICIAL
AND GENERALLY NON-IMPACTFUL. LOOKING AT THE LATEST NBM, CHANCES
FOR 48-HOUR RAIN AMOUNTS EXCEEDING 1 INCH FROM 5 PM THURSDAY TO
5 PM SATURDAY ARE AROUND 40-70% FOR THE COAST AND COAST RANGE,
10-30% ALONG THE I-5 CORRIDOR, AND GREATER THAN 80% ACROSS THE
CASCADES DUE TO WESTERLY FLOW BRINGING OROGRAPHIC ENHANCEMENT.
WILL NOTE THAT THE WESTERN-MOST PARTS OF THE WILLAMETTE VALLEY
(INCLUDING MCMINNVILLE AND CORVALLIS) ONLY HAVE A 5-10% CHANCE
OF EXCEEDING 1 INCH DURING THIS TIMEFRAME DUE TO POTENTIAL
RAINSHADOWING FROM THE COAST RANGE.
BY FRIDAY AFTERNOON, THE UPPER-LEVEL TROUGH MOVES FURTHER SOUTH
AND EVENTUALLY CENTERS ITSELF RIGHT OVER-TOP THE PACIFIC
NORTHWEST AS A CLOSED LOW ON SATURDAY. TEMPERATURES WILL FURTHER
COOL ALOFT ALLOWING FOR INCREASING ATMOSPHERIC INSTABILITY
DURING THE DAYTIME HOURS AND FACILITATING CAPE VALUES OF 50-100
J/KG FRIDAY AFTERNOON AND 100-200 J/KG LATE SATURDAY MORNING
INTO THE AFTERNOON. THIS INSTABILITY PLUS SUFFICIENT LIFT FROM
THE LOW WILL SUPPORT A 10-20% CHANCE FOR THUNDERSTORMS ACROSS NW
OREGON AND SW WASHINGTON FRIDAY AFTERNOON, AND A 15-25% CHANCE
FOR THUNDERSTORMS SATURDAY AFTERNOON. FOR NOW, ANY CONVECTION
APPEARS RATHER WEAK AND UNORGANIZED (OUR TYPICAL POST-FRONTAL
POP-UP STORMS). LREF GUIDANCE SUGGESTS EFFECTIVE SHEAR REMAINS
BELOW 35 KT; THEREFORE, CHANCES THESE THUNDERSTORMS BECOME
SEVERE ARE UNLIKELY (<5%). OTHERWISE, ANY PASSING THUNDERSTORMS
MAY PRODUCE LIGHTNING, BRIEF HEAVY RAIN, ERRATIC WINDS, AND/OR
SMALL HAIL. ALSO CAN'T RULE OUT A COLD AIR FUNNEL CLOUD OR TWO
GIVEN THE TIME OF YEAR.
THE LATTER HALF OF THE WEEKEND INTO EARLY NEXT WEEK THE
MAJORITY OF ENSEMBLE MEMBERS ARE SHOWING THE BROADER UPPER-
LEVEL LOW FEATURE SHIFTING EASTWARD, RETURNING RELATIVELY DRIER
CONDITIONS AND A WARM-UP OF A FEW DEGREES. WILL STILL MAINTAIN
PRECIPITATION CHANCES ACROSS THE COAST RANGE AND CASCADES AS
WESTERLY FLOW CONTINUES TO SUPPORT OROGRAPHIC ENHANCEMENT OF
PRECIPITATION, HOWEVER, ANY ADDITIONAL RAIN AMOUNTS APPEAR VERY
LIGHT. STILL, WE'LL HAVE TO KEEP AN EYE ON SUBTLE SHORTWAVE
FEATURES ROTATING INTO THE REGION NORTH TO SOUTH ON THE BACK
SIDE OF THE UPPER-LEVEL LOW WHICH MAY EXPAND THE COVERAGE OF
SHOWERS TEMPORARILY - LOW CONFIDENCE ON THE PLACEMENT/TIMING OF
THESE SMALLER SHORTWAVE FEATURES. WESTERLY WINDS THROUGHOUT THIS
COOL AND WET PATTERN WILL BE BREEZIEST ALONG THE CENTRAL
COLUMBIA RIVER GORGE AND ACROSS UPPER HOOD RIVER VALLEY, WITH
CHANCES FOR ISOLATED WIND GUSTS EXCEEDING 45 MPH AROUND 10-35%
FROM FRIDAY THROUGH EARLY NEXT WEEK, WITH THE HIGHEST CHANCES ON
SUNDAY AND MONDAY. -10/99
AVIATION
SATELLITE IMAGERY AS OF EARLY WEDNESDAY MORNING
DEPICTS WIDESPREAD MARINE STRATUS ALONG THE COAST RESULTING IN
LIFR/IFR CIGS. EXPECT STRATUS TO HOLD ON ALONG THE ENTIRE COAST
THROUGH AT LEAST 17-18Z WED. AFTER 18Z WED, INCREASED MIXING
FROM DAYTIME HEATING WILL SUPPORT STRATUS BREAKING OUT FOR
PARTS OF THE COAST, RETURNING VFR CONDITIONS. BASED ON THE
PERSISTENT PATTERN THE LAST COUPLE DAYS, TRENDS FAVOR KAST
CLEARING OUT AFTER 18Z WED, WHILE IFR STRATUS HOLDS AT KONP. IF
KONP DOES CLEAR OUT, IT WOULD BE VERY BRIEF AND SOMETIME BETWEEN
19-23Z WED. EITHER WAY, THERE IS HIGH CONFIDENCE THAT MARINE
STRATUS WILL FILL BACK IN AND RETURN WIDESPREAD IFR CONDITIONS
ALONG THE COAST AFTER 02-03Z THU. FOR WILLAMETTE VALLEY
TERMINALS, VFR CONDITIONS PREVAIL THROUGHOUT THE TAF PERIOD WITH
FEW/SCT HIGH CLOUDS AROUND 25 KFT. LIGHT WINDS UNDER 5 KT
THROUGH 18Z WED, BECOMING WEST-NORTHWESTERLY AND INCREASING
AROUND 8-11 KT WITH GUSTS UP TO 18-20 KT ACROSS MOST TERMINALS
BETWEEN 22Z WED-03Z WED. WINDS GRADUALLY EASE IN THE EVENING.
KPDX AND APPROACHES...VFR WITH FEW/SCT HIGH CLOUDS THROUGH THE
TAF PERIOD. LIGHT WINDS UNDER 5 KT, BECOMING NORTHWESTERLY AND
INCREASING TO 9-11 KT WITH GUSTS UP TO 20 KT BETWEEN 23Z
WED-03Z THU. -10
MARINE
HIGH PRESSURE WILL MAINTAIN NORTHWEST WINDS ACROSS THE
COASTAL WATERS THROUGH THURSDAY MORNING. WINDS ARE GENERALLY
EXPECTED TO REMAIN UNDER 20 KT. WEAKENING HIGH PRESSURE WILL GIVE
WAY TO A FRONTAL SYSTEM APPROACHING THE AREA ON THURSDAY. WINDS
ARE EXPECTED TO BACK WEST TO SOUTHWESTERLY THURSDAY AFTERNOON
BEFORE THE COLD FRONT PUSHES ACROSS THE COASTAL WATERS
THURSDAY NIGHT INTO FRIDAY. SOUTHWEST WINDS ARE EXPECTED TO BE
STRONGEST ACROSS THE INNER COASTAL WATERS (UP TO 10 NM
OFFSHORE) AND NORTH OF CAPE FOULWEATHER, BUT THERE IS ONLY
AROUND A 10-20% CHANCE OF WIND GUSTS EXCEEDING 21 KT AT ANY
GIVEN HOUR THROUGH FRIDAY MORNING. WEST TO NORTHWEST WINDS WILL
PERSIST BEHIND THE FRONT LATER FRIDAY AND INTO THE WEEKEND AS
WEAK LOW PRESSURE LINGERS NEAR VANCOUVER ISLAND. HIGH PRESSURE
GRADUALLY BUILDS ACROSS THE WATERS LATE WEEKEND. SEAS AROUND 3-5
FT THROUGH FRIDAY, BUILDING TO 6-9 FT THIS WEEKEND AS A WEST-
NORTHWESTERLY SWELL MOVES IN. -10/DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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