256
FXUS66 KPQR 222137
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
237 PM PDT TUE APR 22 2025
SYNOPSIS
DRY WEATHER WITH CLEAR SKIES THROUGH THURSDAY AS
HIGH PRESSURE BUILDS OVER THE REGION. PATTERN CHANGE RETURNS
THURSDAY NIGHT INTO FRIDAY AS AN APPROACHING SYSTEM RETURNS
COOLER AND WETTER WEATHER HEADING INTO THE WEEKEND.
SHORT TERM...NOW THROUGH THURSDAY NIGHT
HIGH PRESSURE WILL
MAINTAIN DRY WEATHER WITH CLEAR SKIES ACROSS NORTHWEST OREGON
AND SOUTHWEST WASHINGTON THROUGH THURSDAY. ZONAL FLOW ALOFT
WILL TURN NORTHERLY TODAY INTO WEDNESDAY AS AN UPPER LEVEL RIDGE
OVER THE NORTHEAST PACIFIC SHIFTS INTO THE PACIFIC NORTHWEST.
EXPECT AFTERNOON HIGHS TO GRADUALLY WARM UP THE NEXT COUPLE
DAYS, WITH THURSDAY BEING THE WARMEST DAY. HIGHS ARE FORECAST IN
THE UPPER 60S TO LOW 70S ON WEDNESDAY FOR INTERIOR VALLEYS, AND
MID TO UPPER 70S ON THURSDAY. CAN'T RULE OUT REACHING 80 DEGREES
IN THE GREATER PORTLAND/VANCOUVER METRO AREA (NBM GUIDANCE
SUGGESTS A 30-50% PROBABILITY OF EXCEEDING 80 DEGREES). ALTHOUGH
NIGHTS WILL BE CLEAR, FROST THREAT IS NOT EXPECTED AS LOWS ARE
FORECAST IN THE UPPER 30S TO LOW 40S WEST OF THE HIGH CASCADES.
WINDS THROUGHOUT THE NEXT COUPLE DAYS WILL GENERALLY BE LIGHT
AND NORTH-NORTHWESTERLY, WITH GUSTS TO 20-25 MPH ALONG THE
COAST TODAY AND WEDNESDAY AFTERNOON.
THURSDAY NIGHT, THE NEXT UPPER LEVEL TROUGH WILL APPROACH THE
PACIFIC NORTHWEST, TURNING FLOW ALOFT MORE SOUTHERLY TO
SOUTHEASTERLY. THIS KIND OF PATTERN TYPICALLY HELPS ADVECT MORE
MOISTURE FROM THE SOUTH AS WELL AS INSTABILITY AS COLDER AIR
FILTERS IN ALOFT. THIS IS THE KIND OF PATTERN THAT COULD LEAD TO
ELEVATED THUNDERSTORMS, ESPECIALLY IN THE LINN AND LANE COUNTY
CASCADES. AS OF NOW, IT'S MAINLY THE NAM MODEL SHOWING 700-300
MB MUCAPE VALUES OF 100-150 J/KG THURSDAY EVENING. THE OTHER
GLOBAL MODELS AREN'T QUITE SHOWING MUCAPE VALUES OF THIS
MAGNITUDE YET, SO DECIDED TO ONLY INCREASE THUNDER PROBABILITIES
SLIGHTLY FROM NBM IN THE LINN/LANE COUNTY CASCADES TO AROUND
10-15% THURSDAY EVENING. -ALVIZ
LONG TERM...FRIDAY TO MONDAY
FRIDAY MARKS A PATTERN CHANGE TO
COOLER AND WETTER WEATHER. THE MAJORITY OF ENSEMBLE MEMBERS FROM
THE GEFS, EPS, AND GEPS ARE IN AGREEMENT OF AN UPPER LEVEL
TROUGH TOWARD NORTHERN CALIFORNIA. AS THIS TROUGH MOVES INTO
CALIFORNIA, THIS WILL BRING SHOWERS INTO NORTHWEST OREGON AND
SOUTHWEST WASHINGTON FROM THE SOUTH/SOUTHEAST AS MOISTURE WRAPS
AROUND THE LOW. PROBABILITIES FOR 24 HOUR RAINFALL EXCEEDING
0.25 INCH FROM 5 AM FRIDAY TO 5 AM SATURDAY ARE AROUND 15-35%
ALONG THE COAST AND WILLAMETTE VALLEY, AND 40-70% ACROSS THE
COAST RANGE AND CASCADES. HIGHS WILL ALSO DROP INTO THE UPPER
50S TO LOW 60S FOR MOST AREAS WEST OF THE CASCADES. EXPECT A
COOL WEEKEND WITH LINGERING SHOWERS ON SATURDAY AS THE
AFOREMENTIONED LOW TRACKS EASTWARD INTO THE INTERMOUNTAIN WEST.
BY SUNDAY-MONDAY, PRECIPITATION CHANCES DECREASE AS THE MAJORITY
OF ENSEMBLE MEMBERS SUGGEST HIGH PRESSURE RE-BUILDING OVER THE
AREA AND RETURNING DRIER WEATHER. -ALVIZ
AVIATION
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD ACROSS
NW OREGON AND SW WASHINGTON. MOSTLY CLEAR SKIES ACROSS THE REGION
EXPECTED, THOUGH SCATTERED CUMULUS AROUND 2-4 KFT MAY DEVELOP
UNDER FAIR, NORTHERLY FLOW. NORTHERLY WINDS GENERALLY LESS THAN 10
KTS THROUGH THE TAF PERIOD FOR MOST AREAS. GUSTS AROUND 20 KT
POSSIBLE ALONG THE COAST. THERE IS A CHANCE (20-30%) FOR A WEAK MARINE
STRATUS TO PUSH ONSHORE AFTER 3Z AND RECEDING BY 18Z. IF THIS
OCCURS, ONLY KAST AND KONP WOULD BE AFFECTED.
PDX AND APPROACHES...VFR CONDITIONS OVER THE TAF PERIOD. COULD SEE
SOME SCATTERED CUMULUS DEVELOP AROUND 2-3 KFT WITH FAIR, NORTHERLY
FLOW. NORTH WINDS LESS THAN 10 KTS THROUGH THE TAF PERIOD. -BATZ
MARINE
STRONG HIGH PRESSURE OFFSHORE ALONG WITH A SURFACE
LEVEL THERMAL TROUGH DEVELOPING AND STRENGTHENING OVER THE
SOUTHERN AND CENTRAL OREGON COAST WILL MAINTAIN NORTHERLY WINDS
ACROSS ALL WATERS THROUGH THE MIDDLE OF THE WEEK. AS THE THERMAL
TROUGH STRENGTHENS OVER THE COAST, THESE WINDS ARE EXPECTED TO
SPREAD NORTH ALONG THE NORTHERN OREGON AND SOUTHERN WASHINGTON
COASTAL WATERS, WITH GUSTS 25-30 KTS POSSIBLE AT TIMES. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT FOR ZONES (EXCEPT THE COLUMBIA
RIVER BAR) UNTIL 11 PM WEDNESDAY. STRONGEST WINDS ARE EXPECTED TO
EBB AND FLOW DIURNALLY, STRONGEST IN THE LATE AFTERNOON TO
OVERNIGHT HOURS, BACKING OFF IN THE MORNING HOURS. WINDS MAY DROP
BELOW SMALL CRAFT ADVISORY CRITERIA DURING THE OVERNIGHT HOURS
BEFORE INCREASING DURING THE DAY. HAVE DECIDED TO EXTEND THE
ADVISORY FOR ALL ZONES INSTEAD OF BREAKING UP TIMEFRAME GIVEN THE
SHORT LULL. SEAS ARE EXPECTED TO PERSIST AROUND 6 TO 8 FT AROUND
10 SECONDS THROUGH THE MIDDLE OF THE WEEK. -BATZ
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 11 PM PDT WEDNESDAY FOR PZZ251>253-
271-272.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT WEDNESDAY FOR PZZ273.
WWW.WEATHER.GOV/PORTLAND
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