015
FXUS66 KPQR 171717
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1017 AM PDT FRI APR 17 2026
SYNOPSIS
MILD SPRINGTIME CONDITIONS EXPECTED THROUGH THE
WEEKEND. SCATTERED LIGHT SHOWERS ARE POSSIBLE ON SATURDAY AS A
WEAK COLD FRONT APPROACHES, HOWEVER, TRENDS CONTINUE TO WEAKEN
THIS SYSTEM. CONFIDENCE DECREASES AS WE HEAD INTO NEXT WEEK. A
LARGE UPPER LEVEL LOW IS EXPECTED SET UP OFF THE NORTHERN
CALIFORNIA AND SOUTHERN OREGON COASTS AND SLIGHT ADJUSTMENTS IN
LOCATION WILL DETERMINE OVERALL CONDITIONS.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
LIGHT AND WIDELY
SCATTERED SHOWERS CONTINUE TO SHOW UP ON RADAR AND ARE EXPECTED
TO DISSIPATE BEFORE DAWN. SKIES HAVE CLEARED OVER MOST OF THE
AREA WITH THE EXCEPTION BEING THE CENTRAL AND NORTHERN
WILLAMETTE VALLEY, INTO THE PORTLAND METRO WHERE MID LEVEL
CLOUDS HAVE THICKENED. WHERE CLOUD COVER REMAINS THIN,
TEMPERATURES HAVE DROPPED INTO THE LOW TO MID 30S WITH EFFICIENT
RADIATIVE COOLING. EXPECTING TEMPERATURES TO CONTINUE DROPPING
OVER THE NEXT FEW HOURS WITH THE MOST SHELTERED LOCATIONS
REACHING AROUND 30. FREEZE WARNINGS REMAIN IN EFFECT THROUGH 9
AM ACROSS THE SOUTHERN WILLAMETTE VALLEY, CASCADE FOOTHILLS IN
OREGON, AND THE UPPER HOOD RIVER VALLEY WHERE TEMPS ARE EXPECTED
TO BOTTOM OUT IN THE LOW 30S. ELSEWHERE, A FROST ADVISORY
REMAINS IN EFFECT FOR LOWS EXPECTED TO DIP INTO THE MID 30S,
SUPPORTING FROST DEVELOPMENT. LOCATIONS NOT UNDER A WARNING OR
ADVISORY INCLUDE THE PORTLAND/VANCOUVER METRO, THE NORTHERN
OREGON COAST, THE SOUTHERN WASHINGTON COAST, AND COLUMBIA RIVER
GORGE BELOW 1500 FEET WHERE TEMPERATURES ARE EXPECTED TO BE A
FEW DEGREES WARMER IN THE UPPER 30S TO LOW 40S.
CONDITIONS TREND WARMER TODAY WITH TEMPERATURES TOPPING OUT
NEAR NORMAL IN THE UPPER 50S TO LOW 60S INLAND AND MID TO UPPER
50S ALONG THE COAST. A WEAK THERMAL TROUGH IS EXPECTED TO
DEVELOP, LEADING TO LIGHT OFFSHORE FLOW ALONG THE EASTSIDE OF
THE COAST RANGE AND CASCADES AND LIGHT NORTHERLY FLOW WITHIN THE
WILLAMETTE VALLEY. LOWS TONIGHT ARE EXPECTED TO BE A TAD WARMER
WITH CLOUD COVER PERSISTING OVERNIGHT. THE PROBABILITY FOR
BELOW FREEZING TEMPERATURES REMAINS CONFINED TO THE HIGH
CASCADES AND THE HIGHER ELEVATIONS OF THE UPPER HOOD RIVER
VALLEY. UPPER 30S WILL BE POSSIBLE FOR MOST LOCATIONS ASIDE FROM
THE COASTAL ZONES WITH THE COOLEST TEMPERATURES EXPECTED IN THE
SOUTHERN WILLAMETTE VALLEY. PROBABILITIES FOR TEMPERATURES TO
DROP BELOW 37 ARE 40-50% IN THE SOUTHERN WILLAMETTE VALLEY AND
THE NORTHERN COAST RANGE WHILE ELSEWHERE INLAND, CHANCES TOP OUT
AT 10-30%. THE WARMING TREND CONTINUES INTO SATURDAY WITH
INLAND HIGHS EXPECTED TO REACH THE LOW 70S AND UPPER 50S TO LOW
60S ALONG THE COAST.
LONG TERM...SUNDAY THROUGH THURSDAY
THE FORECAST THROUGH THE
LONG-TERM PERIOD HINGES ON THE PROGRESSION OF AN UPPER-LEVEL LOW
TRACKING SOUTHWARD FROM THE GULF OF ALASKA OVER THE NORTHEASTERN
PACIFIC FROM SUNDAY INTO THE MIDDLE OF NEXT WEEK. CONSENSUS
REMAINS LARGELY SPLIT WITH MAYBE A SLIGHT INCREASE IN AGREEMENT
FOR MONDAY. ENSEMBLE MEMBERS SHOW SLIGHTLY LESS SPREAD IN THE
POSITION OF THE UPPER LOW OFF THE NORTHERN CALIFORNIA OR
SOUTHERN OREGON COASTS. SOME OF THESE SOLUTIONS MAINTAIN
STRONGER RIDGING OVERHEAD AND THEREFORE RESULT IN WARMER AND
DRIER CONDITIONS. IF THE PLACEMENT OF THE LOW IS CLOSE ENOUGH TO
TRANSPORT MOISTURE FROM THE SOUTH UP TOWARD THE CASCADES, THESE
WARMER TEMPERATURES COULD ALSO SUPPORT AFTERNOON/EVENING
CONVECTION MONDAY OR TUESDAY, HOWEVER THE CHANCES OF THIS REMAIN
TOO LOW TO INCLUDE IN THE FORECAST AT THIS LEAD TIME. THE OTHER
HALF OF ENSEMBLE MEMBERS PLACE THE LOW FARTHER TO THE NORTH AND
EAST, CLOSER TO THE LOCAL AREA, YIELDING HIGHER CLOUD COVER,
NEAR TO BELOW- NORMAL TEMPERATURES, AND POTENTIAL RAIN SHOWERS.
DESPITE THIS PERIOD OF HIGH UNCERTAINTY, THERE IS ACTUALLY
HIGHER CONFIDENCE TOWARD THE MIDDLE OF THE WEEK AS THE LOW
EVENTUALLY TRACKS INLAND, AND NORTHWESTERLY ONSHORE FLOW ALOFT
TENDS TO RETURN TEMPERATURES TO NEAR-NORMAL VALUES WITH CHANCES
FOR RAIN ON WEDNESDAY, THEN WARMING AND DRYING INTO THURSDAY AS
RIDGING BUILDS ANEW. -36/19
AVIATION
VFR CONDITIONS EXPECTED THROUGHOUT THE TAF PERIOD
BENEATH FEW-SCT LOW CLOUDS AT 3-5 KFT AND SCT HIGH CLOUDS AT OR
ABOVE 25 KFT. DIURNAL NORTH TO NORTHWEST WINDS AROUND 5 KT
EXPECTED AT INLAND TERMINALS, AND 8-12 KT ALONG THE COAST. WINDS
EASE TO 3 KT OR LESS TONIGHT, WITH CALM TO LIGHT AND VARIABLE
CONDITIONS ALONG MUCH OF THE WILLAMETTE VALLEY AND LIGHT EAST FLOW
WEST OF THE COLUMBIA RIVER GORGE (KTTD) AND WEST OF COASTAL GAPS
(KAST, KONP). THERE ARE LOW CHANCES (10-15%) FOR MVFR CIGS AT
COASTAL TERMINALS AFTER 06-12Z SAT, BUT ANY OFFSHORE FLOW WILL
LIKELY INHIBIT MARINE STRATUS FORMATION.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGHOUT THE
PERIOD BENEATH FEW-SCT LOW CLOUDS AT 3-5 KT AND SCT HIGH CLOUDS AT
OR ABOVE 25 KFT. DIURNAL WINDS WILL RISE OUT OF THE NORTH TO
NORTHWEST AROUND 5 KT, THEN EASE TO LIGHT AND VARIABLE OVERNIGHT
AFTER 08Z SAT. LIGHT EAST FLOW IS EXPECTED TO DEVELOP WEST OF THE
COLUMBIA RIVER GORGE AS HIGH PRESSURE BUILDS INLAND, BUT EAST
WINDS ARE NOT EXPECTED TO REACH KPDX. -36
MARINE
BENIGN CONDITIONS EXPECTED TO PERSIST INTO THE
WEEKEND. SEAS CONTINUE TO TREND DOWN AND ARE EXPECTED TO DROP
BELOW 5 FEET THIS AFTERNOON. WINDS TURN NORTHEASTERLY THIS
MORNING AS A WEAK THERMAL TROUGH DEVELOPS. WINDS WILL GENERALLY
BE LIGHT AT LESS THAN 10 KT BUT COULD SEE SLIGHTLY STRONGER
WINDS UP TO 15 KT OUT TO 30 NM FROM CAPE FALCON SOUTH TO
FLORENCE. A WEAKENING COLD FRONT IS EXPECTED TO APPROACH THE
WATERS ON SATURDAY. THIS WILL VEER WINDS TO THE SOUTH ALONG WITH
POSSIBLE GUSTS TO AROUND 20 KT. THERE IS A 20-30% CHANCE FOR
SMALL CRAFT GUSTS FOR THE OUTER WATERS. SEAS INCREASE SLIGHTLY
TO 6-7 FEET. -19
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY FROM 1 AM TO 8 AM PDT SATURDAY FOR ORZ116>118-
121.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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