484
FXUS66 KPQR 061118
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
400 AM PDT MON APR 6 2026
SYNOPSIS
DRY CONDITIONS WILL PERSIST THROUGH FRIDAY ASIDE
FROM A CHANCE OF SHOWERS OVER THE OREGON CASCADES WEDNESDAY
EVENING THROUGH FRIDAY TO THE SOUTH OF CLACKAMAS COUNTY. HIGH
PRESSURE WILL MAINTAIN WELL ABOVE NORMAL TEMPERATURES FOR THIS TIME
OF YEAR THROUGH MONDAY. ONSHORE FLOW RETURNS TUESDAY AND WEDNESDAY,
BRINGING RELATIVELY COOLER TEMPERATURES. TRENDING RELATIVELY WARMER
AGAIN THURSDAY INTO FRIDAY WITH LIGHT OFFSHORE FLOW DEVELOPING.
SHOWER CHANCES RETURN TO NORTHWEST OR AND SOUTHWEST WA ON SATURDAY
AND SUNDAY.
DISCUSSION...NOW THROUGH SUNDAY NIGHT
MOSTLY CLEAR SKIES AND CALM
WINDS REMAIN IN PLACE OVER THE AREA MONDAY MORNING, ASIDE FROM AN
AREA OF LOW STRATUS THAT IS BEGINNING TO PUSH ONTO THE CENTRAL OREGON
COAST FROM NEWPORT TO FLORENCE. ALTHOUGH HIGH PRESSURE IS STILL ON
TRACK TO WEAKEN A BIT TODAY WITH 850 MB TEMPERATURES COOLING
SLIGHTLY, ABUNDANT SUNSHINE WILL ALLOW TEMPERATURES TO WARM WELL INTO
THE 70S ONCE AGAIN THIS AFTERNOON. THE ONLY EXCEPTION IS AT THE COAST
WHERE THE RETURN OF ONSHORE FLOW WILL BRING RELATIVELY COOLER
TEMPERATURES COMPARED TO SUNDAY. SEVERAL RECORD HIGH TEMPERATURES
WERE EITHER TIED OR BROKEN ON SATURDAY WITH OBSERVED HIGHS IN THE MID
TO UPPER 70S (RECORDS WERE TIED OR BROKEN AT PORTLAND, EUGENE, SALEM,
HILLSBORO, AND VANCOUVER). A FEW MORE RECORD HIGHS MAY BE TIED OR
BROKEN ON MONDAY AS FORECAST HIGHS ARE ONCE AGAIN IN THE MID TO UPPER
70S. IT IS NOT RECOMMENDED TO COOL OFF IN LOCAL LAKES AND RIVERS AS
WATER TEMPERATURES ARE CURRENTLY FRIGID ENOUGH TO RESULT IN COLD
WATER SHOCK, WHICH CAN BECOME LIFE THREATENING.
BEGINNING LATE MONDAY INTO TUESDAY, A WEAK AND DRY COLD FRONT
ASSOCIATED WITH A LOW PRESSURE SYSTEM MOVING EAST THROUGH BRITISH
COLUMBIA IS SLATED TO MOVE OVER THE REGION. AHEAD OF THIS, MODELS ARE
SHOWING UPPER LEVEL FLOW BECOMING WESTERLY WITH A VERY SUBTLE
UPPER SHORTWAVE ASSOCIATED WITH THE FRONT. THIS WEAK FEATURE COULD
BRING JUST ENOUGH OROGRAPHIC LIFT FOR ISOLATED SHOWERS OVER THE
SOUTHERN LANE COUNTY CASCADES MONDAY AFTERNOON (15-20% CHANCE),
MAINLY ALONG THE CREST. HIGHER CHANCES WILL BE EAST OF THE CASCADE
CREST.
TEMPERATURES THEN TREND COOLER TUESDAY AND WEDNESDAY BEHIND THE FRONT
WITH DRY NORTHWEST FLOW ALOFT AND RELATIVELY STRONGER LOW-LEVEL
ONSHORE FLOW. THE NBM CONTINUES TO DEPICT LOW MODEL SPREAD FOR
TEMPERATURES BOTH DAYS, SUGGESTING HIGH TEMPERATURES WILL LIKELY WIND
UP IN THE LOW TO MID 60S, EXCEPT 55-60 DEGREES AT THE COAST. BEYOND
WEDNESDAY, MODEL ENSEMBLE GUIDANCE CONTINUES TO SHOW A BRIEF WARMING
TREND THURSDAY THROUGH FRIDAY DUE TO SHORTWAVE RIDGING ON THE
NORTHEAST PERIPHERY OF AN UPPER LEVEL LOW CENTERED OFF THE
NORTHERN/CENTRAL CALIFORNIA COAST. THE LATEST ITERATION OF THE NBM
HAS TICKED UP ANOTHER DEGREE OR SO, NOW SUGGESTING HIGHS BETWEEN
69-72 DEGREES OVER THE INTERIOR LOWLANDS. THERE IS A 25% CHANCE HIGHS
WILL REACH INTO THE MID 70S BOTH DAYS. WITH THE INCREASING SIGNAL FOR
WARMER TEMPERATURES LATE IN THE WEEK, CHANCES FOR MORNING FROST
REMAIN LIMITED MAINLY TO WEDNESDAY MORNING. PROBABILITIES FOR LOW
TEMPERATURES OF 36 DEGREES OR COLDER RANGE BETWEEN 10-25% OVER THE
INTERIOR LOWLANDS AND INLAND COASTAL COMMUNITIES, EXCEPT
1-5% IN THE PORTLAND METRO TO THE EAST OF THE WEST HILLS, AND
50-80% IN THE UPPER HOOD RIVER VALLEY FROM ODELL TO PARKDALE.
ANYONE WITH SENSITIVE OUTDOOR VEGETATION THAT IS SUSCEPTIBLE TO
FROST DAMAGE SHOULD STAY UP-TO-DATE ON THE TEMPERATURE FORECAST
OVER THE COMING DAYS AND MONITOR FOR POTENTIAL FROST ADVISORIES.
MOSTLY DRY WEATHER WILL PERSIST THROUGH FRIDAY EXCEPT OVER THE OREGON
CASCADES SOUTH OF CLACKAMAS COUNTY. ENSEMBLE GUIDANCE
INDICATES THE POTENTIAL FOR WRAP-AROUND MOISTURE FROM THE SOUTH
ASSOCIATED WITH THE AFOREMENTIONED UPPER LOW SPINNING OFF OF THE
NORTHERN CALIFORNIA COAST. THIS MOISTURE COULD MOVE FAR ENOUGH
NORTH TO PRODUCE SHOWER CHANCES EACH DAY WEDNESDAY THROUGH FRIDAY,
MAINLY DURING THE AFTERNOON AND EVENING HOURS. AN ISOLATED
THUNDERSTORM OR TWO CANNOT BE RULED OUT EITHER DEPENDING ON THE
DEGREE OF INSTABILITY IN PLACE, AND PROBABILITIES FOR THUNDERSTORMS
HAVE INCREASED TO 10-15% OVER THE LANE COUNTY CASCADES ON THURSDAY
AND FRIDAY.
WIDESPREAD CHANCES FOR SHOWERS FINALLY RETURN TO THE AREA NEXT
WEEKEND, HOWEVER EXACT TIMING AND RAIN AMOUNTS REMAIN UNCERTAIN. BY
NEXT SATURDAY AFTERNOON, THE 500 MB CLUSTER ANALYSIS OF THE GEFS,
EPS, AND GEPS NOW INDICATES THREE POTENTIAL SOLUTIONS. ONE SOLUTION
SHOWS AN ELONGATED WEAK UPPER LOW OFF THE CENTRAL CALIFORNIA COAST,
RESULTING IN SOUTHERLY FLOW ALOFT OVER THE PACIFIC NORTHWEST (22%
CHANCE THIS SOLUTION VERIFIES). THIS SOLUTION WOULD LIKELY BRING AT
LEAST SOME SHOWERS INTO THE AREA AS THE SOUTHERLY FLOW ALOFT WOULD
ALLOW FOR INCREASING MOISTURE AND INSTABILITY, AND POSSIBLY EVEN
ISOLATED THUNDERSTORMS (ESPECIALLY OVER THE CASCADES). THE SECOND
SOLUTION (28% CHANCE OF VERIFYING) SHOWS TWO DISTINCT CLOSED LOWS,
ONE OFF THE WA/OR COAST AND ONE OFF THE SOUTHERN CA COAST. THIS
SOLUTION COULD ALSO BRING SHOWERS INTO THE AREA, AS LONG AS THE MORE
NORTHERN UPPER LOW TRACKS OVERHEAD. THE THIRD SOLUTION (50% CHANCE OF
VERIFYING) SUGGESTS A CLOSED LOW OVER THE SOUTHERN CA COAST WITH SOME
DEGREE OF WEAK TROUGHING FOCUSED OVER BRITISH COLUMBIA AND/OR
NORTHERN WA, RESULTING IN DRY WESTERLY FLOW ALOFT FOR NORTHWEST OR
AND SOUTHWEST WA WITH NEAR NORMAL OR EVEN SLIGHTLY ABOVE NORMAL 500
MB HEIGHTS. THIS WOULD BE THE WARMEST AND DRIEST SOLUTION, ALBEIT
COOLER THAN WHAT IS EXPECTED THURSDAY AND FRIDAY. THIS UNCERTAINTY IN
THE OVERALL PATTERN HAS RESULTED IN A 20-40% CHANCE OF RAIN SHOWERS
WEST OF THE CASCADES AND A 40-60% CHANCE OVER THE CASCADES. CHANCES
FOR SHOWERS INCREASE BY ANOTHER 5-15% FOR ALL LOCATIONS ON SUNDAY.
EVEN IF SHOWERS DO RETURN ON SATURDAY AND/OR SUNDAY, GUIDANCE
SUGGESTS RAIN AMOUNTS WILL MOST LIKELY BE LIGHT. PROBABILITIES FOR
48-HOUR RAIN TOTALS BELOW 0.25" FROM 5AM SATURDAY THROUGH 5AM MONDAY
ARE AROUND 70-75%, EXCEPT 55-70% AT THE COAST AND 40-50% OVER THE
CASCADES. -23/03
AVIATION
AT 11Z MONDAY, VFR FLIGHT CONDITIONS WERE CONTINUING
TO BE OBSERVED ACROSS THE AREA WITH MOSTLY CLEAR SKIES ALONG WITH
CALM WINDS. SATELLITE OBSERVATIONS DEPICTED AN AREA OF LOW STRATUS
OVER THE OREGON COASTAL WATERS FROM KONP SOUTHWARD ASSOCIATED WITH
A SOUTHERLY WIND REVERSAL. THIS STRATUS DECK IS JUST BEGINNING TO
PUSH ONTO THE COAST AT KONP, AND IS EXPECTED TO BEGIN IMPACTING THE
TERMINAL BY 12Z MONDAY. CONFIDENCE IS LOWER REGARDING THE EXACT
TIMING LOW STRATUS WILL PUSH FAR ENOUGH TO THE NORTH TO BEGIN
IMPACTING KAST.
THE LATEST OBSERVATIONS AND GUIDANCE NOW SUGGESTS THIS STRATUS DECK
MAY TAKE LONGER TO REACH KAST THAN WHAT WAS INITIALLY ANTICIPATED,
POTENTIALLY HOLDING OFF UNTIL AS LATE AS 00-03Z TUESDAY. THAT SAID,
THERE IS A 30-40% LOW STRATUS REACHES KAST AT ANY GIVEN HOUR BETWEEN
16-00Z. PROBABILITIES QUICKLY INCREASE TO 80-90% BY 03Z TUESDAY. CIGS
WILL MOST LIKELY BE NEAR OR BELOW 1000 FT WITH THIS STRATUS DECK ONCE
IT MOVES INLAND. VISIBILITY REDUCTIONS ARE ALSO LIKELY. MEANWHILE,
INLAND TERMINALS WILL REMAIN MOSTLY CLEAR INTO MONDAY NIGHT WITH
LIGHT ONSHORE WINDS DEVELOPING MONDAY AFTERNOON AND EVENING.
KPDX AND APPROACHES...EXPECT VFR FLIGHT CONDITIONS TO PERSIST
THROUGH MONDAY NIGHT WITH A FEW HIGH CLOUDS FROM TIME TO TIME. CALM
WINDS WILL GIVE WAY TO NORTHWEST WINDS AROUND 5-9 KT BY 00Z TUESDAY
AS A SEA BREEZE PUSHES UP THE COLUMBIA RIVER. -23
MARINE
A SOUTHERLY WIND REVERSAL HAS DEVELOPED OVER THE SOUTHERN
WATERS EARLY MONDAY MORNING. THIS WILL BE SHORT-LIVED, AS A NORTHERLY
FLOW REGIME WILL RETURN BY MONDAY AFTERNOON AND THEN PERSIST THROUGH
THE REMAINDER OF THE WEEK. SEAS SHOULD BECOME STEEP ENOUGH FOR A
PERIOD OF MARGINAL SMALL CRAFT ADVISORY CONDITIONS TUESDAY THROUGH
TUESDAY NIGHT WITH WIND GUSTS UP TO 20-25 KT AND SEAS BETWEEN 6 AND 9
FT AT 8 TO 9 SECONDS. SEAS AND WINDS DECREASE SLIGHTLY ON WEDNESDAY.
SEAS ARE THEN EXPECTED TO REBUILD TOWARDS 7 TO 9 FT TOWARDS THE
VERY END OF THE WEEK IN RESPONSE TO A FRESH NORTHWESTERLY SWELL
THAT WILL IMPACT THE WATERS. GIVEN A DOMINANT WAVE PERIOD AROUND 8
TO 9 SECONDS, SEAS WILL BECOME STEEP AGAIN. IN ADDITION, NORTHERLY
WINDS WILL INCREASE SLIGHTLY WITH GUSTS TOPPING OUT CLOSE TO 20
KT. THERE IS A 40-70% CHANCE MAX WIND GUSTS WILL EXCEED 21 KT ON
FRIDAY OVER THE OUTER WATERS AND A 20-40% CHANCE OVER THE INNER
WATERS. BETWEEN THE STEEPER SEAS AND INCREASING CHANCES FOR WIND
GUSTS OVER 21 KT, IT IS LIKELY ANOTHER ROUND OF MARGINAL SMALL
CRAFT ADVISORIES WILL BE WARRANTED. -23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 AM TUESDAY TO 5 AM PDT WEDNESDAY
FOR PZZ251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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