332
FXUS66 KPQR 182030
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
130 PM PDT MON MAY 18 2026
SYNOPSIS
DRY AND BENIGN WEATHER IS EXPECTED ACROSS THE
REGION THROUGH MUCH OF THE NEXT WEEK AS HIGH PRESSURE BUILDS
OVER THE NORTHEAST PACIFIC, RESULTING IN A WARMING TREND. WEAK
SYSTEMS ALOFT MAY BRING ENHANCED CLOUD COVER ON SOME DAYS, BUT
RAIN CHANCES ARE MINIMAL.
DISCUSSION...NOW THROUGH SUNDAY NIGHT
CONCERNS FOR HAZARDOUS
WEATHER REMAIN MINIMAL THROUGH THE UPCOMING WEEK. THERE IS HIGH
CONFIDENCE THAT UPPER-LEVEL RIDGING AND SURFACE HIGH PRESSURE
WILL BUILD OVER THE NORTHEAST PACIFIC, ALTHOUGH UNCERTAINTY IN
THE AMPLITUDE AND POSITION OF THE UPPER RIDGE INCREASES LATER IN
THE FORECAST PERIOD. THROUGH THE END OF THE WORKWEEK, WHILE THE
RIDGE AXIS REMAINS WELL OFFSHORE, UPPER SHORTWAVES WITHIN
NORTHWESTERLY FLOW ALOFT MAY PRODUCE INCREASED CLOUD COVER ON
CERTAIN DAYS INCLUDING TUESDAY INTO WEDNESDAY MORNING, BUT
CHANCES FOR RAINFALL REMAIN 5-10% ALONG THE CLATSOP AND PACIFIC
COUNTY COASTS AND IN THE WILLAPA HILLS, AND LOWER ELSEWHERE. ON
CLEARER NIGHTS, AREAS OF FOG ARE MOST LIKELY TO DEVELOP WITHIN
SHELTERED VALLEYS. AS THE RIDGE AXIS SHIFTS EAST, TEMPERATURES
WILL TREND UPWARD THROUGH AT LEAST THURSDAY, REACHING THE 60S ON
THE COAST AND UPPER 70S TO LOW 80S ALONG THE I-5 CORRIDOR. AT
THIS TIME, THERE IS MINOR HEATRISK FORECAST ACROSS THE REGION,
MEANING THOSE WHO ARE MOST SENSITIVE TO HEAT MAY BE AFFECTED,
HOWEVER THERE ARE 15-25% CHANCES MODERATE HEATRISK OCCURS IN
SOME URBAN AREAS ALONG I-5 IF DAYTIME HIGHS END UP SLIGHTLY
HOTTER, INCLUDING THE PORTLAND/VANCOUVER METRO, SALEM, AND
ALBANY/CORVALLIS AREAS.
LATER IN THE FORECAST PERIOD, FROM FRIDAY THROUGH NEXT WEEKEND,
UNCERTAINTY IN THE EVOLUTION AND POSSIBLE BREAK-DOWN OF THE
UPPER-LEVEL RIDGE INTRODUCES SIMILAR UNCERTAINTY IN FORECAST
TEMPERATURES AND PRECIPITATION. FORECAST DAYTIME HIGHS CURRENTLY
TREND DOWNWARD THROUGH THE HOLIDAY WEEKEND AS CHANCES INCREASE
THAT RIDGING DEAMPLIFIES OR IS REPLACED BY AN UPPER TROUGH, BUT
THERE IS AN INCREASINGLY WIDE RANGE OF POSSIBLE OUTCOMES. THE
80%-CONFIDENCE ENVELOPES (THE DIFFERENCE BETWEEN THE 10TH AND
90TH PERCENTILES) IN TEMPERATURE WIDEN FROM 8-13 DEGREES ON
FRIDAY AND SATURDAY TO 16-18 DEGREES ON SUNDAY AND MONDAY ALONG
THE I-5 CORRIDOR. THERE IS GREATER CONSENSUS THAT THE RIDGE
WILL BREAK DOWN LATE SUNDAY INTO MONDAY, YIELDING INCREASING
CHANCES OF COOLER TEMPERATURES AS WELL AS THE HIGHEST CHANCES OF
RAINFALL, 25-50%, IN OVER A WEEK. -36
AVIATION
HIGH PRESSURE WILL MAINTAIN FAIR CONDITIONS WITH
HIGH LEVEL CLOUDS MOVING OVERHEAD THROUGH THE DAY. NORTHWEST
FLOW OF 5-10 KT THROUGH THE DAY WITH WIND GUSTS ALONG THE COAST
UP TO 20 KT POSSIBLE. WINDS RELAX THIS EVENING AND OVERNIGHT.
MARINE STRATUS PUSHED BACK TOWARD THE COAST THIS EVENING, MAINLY
ALONG THE NORTHERN OREGON AND SOUTHERN WASHINGTON COAST.
PROBABILITIES INCREASE TO 60-90% FOR DEVELOPMENT BETWEEN 02-06Z
WEDNESDAY FOR KAST AND MUCH LOWER AT 20-30% FOR KONP. GUIDANCE
SUGGESTS STRATUS DEVELOPING ALONG THE COLUMBIA RIVER TOWARD THE
PORTLAND/VANCOUVER METRO BETWEEN 10-1Z WEDNESDAY.
KPDX AND APPROACHES...VFR CONDITIONS EXPECTED THROUGH AT LEAST
06Z TUESDAY. HIGH CLOUDS EXPECTED TO CLEAR OUT THIS AFTERNOON.
LIGHT NORTHWEST WINDS EXPECTED TO INCREASE TO 8-10 KT BY 22Z
THIS AFTERNOON. STRATUS PUSHING INLAND ALONG THE COLUMBIA RIVER
COULD REACH THE METRO BETWEEN 10-16Z TUESDAY WITH A 30-60%
CHANCE FOR SUB-VFR CIGS, MAINLY FOR KTTD AND KPDX. -19
MARINE
NORTHERLIES ARE EXPECTED TO PERSIST THROUGH MUCH OF
THE WEEK AS THE SUMMER-LIKE PATTERN SETTLES IN. STRONGEST WINDS
ARE EXPECTED DURING THE AFTERNOON AND EVENING PERIODS AS A
SURFACE THERMAL TROUGH STRENGTHENS OVER THE SOUTHERN OREGON
COAST. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE INNER COASTAL
WATERS SOUTH OF CAPE FOULWEATHER LATER THIS AFTERNOON INTO THIS
EVENING FOR GUSTS UP TO 25 KT. SIMILAR CONDITIONS ARE EXPECTED
ON TUESDAY. SEAS AROUND 6 TO 8 FEET ARE EXPECTED THROUGH THE
WEEK AS WELL. CHANCES INCREASE ON WEDNESDAY AND THURSDAY FOR
MORE WIDESPREAD WIND GUSTS FOR ALL MARINE ZONES.
SMALL CRAFT ADVISORIES IS IN PLACE FOR THE COLUMBIA RIVER BAR
FOR EARLY TUESDAY MORNING DUE TO STRONG EBB CURRENTS WHICH WILL
PRODUCE CONDITIONS HAZARDOUS TO SMALL CRAFT. STRONG EBB CURRENTS
ARE POSSIBLE DURING THE MORNING HOURS EACH DAY THIS WEEK. -19/DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 5 AM TO 9 AM PDT TUESDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 11 PM PDT THIS EVENING FOR PZZ253.
WWW.WEATHER.GOV/PORTLAND
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