064
FXUS66 KPQR 291018
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
318 AM PDT WED JUL 29 2026
SYNOPSIS
ONSHORE FLOW PERSISTS THROUGH MUCH OF THE NEXT WEEK,
WHILE HIGH PRESSURE BUILDING OFFSHORE WILL SEE TEMPERATURES
TREND WARMER THROUGH FRIDAY. A FRONTAL SYSTEM SATURDAY WILL
BRING THE NEXT CHANCES FOR LIGHT RAIN AND USHER IN A BROAD
PATTERN CHANGE THIS WEEKEND INTO NEXT WEEK.
SHORT TERM...NOW THROUGH FRIDAY
BROAD UPPER-LEVEL RIDGING
CURRENTLY CENTERED OVER THE ROCKIES WILL BUILD AND RETROGRADE
WESTWARD OVER THE GREAT BASIN THROUGH FRIDAY, INCREASING HEIGHTS
ALOFT LOCALLY AND SUPPORTING A WARMING TREND ACROSS THE REGION.
TEMPERATURES NEAR NORMAL IN THE MID 60S ON THE COAST AND LOW 80S
WITHIN INLAND VALLEYS ARE EXPECTED TODAY AND TOMORROW AS WEAK
WAVES WITHIN THE SOUTHWESTERLY FLOW ALOFT WILL KEEP HEAT FROM
RISING TO HAZARDOUS LEVELS. EVEN ON FRIDAY, TEMPERATURES WILL
MOST LIKELY PEAK IN THE MID 60S TO LOW 70S AT THE COAST AND MID
TO UPPER 80S INLAND, SUPPORTING GENERALLY MINOR HEATRISK. THE
WARMEST LOCATIONS WITH THE HIGHEST CHANCE (25-45%) OF REACHING
MODERATE HEATRISK WILL BE THE TUALATIN VALLEY. OTHERWISE, A
TYPICAL SUMMERTIME PATTERN WILL SEE DRY WEATHER AND MORNING
CLOUDS, ESPECIALLY ALONG THE COAST, CLEARING TO MOSTLY SUNNY
SKIES EACH AFTERNOON. -36
LONG TERM...FRIDAY NIGHT THROUGH TUESDAY
A MORE SUBSTANTIAL
PATTERN SHIFT WILL BEGIN FRIDAY NIGHT INTO SATURDAY AS AN UPPER
TROUGH MOVES FROM THE GULF OF ALASKA INLAND OVER THE PACIFIC
NORTHWEST. THIS SYSTEM WILL BRING A COLD FRONT INTO THE COAST ON
SATURDAY. RAIN MAY BEGIN ALONG THE SOUTHERN WASHINGTON AND FAR
NORTHERN OREGON COASTS AS EARLY AS FRIDAY NIGHT, BUT IS MOST
LIKELY ON SATURDAY MORNING. THE HIGHEST CHANCES FOR RAINFALL OF
0.01 INCHES OR MORE ARE 35-55% ALONG THE COAST AND COASTAL
TERRAIN NORTH OF FLORENCE WITH THE ODDS INCREASING TO THE NORTH,
AS WELL AS ALONG THE CASCADES NORTH OR-22 (OR FROM THE MARION-
LINN COUNTY LINE NORTHWARD). ANY RAINFALL WILL MOST LIKELY BE
VERY LIGHT, AMOUNTING TO NO MORE THAN 0.05-0.10 INCHES. NEAR TO
SLIGHTLY BELOW NORMAL HIGH TEMPERATURES IN THE 60S AND 70S ARE
EXPECTED THROUGH THE WEEKEND IN THE WAKE OF THE FRONTAL PASSAGE.
AS THE PROGRESSIVE UPPER TROUGH EXITS EASTWARD, THERE IS
INCREASED UNCERTAINTY IN THE EVOLUTION OF THE PATTERN BY EARLY
NEXT WEEK. LONG-RANGE ENSEMBLES DEPICT A HIGH PROBABILITY OF
STRONG UPPER-LEVEL RIDGING DEVELOPING OVER THE FOUR CORNERS, BUT
WHETHER THAT WILL TRANSLATE TO HOT WEATHER LOCALLY IS MORE
UNCERTAIN. WHILE WARMER TEMPERATURES COMPARED TO THE WEEKEND ARE
ALL BUT CERTAIN, THE SPREAD OF POTENTIAL SOLUTIONS REMAINS WIDE;
A BEST FORECAST AT THIS LEAD TIME IS FOR AFTERNOON HIGHS IN THE
70S ALONG THE COAST AND UPPER 80S TO LOW 90S INLAND, HOWEVER
THERE IS A 25% CHANCE HIGH FAIL TO REACH EVEN 85 DEGREES INLAND,
AS WELL AS A 25% CHANCE OF REACHING 95 DEGREES ON TUESDAY AND
WEDNESDAY WITHIN THE WILLAMETTE VALLEY. -36
AVIATION...THROUGH 06Z THURSDAY
AREAS OF LOW CLOUD COVER ARE
SLOWLY SPREADING ALONG THE IMMEDIATE COASTLINE WITH A MIX OF
VFR TO LIFR CONDITIONS. UNCERTAINTY REMAINS MODERATE REGARDING
THE EXACT PROGRESSION OF CEILING HEIGHTS INTO THE MORNING ACROSS
THE REGION, AS WELL AS WHETHER OR NOT CLOUD COVER WILL BE
PREDOMINATELY SCATTERED OR BROKEN COME THE SUNRISE HOURS. THE
LATEST GUIDANCE SUGGESTS A BROKEN CLOUD DECK WILL ATTEMPT TO
FILL IN OVER PORTIONS OF THE WILLAMETTE VALLEY AND PORTLAND
METRO BETWEEN 08-13Z. HOWEVER, PROBABILITIES CURRENTLY FAVOR
LOW-END VFR CEILINGS WITH THIS POTENTIAL STRATUS DECK.
PROBABILITIES FOR MVFR CEILINGS BELOW 3000 FT PEAK BETWEEN
10-16Z WEDNESDAY ARE STILL BETWEEN 15-30% AT ALL INLAND TAF
SITES. MUCH HIGHER CONFIDENCE IN WIDE-SPREAD VFR CONDITIONS BY
THE 18Z ONWARD AS THE STRATUS QUICKLY DISSIPATES.
KPDX AND APPROACHES...VFR CONDITIONS IN PLACE LATE THIS EVENING
WILL MOST LIKELY REMAIN IN PLACE THROUGH THE TAF PERIOD. THAT
SAID, WE'LL STILL HAVE TO WATCH LOW STRATUS FORMATION NEAR
SUNRISE AS THERE IS ~20% CHANCE FOR MVFR CEILINGS BELOW 3000 FT
BETWEEN 12-16Z. VFR CIGS/VIS ARE HEAVILY FAVORED AFTER THIS
POINT. WINDS GENERALLY REMAIN OUT OF THE NORTHWEST AT 5-10
KNOTS. -99/23
MARINE
BUOY OBSERVATIONS FROM EARLY WEDNESDAY MORNING SHOW
SEAS CONTINUING AT 4-6 FT, WHICH ARE EXPECTED TO PERSIST THROUGH
MUCH OF THE WEEK WITH A DOMINANT WEST TO NORTHWEST SWELL AT 7-9
SECONDS AND A SECONDARY LONG-PERIOD SOUTH-SOUTHWESTERLY SWELL.
A FRONTAL SYSTEM APPROACHING THE WATERS LATE THIS WEEK WILL SEE
NORTHERLY FLOW BACK AHEAD OF THE WEAK SURFACE FRONT BEGINNING
THURSDAY. CHANCES FOR LIGHT RAIN PEAK LATE FRIDAY NIGHT INTO
SATURDAY MORNING DURING THE FRONTAL PASSAGE.
BEHIND THE BOUNDARY, INITIAL WESTERLY FLOW WILL VEER OUT OF THE
NORTH THROUGH THE WEEKEND AS SURFACE HIGH PRESSURE BUILDS
OFFSHORE. CHANCES FOR MAXIMUM WIND GUSTS OF AT LEAST 20-25 KT
PEAKS AT 85-95% ACROSS THE WATERS FROM SUNDAY THROUGH AT LEAST
TUESDAY, WITH THE HIGHEST CHANCES OFF THE CENTRAL OREGON COAST.
CHANCES THAT PEAK AFTERNOON GUSTS REACH GALE-FORCE IS THE
HIGHEST ON MONDAY AFTERNOON, SOME 30-50% WITHIN 10 NM SOUTH OF
CAPE FALCON AND 25-45% BEYOND 10 NM. CHANCES FOR GALE-FORCE
GUSTS NORTH OF CAPE FALCON ARE LOWER, ONLY 5-20%. -36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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