251
FXUS66 KPQR 131736
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1036 AM PDT THU AUG 13 2026
SYNOPSIS
WARM AND DRY CONDITIONS EXPECTED THROUGH THE
WEEKEND WITH PERSISTENT ONSHORE FLOW. SKIES BECOME HAZY THIS
AFTERNOON AS SOME WILDFIRE SMOKE DRIFTS OVER THE AREA. SLIGHT
CHANCE (10-15%) FOR THUNDERSTORMS OR SHOWERS OVER THE CASCADES
FRIDAY AND SATURDAY AFTERNOONS, WITH THE HIGHEST CHANCES ALONG
THE CREST. THERE ARE LOW CHANCES FOR MORE WIDESPREAD RAIN
RETURNING EARLY NEXT WEEK, BUT SIGNIFICANT RAIN DOES NOT APPEAR
LIKELY AT THIS TIME.
DISCUSSION...TODAY THROUGH WEDNESDAY
NIGHTTIME RGB SATELLITE
SHOWS MARINE STRATUS SOLIDLY ENTRENCHED ALONG THE COAST, WHILE
BROKEN TO SCATTERED CLOUDS ARE DEVELOPING AROUND THE PORTLAND METRO
AREA. ANY MORNING CLOUDS WILL SCATTER OUT ACROSS INLAND LOWLANDS BY
AFTERNOON PROVIDING ANOTHER DAY OF MOSTLY SUNNY SKIES AND
TEMPERATURES WARMING INTO THE MID-80S. UPPER LEVEL TROUGHING REMAINS
OVER THE REGION TODAY WITH ONSHORE FLOW IN THE LOWER LEVELS. ONE
NUANCE, HOWEVER, IS IN THE MID-LEVELS OF THE ATMOSPHERE (5,000-
10,000 FT ABOVE GROUND), WHERE FORECAST SOUNDINGS ARE SHOWING LIGHT
EASTERLY WINDS RETURNING, INCLUDING NEAR THE GRASSHOPPER FIRE. THIS
COULD CAUSE SOME WILDFIRE SMOKE TO DRIFT ACROSS PORTIONS OF
NORTHWEST OREGON AND SOUTHWEST WASHINGTON BY THIS AFTERNOON, MAINLY
CAUSING HAZY SKIES. CAN'T RULE OUT SOME OF THIS SMOKE MIXING DOWN TO
THE SURFACE AS WELL. HOWEVER, THIS SMOKE IS EXPECTED TO BE SHORT-
LIVED AS WINDS FROM THE WEST RETURN THURSDAY NIGHT INTO FRIDAY
MORNING AND PUSH SMOKE EASTWARD AND CLEAR THE AIR ONCE AGAIN.
BY FRIDAY, THE UPPER LEVEL TROUGH BROADENS EVEN FURTHER OFF THE U.S.
WEST COAST. AS MORE SOUTHERLY FLOW ALOFT RETURNS OVER THE AREA, WILL
SEE INCREASING INSTABILITY AND MONSOONAL MOISTURE THAT WILL SUPPORT
A 10-20% CHANCE FOR THUNDERSTORMS ACROSS THE CASCADES EACH
AFTERNOON, BOTH FRIDAY AND SATURDAY, WITH THE HIGHEST CHANCES ALONG
THE CREST OF THE CASCADES. OTHERWISE, THE GENERAL AIRMASS REMAINS
TOO DRY TO SUPPORT ANY WIDESPREAD PRECIPITATION FROM THIS TROUGH.
GUIDANCE SUGGESTS HIGH CONFIDENCE FOR NEAR TO SLIGHTLY ABOVE AVERAGE
TEMPERATURES FOR MID-AUGUST THROUGH THE WEEKEND, WITH AFTERNOON
HIGHS WARMING INTO THE MID TO UPPER 80S ACROSS INTERIOR VALLEYS. BY
SUNDAY, THERE IS INCREASING CONFIDENCE OF THE UPPER TROUGH OFFSHORE
BECOMING MORE ELONGATED WITH LOW PRESSURE DROPPING SOUTH, WELL OFF
THE CALIFORNIA COAST. THIS COULD ALLOW FOR UPPER RIDGING OVER THE
INTERMOUNTAIN WEST TO SHIFT SLIGHTLY WEST, NUDGING INTO THE PACIFIC
NW. BUT THE MAIN AXIS OF THE RIDGE IS EXPECTED TO STAY EAT OF THE
REGION.
THE POSSIBILITY FOR WIDESPREAD RAIN EARLY NEXT WEEK HAS DROPPED
SIGNIFICANTLY, AS CHANCES FOR MEASURABLE PRECIPITATION (>0.01") ARE
VERY LOW (15% OR LESS) ACROSS THE AREA MONDAY THROUGH WEDNESDAY.
CLUSTER ANALYSIS OF 500 MB HEIGHTS CONTINUES TO SHOW A WIDE RANGE OF
THE MAGNITUDES AND PLACEMENTS OF AN UPPER LEVEL TROUGH OFFSHORE.
STILL, A SLIGHT COOLING TREND TO CLOSER TO AVERAGE TEMPERATURES IS
POSSIBLE BY THE MIDDLE OF NEXT WEEK. DH/10
AVIATION
WESTERLY FLOW ALOFT BECOMES SOUTHWESTERLY AS AN UPPER
LEVEL TROUGH MOVES SLOWLY OVER THE AIRSPACE, WITH NORTH/NORTHWEST
FLOW PERSISTING AT THE SURFACE. THIS SCENARIO IS RESULTING IN A
RATHER INTERESTING SET UP FOR THE AIRSPACE AS A WHOLE. FOR THE
COAST, MVFR MARINE STRATUS FOR NEARLY THE ENTIRE TAF PERIOD WITH
A 50% CHANCE OF CONDITIONS CLEARING TO VFR FOR A FEW HOURS AT ANY
POINT BETWEEN 19Z THU TO 00Z FRI. IF VFR CONDITIONS DEVELOP,
EXPECT MVFR/IFR CONDITIONS TO RETURN AROUND 00Z-03Z FRIDAY AND
PERSIST THROUGH THE REMAINDER OF THE TAF PERIOD.
INLAND LOCATIONS CURRENTLY EXPERIENCING MVFR CONDITIONS ARE
EXPECTED TO SLOWLY IMPROVE TOWARDS VFR OVER THE NEXT FEW HOURS.
HOWEVER, FROM 20Z THURSDAY THROUGH 06Z FRIDAY, SMOKE WILL LIKELY
MIX DOWN AT TIMES AND COULD IMPACT VISIBILITIES, WITH SMOKE IN
THE MID LEVELS, SLANT RANGE VISIBILITIES COULD ALSO BE IMPACTED
AT ANYTIME THROUGH 06Z FRIDAY FOR INLAND LOCATIONS FROM KSLE
NORTHWARD. EXPECT MVFR CONDITIONS TO RETURN FOR LOCATIONS SOUTH OF
KSLE STARTING AROUND 12Z-14Z FRIDAY AS MARINE STRATUS IS EXPECTED
TO RETURN.
NORTH TO NORTHWEST WINDS INCREASE TO 8-10 KTS AFTER 21Z THURSDAY,
BEFORE BECOMING LESS THAN 6 KTS AFTER 05Z FRIDAY.
KPDX AND APPROACHES...SLOW IMPROVEMENT FROM MVFR TOWARDS VFR OVER
THE NEXT FEW HOURS. HOWEVER, FROM 20Z THURSDAY THROUGH 06Z FRIDAY,
SMOKE WILL LIKELY MIX DOWN AT TIMES AND COULD IMPACT
VISIBILITIES, WITH SMOKE IN THE MID LEVELS, SLANT RANGE
VISIBILITIES COULD ALSO BE IMPACTED AT ANYTIME THROUGH 06Z
FRIDAY. NORTH TO NORTHWEST WINDS INCREASE TO 8-10 KTS AFTER 21Z
THURSDAY, BEFORE BECOMING LESS THAN 6 KTS AFTER 05Z FRIDAY. /42
MARINE
NO SIGNIFICANT CHANGES AS HIGH PRESSURE OFFSHORE WILL
CONTINUE TO SUPPORT NORTHERLY WINDS AND FAIRLY BENIGN
CONDITIONS ACROSS THE COASTAL WATERS THROUGH THE WEEK AND INTO
THE WEEKEND. WINDS FROM THE NORTH TO NORTHWEST WITH GUSTS LESS
THAN 21 KTS WILL CONTINUE THROUGH AT LEAST THE END OF THE WEEK.
WIND DRIVEN SEAS ARE EXPECTED TO REMAIN AROUND 3 TO 6 FT THROUGH
THE WEEK. DH/03
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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