textproduct: Portland

DISCUSSION...Now through Monday

A broad trough over the northeast Pacific is beginning to shift eastward towards the Pacific Northwest, resulting in a trend towards modest cooling temperatures. Today is the only exception, with high temperatures generally in the mid to upper 80s across the interior lowlands and 60s along the coast. Onshore flow will become increasingly established this afternoon and evening, with winds turning westerly as a stronger marine push develops tonight. Marine air should spread inland through the overnight hours, while any lingering wildfire smoke is displaced east of the Cascades by Wednesday. Along with this marine push, fog may push into the coast as a result of fog formation over the ocean, bringing a potential reduction of visibility, primarily near the coastline.

The upper trough will continue progressing toward the Pacific Northwest on Wednesday, with the axis shifting farther northeast and bringing additional cooling. Increasing onshore influence should result in areas of low stratus across the interior lowlands Wednesday morning, which will limit afternoon warming. Highs are expected to reach the lower 80s inland, with cooler conditions along the coast.

The broader pattern remains favorable for continued troughing across the Pacific Northwest through the latter half of the week. Several smaller-scale disturbances are expected to rotate through the trough, reinforcing the cooler regime. Temperatures should continue trending downward, with the potential for additional marine pushes and increasing cloud cover. Precipitation chances remain relatively limited but are expected to increase somewhat as the pattern becomes more active. A weak frontal passage is possible Thursday, followed by another weak front Saturday, with precipitation chances generally around 10-20%. Neither system appears particularly wet at this point, though timing and strength will be refined as the week progresses.

By late weekend, ensemble guidance suggests the upper-level pattern begins to flatten, which could allow temperatures to rebound toward the 80s. However, ensemble guidance also suggests a broad trough may dig south into the PNW Monday into Tuesday, bringing a possibility of more rain. Confidence is lower during this portion of the forecast as the evolution of the trough and embedded disturbances remains somewhat uncertain. ~12

AVIATION...Through 21Z Wednesday

Dry, southwest flow aloft today as upper level ridge of high pressure shifts east. Satellite imagery this afternoon shows marine stratus breaking up along the coast, while terminal observations show a mix of MVFR to VFR CIGs with the lingering stratus decks. Expect marine stratus to fill back in at coastal locations this evening by 00-02z Thu with conditions deteriorating anywhere from low-end MVFR to LIFR. Best chances for LIFR conditions will be at KONP (40-50% chance) where VIS may also be reduced due to fog overnight.

Wildfire smoke from the Austin fire will continue to shift east of PDX later this afternoon as a strong marine push of westerly winds arrives. VFR conditions are expected across inland terminals through at least 10z Wednesday. There is around a 30-50% chance that marine stratus with MVFR CIGs pushes inland after 12-14z Wed morning. Expect southwest winds to become slightly more westerly this afternoon before easing later this evening.

KPDX AND APPROACHES...VFR conditions expected with smoke aloft gradually drifting eastward this afternoon. With a stronger marine push tonight, marine stratus could push inland with around a 30-50% chance of MVFR CIGs after 14z Wednesday. SSW winds around 4-7 kt expected to become westerly after 22z. /DH

MARINE

A weak meso-low is moving up the north Oregon coast this afternoon bringing gusty south-southwest winds to the inner waters. Will maintain the Small Craft Advisory for gusts up to 25 kt for the inner waters north of Cape Falcon and the Columbia River Bar through 7 PM this evening. Otherwise, high pressure will build north along the coast tonight as low pressure well offshore weakens as it moves northeast toward Vancouver Island through Wednesday night. Southerly winds ease overnight before increasing again on Wednesday as a weak front approaches the outer waters. Another weak front approaches the inner waters Thursday morning, briefly increasing southerlies again, but in general, winds are expected to remain below 20 kt.

High pressure begins to rebuild over the waters later Thursday into Friday returning north to northwest winds across the coastal waters into the weekend. Predominately wind driven seas are expected to remain around 3 to 6 ft through the weekend. Somewhat more active pattern may return early next week. /DH

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 7 PM PDT this evening for PZZ210-251.