textproduct: Portland

SYNOPSIS

Unseasonably warm and dry weather persists through Thursday with areas of early morning valley and coastal fog. Weak offshore flow will bring slightly warmer temperatures Wednesday and Thursday, before a trough brings a return to cooler temperatures with chances for light rain Friday into Saturday. Cool nights will bring chances for morning frost in rural valleys away from urban cores this weekend into next week.

LONG TERM...Friday through Monday

A strong ensemble consensus continues to support upper-level troughing returning to the region from Friday through this weekend. The large majority of members bring rain into the Oregon and Washington coasts late Friday morning or early Friday afternoon, reaching inland to the I-5 corridor by Friday mid- afternoon. Chances for light rain showers persist into Saturday as the trough elongates and ultimately looks to pinch off into a closed low which drifts south over California. Mean 48-hour rainfall totals from Friday through Saturday night are generally less than 0.1 inches, higher to the north and on western slopes of terrain, and lower to the south and on eastern slopes. There is a 10% chance of up to 0.2-0.4 inches of rain at low elevations, and higher amounts in excess of 0.5 inches in areas of terrain.

As the core of cold air within the upper trough moves overhead this weekend, temperatures will fall to much more seasonable levels with afternoon highs largely in the 60s. Morning lows will similarly cool, yielding increasing chances for frosty temperatures in the low to mid 30s from Friday night through Monday night. Frost may occur as early as Friday night in the Upper Hood River Valley, with 30-40% chances of falling to 36F or lower near Parkdale and Dee. Saturday and Sunday nights look to be the coldest, with nearly 10% chances for frost in Hood River proper, 50% near Odell, and 90% in Parkdale and Dee. Elsewhere, frost chances reach 15-35% in north Oregon Coast Range valleys, the central and southern Willamette Valley away from urban cores, and the Cascade foothills from Cowlitz County south to Lane County on Sunday night. Chances for a true freeze peak Sunday night at 50-60% near Parkdale and Dee and 15-20% near Odell in the Upper Hood River Valley, and at 20-35% along the OR-58 corridor between Eugene and Oakridge. Those with agricultural interests or home growers with sensitive outdoor plants should continue to monitor the forecast this week.

As the closed upper low then drifts to the south, rising heights aloft in the Pacific Northwest could again favor a drying and warming trend early next week. -36

AVIATION...Through 12z Wednesday

Latest terminal observations and satellite imagery depict widespread IFR/LIFR cigs along the coast with increasing coverage of restricted vis to the south, while at inland terminals, low clouds are also increasing in coverage, especially along the Cowlitz, lower Columbia, and northern Willamette Valleys, where IFR/LIFR cigs are becoming increasingly widespread. Heading into the hours around sunrise, chances for LIFR vis/cigs will peak around 70% in areas where low clouds are already developing, and closer to 50% elsewhere in low terrain where clear skies will likely start filling in supporting at least IFR cigs/vis. The exception to this trend may be near KAST, where higher winds this morning may aid in maintaining high-end MVFR or VFR vis despite the low cloud deck. As daytime heating and diurnal winds build through this morning, low clouds and vis obstructions will tend to mix out by 16-19z Tue inland and 17-20z Tue along the coast, with high confidence in widespread VFR conditions by this afternoon.

Light winds this morning will build out of the north to northwest to 5-10 kt inland and to 10-15 kt with gusts around 20 kt along the coast by this afternoon.

KPDX AND APPROACHES...IFR conditions beneath low stratus likely to prevail through at least 17z Tue, with chances for LIFR cigs/vis peaking at around 60% between 14-16z Tue. Low clouds and vis obstructions will tend to mix out by 17-19z Tue, with high confidence in VFR conditions by this afternoon. Diurnal northwest winds rise to 5-7 kt this afternoon. -36

MARINE

High pressure offshore will continue to maintain diurnal northerly winds through the week with peak afternoon and evening wind gusts of 20-25 kt today through Thursday. Small Craft Advisories are now in effect across the waters from 2 PM PDT this afternoon into tonight. Expect largely wind-driven seas around 4-6 ft through midweek, with a west-northwest swell of 3-4 ft at 10-12 seconds. High pressure aloft will also support areas of dense fog developing nightly through the morning hours as cloud bases are compressed down to the surface. Dense Fog Advisories for visibility of 1 NM or less also remain in effect across the waters until noon PDT today.

More active marine conditions are likely in the latter half of the week as troughing over the Gulf of Alaska generates a building northwest swell. Seas will increase to 7-10 ft Wednesday into Thursday, with the longer-period swell also supporting a moderate risk for sneaker waves at the coast. Chances for rain return to the region Friday into the weekend, though rain amounts are not expected to be impactful. -36/03

CLIMATE

Daily record high temperatures for October 8

LocationValue (Year)

Astoria81 (1951, 1971) Portland Int'l87 (2022) Vancouver, WA89 (1891) Hillsboro89 (2022) McMinnville88 (2022) Salem84 (1971, 2022) Eugene83 (1934, 1943)

PQR WATCHES/WARNINGS/ADVISORIES

OR...None.

WA...None.

PZ...Dense Fog Advisory until noon PDT today for PZZ210-251>253- 271>273.

Small Craft Advisory from 2 PM this afternoon to 2 AM PDT Wednesday for PZZ210-251>253.

Small Craft Advisory from 2 PM this afternoon to 5 AM PDT Wednesday for PZZ271>273.