textproduct: Portland

SYNOPSIS

Unseasonably warm and dry conditions continue through Thursday with areas of early morning valley and coastal fog. Weak offshore flow will see slightly warmer temperatures midweek, before a trough brings a return to cooler temperatures with chances for light rain Friday into the weekend.

LONG TERM...Friday through Sunday

Late in the week and into this weekend, long-range ensemble guidance supports an upper- level trough developing over the Pacific Northwest, bringing a return to onshore flow, cooler and more seasonable temperatures, and low chances for light rain. While there continues to be uncertainty in its evolution, the majority of ensemble members still maintain light rain arriving along the north Oregon and south Washington coast around midday Friday, reaching inland areas by Friday afternoon. Potential rainfall amounts continue to look very light, with a 10% or less chance for even 0.1 inches of rain for most.

As the core of the upper trough moves overhead, much cooler air aloft will allow for sharply cooler low temperatures Saturday and especially Sunday morning. Chances for temperatures in the mid 30s supporting frost will reach 25-35% in the Upper Hood River Valley around Parkdale and Dee on Saturday morning, increasing to 35-65% and including lower elevations near Odell on Sunday morning, as well as near 10% in Hood River proper. Chances for frost will also reach 30-50% in north Oregon Coast Range valleys, 15-30% in the southern Willamette Valley and Cascade foothills from Cowlitz County south to Lane County, and 5-10% in the central Willamette Valley on Sunday. Chances for a true freeze Sunday morning are limited to 25-35% in the Upper Hood River Valley near Parkdale and Dee, and 5-10% along OR-58 between Eugene and Oakridge. Those with agricultural interests or home growers with sensitive outdoor plants should continue to monitor the forecast this week. -36

AVIATION...Through 18z Tuesday

At 1745z Mon, IFR/LIFR cigs and/or vis observations continue along the coast. As diurnal northwest winds increase to 10-15 kt with gusts of 20-25 kt after 17- 19z Mon, mixing will help lift and break up low clouds, with a period of VFR conditions favored after 20-21z Mon. However, there's a 20-35% chance that IFR/LIFR conditions do not improve to VFR at all in the TAF period. Wind are expected to ease below 10 kts after 00-03z Tue, allowing the return of marine stratus and IFR/LIFR restrictions through the rest of the TAF period.

At inland terminals, fog and low stratus are dissipating as temperatures warm. VFR conditions should return at all inland terminals by 19-20z Mon. Fog/low stratus are likely to return at most terminals again around sunrise Tuesday, with IFR/LIFR conditions expected by 12-14z. Expect these conditions to remain through around 17-20z Tue. North to northwest winds today rise to 7- 10 kt after 21z, falling below 5 kts after 00-04z Tue.

KPDX AND APPROACHES...Stratus is expected to scatter out by 19-20z Mon with conditions returning to VFR. There's high confidence that fog/low stratus returns Tuesday morning around 11-13z with IFR/LIFR conditions. Expect these conditions to remain through 18-20z Tue. North to northwest winds increase to around 6-8 kts after 21z Mon, decreasing to less than 5 kts after 02-04z Tue. -03

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 Wednesday. Small Craft Advisories remain in effect from 11 AM until 11 PM PDT today within 10 NM south of Cape Falcon and out to 60 NM south of Cape Foulweather. 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 as cloud bases are compressed down to the surface. Dense Fog Advisories for widespread visibility of 1 SM or less also remain in effect across the coastal waters including the Columbia River Bar 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 and chances for rain return to the region Friday into the weekend. Seas will increase to 7-10 ft Wednesday into Thursday, with the longer-period swell also supporting a moderate risk for sneaker waves to the coast. -36

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 11 AM this morning to 11 PM PDT this evening for PZZ252-253-273.