textproduct: Portland

SYNOPSIS

Largely dry weather expected through midweek. Above average temperatures today and Wednesday. Chances for wetter and cooler weather return late in the week with potential for a more robust system over the weekend.

DISCUSSION...Now through Monday

Dry conditions are expected through at least Thursday. The upper level low continues to pinch off from the main flow as it drops south toward California today. In its wake, shortwave ridging will build into the PacNW today. Cloud cover will dissipate through the day with light offshore winds developing on the eastern flanks of the Cascades and coast range and through the western Columbia River Gorge. These offshore winds are not expected to be impactful though they may be locally gusty up to 40 mph in the typical spots within the Gorge. Highs jump to around10 degrees above normal today and Wednesday, translating to afternoon highs in the 60s on the coast and in terrain, and in the low to mid 70s within inland valleys.

The latter half of the week again trends toward cooler temperatures and modest chances for rain. Cluster analysis shows good agreement in troughing developing over the Gulf of Alaska and dropping southeast toward the PacNW Thursday into Friday. This pattern would favor a return to near normal temperatures and chances for light precipitation. Currently, the best chances for precipitation are over the Cascade Foothills and areas east of I-5 but remain rather low at 20-40%. Rainfall associated with this system is not expected to be noteworthy if it occurs at all. Overnight lows Thursday and Friday night are expected to be much cooler than the start of the week. More widespread temperatures below 37 degrees are possible throughout the central and southern Willamette Valley, Cascade Foothill valleys, and parts of the coast range valleys. If trends continues, will likely need Frost Advisories for some or all of these locations.

Details heading into the weekend remain murky as ensembles solutions remain undecided in regards to the developing pattern. There is a low to moderate chance that a robust shortwave develops over the Gulf of Alaska and drops southward, supporting a surface low as it approaches the PacNW. Around 30-40% of ECMWF ensemble members depict both of these features heading into Saturday and Sunday. However, there is a noticeable trend in several of the members to keep the core of the surface low offshore and even has it retrograding back out to sea during the latter half of the weekend. This current trend signal lower potential for much needed rainfall across the area but also lower chances for impactful winds across the region. Given this potential system is still several days out, details remain unclear and will hopefully be fleshed out in the coming days. -19

AVIATION...Through 18Z Wednesday

VFR flight conditions will continue across the area through 18Z Wednesday with scattered thin high clouds from time to time. Ceilings with these high clouds are above 20 kft. Offshore winds will strengthen a bit between 17-21Z Tuesday, bringing wind gusts upwards of 15-20 kt at KPDX and KTTD. A few max wind gusts as high as 25 kt are possible at KTTD. Winds will be more northerly at KUAO, KSLE, and KEUG, strongest at KUAO at around 10 kt and generally around 5 kt or less at KSLE and KEUG. Winds weaken this evening into tonight, except at KTTD where easterly winds will continue.

KPDX AND APPROACHES...VFR with a few thin high clouds with ceilings above 20 kft through 18Z Wednesday. Easterly winds around 10 kt with gusts as high as 20 kt expected this afternoon, before winds weaken this evening. -23

MARINE

Northerly winds continue across the waters in the wake of a system that is dropping southward. Widespread wind gusts up to 25 kt will be possible over the outer waters beyond 10 nm offshore through the afternoon. A Small Craft Advisory remains in effect for the outer waters through 5 PM. Beyond 5 PM tomorrow, winds and seas will be on the decrease as high pressure returns.

Winds and seas are set to increase again Thursday into Friday morning with the passage of a weak cold front, especially over the northern waters to the north of Cape Falcon where conditions will likely be hazardous to small craft. There is the potential for a stronger low pressure system over the upcoming weekend, bringing a 20-40% chance for gale force wind gusts and seas over 10 feet. Overall confidence in the exact track and strength of this potential low pressure system is low at this time, and the forecast is worth monitoring over the next several days. -19/23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory until 5 PM PDT this afternoon for PZZ271>273.