textproduct: Portland

SYNOPSIS

Mainly dry conditions will continue through Friday. Low-level offshore flow and abundant sunshine will result in afternoon high temperatures that are around ten degrees above normal for inland valleys through Wednesday. Trending cooler Thursday through Monday with widespread morning frost Friday and Saturday. Chances for rain are mainly focused on the Saturday evening through Sunday morning time frame when chances increase to 30-50%.

DISCUSSION...Now through Monday night

Current satellite and surface weather observations from early Tuesday afternoon depicted mostly clear skies aside from some scattered thin high clouds along with increasing low-level offshore flow. As of 2 PM Tuesday, winds were gusting as high as 30-40 mph in wind-prone areas of the western Columbia River Gorge and Troutdale/northern Gresham area, except up to 45 mph at Crown Point. The observed pressure gradient between Troutdale and the Dalles was around -4.5 mb earlier this afternoon, and model ensemble guidance suggests the gradient will hover close to this range through tonight with only slight weakening, which suggests the ongoing gusty east winds will continue in these areas before dissipating late Wednesday morning into the afternoon. Elsewhere, winds will remain relatively light. Aside from weakening offshore winds tomorrow, conditions will be very similar to what has been observed today. Expect mostly sunny skies and high temperatures in the mid 70s for inland valleys and 60s at the coast.

Confidence is high temperatures will trend cooler Thursday and Friday with highs back into the 60s over the lowlands, except upper 50s at the coast. The cooler temperatures will be in response to an incoming upper level trough and a switch to low-level onshore flow. Temperatures will then remain seasonably cool over the upcoming weekend. The main concern during this time period will be widespread morning frost Friday and Saturday, bringing impacts to those with agricultural interests. Saturday morning is shaping up to be the coldest morning, as this is when some locations could fall below-freezing; the NBM is showing a 25-50% chance for lows of 32 degrees or colder in the southern Willamette Valley, except a 70-80% chance from Creswell to Cottage Grow and near 15% in Eugene.

Moisture will be limited with the aforementioned trough Thursday into Friday, and the latest model guidance now suggests both days will either be completely dry or mostly dry with only trace amounts of rain. NBM PoPs back this up and have fallen below 10-15%, except in the Mt. Hood National Forest where PoPs are near 20%. Even if rain does occur, no impacts are expected.

The highest chance for rain over the next seven days is Saturday evening through Sunday morning as a low pressure system over the northeast Pacific attempts moving closer to the coast. That being said, a significant amount of ensemble guidance has trended drier with today's forecast update as many ensemble members now keep the low pressure system well offshore and/or too far to the north into Canada. As such, PoPs have decreased to 30-50% and forecast rain amounts have decreased as well. Chances for at least 0.25 inches of rain this weekend have decreased to 25-40%. Lastly, chances for impactful winds have also decreased with the potential system this weekend, with only a 1-5% chance for wind gusts of 40-45 mph or stronger. Therefore, impacts are unlikely to occur this weekend and there's a notable chance conditions will remain dry. Chances for rain decrease even more on Monday to 10-15%. -23

AVIATION...Through 06Z Thursday

VFR flight conditions will continue across the area through the TAF period with thin high clouds from time to time. Ceilings with these high clouds are above 15-20 kft. Winds will generally be less than 8 kts at most terminals through the TAF period. The one exception is KTTD and through Cascade gaps where east winds will remain elevated around 8-12 kts through around 09-12z Wed when winds begin decreasing. Winds shift west to northwesterly after 15-18z Wed along the coast as a weak weather system approaches the region from the west.

KPDX AND APPROACHES...VFR with a few thin high clouds with ceilings above 20 kft. Northwest winds less than 6 kts. -03

MARINE

Northerly winds continue across the waters in the wake of a system that is dropping southward. Widespread wind gusts up to 25 kt continue over the northern outer waters beyond 10 nm offshore this afternoon. A Small Craft Advisory remains in effect for the northern outer waters through 5 PM today. Winds have already decreased significantly over the central and southern outer waters, and the Small Craft Advisory that was initially in effect until 5 PM today has been cancelled for these marine zones.

Winds and seas are set to increase again Thursday into Friday morning with the passage of a decaying cool 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 10-30% 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 remains low at this time. It is worth noting that chances have decreased for significant winds and seas with today's forecast update due to a less favorable low track. -23

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...None.