textproduct: Portland

SYNOPSIS

Warm and dry conditions expected through much of the week with morning clouds and afternoon clearing. Daytime highs are expected to be in the 80s through the week. Winds generally out of the west to northwest, strongest in the afternoon and along the Central Columbia River Gorge and Upper Hood River Valley. Spotty chances for light showers arrive Friday night into Saturday, but conditions most likely remain dry. Seasonable weather continues late this weekend into early next week.

DISCUSSION...Today through Monday

Little change to the forecast as predominately dry and warm conditions continue through the week with minimal impacts. The large-scale pattern remains stagnant through the period, with broad and relatively flat upper-level ridging over the Rockies and Great Basin, and broad upper-level troughing over the northeast Pacific. This pattern will support continued onshore flow, maintaining near- normal daily high temperatures in the 80s within inland valleys and 60s along the coast, and overnight lows in the 50s across the region. With moist air flowing into the region, each night will be characterized by marine stratus along the coast with some stratus filtering into the I-5 corridor. These clouds should clear out each afternoon as daytime heating progresses. Expect light winds from the west/northwest for most places, peaking each afternoon. An exception would be the Central Columbia River Gorge and Hood River Valley, where west winds will be strongest with gusts to 25-35 mph this afternoon. Chances for wind gusts exceeding 35 mph today along the Central Gorge are around 30-50%.

The majority of ensemble members are in agreement that upper- level ridging over the Rockies and Great Basin will build late in the workweek, which would favor a brief warm-up on Thursday. However, that warm-up will likely be short-lived as ensemble guidance continues to show the upper-level trough over the northeast Pacific shifting onshore Friday into the weekend, resulting in slightly cooler temperatures and winds coming from the south/southwest. There remains spotty chances (10-25%) for showers across portions of the Coast Range and Cascades, but the overall airmass will remain too dry to support accumulating rainfall from a weak front. Late this weekend into early next week, the trough weakens and most ensemble members suggest a return of zonal flow before another upper-level trough drops down from the Gulf of Alaska and approaches British Columbia. At this point, there still remains uncertainty with the exact magnitude and placement of the trough. However, this would suggest that onshore flow continues across the region with seasonable temperatures for late August. -10

AVIATION...Through 18z Wednesday

Marine stratus that pushed down the Upper Columbia River into the Portland metro area is dissipating as of 1730z Tue with VFR conditions and clear skies expected for all inland areas by 18-20z. Expecting MVFR/IFR conditions to form in the SW WA lowlands and Portland metro area south to KAST between 12-15z Wed, once again improving to VFR by 17-19z Wed. The coast remains socked in with marine stratus. Predominately MVFR/IFR conditions are expected along the coast over the next 24 hours, though there's a 20-30% chance terminals could briefly become VFR at any hour between 19z Tue - 02z Wed. There's also a 60-90% chance of LIFR conditions returning at any hour 00-18z Wed. Westerly to northwesterly winds across all terminals around 4-6 kt, peaking this afternoon and evening up to 8-10 kts before decreasing once again overnight.

KPDX AND APPROACHES...Stratus is dissipating with VFR conditions with mostly clear skies expected after 18z Tue. MVFR/IFR stratus expected to return after 12z Wed, improving to VFR once again by 17-19z Wed. Northwesterly winds 4-7 kt. -03

MARINE

A largely stagnant pattern continues through much of the week with high pressure offshore supporting northerly to northwesterly winds of 8-15 kt and afternoon gusts up to 20 kt. Weak low pressure moving over the northeast Pacific Friday into the weekend will shift winds out of the south to southwest across the waters, but chances for gusts exceeding 21 kt remain low, only 5% or less. High pressure and northerly winds return by Sunday. Seas of 3-6 ft persist through the period. Increasing periods of 12-14 sec today and Wednesday may result in a moderate risk for sneaker waves along the coast. Caution should be used when in or near the water. -10

PQR WATCHES/WARNINGS/ADVISORIES

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