textproduct: Portland

SYNOPSIS

A cooler and progressive westerly flow pattern continues across the region this weekend into next week with below normal temperatures persisting. While dry weather is favored through Monday a weak frontal system renews chances for rainfall Tuesday into early Wednesday, mainly near the coast and across the north Oregon/Southwest Washington Cascades. For the inland valleys, much of this midweek period stays dry.

LONG TERM...Tuesday through Friday

The next meaningful change in the pattern arrives on Tuesday in the form of weakening upper-level trough and accompanying frontal boundary. Confidence for measurable rainfall is highest along the north Oregon Coast/Coast Range into southwest Washington where probabilities for precipitatiion peak around 50-75% Tuesday afternoon and evening before decreasing into Wednesday. It remains to seen whether this weather feature is able to hold together enough to push light rain into the Portland Metro and Willamette Valley as only around 15-25% of the LREF ensemble members forecast greater than trace amounts of rainfall during this Tue/Wed time period. Then conditions trend dry again the second half of Wednesday into Thursday morning.

Beyond this point ensembles diverge in the placement of a potential shortwave trough or ridge feature within the larger scale zonal flow which is anticipated to continue into the end of the week. By late Thursday into Friday, around 20% of Ensemble members show a weak trough moving overhead (cooler, light rain chances), another 25% show straight zonal flow (cooler, mostly dry) and the remaining 65% have some degree of ridging overhead (slightly warmer and dry). Over the next few days we should see ensembles converge towards a solution during this late week period. -99

AVIATION...Through 18Z Sunday

Primarily VFR conditions expected through the TAF period. At 1730z Sat, fog/low stratus is lingering in a few inland valleys, including around KPDX north to KSPB and KEUG. This fog is actively dissipating and should improve to VFR by 18-19z at the latest as winds increase and temperatures warm. A broken cloud deck will spread across the region after 21z Sat, remaining through most of the overnight hours. This is expected to clear over the area sometime on Sunday morning. Similar to this morning, if it clears by 10-13z Sun, patchy fog/low stratus could quickly develop again by 12-15z with MVFR/IFR/LIFR conditions, similar to this morning. There's around a 15-25% chance of this occurring at any terminal. If any fog/low stratus does occur, expect it to dissipate by 17-19z Sun. North winds today increase to around 10-15 kt at the coast and across the central and southern Willamette Valley after 19-20z today, decreasing after 03- 06z Sun.

KPDX AND APPROACHES...Low stratus will improve by VFR by 19z with VFR conditions likely to remain through the rest of the TAF period. There's a 10-15% chance of MVFR/IFR low fog/stratus returning after 10-12z Sun if the high cloud deck that moves in tonight dissipates early enough Sunday morning. North to northwest winds increase to around 8-10 kt after 21z, decreasing after 02-05z Sun. -03

MARINE

Weak high pressure progresses over the waters today while a trough amplifies further out over the eastern Pacific allowing for the return of somewhat calmer conditions, especially compared to yesterday (Friday). However, another round of Small Craft Advisories are in effect beginning this afternoon/evening through early Sunday morning mainly due to northerly wind gusts up to 20-25 kt. Northerly winds hold in place through the weekend before another weak front shifts winds more southwesterly Monday into Tuesday. Will also see a longer period west-northwesterly swell of 5-8 ft at 12-14 seconds in the late Monday to Wednesday time period, resulting in a moderate sneaker wave threat. Seas likely stay in this 5-8ft range the remainder of the week. -99/10

PQR WATCHES/WARNINGS/ADVISORIES

OR...None. WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 5 AM PDT Sunday for PZZ210-251-271.

Small Craft Advisory from 2 PM this afternoon to 5 AM PDT Sunday for PZZ252-253-272-273.