textproduct: Portland

SYNOPSIS

Upper level high pressure remains the controlling feature this late afternoon, keeping the overall pattern dry and warmer than normal through Thursday. Each night will still bring a marine surge, clouds expanding across the coast and pushing inland through gaps, followed by partial to substantial clearing during the day. The next period to watch is Friday into Saturday, when a weak disturbance undercuts the ridge and brings a modest cool-down plus very low-end rain chances (mainly coast and higher terrain north of a line from Lincoln City to Salem). Ridging is favored to rebound late this weekend, returning the region to warmer and dry weather for Sunday into early next week, with some potential for 80 degrees along parts of the I-5 corridor.

DISCUSSION...Now through Tuesday

The big picture hasn't changed since this morning: broad ridging holding firm over the Northeast Pacific into the Pacific Northwest, and it's keeping meaningful precipitation at bay. The day to day weather continues to be shaped by marine air near the surface rather than any nearby storms. Expect the coast to stay coolest with lingering low clouds at times and occasional late-night/early- morning mist or drizzle, while interior valleys spend more time dry with afternoon sunshine once the morning cloud layer retreats.

From tonight through Thursday, plan on a similar repeated cycle compared to previous days. Low clouds expand inland overnight, especially through the Coast Range gaps and into the Willamette Valley, then gradually erode back toward the coast late morning into afternoon. How quickly that burn-off happens will still be the main driver of temperatures each day. If clearing is quicker, inland highs will push toward the upper 70s; if clouds hang on longer, mid to upper 60s becomes more likely. Along the coast and higher terrain, highs generally hold in the upper 50s to upper 60s. Heat impacts remain limited for most, with the main concern confined to those very sensitive to warmer temperatures.

Attention then shifts to late Friday and Saturday. Ensemble guidance continues to cluster around a shortwave disturbance sliding over the top of the ridge and knocking temperatures back closer to seasonal levels. Moisture with this feature looks limited, so rain chances stay on the very lower side, highest at the coast and across higher terrain, mainly north of a line from Lincoln City to Salem (roughly 15-25%). The rest of the area has probabilities less than 10%. East of the Cascades, including the Upper Hood River Valley and the central Gorge, rain chances remain near zero (under 5%). If rain does develop, the most likely scenario brings showers to the coast sometime Friday afternoon and evening, then nudging inland within a few hours. Amounts look light where it does rain, generally under a tenth of an inch. In general, there is lower confidence for precipitation as recent model guidance has trended drier.

By late weekend into Monday, the broader signal returns to rebuilding ridging and another warm-up. Sunday currently looks like the better day for warmer temperatures, with probabilities for 80 degrees along the I-5 corridor around 35-70%, highest within the Portland-Vancouver metro. Confidence in the warm/dry trend is better than the details of exactly how warm each inland valley gets, which will still depend on how far inland morning clouds manage to reach and how quickly they clear. Tuesday continues to support the cooling trend, with zonal aloft and high pressure at the surface over the Northeast Pacific. ~12

AVIATION

Satellite imagery at 04z Wed shows marine stratus socked in along the coast and filling back in inland. There's a 60- 80% chance that MVFR cigs along the coast will lower to IFR after 07- 10z Wed. Stratus is expected to continue filling in over inland areas over the next few hours with MVFR conditions developing between 06-09z Wed. Expect stratus to linger into much of Wednesday for inland areas, not improving to VFR until after 18-21z. Along the coast, IFR conditions will become MVFR by 16-18z Wed, but there's a low chance (around 20%) of conditions improving to VFR through the 06z TAF period. Winds are expected to remain light and variable around 5 kt or less through Wednesday morning, becoming westerly to northwesterly up to 8-10 kts with a sea breeze after 21z Wed.

KPDX AND APPROACHES...VFR conditions are expected to fall to MVFR due to marine stratus sometime between 06-09z Wed. Conditions not expected to improve to VFR again until 19-21z Wed. Winds will be light and variable through Wednesday morning, becoming northwest up to 8-10 kts after 21z Wed. -03

MARINE

A continued southerly surge will bring persistent low stratus through Wednesday with chances for fog and/or drizzle during the overnight and morning hours. Winds late Tuesday afternoon have become westerly around 5 kt. Winds look to turn northerly late Wednesday through much of Thursday, before a weak system moving onshore Friday into Saturday will see southerly flow return with gusts of 15-20 kt and low chances for rain showers.

High pressure rebuilding this weekend will yield strengthening northerly flow, which may become hazardous to small craft late Sunday into Monday with gusts up to 20-25 kt. Chances for gusts to reach 21 kt or higher increase slightly from 50-80% on Sunday to 60-90% on Monday, with higher chances to the south.

Seas will remain fairly steady at 4-7 ft with a persistent westerly to northwesterly swell through this weekend. -36/23

PQR WATCHES/WARNINGS/ADVISORIES

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