727 FXUS66 KPQR 012210 AFDPQR Area Forecast Discussion National Weather Service Portland OR 309 PM PDT Fri Aug 1 2025 .SYNOPSIS...Near average temperatures expected through Saturday. General troughing and increasing onshore flow will bring relatively cooler temperatures Sunday through Thursday with increasing chances for cloud cover, especially during the morning hours. Chances for widespread rain increase Wednesday into Thursday, however uncertainty is high regarding exact rain amounts, if any rain falls at all. && .SHORT TERM...Friday afternoon through Sunday night...Radar, satellite, and lightning observations from early Friday afternoon depicted isolated thunderstorms developing along and just to the east of the Cascade crest from Willamette Pass to Crater Lake. The latest suite of hi-res model guidance captures this area of convection well, suggesting thunderstorms will continue in this area and points east through approximately 8 PM Friday. Elsewhere across northwest OR and southwest WA, conditions remain dry with seasonable temperatures and mostly sunny skies. With very little change to the overall pattern tomorrow, expect conditions to be similar to today with seasonable temperatures, mostly sunny skies in the afternoon, and a slight chance (10-20%) of thunderstorms along the Cascade crest near Willamette Pass and points east. May see some morning low clouds over central/eastern portions of the Portland/Vancouver metro into the south WA/north OR Cascade foothills (50-80% chance according to the HREF). Chances for morning low clouds are near 100% for the coast, Willapa Hills, lower Columbia and Cowlitz Valley. Chances for morning clouds are lowest from Salem to Eugene (20-40%). Conditions trend cooler and cloudier on Sunday in response to a weak upper level shortwave trough that will be moving over the coastal waters towards the coast. Expect mid and high clouds to increase from west to east from sunrise onward. The increasing cloud cover through the day, combined with cooler temperatures aloft, will support cooler temperatures with daytime highs generally in the 70s, except 60s at the coast. Sunday also features a 15-35% chance of showers over the Oregon Cascades during the afternoon and evening hours, which is in response to the incoming shortwave trough and increasing moisture. Despite the increase in moisture, models and their ensembles suggest instability will be quite limited due to the increase in cloud cover early in the day. As such, thunderstorms over the Cascades are unlikely to occur. That being said, there is a small chance the aforementioned trough and cloud cover ahead of it progresses slower than anticipated, which would support more unstable conditions near the Cascade crest. NBM thunder probabilities hint at this possibility, showing a 10-20% chance of thunder near the crest in Lane County. -TK .LONG TERM...Monday through Thursday night...Minimal changes to the long term forecast with today`s update. The forecast for next week remains highlighted by onshore flow, near to slightly below average temperatures for early August, and a mix of sun and clouds each day with clouds being most prevalent during the morning hours. This mild weather pattern is in response to a series of two or three shortwave troughs that move over the area during the early to middle part of next week, each one helping to deepen the marine layer. There is also a 15-30% chance of light rain or drizzle with low marine stratus along/near the coast Tuesday and Wednesday, mainly to the north of Newport. Inland areas are more likely to stay dry. Chances for more widespread rain increase late Wednesday night into next Thursday, however model spread for QPF remains very large and overall confidence regarding rain amounts remains low. Models and their ensembles still suggest there are two possible scenarios that could play out. The first scenario would be continued upper level troughing over the area, which would support cooler temperatures and potential widespread rain. The second scenario would be the gradual development of upper level ridging from the west or a trough that deamplifies after pushing inland, bringing dry weather with slightly warmer temperatures. WPC`s cluster analysis now shows better agreement for some degree of troughing Wednesday into early Thursday, however uncertainty remains in the amplitude of this trough (40% of model variance can be explained by uncertainty regarding the amplitude of this trough, according to 500 mb EOF patterns). Overall model spread for QPF remains large due to these uncertainties, ranging from no rain at all to around one inch of rain. Note the wettest ensemble guidance is showing up in the ENS ensemble rather than the GEFS or GEPS. Rain chances are highest over southwest WA and the Portland/Vancouver metro, and lowest from Salem to Eugene-Springfield. The NBM continues to show a 10-30% chance for 0.25 inches of rain or more with this potential system, except 40% over the Long Beach Peninsula, Willapa Hills, and Astoria area and 5-10% in Lane County. -TK && .AVIATION...Generally VFR conditions are in place this afternoon with the last lingering coastal stratus near Newport beginning to pull offshore. Headed into the evening expect slightly more robust onshore flow that beyond bringing degraded flight conditions to the coast likely pushes MVFR CIGs into the Portland/Vancouver Metro for Saturday morning. However confidence remains lower whether low clouds will impact KUAO, KSLE, and KEUG. Come Saturday afternoon CIGs trend back to VFR. PDX AND APPROACHES...VFR conditions continue through the evening hours. High resolution guidance is still bullish on bringing MVFR cigs into the local area 14-17z Saturday. Winds generally stay less than 10-15 knots. -Schuldt && .MARINE...Overall fairly calm conditions persist through the weekend as an area of surface high pressure sits across the waters. Northwest winds in the afternoon and evening hours will occasionally gust up to 14-20 knots but Small Craft conditions are not anticipated. However, given the pattern we`ll have to keep an eye out for fog across the coastal waters, potentially dense at times, tonight into Saturday morning which would reduce visibility to 1NM or less. At the very least marine stratus will be prolific Saturday morning. Come Tuesday an approaching surface trough brings about a southerly wind shift across all waters for albeit with wind gusts likely remaining below small craft conditions. Later in the week guidance does hint at the potential arrival of a slightly stronger trough which would push wind gusts closer to 21 knots - the NBM suggests a 30-40% chance for Small Craft Winds across the southern Waters by Friday. -Schuldt && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland