


Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
463 FXUS66 KPQR 172221 AFDPQR Area Forecast Discussion National Weather Service Portland OR 321 PM PDT Fri Oct 17 2025 .SYNOPSIS...Transient shortwave ridging tonight will bring chilly overnight temperatures and areas of frost for some inland valleys. A robust frontal system arrives late Saturday into Sunday, bringing widespread soaking rain to the area with gusty southerly winds. Trending drier Sunday night into early next week, however some uncertainty remains with a 20-45% chance of rain returning by Wednesday. A stronger weather system is possible late next week, though uncertainty is high in details this far out. && .SHORT TERM...Friday Afternoon through Sunday Night...There has been very little change to the forecast. Visible satellite imagery early Friday afternoon shows a band of low clouds with drizzle over northern Oregon slowly dissipating as the front that moved into the region this morning continues moving southeast. Transient ridging will build into the area behind this front this afternoon into early Saturday, setting the stage for clear skies and calm winds tonight. This will lead to chilly temperatures once again for inland valleys tonight into Saturday morning. The coldest areas will likely be the Upper Hood River Valley, south WA Cascade foothills, Battle Ground and Ridgefield areas. Confidence is generally over 70-80% these zones will see low temperatures dip to 33-36 degrees, and Frost Advisories remain in effect tonight into Saturday morning. Meanwhile, a Freeze Warning remains in effect for the Upper Hood River Valley for low temperatures as cold as 29-30 degrees. While patchy frost is also possible in portions of the southern Willamette Valley, especially east of I-5, confidence remains too low to include these zones in the Frost Advisory. This is due to potential low clouds or fog that may develop instead of frost; the latest HREF and REFS runs indicate a chance for low cloud development late Friday night or early Saturday morning, which would favor temperatures bottoming out in the upper 30s with minimal frost concerns. The overall weather pattern beyond Friday morning does not favor widespread frost or freeze concerns, so this round of frost/freeze headlines may wind up being the last of this growing season. Despite the chilly temperatures in place Saturday morning, temperatures will rebound nicely in the afternoon with highs in the 60s, except near 70 degrees in Eugene-Springfield, Creswell, Blue River, Lowell and Oakridge. These areas will see sunny skies throughout the day, however northern areas will see clouds begin to increase ahead of the next frontal system. Models are in good agreement on the timing of this front, bringing stratiform rain to southwest Washington and the north Oregon coast Saturday evening and then the rest of northwest Oregon from Lane County northward Saturday night into Sunday morning. Persistent stratiform rain will transition to post-frontal showers by late Sunday morning or early Sunday afternoon. This is when forecast soundings show 850 mb temperatures cooling to +1 to +2 degrees Celsius, with SBCAPE values increasing to 100-200 J/kg and equilibrium levels generally below -10 degrees Celsius. However, 0-3 km AGL bulk shear values are fairly high at 30-35 kt (have opted to use 0-3 km AGL bulk shear values instead of 0-6 km as cloud tops generally look to stay near or below 3 km). Both speed shear and directional shear are in place, as the wind direction will veer with height for a few hours or so as the upper level trough axis moves overhead. The limited instability and shallow nature of Sunday`s convection suggests overall lightning activity will most likely be limited (which helps explain why NBM thunder probabilities only peak around 10-20%). However, whether lightning occurs or not, stronger showers will have the potential to produce a funnel cloud, landspout, or gusty outflow winds up to 45 mph given the environmental wind profile in place, meaning highly localized wind damage is possible. Note southerly winds will be breezy in general Saturday night and Sunday, even away from showers and thunderstorms. Currently expecting southerly wind gusts up to 20-30 mph for inland areas and up to 30-40 mph for the south WA/north OR coast. Gusts up to 40-50 mph appear likely in the high Cascades. Winds will weaken Sunday night while any lingering showers begin to dissipate. -23/03 .LONG TERM...Monday through next Friday...Most model guidance suggests dry weather with seasonable temperatures, relatively light winds and a mix of clouds and sun Monday and Tuesday. That said, there remains a handful of GEFS/ENS ensemble members with light QPF amounts Monday morning/afternoon and Tuesday morning/afternoon as a pair of weak upper level impulses move overhead. As such, there is a 10-30% chance of light rain showers on Monday for the south WA/north OR coast and 15-35% chance on Tuesday everywhere, with highest chances in southwest WA and along the south WA/north OR coast. Chances for rain gradually increase late Wednesday through Thursday night, peaking near 75-90% by early Friday morning, as another potentially stronger weather system approaches the area. This system has the potential to bring more impactful rain amounts and gusty south winds, however uncertainty is high in regards to exact rain amounts and exact wind speeds, as the outcome will be highly dependent on the exact track and strength of a negatively tilted trough and associated deepening surface low that will be moving somewhere over the coastal waters during that time. Ensemble low locations vary significantly both spatially and temporally, with some ensemble guidance suggesting a fairly weak low with minimal impacts, while other members suggest a very strong low capable of wind damage somewhere along the Washington, Oregon, or northern California coast. There is currently a 15-25% chance for max wind gusts of 45 mph or stronger across all of northwest Oregon and southwest Washington, except for a 35-50% chance at the coast and on exposed ridges in the Coast Range and Cascades. This system will also bring a 50-75% chance of 1" of rain or more in the Willamette Valley and a 40-60% chance of 3" of rain or more along the coast and terrain for Thursday and Friday, with additional rain chances continuing into the weekend. -23/03 && .AVIATION...Satellite imagery and terminal observations as of Friday afternoon depicts VFR conditions with scattered cloud cover as the weak front from this morning has exited the region. VFR conditions with FEW/SCT clouds persist through tonight. With some clearing tonight, can`t rule out some fog development across the Willamette Valley. Guidance suggests a 20-40% chance for LIFR VIS/CIGs after 10-12z Sat, with the highest chances in the central and southern Willamette Valley. Fog development will depend on how much existing cloud cover there is and if the ground saturates. Northwesterly winds 10-15 kt along the coast and 4-7 kt inland will gradually ease tonight. KPDX AND APPROACHES...VFR conditions with a 15-25% chance for LIFR/IFR VIS and CIGs from 11-17z Sat. Northwesterly winds around 5 kt or less. -10 && .MARINE...High pressure will maintain northerly winds around 10-15 kt tonight. Seas build overnight to 10-12 ft at 15-16 seconds as a northwesterly swell arrives from a dying low pressure system over the Gulf of Alaska. This will be hazardous to small craft, so Small Craft Advisories are in effect across all waters including the Columbia River Bar through at least Saturday. The weather pattern remains active Saturday night into early next week as a stronger frontal system progresses through the waters and brings breezy southerly to westerly winds. Marine conditions quickly amplify as a higher northwesterly swell enters the waters, building seas above 15 ft at 15 seconds (>90% chance) on Sunday. Chances for seas above 20 ft have decreased and are less than 10%, indicating increasing confidence is the wave height forecast. In addition to increasing seas, winds will likely gust up to 25-30 kt. Brief and isolated gale forced wind gusts up to 35 kt are possible over the northern and central inner waters (Cape Shoalwater to Cape Foulweather) including the Columbia River Bar during the frontal passage Saturday night into early Sunday morning. Seas will decrease later Monday into Tuesday morning, bottoming out around 7-9 ft at 12-13 seconds before another potent northwesterly swell arrives Tuesday afternoon and evening pushing seas into the 10-15 ft range again. Active weather continues later in the week. -10/23 && .BEACH HAZARDS...A northwest swell of 10-12 ft at 15-16 seconds seconds is expected to enter the waters Friday evening. This increase in wave energy will support a high threat for sneaker waves through this weekend. A Beach Hazards Statement remains in effect across the central and north Oregon coast and the south Washington coast through Sunday evening. Sneaker waves can run up significantly farther on a beach than normal, including over rocks, logs, and jetties. Sneaker waves can suddenly knock people off of their feet and quickly pull them into the ocean which may lead to serious injury or drowning. Caution should be used when in or near the water. Always keep an eye on the waves, and be especially watchful of children and pets. Remember, never turn your back on the ocean! -10/23 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Frost Advisory from midnight tonight to 9 AM PDT Saturday for ORZ104. Freeze Warning from midnight tonight to 9 AM PDT Saturday for ORZ121. WA...Frost Advisory from midnight tonight to 9 AM PDT Saturday for WAZ205-208. PZ...Small Craft Advisory until 5 AM PDT Sunday for PZZ210-251-252- 271-272. Small Craft Advisory until 8 PM PDT Saturday for PZZ253-273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland