


Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
490 FXUS66 KPQR 181113 AFDPQR Area Forecast Discussion National Weather Service Portland OR 400 AM PDT Sat Oct 18 2025 .SYNOPSIS...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, aside from the south WA/north OR coast where light rain appears increasingly likely Monday night into Tuesday morning. A stronger weather system is possible late next week, bringing heavier rain and the potential for impactful wind gusts. However, uncertainty remains high for exact wind gusts and rain amounts. && .SHORT TERM...Now through Sunday Night...Not much change to the short term forecast with today`s update. The forecast is generally on track as high pressure remains in place Saturday morning, bringing mostly clear skies and light winds aside from some patchy fog and low clouds in the Cascade and Coast Range valleys. As expected, the coldest areas this morning are generally over the Upper Hood River Valley, south WA Cascade foothills, and Battle Ground area where temps have dipped into the 30s. Frost or freeze headlines remain in effect for these areas through 9 AM Saturday. Elsewhere, temperatures are generally in the low to mid 40s. 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 aside from patchy morning fog, however northern areas will see clouds begin to increase ahead of the next frontal system. Models remain 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 mid Sunday morning. 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 late Sunday morning/early afternoon. 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 15-25%). 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 25-30 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. Now would be a good time to secure any loose outdoor objects you may have. Winds will weaken Sunday night while any lingering showers begin to dissipate. -23/03 && .LONG TERM...Monday through next Saturday...Most model guidance suggests mainly dry weather with seasonable temperatures, relatively light winds and a mix of clouds and sun Monday and Tuesday. The main exception to that will be the south WA/north OR coast where there is a 30-50% chance of light rain. The highest chance of rain is Monday night and Tuesday morning. Inland areas have a 10-20% chance of light rain Tuesday. Chances for more substantial rain gradually increase late Wednesday through Friday, peaking near 80-90% by early Friday morning. This is when a moisture-rich frontal boundary with an axis of heavier rain will take aim at western WA/OR, bringing widespread rain and gusty southerly winds to the region. Although confidence is high conditions will trend much wetter and breezier Friday into next Saturday, confidence remains low for exact wind speeds, rain amounts, and associated impacts. Given the relatively low river levels heading into this system, river flooding is not expected despite river rises and forecast uncertainty on rain amounts. What appears to be more concerning is the potential for damaging wind gusts late Friday into next Saturday, but only if a deep surface low winds up tracking towards the coast like some ensemble members from the ENS show. 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. That said, the ENS has begun showing more ensemble clustering for a strong low with a central pressure somewhere between 960-980 mb moving near Astoria. This scenario would result in impactful wind damage. On the contrary, there are still a relatively larger number of ensemble members that show either a weaker low and/or a different low position that remains further offshore. In addition, the GEFS also suggests a weaker low with a central pressure around 990-1000 mb, with only one or two members pushing a stronger low inland. In other words, we have a low probability for a moderate to high impact wind event that bears watching over the coming days. There is currently a 15-30% chance for max wind gusts of 45 mph or stronger across all of northwest Oregon and southwest Washington, except for a 40-60% chance at the coast and on exposed ridges in the Coast Range and Cascades. Probabilities for max wind gusts over 55 mph range between 5-15%, except 20-30% at the coast and over higher terrain. If wind speeds of this magnitude were to occur, extensive tree damage and power outages would be expected, especially given how many trees still have foliage on them. -23 && .AVIATION...Clear skies and light winds remain in place Saturday morning in response to high pressure. Patchy fog and low clouds have developed in portions of the Cascade foothills and Coast Range valleys, but has generally stayed out of the Willamette Valley. That said, guidance continues to suggest there is a 20-40% chance for LIFR to IFR vis/cigs to develop sometime between 12-15z Saturday, with the highest chances in the central and southern Willamette Valley. Areas of patchy fog and low clouds should dissipate by 18-20z Saturday. Attention then turns to Saturday evening/night. Cloud cover will develop from northwest to southeast across the area after 00-03z Sunday in response to an incoming frontal system. This system will bring widespread MVFR cigs and rain to all terminals beginning Saturday evening. Cannot rule out a brief period of IFR cigs at the coast between 04-09z Sunday as the front pushes inland, especially at KONP where chances for cigs below 1000 ft peak around 65% during that time. Chances for IFR cigs for inland TAF sites range between 10-20%. Gusty south to southwest winds will also accompany the frontal passage, with gusts up 30 kt expected at the coast. Winds will increase inland as well, with gusts up to 25-30 kt likely for all inland TAF sites between 06-12z Sunday. KPDX AND APPROACHES...Clear skies and light winds will continue through at least 12z Saturday. There is a 20-30% chance for a brief period of LIFR to IFR vis/cigs to develop sometime between 12-15z Saturday, before dissipating by 18z Saturday. MVFR cigs and rain will likely develop towards 06-08z Sunday as a front pushes inland. Gusty southerly winds up to 25 kt will also accompany the frontal passage. -23 && .MARINE...Seas have increased 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 remain in effect across all waters including the Columbia River Bar Saturday night, before hazardous seas up to 20 ft develop Sunday behind a frontal system. 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, with seas peaking somewhere between 15 to 20 ft. Chances for seas above 20 ft remain less than 10%, except over the northern outer waters from 40 to 60 NM offshore where there is a 30-50% chance for seas over 20 ft. 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 evening into Saturday night. 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 up to around 15 ft range again. An active weather pattern is then expected to continue late Wednesday through Friday night with a period of storm force wind gusts of 48 kt or stronger possible (20-40%, except for a 50% chance over the northern inner waters, including the Columbia River Bar). -23/10 && .BEACH HAZARDS...A northwest swell of 10-12 ft at 15-16 seconds seconds has entered the coastal waters as expected. 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 northern 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 until 9 AM PDT this morning for ORZ104. Freeze Warning until 9 AM PDT this morning for ORZ121. WA...Frost Advisory until 9 AM PDT this morning for WAZ205-208. PZ...Small Craft Advisory until 8 AM PDT Sunday for PZZ210-251>253- 271>273. Hazardous Seas Warning from 8 AM Sunday to 5 AM PDT Monday for PZZ251>253-271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland