FXUS66 KPQR 292146 AFDPQR Area Forecast Discussion National Weather Service Portland OR 246 PM PDT Sat Mar 29 2025 && .SYNOPSIS...Weakening showers today as ridging builds into the area. Saturday night into Sunday a brief break in the precipitation as well as a slight warming trend is expected. By the start of the upcoming week, a broad area of low pressure will bring a return of cooler temperatures, rain and Cascade snow by late Sunday night/Monday and these conditions look to persist through the upcoming week. && .DISCUSSION...Today through Friday...There are still a few very weak showers throughout the region, mostly virga, but all precipitation tapers off throughout the rest of this afternoon. Shortwave ridging builds in this evening, and the majority of tonight and Sunday will be dry. Sunday's high temp will be slightly warmer than previous days, with a high around the low 60s in the northern Willamette Valley/SW Washington lowlands, closer to the mid/upper 50s at the southern Willamette Valley and coast. The next system arrives on Sunday night/Monday is a rather broad, vertically stacked low, with the surface low expected to be around 988 mb and centered around 45.75N/136.40W on Monday. This low will slowly weaken and travel southeastward through the upcoming week, with models showing landfall in-between Florence, OR and the OR/CA border. As this low moves southeastward, it will send multiple fronts across the region. This will result in south/southeasterly flow, that along with moderate warming and a moisture latent atmosphere will result in around a 10-20% probability for thunderstorms come Monday afternoon and continue through the late Monday evening. Cool and moist conditions will continue as the low continues to trudge southeastward and will bring widespread precipitation along with 850 mb temperatures dipping down towards -0C to -4C. This will result in a lowering of snow levels to 2500-3000 feet. Have decided not to issue a Winter Weather Advisory for the initial wave of mountain snow. NBM guidance shows only around a 40-60% chance for 6 inches or greater of snowfall accumulation at Cascades elevations between 3000-5500 ft, with closer to 70% chance above 5500 ft. Combined with the fact that snow levels will be closer to 4000-5000 shortly before the precipitation and only slowly falling once the initial front pushes in, snowfall accumulations at any impactful areas has potential to underperform model guidance. Ultimately, with showery precipitation continuing throughout the majority of the upcoming week, snow accumulations will at some point exceed 6 inches in the southern Cascades, but at least for the initial wave of precipitation, Advisory-level snowfall rates are not expected. Cluster analysis shows around a 60% chance of returning to ridging next Friday, possibly indicating drier conditions returning at that point. /JLiu && .AVIATION...Primarily VFR conditions are expected through the TAF period. A weak shortwave ridge has built overhead this afternoon helping to keep shower activity confined to the coast range and Cascades, otherwise dry weather prevails. Headed through the evening these showers likely end with the overall upper-level flow becomes more easterly by Sunday morning. We'll need to watch the evening and overnight period before both easterly winds and high clouds increase during which partial clearing and ample surface moisture may potentially lead to isolated pockets of valley fog - 20-30% chance at KEUG, KSLE, KUAO and KHIO. It appears the development of easterly winds at KTTD, KAST, KONP, and to some extent KPDX should mitigate this isolated fog potential at these sites. On that note winds likely become breezy through the Columbia Gorge on Sunday with gusts around 20-30 knots expected at KTTD. Late in the period the arrival of a frontal boundary south to north will spread light rainfall across the region, mainly between 21-23z Sunday at most terminals. PDX AND APPROACHES...VFR conditions persist with dry conditions expected through most of the period. Expect a switch to northerly winds this evening before turning easterly Sunday morning. A frontal boundary likely brings light rain to the terminal late Sunday afternoon ~22-00z but CIGs should hold AOA 5-10kft. -Schuldt && .MARINE...Today a weak ridge of high pressure has moved over the waters leading to somewhat calmer conditions with wave heights of 6-8ft at 10 seconds. Going through tonight into Sunday morning winds likely turn offshore becoming locally breezy through coastal gaps. Winds then turn southerly by Sunday afternoon and increase through Sunday night as another frontal system approaches from the southwest. High resolution guidance indicates a 75-90% chance for low end Gale force winds later Sunday afternoon into Sunday night across the inner and outer waters south of Cape Falcon which has prompted the issuance of a Gale Warning. However, confidence is a bit lower for frequent gusts above 34 kt north of Cape Falcon so have decided to issue a Small Craft Advisory here - we'll almost certainly see gusts between 25-30 knots late Sunday through Monday morning. It's worth noting there is at least some minor uncertainty as to the location/strength of a surface low associated with the frontal boundary and should models trend stronger with this feature the Small Craft may need to be upgraded - something to watch. Seas will build again into the low teens late Sunday night (wind wave driven) due to the aforementioned weather system. After a rather brief lull we'll see the arrival of a fresh southwesterly swell late Monday into Tuesday pushes seas up into the low to mid teen yet again before decreasing Tuesday night into Wednesday. Seas level out around 5-7 ft at 9-10 seconds for the middle to end of the week as north-northwesterly flow resides aloft. -Schuldt && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 11 AM PDT this morning for PZZ251>253- 271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland