An upper-level trough progressing over the area brought showers and thunderstorms to SW Washington and NW Oregon. Heavy rain was reported in downtown Portland, with multiple reports and pictures showing streets flooded.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PQR wrote it up.
An upper-level trough progressing over the area brought showers and thunderstorms to SW Washington and NW Oregon. Heavy rain was reported in downtown Portland, with multiple reports and pictures showing streets flooded.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Portland, OR wrote its last area forecast discussion before the first event at Sep 12, 1:56 PM PST, 4 minutes earlier.
Area Forecast Discussion National Weather Service Portland OR 256 PM PDT Wed Sep 12 2018 .SYNOPSIS...Cool and showery weather will continue through the weekend as a broad trough of low pressure lingers over the Pac NW. Stronger showers may produce a few lightning strikes and small hail this afternoon and evening. Drier and warmer weather looks to return for a few days early next week as weak upper level ridging briefly builds into the region. && .SHORT TERM...This afternoon through Saturday...Widespread showers with isolated thunderstorms have developed this afternoon, as expected. Expect showers and any thunder chances to taper off around sunset with the end of diurnal heating. Models continue to show a series of shortwave disturbances moving across the region through the week, which will continue a chance of showers each day, especially across the higher terrain where low level onshore flow and orographics remain the best. The pattern doesn't change a whole lot through Saturday. except any chance for thunderstorms after today looks limited. Can't completely rule out a stray thunderstorm Thursday, but won't put it in the forecast at this point as confidence is too low. With the trough remaining overhead, temperatures stay cool through Saturday, upper 60s to around 70 inland and low 60s along the coast. Bowen .LONG TERM...Saturday night through Wednesday. The 12Z GFS and 12Z ECWMF models continue toward holding the upper trough over the Pacific Northwest through this weekend. The models are also in agreement for the start of next week. Expect cool and showery weather through at least Sunday night. As a result PoPs have increased slightly and lowered temperatures slightly. As next week starts a shortwave ridge enters the area, which looks to flatten out Monday afternoon, and transitions more into a zonal onshore flow pattern by Tuesday night. This ridging into zonal flow pattern will provide a drying and slight warming trend for the region during the middle of the week. /42 && .AVIATION...Widespread showers and isolated thunderstorms continue across the forecast area. Expect generally VFR conditions through the evening with reduced MVFR cigs/vsbys in heavier showers. Thunder threat comes to an end after about 04z, with decreasing showers in a slowly stabilizing air mass overnight. Expect cigs to be mostly VFR early tonight across the interior, with a reduction to MVFR possible across the Willamette Valley overnight. Along the coast, lower MVFR to local IFR possible overnight with the best chance for lowest cigs around KONP. Showers continue in onshore flow Thursday but with improvement to VFR expected for most locations. KPDX AND APPROACHES...VFR conditions with showers continuing this evening, through strongest showers may contain lightning and bring temporary MVFR conditions. There remains a potential for thunderstorms in/around the terminal through around 04z. Otherwise, expect VFR conditions early tonight with cigs possibly lowering to MVFR late tonight after 12Z. Cullen && .MARINE...Low pressure stalls off the coast of Washington before slowly drifting south over the next few days. This will maintain south to southwesterly winds over the coastal waters. On Thursday, the low starts to get closer to shore, which will increase the pressure gradient. This will bring slightly stronger winds to the coastal waters, perhaps approaching advisory criteria. The low finally moves inland on Friday, but another low starts its descent down the coastline from the Gulf of Alaska for the weekend. While winds may turn westerly for a time on Friday, winds turn right back to southerly late Friday as that low starts its approach. Seas will hold at 4 to 7 feet through the week, though a small but longer period swell may arrive late Friday or Saturday. Cullen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. This area is commonly referred to as the CWA or forecast area.
The national radar mosaic for the moment the first event began.
1 heavy rain. Local standard time, as filed.
Standing water reported near NE 28th Ave between Glisan and Burnside. Trimet MAX lines were temporarily closed due to standing water between Lloyd Center and Hollywood. Rain guage at the Portland Airport reported 0.82 of an inch of rain.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2018Every state in 2018This day in weather historyWarnings in Oregon, September 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 786588.