Heavy showers developed over the Portland metro area in the afternoon as a cool upper trough remained over the region. Minor flooding occurred in the area.
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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.
Heavy showers developed over the Portland metro area in the afternoon as a cool upper trough remained over the region. Minor flooding occurred in the area. The greatest impacts were to a southwest Portland neighborhood where 14 homes were affected.
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 May 8, 2:23 PM PST, 37 minutes earlier.
Area Forecast Discussion National Weather Service Portland OR 323 PM PDT Mon May 8 2023 .SYNOPSIS....Low pressure aloft moving across eastern Oregon will help initiate showers and thunderstorms across the region today through this evening. Showers diminish tonight, with generally drier conditions Tuesday onward for our region. An exception would be slight chances for thunderstorms in the Linn and Lane County Cascades Wednesday. Robust ridging develops later in the week, bringing summer-like temperatures. && .SHORT TERM...Today through Wednesday: As of 3pm PDT, radar and satellite imagery is showing cumulus clouds and showers popping up across the region, mostly over the Coast Range and Cascades. This is due to a shortwave trough aloft that is bringing more instability and moisture to the area as it moves through eastern Oregon. As daytime heating progresses this afternoon, expect more showers to develop with a 20-30% chance of thunderstorms across the Willamette Valley, Cascades and north Oregon Coast Range through 7pm tonight. Thunderstorms that initiate in the Cascades could move into the Valley. Thunderstorm coverage will generally be isolated/scattered and stagnant, so locations that do receive thunderstorms may see brief periods of heavier showers and/or small hail. Expect thunderstorm chances to diminish in the late evening once we begin cooling down at the surface. Tonight through Wednesday, expect drier weather across the region as the current shortwave trough moves eastward into the Intermountain West. Deterministic models (GFS/Euro/Canadian/NAM) point at another another shortwave trough moving in to the region Wednesday, however it's much weaker and is not expected to bring a lot of moisture for enhanced precipitation. Despite this, it does provide some initiation for a 15-24% chance of thunderstorms in the Linn and Lane County Cascades between mid-morning and late afternoon Wednesday. Once this final shortwave moves through, more robust ridging will begin and we enter our much drier and warmer pattern change. -Alviz .LONG TERM...Thursday through Monday: There is excellent agreement among deterministic and ensemble model guidance that strong high pressure/ridging will build across western North America later this week into the weekend. This will lead to a pattern change towards temperatures up to 25 degrees above normal. Thursday and Friday look to be in the mid 70s to mid 80s, with Mother's Day weekend currently being the hottest period of the long term forecast. Current NBM guidance shows a 70-90% chance of high temps exceeding 90 degrees on Saturday in the central/northern Willamette Valley, and a 40-60% chance of that same threshold in the southern Valley. On Sunday, NBM shows a 75-85% chance of high temps exceeding 90 degrees across the entire Valley. Deterministic GFS/Euro/Canadian models show a thermal trough developing along the coast Saturday morning, which will induce offshore flow and downsloping winds to heat up the Valley. Some locations in the Valley may struggle to fall below 60 degrees Sun and Mon morning, which would limit overnight cooling relief. Uncertainty remains with how much and when downsloping east flow will peak this weekend, especially for the coast. Current NBM guidance shows a large spread of maximum high temperatures for Sunday. For example, at KONP the 25th percentile for high temps on Sunday is 68 degrees, while the 75th percentile is 90 degrees. A similar spread of uncertainty for Sun max temps are seen up the coast to KAST. If the thermal low moves offshore, then the coast could see a southerly flow reversal and onshore flow will keep temperatures cooler. If not, then expect to keep warm. Temperatures lower a few degrees Monday with weak onshore flow, but is forecast to still be hot. Higher pressure generally remains, but based on WPC clusters, 16% of ensemble members show troughing moving towards the west coast. This could explain some of the slight chances for precipitation at the end of the long term forecast. On a final note, be sure to make preparations for this heat. Excessive heat is the number one weather-related killer. Stay cool, hydrated, and find plenty of shade. In addition, if you travel to the local lakes/rivers, remember that the water temperature will still be very cold. Sudden exposure to cold water drains body heat faster than cold air, so cold water shock can also pose life-threatening risks. Wearing a life jacket will significantly increase chances of survival. -Alviz/Bonk && .AVIATION...18z TAFs: Band of showers stalled over the central Valley near KSLE and is dissipating. Areas of MVFR continue however south of KSLE for the inland areas. Now convection is increasing over the Cascades and coastal mountains. Latest hi- res models showing showers to develop over the north coast range and track into the north Willamette Valley, affecting KHIO, KPDX, KTTD. There is a 10-25% chance for thunderstorm through about 03Z with the highest chances over the north valley & southwest WA. Guidance indicating MVFR continues on the central coast (KONP) tonight and Tue. Guidance also expanding MVFR conditions north to KAST after 08Z Tue. Inland areas have a 20-60% chance for MVFR developing after 11Z Tue through 18Z Tue. For detailed Pac NW aviation weather information, go online to: http://weather.gov/zse KPDX AND APPROACHES...Showers will approach the terminal from the west per latest hi-res models, but some showers will also be developing over the Cascade foothills. There is about a 20-25% percent chance for thunderstorms through 03Z. Showers depart to the east by 06z Tue. Later tonight there is a 30-50% chance for MVFR cigs 11-18Z Tue. /mh && .MARINE...Weak winds across the area with as a broad low pressure areas heads into CA. Northwest wind has strengthened on the coast this evening. Could see a few gusts to around 20 kt this afternoon in the northern nearshore waters, but not anticipating the need for any headlines at this time. After northerlies diminish this evening, a disorganized trough of low pressure will linger over the region and result in light winds through Tuesday. Quiet conditions continue through the middle of the week as high pressure begins to build overhead on Wednesday, bringing a decrease in showery weather but otherwise maintaining light winds. Expect a more summer-like northerly wind regime to develop by the end of the week as inland heating induces a surface thermal trough and tightens the coastal pressure gradient. Seas will be dominated through the week by a 4-5 ft westerly swell with a period around 10 seconds. The recent full moon on May 5th will produce stronger tidal currents during the morning ebb cycle. Those moving in and out of harbors and crossing coastal bars should use caution and be aware of any bar restrictions in place. /mh /CB && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Heavy rains around 1 inch in a half hour to an hour resulted in Ash Creek in southwest Portland to over flow. Around 14 homes had varying amounts of flooding.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Oregon in 2023Every state in 2023This day in weather historyWarnings in Oregon, May 2023
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: 1103368.