Rainfall during May was 100 to 150 percent above normal in the Rock River watershed, especially during the middle of the month. This caused the Rock River near Moline to briefly rise to its major flood stage around 1 AM CDT on May 21st.
Every event with a place to put it. Tap one for its entry below.
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 DVN wrote it up.
Rainfall during May was 100 to 150 percent above normal in the Rock River watershed, especially during the middle of the month. This caused the Rock River near Moline to briefly rise to its major flood stage around 1 AM CDT on May 21st.
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 Quad Cities, IA wrote its last area forecast discussion before the first event at May 20, 9:15 PM CST, 2 hours 45 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 1015 PM CDT Wed May 20 2020 ...HYDROLOGY UPDATE... .SYNOPSIS... Issued at 255 PM CDT Wed May 20 2020 Surface high pressure sits to our northeast with persistent, easterly to southeasterly flow at the surface. Water vapor imagery continues to show the closed upper level low over eastern Tennessee and Kentucky early this afternoon with low closed sprawled across the region and into the Red River Valley of the North. Temperatures were generally in the lower 60s across the area with KCID the cool spot at 59 degrees. && .SHORT TERM...(This Evening through Thursday) ISSUED AT 255 PM CDT Wed May 20 2020 The main forecast concern is really cloud cover. Models are in pretty good agreement on the synoptic setup and decent agreement on the RH fields with the GFS faster to lift the ceilings overall. All synoptic models are depicting little change in the overall 500 MB pattern as the upper level shifts into eastern Kentucky and Tennessee with a closed off area of high pressure in the Northern Great Lakes. This is helping to create a block in the flow which means the forecast will not be changing in the short term. Model soundings and time series depict an inversion remaining in place across the area through Thursday with low level moisture trapped by that inversion leading to continued mostly cloudy skies across the area. Temperatures tonight will be in the mid to upper 50s across the area once again with high temperatures on Thursday in the upper 60s. .LONG TERM...(Thursday Night through Wednesday) ISSUED AT 255 PM CDT Wed May 20 2020 Friday The slow moving Ohio Valley low finally pulls far enough east to lessen its influence on the local area. Although it may be difficult to get rid of the clouds, the cloud deck should begin to thin later in the day. Temperatures will respond with highs reaching the low to mid 70s. A convectively induced 500mb vorticity max, and warm air advection on the nose of an attendant low-level jet, will spread an area of showers and thunderstorms into the region Friday night. Marginal instability and shear should preclude the threat for severe weather. The main impact from the storms will be heavy downpours as PWATs reach 1.25 inches. This Weekend Ongoing convection is possible Saturday morning before this initial round of isentropic lift shifts NE of the area. Residual cloud debris may act to hold down temps into the afternoon. Therefore, may have to lower temps a few more degrees from the current forecast, which is slightly below the model blend. Nonetheless, widespread 70s to near 80 F is expected, along with increasingly humid conditions as dewpoints reach above 60 F. For Sunday, the model blend is in the low to mid 80s for highs which would be the warmest day of the season so far. Of course, max temps will depend on the amount of cloud cover and areal coverage of storms. Latest model runs indicate a chance for scattered activity redeveloping during the afternoon, becoming more numerous into the evening and at night. It's too early to assess the risk for severe weather. However, moderate instability and 30+ kts of deep layer shear is a setup we'll have to monitor as we get closer. Next Week A slow moving cold front may stall across the area into next week as shown by the ECMWF and CMC. This would keep periodic chances for showers and storms going through the middle of the week. The GFS is an outlier being more progressive with the front. A renewed push of SW flow aloft points toward continued warm 850mb temps with surface highs near 80 F. Uttech && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) ISSUED AT 612 PM CDT Wed May 20 2020 Low clouds will continue to linger overnight through most of Thursday with ceilings primarily MVFR. Initial VFR ceilings at DBQ and MLI will likely lower to below 3000 ft this evening. Early morning MVFR ceilings from 1500 to 2500 agl at all sites will gradually lift through the day Thursday. VFR conditions are forecast by 21Z at CID and DBQ, but confidence was not high enough to go beyond MVFR this cycle at BRL and MLI. && .HYDROLOGY... Issued at 1015 PM CDT Wed May 20 2020 The Rock River at Joslin and Moline is cresting tonight at both sites and is forecast to slowly fall and drop below flood stage early next week. Joslin is cresting around 15 feet and Moline at 13.9, just below major flood stage of 14.0 feet. The La Moine River at Colmar crested last night and will likely drop below flood stage shortly after midnight tonight. Dry weather is expected through Friday, but rain chances return for the weekend into early next week. The overall weather pattern may support locally heavy rainfall. This could delay the rate of fall of flood waters on the Rock and La Moine Rivers, and possibly lead to rises on other tributary rivers. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SYNOPSIS...Cousins SHORT TERM...Cousins LONG TERM...Uttech AVIATION...Sheets HYDROLOGY...Sheets
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 343 AM CDT Wed May 20 2020 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-210845- Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson- Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson- Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll- Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson- Warren-Hancock-McDonough-Scotland-Clark- 343 AM CDT Wed May 20 2020 This Hazardous Weather Outlook is for portions of north central Illinois...northwest Illinois...west central Illinois...east central Iowa...northeast Iowa...southeast Iowa and northeast Missouri. .DAY ONE...TODAY AND TONIGHT Area rivers are experiencing flooding. Please see the latest Flood Statements and Flood Warnings for details. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY There is a daily chance for thunderstorms Friday night through Tuesday. It is too early to determine if any storms will be severe. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
The Rock River near Moline Illinois briefly hit its major flood stage of 14 feet around 1 AM CDT on May 21 and quickly fell below.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2020Every state in 2020This day in weather historyWarnings in Illinois, May 2020
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: 893658.