Heavy rain produced flash flooding across portions of northern Illinois during the afternoon of August 7th.
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 LOT wrote it up.
Heavy rain produced flash flooding across portions of northern Illinois during the afternoon of August 7th.
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 Chicago, IL wrote its last area forecast discussion before the first event at Aug 7, 1:28 PM CST, 17 minutes earlier.
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 228 PM CDT Tue Aug 7 2018 .SHORT TERM... 228 PM CDT Today through Tonight... Evolution and timing of shower/thunderstorms late this afternoon and evening are primary near-term forecast concerns. Regional radar mosaic depicts an area of rain/isolated thunderstorms spreading northeast across the forecast area this afternoon. This activity is in association with a mid-level short wave, which will continue its transit of the area through late afternoon. Extensive cloud cover has helped to limit destabilization, with temps becoming further cooled by rainfall across areas north of I-80, thus there has been relatively little lightning with this activity. Still, RAP soundings and SPC mesoanalysis date depicts 500-1000 J/kg of MLCAPE exists, particularly along an axis of slightly higher dew points roughly along I-80 into northwest Indiana. This location may have a greater potential for isolated/scattered thunderstorm development this afternoon into early evening as the mid-level wave approaches. 35-40 kt mid-level speed max will also produce an increase in deep layer shear, suggesting at least an isolated strong/severe wind potential with any more organized cells or clusters. Much of the convective rainfall moving across north central Illinois is fairly low-topped, with shallow reflectivity centroid heights, which suggests these may be more efficient rainfall producers than their returns would indicate. This is also supported by low visibility observations as these cores pass various AWOS/ASOS platforms. Bulk of this precipitation looks to move through the Chicago metro by 430-530 pm, though additional more isolated to scattered showers and thunderstorms are possible into early evening as another short wave drops southeast across the Upper Mississippi Valley into tonight. Loss of diurnal instability should result in diminishing coverage by/after sunset however. Moist low levels, wet ground and light winds will likely allow for patchy fog development again tonight, especially across areas north of I-80 where heavier rainfall is likely this afternoon/early evening. The second short wave is progged to clear the forecast area by midday Wednesday. Given poor diurnal timing, have maintained only slight chance pops mid-late morning for our southeast counties, with rain potential generally decreasing by early afternoon as the upper trough axis moves east of the area. Column dries out in mid and upper levels in the afternoon in the wake of this wave, which should allow for partly/mostly sunny skies and for temps to warm into the low-mid 80s most areas, though light onshore flow will keep things just a bit cooler along Lake Michigan. Ratzer && .LONG TERM... 331 AM CDT Wednesday through Monday... Throughout mid into late week, a transition to more of a northwesterly flow aloft will be seen. The moisture through the column will ease some, but in the low-levels looks to only ease slightly (dew points remaining 65-70). A weak surface trough/cool front is forecast to move southward on Thursday afternoon or night with a chance for storms along this given that low-level moisture. After this, the global models the past 48 hours have trended toward an upper low developing over the Great Lakes thanks to a retrograding Bermuda high. The CWA is forecast to be under the western half of the upper low during the weekend. The slight cool pocket and associated ascent with this does warrant chances of showers and possibly storms, probably with afternoon through early evening most favored. The blend provided PoPs look too widespread and high especially Friday into Saturday, before the center of mid-level circulation has fully developed. Have collaborated lower at this time. For temperatures, Thursday ahead of the aforementioned trough with southwest surface winds looks to be warm right now, with a high of 90 possible. Otherwise, highs in the 80-84 range are favored. MTF && .AVIATION... For the 18Z TAFs... 1253 pm...Forecast concerns include a lake breeze/wind shift... showers with isolated thunderstorms this afternoon and fog/low clouds overnight/Wednesday morning. A lake breeze formed late this morning and became stationary but is now slowly shifting westward. Confidence of how soon this lake breeze will reach ord/mdw is low and timing tweaks are likely. Ahead of this lake breeze winds became southwesterly in response to the wave moving out of Iowa. Confidence for wind directions is low and should eventually favor a light north/northeast direction by late afternoon/early this evening with light winds tonight. An area of rain over northwest IL will slowly move east/northeast this afternoon. There has been an occasional lightning strike which will remain possible as it moves across the terminals and for now vicinity thunder mention seems reasonable. The heaviest of this rain is likely to lower vis/cigs to ifr with a period of mvfr vis/cigs likely. Once this activity moves east of the terminals by early evening...there could be an isolated shower this evening but the focus for new development should shift south of the terminals. With the expected light winds and continued moist low levels...in addition to the rain falling this afternoon...fog is expected to develop tonight. Continued with the trends from the previous forecast with the thicker/more widespread fog across rfd/dpa and areas of dense fog will be possible. cms && .MARINE... 152 pm...A weak area of low pressure will move across the southern Great Lakes region tonight as a weak area of high pressure moves across the western Great Lakes region on Wednesday. Strong low pressure will move across Hudson Bay tonight into Wednesday morning. A trailing cold front from this low will move south across the region Wednesday night with generally northerly or northeasterly winds prevailing into the weekend. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Hazardous Weather Outlook
National Weather Service Chicago/Romeoville IL
1153 AM CDT Tue Aug 7 2018
ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
081700-
Winnebago-Boone-McHenry-Lake IL-Ogle-Lee-DeKalb-Kane-DuPage-Cook-
La Salle-Kendall-Grundy-Will-Kankakee-Livingston-Iroquois-Ford-
Lake IN-Porter-Newton-Jasper-Benton-
1153 AM CDT Tue Aug 7 2018 /1253 PM EDT Tue Aug 7 2018/
This Hazardous Weather Outlook is for portions of North Central
Illinois...Northeast Illinois and Northwest Indiana.
.DAY ONE...This Afternoon and Tonight.
Weather hazards expected...
Elevated Thunderstorm Risk...with an associated:
Limited damaging wind risk...up to 60 mph.
Limited Flooding Risk.
Limited Fog Risk.
DISCUSSION...
Shower and thunderstorm coverage will increase late morning into
the afternoon, with scattered thunderstorms possibly lingering
into this evening. Some thunderstorms may be capable of producing
isolated damaging winds, primarily over eastern portions of the
outlook area including the southern parts of the Chicago metro
area, kankakee, and parts of northwest Indiana. In addition,
locally heavy rainfall will be possible with some thunderstorms,
which could result in localized flooding.
Patchy dense fog is possible overnight.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Thursday through Sunday...
Limited Thunderstorm Risk.
.SPOTTER INFORMATION STATEMENT...
While there may be a few stronger storms, spotter activation
is not anticipated this afternoon or tonight.
GENERAL STORM MOTION OF THE DAY:
Moving toward the east-northeast at 35 mph.
LMZ740>745-081700-
Winthrop Harbor to Wilmette Harbor-
Wilmette Harbor to Northerly Island-
Northerly Island to Calumet Harbor-Calumet Harbor to Gary-
Gary to Burns Harbor-Burns Harbor to Michigan City-
1153 AM CDT Tue Aug 7 2018
This Hazardous Weather Outlook is for portions of the Illinois
nearshore waters of Lake Michigan and the Indiana nearshore
waters of Lake Michigan.
.DAY ONE...This Afternoon and Tonight.
Weather hazards expected...
Limited Thunderstorm Risk...with an associated:
Limited thunderstorm wind gust risk...up to 45 knots.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Thursday through Sunday...
Limited Thunderstorm Risk.
LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-081700-
Lake Michigan from Michigan City IN to St. Joseph MI 5 NM
offshore to Mid Lake-
Lake Michigan from Seul Choix Point to Rock Island Passage 5 NM
offshore to Mid Lake-
Lake Michigan South of a line from Seul Choix Point to the
Mackinac Bridge and north of a line from Charlevoix MI to South
Fox Island 5 NM offshore-
Lake Michigan from Charlevoix to Point Betsie MI 5 NM offshore to
Mid Lake-
Lake Michigan from Point Betsie to Manistee MI 5 NM offshore to
Mid Lake-
Lake Michigan from Rock Island Passage to Sturgeon Bay WI-
Lake Michigan from Sturgeon Bay to Two Rivers WI 5 NM offshore to
Mid Lake-
Lake Michigan from Two Rivers to Sheboygan WI 5 NM offshore to
Mid Lake-
Lake Michigan from Sheboygan to Port Washington WI 5 NM offshore
to Mid Lake-
Lake Michigan from Port Washington to North Point Light WI 5 NM
offshore to Mid Lake-
Lake Michigan from North Point Light to Wind Point WI 5 NM
offshore to Mid Lake-
Lake Michigan from Wind Point WI to Winthrop Harbor IL 5 NM
offshore to Mid Lake-
Lake Michigan from Winthrop Harbor to Wilmette Harbor IL 5 NM
offshore to Mid Lake-
Lake Michigan from Wilmette Harbor IL to Michigan City IN 5 NM
offshore to Mid Lake-
Lake Michigan Holland to Whitehall MI 5 nm off shore to mid-
line of lake-
Lake Michigan from Whitehall to Pentwater MI 5 NM offshore to Mid
Lake-
Lake Michigan from Grand Haven to Whitehall MI 5 NM offshore to
Mid Lake-
Lake Michigan from Holland to Grand Haven MI 5 NM offshore to Mid
Lake-
Lake Michigan from South Haven to Holland MI 5 NM offshore to Mid
Lake-
Lake Michigan from St. Joseph to South Haven MI 5 NM offshore to
Mid Lake-
1153 AM CDT Tue Aug 7 2018
This Hazardous Weather Outlook is for portions of the open waters
of Lake Michigan.
.DAY ONE...This Afternoon and Tonight.
Weather hazards expected...
Limited Thunderstorm Risk across far southern Lake Michigan this
afternoon and tonight.
.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Wednesday through Sunday...
Limited Thunderstorm Risk.
Ratzer
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www.youtube.com/nwschicagoThe Chicago radar (KLOT), 91 km away, was scanning. The volume nearest the first event began at 19:45 UTC.
6 heavy rain, 3 flood, 1 flash flood. Local standard time, as filed.
Standing water was estimated a few inches deep in multiple locations in Rochelle.
Rainfall of 0.64 inches was measured in ten minutes.
Rainfall of 2.18 inches fell in an hour at Chicago O'Hare Airport with 0.68 inches falling in just 8 minutes.
Rainfall of 2.12 inches was measure in 45 minutes.
Rainfall of 1.50 inches was measured in 45 minutes.
Rainfall of 1.76 inches was measured in one hour.
Numerous flooded viaducts were reported across the north side of Chicago, including a viaduct under railroad tracks at Irving Park Road and Ravenswood where vehicles were stalled in flood water with water up to their doors. A parking lot was flooded at the Norridge Theatre. Roads were closed in some subdivisions due to standing water in Rosemont. The Irving Park Road and Lawrence Avenue viaducts under railroad tracks were flooded in Schiller Park. Numerous vehicles were stalled in the flooded viaducts.
Two to three inches of standing water was reported on 15th Street in St. Charles.
Storm total rainfall of 2.63 inches was measured.
Route 83 was flooded under the railroad tracks between North Avenue and St. Charles Road. The Palmer Drive viaduct was also flooded under the railroad tracks.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2018Every state in 2018This day in weather historyWarnings in Illinois, August 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: 779038, 779037, 779036, 778990, 778989, 778988, 779035, 779039, 778995, 779040.