Several waves of showers and thunderstorms are expected as a series of shortwave disturbances move through the region. These thunderstorms produced locally heavy rainfall with gusty winds.
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The episode as NWS LOT wrote it up.
Several waves of showers and thunderstorms are expected as a series of shortwave disturbances move through the region. These thunderstorms produced locally heavy rainfall with gusty winds.
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 30, 3:11 AM CST, 39 minutes earlier.
Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 411 AM CDT TUE AUG 30 2016 .MESOSCALE DISCUSSION... 336 AM CDT Current batch of thunderstorms orientation has changed where the storm propagation created heavy rain over the same areas of ogle county where radar estimated over 3 inches fell, and now the current propagation has become more nw-se following the instability gradient. There is a pronounced wind signature on the storm in Dekalb county, with radar showing 35 kt or so through the lowest tilts, but this has only translated to 25-30 kt on surface obs. The line has a gust front out ahead of it and therefore strengthening is not anticipated, but additional development is possible as it continues ese, and it has not shown signs of weakening yet. The storms farther south are in a favorable environment to continue as well. KMD && .SHORT TERM... 147 AM CDT Through Wednesday... Concerns in the short term center around what has become a bit of a theme during this latter half of summer with the potential for slow moving heavy rainfall producing showers and thunderstorms. Before getting to storms, like in past nights dewpoint depressions are very low following a period of rainfall today, and with a broad surface high stretched across the Great Lakes and Midwest resulting weak to no wind, fog is occurring with visibility down to as low as 1 mile in spots, locally to 1/4 mile at KJOT. High clouds from low pressure to west continue has kept the fog from getting dense in many areas, but expect that it could be in spots. There will likely be some fog through at least daybreak. The upper pattern features a broad upper level ridge centered across the Ohio/Tennessee Valleys and extending north to the lower Great Lakes. Southwest flow continues to steer moisture around the western and northern fringes of the ridge which happens to be laid out across Northern Illinois. Meanwhile, a weak surface stationary front is also stretched east-west across northern Iowa and into central Illinois. 0z soundings at DVN/ILX still depict around 1.75” of precipitable water with SPC mesoanalysis and model guidance depicting values near 2.00” once again today. RAP soundings depict modest instability develops as well with around 1000 J/KG of MLCAPE (slightly less than yesterday) in a weakly capped low shear environment. Weak shortwaves will continue to slide eastward near surface boundary today, and this combined with subtle southwest warm/moist advection will lead to additional showers and thunderstorms today capable of mainly heavy rainfall. We are already seeing some increase at the moment as weak warm advection ahead of the leading shortwave increases. The HRRR suggests this will continue into the morning hours and it is possible that we just see continued waves of rain showers today, beginning this morning with decent coverage, and then becoming more convective in nature as the day continues. Guidance does depict widely varying solutions with regards to the extent of coverage today, but do generally agree on some favoring to coverage on the I-88 southward corridor given some nod to the current location of the stationary front. The thermodynamic and kinematic environment again will suggest these will continue to be slow movers with heavy rain. Signs of change are evident from a surface analysis where a seasonally strong cold front continues to drive a cluster of thunderstorms across central Minnesota and northwest Wisconsin. It is this front that will move through in the coming days that will bring in a considerably drier and cooler airmass to wrap up meteorological summer. The leading edge of the cold front, still considerably removed from the core of colder air near an upper low in Ontario, will arrive tonight. Continued vorticity advection around the upper high and on the southern end of Canadian upper low, combined with some surface convergence and upper height falls should keep a threat of showers and storms late this afternoon, tonight and into early Wednesday. The cold front will continue southeast on Wednesday. Upper 60s dewpoints hang on long enough in NW Indiana to keep chances for the day, with many areas seeing a much drier day. KMD && .LONG TERM... 147 AM CDT Wednesday night through Labor Day... By Wednesday night it appears the front is through with 50s dewpoints entrenched across northeast Illinois and northwest Indiana. The core of the upper low will head east into Quebec, but a sharp back edge to the trough axis will drive south across Michigan and graze the local area with a more significant push of seasonally colder air on Thursday. Significant thermal differences between this air mass and the warm lake could lead to some lake induced clouds, but the moisture appears shallow enough preclude much more than that in spite of some hints of some weak qpf and the GFS depicting lake induced CAPE of about 200-300 j/kg. Lake equilibrium levels are also quite shallow at around 6-7k ft. Highs hold in the 70s. High pressure takes over for Friday for dry and sunny conditions with highs into the mid to maybe upper 70s. The high retreats east Saturday and southeast flow will allow some temperature recoveries to near 80. Sunday into early next week will feature a return to warmer conditions, possibly quite warm for early September standards as strong southwest flow sets up ahead of deep low pressure that will move through the northern lakes. Labor Day, which some consider the unofficial end of summer, could indeed be quite summer-like with mid 80s for highs and dewpoints back near 70. A cold front will be approaching from the northwest which could bring some thunderstorms into north Central Illinois Labor Day afternoon, with better chances area-wide in the evening into Tuesday. KMD && .AVIATION... For the 09Z TAFs... Scattered thunderstorms ended up developing across portions of northwest and north central Illinois and have begun propagating east and southeast overnight. Northern most end of the heavier storms is near DKB at 09Z and has steadily been tracking east- southeast towards the Chicago terminals. There has been some signs of weakening along the far north end of the line which has gusted out and had some diminishing trends with lightning over the past hour. Instability gradient is oriented NW to SE across the region so think that diminishing trend will continue along the north end of the line as it moves into less unstable airmass over Chicago metro. Storms will likely persist through DPA and will certainly be close to ORD/MDW but given trends opted to just introduce a SHRA for the latter two sites for now. If the northern end of the line persists for another hour may have to change over to TSRA. Previous Discussion for 06Z TAFs... Showers and thunderstorms have dissipated across most of the region late this evening and expect dry conditions through the overnight hours outside of an off chance for an isolated storm developing. Main forecast challenge overnight will be visibility trends with fog once again a concern. Light winds, plenty of moisture, and thinning cirrus has set the stage for fog development. A few locations are already reporting IFR/MVFR visibility and expect a downward trend to continue through the predawn hours. Hit the typical fog prone locations and areas that saw rainfall today the hardest, but as usual with fog forecasts, confidence is not particularly high in the details, and certainly cannot rule out dense fog developing. As we warm up through the morning hours Tuesday, expect scattered slow moving pop-up showers and thunderstorms to once again develop over the region. As has been the case the past couple days, there is no significant source of forcing so cannot pin down precise locations where convection will develop, though do expect coverage to peak mid to late in the afternoon during the warmest part of the day. Coverage should also diminish with sunset. BMD && .MARINE... 254 AM CDT High pressure will be in place across southern Lake Michigan today with fresh southwesterly flow in place across the north end of the lake ahead of an approaching cold front. The front will pass south across the lake tonight into early Wednesday with a strong north to northeast breeze developing behind the front and continuing through Thursday evening. These winds will allow waves to build into the 4 to 6 ft range across southern portions of Lake Michigan which means a small craft advisory may be needed for the Indiana and Illinois nearshore waters starting Wednesday and possibly going through early Friday. Ridge of high pressure will build across the region Friday with southerly flow spreading back across the lake Friday night into Saturday and continuing into early next week. BMD && .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 427 AM CDT TUE AUG 30 2016 ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019- 310930- WINNEBAGO-BOONE-MCHENRY-LAKE ILLINOIS-OGLE-LEE-DE KALB-KANE- DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON- IROQUOIS-FORD-LAKE INDIANA-PORTER-NEWTON-JASPER-BENTON- 427 AM CDT TUE AUG 30 2016 /527 AM EDT TUE AUG 30 2016/ THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL ILLINOIS... NORTHEAST ILLINOIS AND NORTHWEST INDIANA. .DAY ONE...TODAY AND TONIGHT. WEATHER HAZARDS EXPECTED: SIGNIFICANT THUNDERSTORM RISK. ELEVATED FLOODING RISK. ELEVATED EARLY MORNING FOG RISK. DISCUSSION: SEVERAL WAVES OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AS A SERIES OF SHORTWAVE DISTURBANCES MOVE THROUGH THE REGION. WITH A MOIST AIRMASS IN PLACE, LOCALLY HEAVY RAINFALL IS EXPECTED. GUSTY WINDS ARE ALSO POSSIBLE, BUT GUSTS SHOULD REMAIN LESS THAN 40 MPH. IN ADDITION...FLOODING IS EXPECTED ALONG PORTIONS OF THE ILLINOIS AND KANKAKEE RIVERS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. WEDNESDAY... LIMITED THUNDERSTORM RISK. HIGH SWIM RISK. THURSDAY... HIGH SWIM RISK. SUNDAY NIGHT AND MONDAY... LIMITED THUNDERSTORM RISK. IN ADDITION...FLOODING WILL CONTINUE ALONG PORTIONS OF THE ILLINOIS AND KANKAKEE RIVERS. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT. GENERAL STORM MOTION OF THE DAY: MOVING EAST SOUTHEAST AT 20 MPH. && LMZ740>745-310930- 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- 427 AM CDT TUE AUG 30 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE ILLINOIS NEARSHORE WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE WATERS OF LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT. THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. WINDS AND WAVES HAZARDOUS TO SMALL CRAFT ARE EXPECTED WEDNESDAY INTO THURSDAY. THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS LATE SUNDAY INTO MONDAY. && LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868- 870-872-874-876-878-310930- 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 FROM PENTWATER TO MANISTEE MI 5 NM OFFSHORE TO MID 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- 427 AM CDT TUE AUG 30 2016 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE OPEN WATERS OF LAKE MICHIGAN. .DAY ONE...TODAY AND TONIGHT. THUNDERSTORMS ARE POSSIBLE ACROSS LAKE MICHIGAN TODAY. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY. THUNDERSTORMS ARE POSSIBLE ACROSS LAKE MICHIGAN ON SUNDAY AND MONDAY. && KMD 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
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Standing water across approximately one third of the towns roads.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2016Every state in 2016This day in weather historyWarnings in Illinois, August 2016
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: 659562.