A disturbance moved across the area during the early morning hours of August 11th, resulting in a line of showers and thunderstorms that moved eastward across the area. One these storms become severe in Mercer County, near the town of Hamlet, where thunderstorm wind gusts brought 2 to 3 inch tree branches down.
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.
A disturbance moved across the area during the early morning hours of August 11th, resulting in a line of showers and thunderstorms that moved eastward across the area. One these storms become severe in Mercer County, near the town of Hamlet, where thunderstorm wind gusts brought 2 to 3 inch tree branches down.
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 Aug 11, 2:39 AM CST, 2 hours 21 minutes earlier.
Area Forecast Discussion National Weather Service Quad Cities IA IL 339 AM CDT Fri Aug 11 2023 .SHORT TERM...(Today and tonight) Issued at 338 AM CDT Fri Aug 11 2023 Key Messages... 1) A line of thunderstorms will continue to move through the area early this morning before exiting by mid-day 2) Another round of storms will be possible tonight into early morning Saturday, in a couple different locations Current radar reflectivity at 08z/3am early this morning shows a line of thunderstorms, extending from northeast Iowa south towards north-central Missouri. This line of storms will continue to gradually make its way into our region. This convection is associated with a mid-level shortwave trough, which is evident in the mid-level GOES-East water vapor imagery. Additionally, this activity has developed ahead of a southwesterly 30 to 40 knot low- level jet. At this time, no severe storms have been observed, but we are watching the potential for localized strong wind gusts, given the increasing moisture along the LLJ and Pwat values in excess of 1.6", which could lead to a localized wet microburst possibility. We have already seen wind gusts between 35 to 45 mph around Waterloo, Vinton, and Oelwein. Additionally, the moist environment could result in some heavy downpours, which could lead to ponding of water on roadways. This activity will continue to move through early this morning before moving off to the east and southeast late this morning. In total, rainfall amounts could exceed a half inch for a good portion of our area, per the 11.00z HREF localized probability matched mean. Some isolated areas could see up to an inch or more. Clearing skies will then develop in the wake of the convection for a brief period of time before another round of convection is expected to develop this evening into the overnight hours. There are mainly two areas where convection is most likely, per the latest suite of CAMs: 1) along the north to northeastern portions of the forecast area, where an upper-level trough will sweep through tonight, and 2) along the southern periphery of the forecast area where an outflow boundary from this morning's convection could set up. The more favorable instability for convection will be south of our region, but deep-layer shear appears to be substantial, with values around 40 to 50 knots. Most-unstable CAPE values have the potential to be around 500 to 1500 J/kg across our south during the evening hours before diminishing. Strong low- to mid-level flow near the base of the upper trough should produce elongated hodographs, so thinking straight-line winds will once again be the main hazard. With that being said, a Slight Risk (level 2 out of 5) for severe weather remains across the entire forecast area, but tonight's threat continues to have a conditional aspect to it, so uncertainty remains on how things will play out after this morning's round of convection. .LONG TERM...(Saturday through Thursday) Issued at 338 AM CDT Fri Aug 11 2023 Key Messages... 1) The weekend starts off quiet, with lots of sunshine, but another chance of showers and storms returns on Sunday and Sunday night 2) Monday through Wednesday looks to be dry, with perhaps more activity Thursday The upcoming weekend should start off dry and quiet as the upper- level trough shunts off to the east, becoming more negatively-tilted with time. Surface high pressure and upper-level ridging builds into the area, with a slight cool-down in our temperatures. This respite from convection should be short-lived as another chance of storms return for Sunday and Sunday night. An upper-level trough is progged to develop once again, which should become fairly deep in nature. An attendant cold front will sweep through the region Sunday night, which should be the primary mechanism for convection. Instability will be very marginal, but the deep-layer shear should be pretty strong. While the Storm Prediction Center had a Slight Risk going for us over the last few days, the latest outlook for Sunday has pulled the Slight out of our forecast area, and we now have a Marginal Risk (level 1 out of 5) for areas along and south of Waterloo, IA to Moline, IL to Kewanee, IL. The reduction in the severe weather risk falls more in line with what is being depicted in the Colorado State University machine learning severe probabilities, with values well within the Marginal range across our southern areas. The global models prog the upper-level trough to become more cut-off, resulting in an upper-level low traversing through central Minnesota into southern Wisconsin on Monday. Some lingering chances of showers will remain in the picture, with a noticeable cool-down for Monday, with highs in the middle 70s. The cut-off low will eventually move off to the east, with surface high pressure building in for Tuesday and Wednesday. Temperatures will gradually warm up during this time frame. The model guidance begins to deviate on Thursday, with some hints in the global models for a long-wave, upper-level trough to develop during this time frame in our region. However, there are some disagreements in the phasing of this trough, so larger uncertainty remains for Thursday. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 1250 AM CDT Fri Aug 11 2023 The main focus for this TAF set continues to be on a line of thunderstorms that is currently situated over central Iowa early this morning. This activity will continue to track eastward, and eventually impact the local TAF terminals. Flight conditions should deteriorate to MVFR, at least, along with some locally gusty winds. There is some uncertainty on the precise onset timing of this activity based on the latest high-res model suite. This activity is expected to be done by around sunset or after this morning, with clearing skies from west to east behind the storms late this morning into the afternoon. West winds should strengthen this afternoon, with gusts to around 20 kts. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && SHORT TERM...Schultz LONG TERM...Schultz AVIATION...Schultz
Hazardous Weather Outlook National Weather Service Quad Cities IA IL 411 AM CDT Fri Aug 11 2023 IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007- 009-015>018-024>026-034-035-MOZ009-010-120915- 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- 411 AM CDT Fri Aug 11 2023 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 Strong thunderstorms will continue to move through the area early this morning. Wind gusts of 40 to 50 mph are possible in the strongest storms this morning. Otherwise, frequent lightning and heavy rainfall are expected with these storms. Additional thunderstorms will be possible this evening through tonight. There remains a Slight Risk (level 2 out of 5) of severe weather today. The most likely areas to see storms will be along Highway 20 and for areas south of Highway 34. Damaging winds and large hail will be the main threats. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY Another round of thunderstorms will be possible for Sunday afternoon through Sunday night. There is a Marginal Risk (level 1 out of 5) for strong to severe storms, mainly along and south of a line from Waterloo, Iowa to Moline, Illinois to Kewanee, Illinois. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed early this morning, and once again this evening into tonight. GENERAL STORM MOTION OF THE DAY: Moving toward the east to southeast at 40 to 50 mph. JTS
Special Weather Statement
National Weather Service Quad Cities IA/IL
251 AM CDT Fri Aug 11 2023
IAZ040-041-051-052-063-064-076>078-110830-
Linn IA-Buchanan IA-Delaware IA-Keokuk IA-Iowa IA-Benton IA-
Washington IA-Louisa IA-Johnson IA-
251 AM CDT Fri Aug 11 2023
...Strong thunderstorms will impact portions of Linn, Buchanan,
western Delaware, northern Keokuk, Iowa, Benton, northern Washington,
northwestern Louisa and Johnson Counties through 330 AM CDT...
At 250 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from Tripoli to near Keswick. Movement was east at
50 mph.
HAZARD...Winds in excess of 40 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could cause minor tree limb damage and blow
around unsecured objects. Minor damage to outdoor objects
is possible.
Locations impacted include...
Cedar Rapids, Iowa City, Independence, Vinton, Manchester, Marengo,
Marion, Coralville, North Liberty, Hiawatha, Mount Vernon, Robins,
Williamsburg, Belle Plaine, Jesup, Center Point, Kalona, Fairfax,
Solon and Tiffin.
This includes the following highways...
Interstate 80 in Iowa between mile markers 205 and 250.
Interstate 380 between mile markers 1 and 55.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4151 9230 4230 9230 4230 9206 4264 9208
4264 9142 4136 9142 4145 9238 4151 9238
TIME...MOT...LOC 0750Z 270DEG 42KT 4280 9226 4152 9225
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
SpeckSpecial Weather Statement
National Weather Service Quad Cities IA/IL
319 AM CDT Fri Aug 11 2023
IAZ040>042-051>053-110900-
Linn IA-Buchanan IA-Delaware IA-Benton IA-Dubuque IA-Jones IA-
319 AM CDT Fri Aug 11 2023
...Strong thunderstorms will impact portions of northern Linn,
Buchanan, Delaware, northeastern Benton, west central Dubuque and
northwestern Jones Counties through 400 AM CDT...
At 318 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Hazleton to Urbana. Movement was east at
40 mph.
HAZARD...Wind gusts of 45 to 55 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Strong winds could break tree limbs, knock down weak trees
and blow around unsecured objects. Minor damage to outdoor
objects is possible.
Locations impacted include...
Independence, Manchester, Dyersville, Monticello, Center Point,
Urbana, Central City, Edgewood, Winthrop, Hazleton, Earlville,
Walker, Coggon, Hopkinton, Quasqueton, Lamont, Delhi, Colesburg, Ryan
and Rowley.
This includes Interstate 380 between mile markers 39 and 46.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is occurring and may lead to localized flooding.
Do not drive your vehicle through flooded roadways.
Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4218 9114 4220 9192 4264 9195 4265 9113
TIME...MOT...LOC 0818Z 265DEG 33KT 4263 9186 4222 9188
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH
SpeckSpecial Weather Statement
National Weather Service Quad Cities IA/IL
352 AM CDT Fri Aug 11 2023
IAZ040>042-051>054-064>067-ILZ001-110930-
Jo Daviess IL-Clinton IA-Linn IA-Buchanan IA-Delaware IA-Benton IA-
Jackson IA-Muscatine IA-Dubuque IA-Cedar IA-Jones IA-Johnson IA-
352 AM CDT Fri Aug 11 2023
...Strong thunderstorms will impact portions of northwestern Jo
Daviess, northwestern Clinton, Linn, southeastern Buchanan, Delaware,
southeastern Benton, western Jackson, north central Muscatine,
Dubuque, Cedar, Jones and northeastern Johnson Counties through 430
AM CDT...
At 352 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from Holy Cross to near Fairfax. Movement was east
at 40 mph.
HAZARD...Wind gusts of 45 to 55 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Strong winds could break tree limbs, knock down weak trees
and blow around unsecured objects. Minor damage to outdoor
objects is possible.
Locations impacted include...
Cedar Rapids, Dubuque, Maquoketa, Anamosa, Manchester, Galena,
Tipton, West Branch, Mechanicsville, Stanwood, Marion, Hiawatha,
Mount Vernon, Asbury, Dyersville, Monticello, Robins, Center Point,
Cascade and Lisbon.
This includes the following highways...
Interstate 80 in Iowa between mile markers 252 and 267.
Interstate 380 between mile markers 7 and 36.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is occurring and may lead to localized flooding.
Do not drive your vehicle through flooded roadways.
Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4264 9071 4251 9064 4251 9024 4156 9118
4196 9201 4265 9133 4265 9090 4268 9089
TIME...MOT...LOC 0852Z 290DEG 34KT 4262 9102 4188 9176
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...55 MPH
SpeckSpecial Weather Statement
National Weather Service Quad Cities IA/IL
424 AM CDT Fri Aug 11 2023
IAZ063-064-076-077-087-111015-
Keokuk IA-Iowa IA-Washington IA-Jefferson IA-Johnson IA-
424 AM CDT Fri Aug 11 2023
...A strong thunderstorm will impact portions of Keokuk, southern
Iowa, Washington, western Jefferson and southwestern Johnson Counties
through 515 AM CDT...
At 423 AM CDT, Doppler radar was tracking a strong thunderstorm 7
miles northwest of What Cheer, or 8 miles south of Montezuma, moving
southeast at 40 mph.
HAZARD...Wind gusts of 45 to 55 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Strong winds could break tree limbs, knock down weak trees
and blow around unsecured objects. Minor damage to outdoor
objects is possible.
Locations impacted include...
Fairfield, Washington, Sigourney, Kalona, Wellman, North English,
Hedrick, Brighton, What Cheer, Richland, Delta, Maharishi Vedic City,
Keswick, South English, Packwood, Parnell, Millersburg, Harper,
Martinsburg and Pleasant Plain.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is occurring and may lead to localized flooding.
Do not drive your vehicle through flooded roadways. Stay away from
flooded areas. Report any flooding to local law enforecement
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4151 9241 4151 9230 4168 9230 4146 9156
4094 9196 4104 9218 4116 9218 4116 9241
TIME...MOT...LOC 0923Z 293DEG 33KT 4146 9247
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...55 MPH
SpeckSpecial Weather Statement
National Weather Service Quad Cities IA/IL
524 AM CDT Fri Aug 11 2023
IAZ076>078-087>089-098-099-ILZ025-111130-
Henderson IL-Henry IA-Keokuk IA-Des Moines IA-Washington IA-
Van Buren IA-Lee IA-Louisa IA-Jefferson IA-
524 AM CDT Fri Aug 11 2023
...A strong thunderstorm will impact portions of Henry, southeastern
Keokuk, Des Moines, southern Washington, northeastern Van Buren,
northeastern Lee, southern Louisa and Jefferson Counties through 630
AM CDT...
At 523 AM CDT, Doppler radar was tracking a strong thunderstorm over
Pleasant Plain, or 9 miles northeast of Fairfield, moving east at 45
mph.
HAZARD...Wind gusts up to 50 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Strong winds could break small tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Burlington, Fairfield, Mount Pleasant, Washington, Wapello, Oquawka,
West Burlington, New London, Mediapolis, Winfield, Wayland, Danville,
Morning Sun, New Boston, Brighton, Richland, Salem, Middletown,
Lockridge and Crawfordsville.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is occurring and may lead to localized flooding.
Do not drive your vehicle through flooded roadways. Stay away from
flooded areas. Report any flooding to local law enforecement
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4112 9218 4134 9185 4116 9099 4110 9095
4107 9095 4092 9096 4090 9101 4082 9109
4067 9112 4064 9121 4064 9126 4104 9218
TIME...MOT...LOC 1023Z 289DEG 38KT 4112 9187
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH
SpeckSpecial Weather Statement
National Weather Service Quad Cities IA/IL
537 AM CDT Fri Aug 11 2023
IAZ067-068-078-ILZ015-016-024>026-111115-
Warren IL-Mercer IL-Henderson IL-Rock Island IL-Henry IL-Scott IA-
Muscatine IA-Louisa IA-
537 AM CDT Fri Aug 11 2023
...Strong thunderstorms will impact portions of northwestern Warren,
Mercer, northeastern Henderson, Rock Island, southwestern Henry,
south central Scott, southeastern Muscatine and east central Louisa
Counties through 615 AM CDT...
At 537 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from Buffalo to near Fruitland. Movement was
southeast at 35 mph.
HAZARD...Winds in excess of 40 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could cause minor tree limb damage and blow
around unsecured objects.
Locations impacted include...
Davenport, Moline, Rock Island, Muscatine, Aledo, Cambridge, Milan,
Coal Valley, Burgess, Orion, Blue Grass, Buffalo, Andalusia, Viola,
Millersburg, Matherville, New Boston, Alpha, Sherrard and Keithsburg.
This includes the following highways...
Interstate 74 in Illinois between mile markers 4 and 7, and between
mile markers 17 and 30.
Interstate 280 between mile markers 4 and 18.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is occurring and may lead to localized flooding.
Do not drive your vehicle through flooded roadways.
Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4130 9013 4098 9081 4132 9123 4156 9066
TIME...MOT...LOC 1037Z 309DEG 29KT 4148 9069 4131 9109
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH
SpeckThe Quad Cities radar (KDVN), 35 km away, was scanning. The volume nearest the first event began at 11:02 UTC.
1 thunderstorm wind. Local standard time, as filed.
A member of the public reported a few 2-3 inch diameter tree branches were blown down south of Hamlet.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Illinois in 2023Every state in 2023This day in weather historyWarnings in Illinois, August 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: 1129597.