A very unstable airmass was in place over Iowa.  The stationary front that had been south of the state over the past several days began to lift north and extended from southwest into east central Iowa on the afternoon of the 28th.  Temperatures warmed into the low to mid 80s, with dewpoints in the upper 60s to low 70s.  CAPE increased to between 3000 and 4000 J/kg by mid afternoon.  Downdraft CAPE rose to 800 to 1000 J/kg, while CAPE in the -10 to -30 C layer of the atmosphere was in the 600 to 800 J/kg range.  The freezing level was still a relatively low 12,700 feet.  A 35 kt low level jet was in place with considerable moisture transport.  Precipitable water values increased to 1.4 to 1.7 inches, or about two standard deviations above normal.  The atmosphere was fairly strongly sheared with 45 to 50 kts of available shear.  Thunderstorms developed around the warm front and became severe quite quickly.  A funnel cloud was observed in Ringgold County.  The primary mode of severe weather during the late afternoon was hail with numerous reports of three quarter to one and one half inch diameter hail.  Two and one half inch diameter hail fell in Monroe County north of Lovilia.  Flash flooding occurred in Monroe County, where 3 inches of rain fell in a short period of time.  An unofficial report of 10 inches of rain was received from southwest of Eddyville in Monroe County.  Major flooding occurred in the area.  Numerous roads and highways were flooded across southern Iowa, some with water of 3 to 5 feet in depth.  Road washouts were reported as well as culvert washouts.

Flash Flood in MONROE, IOWA
From 28-MAY-13 19:13:00 to 28-MAY-13 20:00:00 (CST-6)
Location: MELROSE
Flood cause: Heavy Rain
Property damage: 500.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Monroe County law enforcement reports that downtown Melrose and most of the streets in town were under water with water flowing into some buildings, including the community center with water surrounding several trailer homes. Most streets were impassible.

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 19:45:00 to 28-MAY-13 23:30:00 (CST-6)
Location: OTTUMWA
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported flash flooding along 140th Ave on the north side of Ottumwa.  Water moving down the road 1 to 2 feet deep.

Flash Flood in WAYNE, IOWA
From 28-MAY-13 19:55:00 to 29-MAY-13 00:30:00 (CST-6)
Location: MILLERTON
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over County Road J22 just east of Millerton.

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 18:45:00 to 28-MAY-13 23:30:00 (CST-6)
Location: RUTLEDGE
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water flowing over 74th St near Albia Road.

Flash Flood in WAYNE, IOWA
From 28-MAY-13 20:05:00 to 28-MAY-13 21:30:00 (CST-6)
Location: SEYMOUR
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water across County Road S60 just north of Seymour.

Hail in APPANOOSE, IOWA
From 28-MAY-13 19:38:00 to 28-MAY-13 19:38:00 (CST-6)
Location: EXLINE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Also included a 40 to 50 MPH wind.

Hail in UNION, IOWA
From 28-MAY-13 17:08:00 to 28-MAY-13 17:08:00 (CST-6)
Location: CRESTON
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Flash Flood in MONROE, IOWA
From 28-MAY-13 19:13:00 to 28-MAY-13 20:00:00 (CST-6)
Location: LOVILIA
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Monroe County law enforcement reports that several streets in and around Lovilia remain closed due to water over roads. The intersections of 110th, 115th and 130th are closed due to water over the road.

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 18:45:00 to 28-MAY-13 23:30:00 (CST-6)
Location: (OTM)OTTUMWA INDSTRL
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Large propane tank washed away along Keb Lane just north of Ottumwa.

Hail in LUCAS, IOWA
From 28-MAY-13 15:00:00 to 28-MAY-13 15:00:00 (CST-6)
Location: CHARITON MUNI ARPT
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Law Enforcement

Hail in LUCAS, IOWA
From 28-MAY-13 15:00:00 to 28-MAY-13 15:00:00 (CST-6)
Location: LUCAS
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Hail in MADISON, IOWA
From 28-MAY-13 17:54:00 to 28-MAY-13 17:55:00 (CST-6)
Location: WINTERSET
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

Hail in APPANOOSE, IOWA
From 28-MAY-13 19:47:00 to 28-MAY-13 19:47:00 (CST-6)
Location: CINCINNATI
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Flood in MONROE, IOWA
From 28-MAY-13 18:35:00 to 29-MAY-13 03:30:00 (CST-6)
Location: MELROSE
Flood cause: Heavy Rain
Property damage: 250.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reports that all streets in Melrose are now under water.  Some spots are standing and some flowing. Water depth 6 to 8 inches.

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 19:00:00 to 28-MAY-13 23:30:00 (CST-6)
Location: BIDWELL
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flood damage to the railroad tracks near 87th St and Highway 34.

Hail in UNION, IOWA
From 28-MAY-13 17:05:00 to 28-MAY-13 17:05:00 (CST-6)
Location: CRESTON
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Fire Department/Rescue

Hail in UNION, IOWA
From 28-MAY-13 17:07:00 to 28-MAY-13 17:07:00 (CST-6)
Location: CRESTON
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 19:30:00 to 28-MAY-13 23:30:00 (CST-6)
Location: CHILLICOTHE
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Flood damage to the railroad tracks near the 12000 block on Rock Bluff Road due to the South Avery Creek.

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 20:15:00 to 28-MAY-13 23:30:00 (CST-6)
Location: OTTUMWA
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Culvert washed out on Rock Bluff Road near 155th Ave.

Flash Flood in MONROE, IOWA
From 28-MAY-13 16:38:00 to 28-MAY-13 20:00:00 (CST-6)
Location: LOVILIA
Flood cause: Heavy Rain
Property damage: 150.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Gravel beginning to wash away a portion of east 19th/115th Trail and a significant amount of standing water west of 14th and south of Lovilia.

Hail in DECATUR, IOWA
From 28-MAY-13 16:55:00 to 28-MAY-13 17:05:00 (CST-6)
Location: VAN WERT
Magnitude: 1.00 
Property damage: 1.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Hail in WAYNE, IOWA
From 28-MAY-13 17:25:00 to 28-MAY-13 17:25:00 (CST-6)
Location: HUMESTON
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: Social Media

Social Media report of quarter to half dollar size hail in Humeston.

Funnel Cloud in RINGGOLD, IOWA
From 28-MAY-13 16:30:00 to 28-MAY-13 16:30:00 (CST-6)
Location: ELLSTON
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in MONROE, IOWA
From 28-MAY-13 18:10:00 to 28-MAY-13 20:00:00 (CST-6)
Location: AVERY
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Public

Public reported about 10 inches of rain along highway 137 with flash flooding a few miles southwest of Eddyville.

Flash Flood in LUCAS, IOWA
From 28-MAY-13 18:11:00 to 28-MAY-13 20:00:00 (CST-6)
Location: RUSSELL
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Fire Department/Rescue

Several spots have fast flowing water 3 to 4 inches deep across 500th Ave or County line between Lucas and Monroe County.

Heavy Rain in MONROE, IOWA
From 28-MAY-13 13:43:00 to 28-MAY-13 14:43:00 (CST-6)
Location: LOVILIA
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter in Lovilia reported 2.5 inches of rain in the past hour.

Flash Flood in APPANOOSE, IOWA
From 28-MAY-13 20:29:00 to 29-MAY-13 00:30:00 (CST-6)
Location: JEROME
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over County Highway J46 between 105th Ave and 110th Ave.

Flash Flood in LUCAS, IOWA
From 28-MAY-13 21:00:00 to 28-MAY-13 23:30:00 (CST-6)
Location: RUSSELL
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over 242nd Ave due to Wolf Creek flooding.

Thunderstorm Wind in APPANOOSE, IOWA
From 28-MAY-13 19:35:00 to 28-MAY-13 19:35:00 (CST-6)
Location: CENTERVILLE ARPT
Magnitude: 56.00 MG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: AWOS

Flood in DALLAS, IOWA
From 28-MAY-13 14:01:00 to 28-MAY-13 20:00:00 (CST-6)
Location: ADEL
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Highway 169 will be closing due to flooding north of Adel.

Flash Flood in LUCAS, IOWA
From 28-MAY-13 21:25:00 to 28-MAY-13 23:30:00 (CST-6)
Location: WILLIAMSON
Flood cause: Heavy Rain
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over 510th St just north of Chariton from the Little White Breast Creek.

Flash Flood in WAPELLO, IOWA
From 28-MAY-13 18:20:00 to 28-MAY-13 23:30:00 (CST-6)
Location: OTTUMWA
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter reports that flash flooding with water 2 to 5 feet deep swept down the street carrying logs and debris with it.  At the bottom of the street there was a car in the water with a depth of 5 feet.

Flood in LUCAS, IOWA
From 28-MAY-13 21:00:00 to 29-MAY-13 03:30:00 (CST-6)
Location: CHARITON
Flood cause: Heavy Rain
Property damage: 200.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Water over 450th St due to the Chariton River.

Hail in WAPELLO, IOWA
From 28-MAY-13 15:55:00 to 28-MAY-13 16:05:00 (CST-6)
Location: EDDYVILLE
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 5.00K
Reported by: SHAVE Project

Hail in MONROE, IOWA
From 28-MAY-13 15:42:00 to 28-MAY-13 15:52:00 (CST-6)
Location: AVERY
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Trained Spotter

A few stones slightly larger.  Hail piled up in drifts.  Some wind with half inch diameter hail with tree limbs down.  Hail lasted 10 minutes.

Hail in RINGGOLD, IOWA
From 28-MAY-13 16:11:00 to 28-MAY-13 16:21:00 (CST-6)
Location: CLEARFIELD
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Flash Flood in MONROE, IOWA
From 28-MAY-13 16:15:00 to 28-MAY-13 20:00:00 (CST-6)
Location: WELLER
Flood cause: Heavy Rain
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Water over the road from a creek out of its banks on 120th St west of Lovilia.  Water was 3 feet deep and moving swiftly across the road.