A powerful and cold upper level low tracked northeast across the Tennessee Valley during the late evening of the 10th and early morning of the 11th.  Numerous showers and thunderstorms produced an initial 1 to 2 inches of rain from the evening of the 10th into the overnight hours of the 11th.  A few of the stronger storms produced small hail.  One line segment produced wind damage as well in northeastern Cullman County.  A lightning strike sparked a blaze in Scottsboro.  Minor street flooding was reported in parts of northern Madison County during this period.
As the low moved across during the mid to late morning hours, another round of heavy rainfall and strong thunderstorms occurred.  The strong storms produced prolific amounts of small hail, in some cases coating the ground, and very frequent lightning strikes. The strikes knocked power out in Gurley and in portions of Huntsville.  The secondary area of rain produced another 1 to 3 inches of rainfall, producing urban flash flooding in central and northeast Huntsville, and submerging at least one vehicle and pushing flood waters into a few homes.  The runoff also created rapid rises on creeks and streams in the area.

Thunderstorm Wind in CULLMAN, ALABAMA
From 11-JAN-12 04:55:00 to 11-JAN-12 04:57:00 (CST-6)
Location: BAILEYTON
Magnitude: 61.00 EG
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Newspaper

A fast moving miniature supercell with a pronounced and shallow bounded weak echo region on radar tore the roof off a barn and knocked down and uprooted multiple trees.  The damage occurred near the intersection of County Road 1769 about one mile north of Highway 67.  Residents took refuge in a tornado shelter and remarked that the winds blew through and ended in less than a minute.

Flash Flood in MADISON, ALABAMA
From 11-JAN-12 09:56:00 to 11-JAN-12 13:00:00 (CST-6)
Location: HAZEL GREEN
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Flash flooding was reported along Nix Road.

Flash Flood in MADISON, ALABAMA
From 11-JAN-12 09:56:00 to 11-JAN-12 13:00:00 (CST-6)
Location: JEFF
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Flash flooding was reported at Nick Fitcheard Road and Bob Wade Lane.

Flash Flood in MADISON, ALABAMA
From 11-JAN-12 09:56:00 to 11-JAN-12 13:00:00 (CST-6)
Location: MONROVIA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Flash flooding was reported on Plummer Road just east of Indian Creek Road.

Lightning in MADISON, ALABAMA
From 11-JAN-12 09:23:00 to 11-JAN-12 09:23:00 (CST-6)
Location: HUNTSVILLE
Property damage: 1.00K
Crop damage: 0.00K
Reported by: State Official

Lightning struck nearby the National Space Science and Technology Center (NSSTC) which houses the National Weather Service, NASA and University of Alabama at Huntsville atmospheric science department.  The lightning destroyed two network hubs and a network card.

Thunderstorm Wind in LAUDERDALE, ALABAMA
From 10-JAN-12 22:55:00 to 10-JAN-12 22:57:00 (CST-6)
Location: RHODESVILLE
Magnitude: 43.00 EG
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Emergency Manager

A tree was knocked down onto County Road 189 west of Oakland.

Lightning in CULLMAN, ALABAMA
From 11-JAN-12 01:55:00 to 11-JAN-12 01:55:00 (CST-6)
Location: PHELAN
Property damage: 40.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Lightning struck the Emergency Management Agency office, knocking out communications and damaging electronic equipment.

Flash Flood in MADISON, ALABAMA
From 11-JAN-12 09:56:00 to 11-JAN-12 13:00:00 (CST-6)
Location: NEBO
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Flash flooding was reported along Old Railroad Bed Road.

Flash Flood in MADISON, ALABAMA
From 11-JAN-12 09:56:00 to 11-JAN-12 13:00:00 (CST-6)
Location: HUNTSVILLE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Newspaper

Flash flooding was reported at numerous locations in northeast through central Huntsville, especially in poor drainage areas.  Dallas Branch Creek and other creeks went out of their banks, and combined with poor drainage to produce flooding of streets, homes and basements, especially in the Five Points area.  An automobile was stranded on Kimberly Lou Boulevard.  An occupied vehicle was stranded at Owens Drive and Sun Valley Road.  Water flooded the Jaycees Building.
Here is a list of roads and intersections that were impacted by flash flooding, and in many cases were either impassible or closed:
1300 block of Fairmont Road, Bob Wallace Avenue at Poincianna Street, Drake Avenue and Dupree Drive, Oakwood Avenue, Maysville Road, Giles Drive, South Hall Drive, 15th Avenue at 1st Street, Pansy Street at Bonita Drive, McKinley Avenue at Maysville Road and Truman, California Drive, and Whitesburg Drive.