A large thunderstorm complex moved from eastern Kentucky into West Virginia during the late afternoon on the 8th.  In the wake of that feature, a strong upper air disturbance helped refire convection over southern Kentucky.  Those thunderstorms moved east into southern West Virginia just after dark.  One of these cells had strong rotation in McDowell County. No tornadoes were observed, but wind damage was reported.
The storms lost their rotation later that evening, but a narrow broken train of showers and thunderstorms continued to roll east out of Kentucky and into southern West Virginia after midnight, during the early morning hours of Saturday, May 9th.  This west to east train of showers and thunderstorms affected mainly eastern Mingo, Wyoming, northern McDowell, and extreme southern Raleigh Counties.  The heaviest rains were mostly from 2300E on the 8th to 0400E on the 9th. The 12 hour rain amounts from 1700E on the 8th through 0500E on the 9th were mostly 2.5 to 4 inches in the west to east band.  The north to south width of this heavy rain axis was only about 30 miles. A few rain amounts exceeded 4 inches, mainly near the county border with Mingo and Wyoming.  Amounts may have exceeded 4 inches over the mountains south of Pineville.  The highest measured 24 hour total was 4.4 inches from R.D. Bailey Lake.  An automatic gauge on Horsepen Mountain measured 3.98 inches.  In Wyoming County, Pineville had 3.95 inches, while Mullens measured 3.02 inches.  Oceana was just north of the heaviest, with 2.76 inches.  Meanwhile, Iaeger of McDowell County was just south of the heaviest axis.  Iaeger measured 2.75 inches.  An automatic gauge along Huff Knob in southern Raleigh County measured 2.66 inches.
Small stream flooding increased after 0130E on the 9th.  The peak of the small stream flooding was on either side of dawn.  Water cascaded down steep mountainsides, sometimes creating their own water channels and landslides.  Rocks were swept down these mountainsides, collecting 3 to 4 feet deep in the valleys.  Trees were also knocked down by these landslides, some falling into homes.
The worst of the small stream flooding occurred along such creeks at Pigeon, Horesepen, Gilbert, Bens, Beech, and Mate Creeks in eastern Mingo County, plus Huff, Indian, and Pinnacle Creeks in Wyoming County.  This included such communities as Pie, Musick, Varney, Taylorsville, Delbarton, Red Jacket, North Matewan, Gilbert, Baisden, Hanover, and Fanrock.  However, the serious flooding still stretched further east, to encompass the headwaters of the Guyandotte River, upstream of Mullens.  This included the Rhodell vicinity in southern Raleigh County.
Many residents along these small streams were forced to seek higher ground and wait out the flood.  Luckily, no one drowned.
Some of the heavier rain actually fell east of Guyandotte Mountain and flooded the headwaters of Piney Creek.  Piney Creek flows north into the Kanawha River.  This includes the Jonben vicinity of Raleigh County.
The small stream flooding lead to river flooding along the Guyandotte River. Man crested near 17.8 feet near dawn on the 9th.  Flood stage is 15 feet. Further down the river, Logan crested around its 23 foot flood stage during the mid morning hours.  R. D. Bailey Dam held back much of the headwater flow.  The lake elevation rose about 65 feet in the vertical over 4 days, from around 1045 feet to a crest of 1109.85 feet on May 12th.  That was the second highest lake pool elevation for that U.S. Army Corps of Engineers facility.
The Tug Fork River also flooded, but the most serious damage in that river drainage system was still related to the small stream flooding and the runoff down the steep mountainsides.  Williamson crested at 40.7 feet near sunset that Saturday evening.  Flood stage is 27 feet but a flood wall protects the city.  Later that night, Kermit crested at 43.2 feet.  Flood stage is 38 feet at Kermit.
Six miners and 1 supervisor were temporarily trapped in an underground mine near Wharncliffe due to high water.  These miners finally walked out during the early morning of Sunday the 10th.
President Obama issued a major disaster declaration for Mingo, Wyoming, Raleigh, and McDowell Counties.  Over 2300 people from Mingo County registered with FEMA for assistance.  Almost 1200 Wyoming County residents registered.  McDowell County had around 500 register with FEMA, while Raleigh County saw under 300.  A good indication of the number of homes destroyed is the number of households provided with temporary housing assistance.  Over 100 home owners asked for temporary housing.  Around two-thirds of those came from Mingo County, with the other third from Wyoming County.  See FEMA disaster number 1838 for more details.
State preliminary damage assessments had over 300 other homes with major damage.  Several hundred houses had minor damage.  Numerous vehicles were flooded, some even swept into the creeks.  Many small private bridges for residents were destroyed. The main state highway system was also damaged. In Mingo County 5 primary roads and 46 secondary roads were damaged.  In Wyoming County, 4 primary roads and 76 secondary roads were damaged. In McDowell County 4 primary and 34 secondary roads were damaged. Raleigh County had 9 secondary roads damaged. Several schools were flooded.  Gilbert Elementary and Gilbert High were hard hit.  Many small public water systems were damaged.
At one point, the number of Army and Air National Guard troops, assisting in the clean up, reached over 600. The Commonwealth of Virginia sent around 30 National Guard troops to assist.  The National Guard removed around 58,000 tons of debris in Mingo County and about 7,000 tons from Wyoming County.

Thunderstorm Wind in MCDOWELL, WEST VIRGINIA
From 08-MAY-09 20:20:00 to 08-MAY-09 20:20:00 (EST-5)
Location: WELCH
Magnitude: 50.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Numerous trees were blown down.

Flood in LOGAN, WEST VIRGINIA
From 09-MAY-09 04:00:00 to 09-MAY-09 12:00:00 (EST-5)
Location: LOGAN
Flood cause: Heavy Rain
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Department of Highways

Small stream flooding along the Mingo and Wyoming borders was minor.  The strong rise on the Guyandotte River caused flooding along the low spots on Route 10.

Flood in MINGO, WEST VIRGINIA
From 09-MAY-09 01:30:00 to 10-MAY-09 06:00:00 (EST-5)
Location: VERNER
Flood cause: Heavy Rain
Property damage: 24.00M
Crop damage: 0.00K
Reported by: Newspaper

Flood in WYOMING, WEST VIRGINIA
From 09-MAY-09 01:30:00 to 09-MAY-09 14:00:00 (EST-5)
Location: OCEANA
Flood cause: Heavy Rain
Property damage: 10.00M
Crop damage: 0.00K
Reported by: State Official

Flood in MCDOWELL, WEST VIRGINIA
From 09-MAY-09 03:30:00 to 09-MAY-09 13:00:00 (EST-5)
Location: ASHLAND
Flood cause: Heavy Rain
Property damage: 4.00M
Crop damage: 0.00K
Reported by: Department of Highways

Flood in RALEIGH, WEST VIRGINIA
From 09-MAY-09 05:30:00 to 09-MAY-09 13:00:00 (EST-5)
Location: AMIGO
Flood cause: Heavy Rain
Property damage: 2.00M
Crop damage: 0.00K
Reported by: Law Enforcement