Alert archive / Alabama / Flash Flood Watches in 2011

Flash Flood Watch 7, NWS Huntsville, AL

April 25, 201111 counties in Alabama; Franklin County, Lincoln County, Moore County, Tennessee

NWS Huntsville, AL issued this flash flood watch at Apr 25, 2011, 3:41 AM CDT for 11 counties in Alabama; Franklin County, Lincoln County, Moore County, Tennessee. It took effect at Apr 26, 2011, 7:00 AM CDT. It was in force for 39 hr.

The area

The counties it named.

The facts

Issued: Apr 25, 2011, 3:41 AM CDT (08:41 UTC)
In effect from: Apr 26, 2011, 7:00 AM CDT
Expired: Apr 27, 2011, 10:00 PM CDT
In force: 39 hr
Issued by: NWS Huntsville, AL
Flood severity: None

Counties Colbert County, AL, Cullman County, AL, DeKalb County, AL, Franklin County, AL, Jackson County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marshall County, AL, Morgan County, AL, Franklin County, TN, Lincoln County, TN, Moore County, TN

The radar

The Northeast Alabama radar (KHTX), 69 km from the middle of the area, began a volume at 08:44 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Nashville Metro, TN (KBNA), launched 00:00Z, 8.7 hours before the alert went out and 159 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1210 J/kg
Mixed-layer CIN: -7 J/kg
Mixed-layer LCL: 1316 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 107 m²/s²
0-3 km storm-relative helicity: 83 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 5.7

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood watch went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Huntsville, AL wrote its last area forecast discussion before this flash flood watch went out at Apr 25, 1:12 AM CDT, 2 hours 29 minutes earlier.

Area forecast discussion, Apr 25, 1:12 AM CDT, 2 hours 29 minutes before

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Nearby

Flash Flood Watches in Alabama, 2011 Flash Flood Watches in Tennessee, 2011 Every flash flood watch in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.