Alert archive / Alabama / Flash Flood Watches in 2011

Flash Flood Watch 6, NWS Huntsville, AL

April 20, 201111 counties in Alabama; Franklin County, Lincoln County, Moore County, Tennessee

NWS Huntsville, AL issued this flash flood watch at Apr 20, 2011, 1:38 PM CDT for 11 counties in Alabama; Franklin County, Lincoln County, Moore County, Tennessee. It was in force for 14 hr.

The area

The counties it named.

The facts

Issued: Apr 20, 2011, 1:38 PM CDT (18:38 UTC)
Expired: Apr 21, 2011, 3:42 AM CDT
In force: 14 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 18:37 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 12:00Z, 6.6 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1036 m above ground
0-6 km bulk shear: 65 kt
0-1 km storm-relative helicity: 305 m²/s²
0-3 km storm-relative helicity: 414 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.1

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 20, 12:10 PM CDT, 1 hour 28 minutes earlier.

Area forecast discussion, Apr 20, 12:10 PM CDT, 1 hour 28 minutes before

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Hazardous weather outlook, Apr 20, 12:45 PM CDT, 53 minutes before

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In the hours before

Local storm report, Apr 20, 8:46 AM CDT, 4 hours 52 minutes before

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Local storm report, Apr 20, 9:40 AM CDT, 3 hours 58 minutes before

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Local storm report, Apr 20, 9:42 AM CDT, 3 hours 56 minutes before

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Local storm report, Apr 20, 10:04 AM CDT, 3 hours 34 minutes before

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Local storm report, Apr 20, 11:00 AM CDT, 2 hours 38 minutes before

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Local storm report, Apr 20, 11:03 AM CDT, 2 hours 35 minutes before

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The office that day

Everything else NWS Huntsville, AL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 20, 1:52 AM CDT	Special Weather Statement	HUN	Lauderdale	38 min
Apr 20, 3:55 AM CDT	Severe Thunderstorm Warning	HUN	Franklin	35 min
Apr 20, 4:05 AM CDT	Special Weather Statement	HUN	Limestone, Madison	25 min
Apr 20, 4:16 AM CDT	Severe Thunderstorm Warning	HUN	Colbert, Franklin	29 min
Apr 20, 4:29 AM CDT	Severe Thunderstorm Warning	HUN	Colbert, Franklin, Lawrence, Limestone	31 min
Apr 20, 4:44 AM CDT	Special Weather Statement	HUN	Jackson	31 min
Apr 20, 4:56 AM CDT	Severe Thunderstorm Warning	HUN	Cullman, Lawrence, Morgan	34 min
Apr 20, 4:59 AM CDT	Special Weather Statement	HUN	Limestone	31 min
Apr 20, 5:19 AM CDT	Severe Thunderstorm Warning	HUN	Cullman, Limestone, Madison, Marshall, Morgan	41 min
Apr 20, 5:25 AM CDT	Severe Thunderstorm Warning	HUN	Jackson, Madison	35 min
Apr 20, 5:33 AM CDT	Severe Thunderstorm Warning	HUN	DeKalb, Jackson, Madison, Marshall	27 min
Apr 20, 5:59 AM CDT	Special Weather Statement	HUN	DeKalb, Jackson	46 min
Apr 20, 6:08 AM CDT	High Wind Warning	HUN	Cullman, DeKalb, Jackson, Marshall, Morgan	61 min
Apr 20, 6:29 AM CDT	Severe Thunderstorm Warning	HUN	DeKalb, Jackson	16 min
Apr 20, 6:42 AM CDT	Severe Thunderstorm Warning	HUN	DeKalb	18 min
Apr 20, 4:47 PM CDT	Severe Thunderstorm Warning	HUN	Colbert, Lauderdale	25 min
Apr 20, 6:51 PM CDT	Special Weather Statement	HUN	Franklin	39 min
Apr 20, 2:54 AM CDT	Special Weather Statement	HUN	Moore	21 min
Apr 20, 3:27 AM CDT	Special Weather Statement	HUN	Franklin	48 min
Apr 20, 4:45 AM CDT	Special Weather Statement	HUN	Franklin, Moore	45 min

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.