Product Guide: Hydrologic Products

The National Weather Service in Huntsville also serves the river community in 11 northern Alabama counties, and three counties in southern Middle Tennessee, including almost the entire Tennessee River basin in North Alabama. We issue summaries, statements, watches, and warnings.  We also serve our forecast area with Flood watches, warnings, and statements when heavy rain threatens.


Hydrologic Outlook (ESF) Latest Hydrologic Outlook
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The "Hydrologic Outlook" is used for three purposes.  First, we issue the Flood Potential Outlook once each spring to discuss the possibility for river flooding during the spring due to snowmelt upstream and runoff due to high soil moisture.  The product is also issued when heavy rain may cause rivers to rise above flood stage. It is usually issued a day or two in advance of the event.   We also issue a Hydrologic Outlook if drought conditions are occurring in the area.
Hydrologic Summary (RVA) Latest Hydrologic Summary
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The "Hydrologic Summary" is a daily report of observed river and lake stages and 24 hour changes for a number of river gauges across the area.  The flood stages, for locations where flood stage has been defined, are also shown.  This product is issued daily between 8am and 9am.
Daily River and Lake Summary (RVD) Latest Daily River & Lake Summary
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The "Daily River and Lake Summary" is a daily report of river stages, 24 hour changes, and a five day forecast.  It also includes a few lake and reservoir stages.  All river points designated as "forecast points" are included in this summary. 
Flood Warning (FLW) Latest Flood Warning
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A "Flood Warning" is issued when river flooding is expected.  It is issued once a river is forecast to go above its designated flood stage at the forecast point.  The warning will be updated by Flood Statements, unless additional flooding is forecast; then another Flood Warning may be issued. 
Flood Statement (FLS) Latest Flood Statement
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A "Flood Statement" is used to update information on a river in flood, or to terminate a flood warning.
Flood Watch (FFA) TN Valley Watches/Warnings
A "Flood Watch" or "Flash Flood Watch" is issued to inform the public and cooperating agencies that current and developing weather is such that there is a threat of rapid flooding (also known as flash flooding), or widespread river flooding.  The occurrence of flooding is neither certain nor imminent.  Persons in the watch area are advised to check flood action plans, keep informed, and be ready to take necessary actions if a warning is issued or flooding is observed.  A flash flood watch may also be issued for a dam break.

Flash Flood Warning (FFW) TN Valley Watches/Warnings
A "Flash Flood Warning" is issued to inform the public that flooding is imminent or in progress.  It focuses on specific counties, communities, streams, or areas. Flash Flood Warnings are issued for flooding usually occurring within 6 hours of heavy rain.
Dam Break Warning (FFW)  
If a dam break has occurred or is imminent, a "Flash Flood Warning" is issued for the dam break.  The warning includes affected counties, the agency verifying the dam break, the name of the dam, the name of the river, the nearest downstream town and its distance from the dam, travel time of the crest, and a forecast of the crest height if known.   
 
 
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