915 Communicating a Record Breaking Heavy Rainfall and an Unprecedented Flash Flooding Event across Northern Louisiana in March 2016

Tuesday, 24 January 2017
Washington State Convention Center
Cynthia K. Palmer, NOAA/NWS, Shreveport, LA; and T. Washington

In March 2016, an abnormally strong upper level low cut off over northern Mexico, causing the associated front to stall over Northern Louisiana for several days.  The south-southwesterly flow aloft ahead of the trough tapped tropical moisture from both the Eastern Pacific and Gulf of Mexico.  This moisture rich environment in combination with the stalled front led to record breaking rainfall and unprecedented flash and river flooding across northern Louisiana between March 8th and 12th.  Medium and extended range deterministic and ensemble guidance leading into this event were in good agreement that rainfall totals would range between 4 to 8 inches over a widespread area.  This model agreement gave the forecasters high confidence to start impact based decision support briefings with emergency managers five days ahead of the onset of rainfall.  A plausible worst case scenario was included in the briefing, which stated widespread 6 to 12 inches of rainfall, with locally higher amounts up to 16 inches possible between Tuesday March 8th and Thursday March 10th, with the focus of this rainfall being along and north of Interstate 20.  Additional briefings and frequent partner emails followed over the next five days leading into the event, continuing to highlight the potential for a prolonged period of heavy rainfall and flash flooding.  Flash Flood Watches were in place more than 36 hours ahead of the onset of rain.  Within hours of the rain beginning on March 8th, the first of the Flash Flood Emergencies was issued.  The Flash Flood Emergencies emphasized that this was an extremely dangerous and life threatening situation, and to seek higher ground immediately.  They also stressed that flood waters were already flowing into homes and high water rescues were underway.  When the rain stopped on March 12th, most areas received between 10 and 20 inches, with local amounts of 29 inches, nearly doubling amounts of the plausible worst case scenario.  Flooding across northern Louisiana was extensive, with flood waters lingering through the end of March. Several lakes hit record high pool stages, and every river, bayou, and stream flooded across the region.  Emergency responders performed numerous high water rescues during the five day rain event, with several areas under mandatory evacuations.  Homes and businesses flooded, and schools closed.  Interstates 20 and 49 along with hundreds of state highways and roads closed as well.  Despite all of the advanced warnings and preparedness efforts, tragically three deaths occurred when people drove around barriers into flood waters and one drown while pulling items out of flooded home.
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