Here is an update concerning the ongoing heavy rain threat today through Saturday in association with a tropical disturbance forecast to move through the Gulf.
Changes from previous update:
- The chance of tropical cyclone development in the northern Gulf has decreased slightly.
- The greatest risk for excessive rainfall has shifted earlier from Friday to Thursday though the heavy rain and flooding risk will still remain elevated on Friday.
- Confidence has increased in rainfall totals and locations of heaviest rainfall.
- Given the disorganized nature of this disturbance, there is increased uncertainty over locations of heaviest rainfall compared to a typical, more organized tropical system moving into our area.
Overview:
- There is a LOW (30 percent) chance of tropical cyclone development today before this disturbance moves inland tonight.
- This disturbance is forecast to move west/west-northwest through the northeastern and north-central Gulf today and Thursday and move inland between midday Thursday and early Friday morning.
- A Flood Watch remains in effect for portions of southeast Louisiana and coastal Mississippi until 1AM Saturday.
Confidence:
- Confidence remains low that this system will develop into a tropical depression or stronger. Even if the system develops into a tropical cyclone, it is expected to remain weak and heavy rainfall impacts will not change.
- Confidence is medium to high that this system will bring a threat of locally heavy rain to coastal areas of southeast Louisiana and southern Mississippi, especially on Thursday and Friday.
- Confidence has increased that the additional rainfall of 2-4″ will remain closer to the coasts of Louisiana and Mississippi, and areas north of Interstate 10 will see lower additional rainfall totals of 0.5 to 2″ through Saturday.
Heavy Rain and Flooding Impacts:
- Portions of coastal Mississippi and Southeast Louisiana have already received 0.5 to 2″ since Wednesday afternoon with lower totals of 0-1″ north of Interstate 10.
- The current forecast calls for an additional 2-4″ of rain across areas along and south of the I-10 corridor with potential for up to 6-8″ in some localized areas along the coast and into the Atchafalaya Basin.
- Ponding of water in low lying and poor drainage areas is likely, and more isolated significant flash flooding in these urban and poor drainage areas along and south of I-10 could occur if the higher rainfall totals are realized through Friday.
- A combination of a neap tide cycle (low range between high and low tide) and winds below tropical storm strength, will result in little to no threat of coastal flooding