Significant Flood Threat For Southeast Texas, Southwest Louisiana Through Saturday

Figure 1. Latest 3-day QPF from the WPC.

There will be a risk for some strong/severe storms over the next 3 days from Texas into the lower Mississippi Valley and Southeast.

The main hazards will be damaging hail and wind gusts. Isolated tornadoes are also a possibility.

However, the severe threat is a secondary concern. The primary focus is going to be heavy rain and the potential for flooding.

With a surface boundary stalling out, multiple waves of widespread thunderstorms and heavy rain will impact south Texas, Louisiana, Mississippi, and parts of Alabama through Saturday. The first round looks to arrive this afternoon/evening and overnight.

Figure 2. HRRR simulated radar loop for 1 PM CDT this afternoon to 12 AM CDT tomorrow morning. Animation: Tropical Tidbits

Based on the 3-day QPF from the Weather Prediction Center (WPC) rainfall amounts of up to 7 – 10″ are still looking likely in southeast Texas and southwest Louisiana (see figure 1). But locally higher amounts are certainly possible.

Rainfall rates up to 2 – 4″ per hour will be possible with stronger storms and/or where cell “training” occurs.

Overall, given the set up, we are looking at a pretty substantial — if not significant — threat for flash flooding from southeast Texas into southwest Louisiana. The WPC has outlined a moderate risk for flooding in their excessive rainfall outlook (see figure 3).

Figure 3. Day 1 excessive rainfall outlook from the WPC.

This means there is up to a 50% chance of flash flood guidance being exceeded.

Not everyone will experience significant flash flooding. Rather, areas that get a lot of precipitation in a short amount of time, and where cell “training” occurs, similar to what happened in and around Houston Tuesday night, will be at risk of significant flash flooding.

Additionally, with many rivers already near or at flood stage, expect river flooding to be an issue.

By Sunday the surface boundary should shift off to the east and allow for a reprieve from the rain.