NWS Update: Heavy Rainfall and Flood Potential through Memorial Day Weekend

本站添加: 2026-05-24

[00:00:00]We wanted to go ahead and give you guys an update uh especially as we go into uh this holiday weekend just on the heavy rainfall and flood potential uh that's existing through Monday as well as talk about the next round that we're expecting um midweek next week. So just some key messages uh first off that flood watch still remains in effect through Monday evening. Showers and thunderstorms are expected today. Some of those may actually be strong to severe. We'll talk about that. Uh the locally heavy rainfall uh possibility is still there. Uh we have the potential for flash flooding specifically uh through Monday evening, but there is a higher potential uh for this afternoon into this evening. Additional intermittent periods of showers and thunderstorms are expected Sunday and Monday uh for parts of the area. We'll kind of talk about how that evolution is going to uh persist. and strong thunderstorms are expected along the coast, especially going into today and tomorrow, which could cause some issues for mariners through the weekend.

[00:01:00]So, what's changed since our last briefing? So, the models are coming into better agreement specifically for the next 24 hours. So, that's helping us with pinpointing specific uh timing as well as potential locations uh for the heaviest rainfall. We are still expecting widespread 2 to four inches specifically along the coast and in that flood watch area with higher amounts of four to six inches that are possible.

[00:01:23]Our confidence has increased and the highest flood potential being this afternoon and evening. Uh location is still a little bit uncertain. Uh the flood threats still exist into Sunday and Monday but will be more isolated in nature.

[00:01:37]So here's the flood watch. As we covered yesterday, we did extend it. Uh so now it includes Trinity, Pulk, Saninto, Walker, Grimes, Washington County as well as everything else that we had shown yesterday morning. Uh most likely rainfall totals in these areas 2 to 4 in. But there is the potential for isolated higher amounts of four to six plus inches. Overall, the main threat is heavy rainfall that could lead to flash flooding as well as uh isolated minor to possibly moderate river flooding over the next few days. So, we are going to have to monitor uh river rivers and bayou conditions in addition to the heavy rainfall threat uh for flash flooding.

[00:02:18]All right, so here's our current satellite. So, you probably were woken up by some nice uh thunder and lightning, especially if you were along the coast uh through the past uh several hours uh this morning. Most of that activity actually has pushed out uh with this short wave that's over in eastern Texas and into Louisiana. But as you can see, we've got another uh another system that's over San Antonio as well as in southern uh Texas that's going to be moving into our area. You can actually see on um on our satellite image here, we've got some uh we've got a boundary here that's going to potentially set us up for allowing more lifting as well as merging with this these short waves that are going to be pushing through later on um into today. So, uh, we've gotten several questions of, you know, we had a lot of the rainfall come through last night. Did that stabilize the atmosphere? Um, yes, in some instances it did, but we do still have instability and lifting with these features, as well as the um higher precipitable water values. They're still near and above the 90th percentile.

[00:03:22]Rainfall rates, we're still expecting them to peak out between the 3 and 4 inch per hour rainfall range. Most likely it's going to be two and a half to three inches, but it is not uncommon for us to see those 3 to 4 inch rainfall rates, especially in those embedded uh more precipitation efficient uh thunderstorms.

[00:03:39]So over the past 24 hours, uh with that first short wave that pushed through, we had widespread half an inch to one and a half inches uh which doesn't sound like a lot, but that is priming uh kind of the soils. we won't have as much time to rebound uh with our uh runoff. So, anywhere we where we see the heaviest rainfall setting up over the next 24 hours, uh we could see an increase in our flood risk. Uh we did have pockets of 2 to three inches. Um and those were from those intense rainfall rates of 2 to three inches per hour. And again, we still see the threat for those higherend rainfall rates going into this afternoon and evening time frame.

[00:04:18]So looking at the forecast, so the most likely forecast, this is what we've got in the forecast right now. You can see we said 2 to four inches, especially along the coast and in the the watch area. Um we are expecting isolated higher amounts of up to 6 in. So this is going through Monday evening time frame.

[00:04:33]So that covers you through um the flood watch time period. What I did want to show you though on the right hand side, this is the href. This is our probability matched mean. Uh basically this is the next 24 hours. This is an ensemble of a lot of those convective allowing models. And so this really does help us hone in on the location of the heaviest rainfall. Uh there is another um model component to this. Uh it's called LPMM that helps us try to figure out what the higher rainfall amounts could possibly be. So overall over the next 24 hours, the href is pinging on a swath of 2 to 5 in um along the coastline and in that watch area. And the LPMM is actually highlighting the potential for five to seven inch um rain the high-end rainfall totals with some of those higher um embedded cells in the in the storms that are moving through.

[00:05:23]Uh so this is kind of coming into more agreement with our flatch uh our flood watch. Uh so that way we can kind of help you with timing out uh the rainfall as well.

[00:05:35]So translating that rainfall into a flood risk. So again, we wanted to make sure we showed you the excessive rainfall outlook for today. Still showing us in a slight risk. I do want to make sure that you um know. So there is an enhanced uh slight risk, which is basically it's a 25% uh chance of seeing the um to seeing flashlight guidance values being exceeded. This is kind of an internal thing that we look at um which is basically along the coast kind of where that swath of heavy rainfall was from the href. So, it's it's kind of like uh we're almost to a moderate, but we're not quite there. Uh so, still messaging the slight excessive rainfall outlook for today. Tomorrow, uh you're going to see when I show you um kind of the timing of the convection, but most of it's going to be pushing off the coast.

[00:06:26]Um the basically the most instability is going to be offshore, but the threat still exists specifically along the coastline, especially if it kind of sets up a little bit further inland. Um, and then most of the threat's going to kind of shift off to Louisiana until next week. Again, localized flash flooding is the primary hazard here. Uh, but I did want to make sure that I um pointed out SPC does have us for a marginal risk um over the next 24 hours. Uh, so the potential for damaging wind gusts and hail is there. Uh, we cannot rule out a brief tornado. I think there's a 2% chance um over the next or for the day one outlook. Um, ultimately though, we want to make sure folks are remaining weather aware and have multiple ways of receiving weather alerts, whether that's from the severe threat or from the flash flood threat.

[00:07:16]So, we talked about the rainfall amounts from the convective allowing models. I wanted to talk about the timing of this.

[00:07:22]Uh, so we did see um the first band kind of move through this morning. Looking at um this first convective allowing model, the HR, um this is what Saturday afternoon would look like. So basically, we're starting to see some convection down in our southwest portion of the area in Madagorta. That is going to increase in coverage uh going into the afternoon hours. Uh this is probably midday going into the afternoon, spreading farther inland. Uh we are going to see these cells propagating pretty quickly. Um but where there are the intense rainfall rates, that's where we're going to see the accumulation of those rainfall totals and and increasing the flood risk uh into tonight. It actually does um kind of clear out um but the potential risk for tomorrow morning still remains along the coast and yesterday I showed you the HR and I also showed you the H the the refs. So the refs also is pinging on the convection this afternoon into this evening starting along the coast and then propagating inland. Um and then overnight uh there is the potential for isolated showers but mostly pretty quiet. Sunday morning.

[00:08:30]Again, the the refs is showing most of the convection offshore. There is still the potential for daytime heating to cause isolated showers and thunderstorms in the afternoon, which is also why we have that um slight chance for excessive rainfall um going into tomorrow. Excuse me, marginal risk for excessive rainfall tomorrow. Um and then on Monday, again, marginal risk um it has pushed off mostly on our eastern portion of our county warning area. Rainfall chances have decreased in comparison to today and tomorrow. Uh 10 to 20% chance for precipitation, but there still exists the potential for localized flash flooding in these areas.

[00:09:10]So, Memorial Day not out of the clear just yet.

[00:09:15]Translating all of this into what could potentially happen with runoff and flood potential along our rivers. So, this was a graphic that the West Gulf River Forecast Center pulled together. So the image on the left hand side shows you the upper soil moisture content and the middle one middle graphic shows you the lower soil moisture content. So basically we have uh gotten rid of for most of the the drought areas droughtstricken areas have improved our soil moisture is quite um at capacity.

[00:09:43]So that means that anywhere we get um heavy rainfall on top of these areas there's not going to be the capacity for it to go into the soils and so we're going to see um more of the straight runoff. Uh looking at that for rivers uh this is the 10% uh probability. So reasonable worst case scenario still expecting rises to action and minor stage as the most likely scenario for most of the rivers but it is possible that we could see isolated moderate to even major flooding uh where some of the heaviest rainfall does set up.

[00:10:17]Now, I did mention uh that we do have this system that's going to be pushing through midweek, and I wanted to take this opportunity to kind of just talk about that a little bit more, especially because we are in a wet period. So, looking at Tuesday into Wednesday time frame, uh you see our flood threat uh ramp back up. We've got the slight risk out for Tuesday along our western portion of our county warning area and then on Wednesday actually expanding to most of the area. Uh so, this is something that we'll need to keep an eye on. And it is still too early to tell exact uh location and amounts. Uh but coming out of a a wet weekend, we want to make sure um even though we'll have time for a lot of the uh runoff to uh to move out, uh we are still going to be primed with wet soils.

[00:11:03]Okay, so main takeaways, a lot going on here. We had that shortwave move off this morning, but it did prime us with about an inch to an inch and a half along a lot of uh through most of the area with isolated pockets of 2 to three inches. The atmosphere will have time to rebound this afternoon um thanks to the another short wave that's going to be moving through in addition to those higher precipitation uh precipitable water values. The highest chance for excessive rainfall and associated flooding is midday today through this evening. U and some of those storms could actually bring damaging winds, hail, and the possibility of an isolated tornado or two. And then there is the potential for additional showers and thunderstorms on Sunday and Monday, but of course the risk does come down. It's not as um high as it is for today. um mainly along the coastline for tomorrow morning. We do want to make sure we're maintaining the message of localized flash flooding and turnaround don't drown, especially for folks who are not used to these rainfall rates and the ponding on roadways or potential street flooding that we could see. And then uh for strong um we are expecting you know some of these strong thunderstorms to be along the coastline. So that could impact mariners through the weekend. uh possibly seeing 40 knot winds and so this is something that we'll have to keep an eye on. Um and then the rainfall potential returns for midweek. So we'll have to keep an eye on that. Confidence is low um on the amounts and locations but definitely something that we'll have to monitor. Main impacts flooded roadways and minor to possible moderate river flooding into next week. And with that I am going to stop the recording and take any questions you may have.