A depression or tropical storm is likely, but don’t be distracted, as this is primarily a major rainstorm for parts of the South

In brief: The National Hurricane Center has declared Potential Tropical Cyclone One, which will likely become a tropical depression or storm as it parallels the Texas coast later today and tomorrow. The primary impacts from this storm will be flooding rainfall from coastal Texas through Mississippi and Alabama, in many cases, very far from the coast.

Editor’s Note: The NHC will begin producing advisories on Potential Tropical Cyclone One this morning. I wrote the below section before seeing that news. The map is updated below.

(NOAA NHC)

So we have two things to talk about today. Both are directly related. The potential for a tropical depression or storm in the northwest Gulf is increasing. However, the primary, if not only impacts to focus on (unless you are a mariner) with this event will be the rainfall. While this may indeed become a tropical storm or depression, again, this should be thought of as a significant rainstorm with flooding potential.

Let’s talk about the disturbance first because that is going to have a direct impact on exactly where the heaviest rain falls. As of this morning, Invest 90L is located in the Rio Grande Valley inland from Brownsville. A look at satellite certainly tells the story. This is absolutely loaded with moisture.

While Invest 90L is potent looking, almost all of its moisture is displaced east of the center. This has implications on where the most serious flooding risks may evolve in the coming days. (WeatherFront)

The one big takeaway I have with this? The moisture associated with 90L is heavily displaced east of the center. In other words, this will keep any organization slow, but it will also mean that the track of the disturbance is extremely important in determining who will see the greatest flooding potential.

So where will 90L track? Well, there’s pretty decent agreement this morning that the disturbance will scoot just offshore of South Texas later today and then curl back north northeast toward southwest Louisiana or the Texas Golden Triangle through Thursday.

Invest 90L is likely to move off the South Texas coast, briefly over the Gulf, then back inland near Port Arthur or Cameron Parish, Louisiana. (Weathernerds.org)

The residence time over the Gulf is going to be short, maybe 24 hours, and given the general disorganization it currently has, I don’t see how this becomes much more than an isolated 40 mph tropical storm. However, it is the moisture that’s the issue here.

With all this moisture funneling northeastward, you can bet there’s a significant heavy rain risk along and east of the track of PTC 1/Invest 90L.

Today’s rainfall will be heaviest in South Texas, at times in the Houston area, and along the immediate coast in Texas and Louisiana and just inland into central Louisiana as well later.

A moderate risk (level 3/4) for excessive rainfall is posted from Corpus Christi through southern Louisiana. (Pivotal Weather)

On Wednesday, that risk will hug the coast southeast of Houston, and then end up in southwest Louisiana.

Flooding risk on Wednesday is highest southeast of Houston and into southwest Louisiana. (Pivotal Weather)

And on Thursday, that risk shifts into Louisiana and Mississippi, maybe Alabama.

The highest rain risk on Thursday expands to the east for Louisiana, Mississippi, and Alabama. (Pivotal Weather)

When all is said and done, we are probably looking at an average of 3 to 8 inches along the coast between Galveston and Vermilion Bay, extending inland between Lake Charles and Montgomery, AL. Isolated pockets within this belt are going to see upwards of 10 to 15 inches of rain potentially, and those will be the areas that are at highest risk for flooding. It would not be a shock to see a “high” risk get issued with the excessive rainfall products above before this ends.

Forecast rainfall over the next 4 days will likely be highest from coastal Texas, across Louisiana, southern Mississippi, and south & central Alabama. (WeatherFront)

Flood watches are posted from Texas through Mississippi, and those will probably expand into Alabama later.

(NWS Jackson, MS)

Bottom line: While this will be a tropical storm in all likelihood, the primary impacts and concerns will be from the rainfall, well away from the coast in many cases. Folks from Texas through Georgia should be monitoring local conditions and local information sources for the very latest.

Significant rain and flash flooding likely on the Gulf Coast this week

In brief: Significant heavy rain and flash flooding will impact much of the western half of the Gulf Coast through midweek. Areas between Corpus Christi and Lake Charles, as well as in southwest Mississippi are likely to see the heaviest rainfall, with max totals reaching or exceed 15 inches in isolated spots.

We continue to watch the situation on the Gulf Coast, and indeed, we’re beginning to see heavy rainfall chances come to fruition. Rain totals as high as 4 to 6 inches occurred in portions of Texas yesterday and overnight. And additional heavy rain is already occurring this morning.

A morning view of radar showing areas of heavy rain, numerous flash flood warnings (green boxes) and highlighted risk areas across Texas and Louisiana. (WeatherFront)

As the day goes on, this heavy rainfall is going to drop south and east some. It will begin to impact coastal areas of Texas, including the Corpus Christi, Houston, and Beaumont areas, as well as much of northern, central, and southwestern Louisiana. Additional heavy rain is likely to bubble up from the Gulf tonight, impacting the coast. Between where the decaying cold front stalls and the tropical moisture hits it will determine who is likely to see the highest rain totals once all is said and done. This would probably be along and southeast of US-59 in Texas and south of I-10 east of Houston into Louisiana.

HREF ensemble view of heavy rain risk through Tuesday morning. Lollipops of lavender and teal indicate the risk of upwards of 10 inches of rainfall will be present in some spots. Don’t focus on the specifics here but rather take this as a potential outcome. (WeatherFront)

Additional waves of heavy rain are likely tomorrow into Wednesday as well as the tropical disturbance we’ve been watching moves back out over water and back ashore once more. This will lead to a building flooding threat across this region over the next few days.

Click to enlarge excessive rainfall outlooks for Monday and Tuesday. (NOAA)

Coastal Texas, southwest Louisiana, and a portion of Mississippi are highlighted in a moderate risk (level 3 of 4) for excessive rainfall today and tomorrow. We could see a portion of this area get upgraded to a high risk if we begin seeing consistent rain in a location. This continues for Wednesday in the Lake Charles, Beaumont, and Houston areas, particularly for the morning hours.

What this means is that while not everyone is going to see significant flooding, there are likely to be pockets of considerable flash flooding across the area, particularly in urban and poor drainage locations. This means streets may become impassable at times, and if you have the ability to reschedule non-urgent travel, it’s recommended. This is the most significant rainfall setup in this area since 2024. As the WPC excessive rainfall discussion put it this morning, “any storms that develop in this environment (will have) an almost unnatural ability to produce heavy rain.

Total anticipated rainfall over the western Gulf Coast through late week. Some smaller areas are likely to see 15 inches or more when all is said and done. (Pivotal Weather)

Total rainfall when all is said and done will average 3 to 10 inches across this region. There may be more isolated locations that see as much as 15 inches or even more. An extremely potent rainfall event for the Gulf Coast.

With respect for tropical development, that matters primarily as any storm could try to consolidate heavy rainfall and focus it on a more specific area. It is not likely that any tropical development would extend beyond depression or low-end tropical storm status. You should be thinking of this as predominantly a heavy rainstorm and flash flooding event for the Gulf Coast.

Elsewhere, no other Atlantic concerns at this time.

Setting up a Southern soaker this week

In brief: The setup for a heavy rainstorm continues to look ripe from Texas into parts of the Southeast this week. Rain is likely to cause areas of flash flooding between Texas and Mississippi or Alabama through Wednesday or Thursday. Tropical development remains unlikely, but even if it were to occur, the primary impacts this week will be due to rain.

A look at the Gulf from late this morning shows the disturbance we’ve been watching for a bit now over Mexico and just south of Texas.

A tropical disturbance over Mexico will become the focal point of a significant rainstorm over the Deep South. (WeatherFront)

While this thing is not organized, nor is it expected to become organized, it will continue to presumably be a source of moisture that, when combined with an approaching front, sets up a potent rainstorm over the Deep South this week.

When we look at precipitable water, or the amount of moisture in the atmosphere this week, we can see a surge of it across Texas and the Gulf Coast. While I am suspicious of the final few frames of the loop below, I think the point stands that there is going to be substantial amounts of moisture available. PWAT values will stand around 50 to 70 mm, or not far off the historical maximums for this time of year. In other words, the atmosphere is going to be loaded with moisture.

A significant surge of moisture this week will help amplify heavy rain from Texas into Louisiana and parts of Arkansas, Mississippi, Alabama, and Georgia.

So we have a disturbance and a cool front, both of which will act as triggers. We have ample moisture. Basically, we have the ingredients in place for a substantial rain event in the South. Now the question becomes: How much and where?

Well, that’s always the challenging part in these events. Let’s start with the big picture. Here’s how much average rainfall is expected over the next 5 days from the National Weather Service.

A stripe of torrential rain is likely from near Brownsville through Corpus Christi, Houston, Lake Charles, and into southern Mississippi. (Pivotal Weather)

So that basically a stripe of 3 to 7 inches of rain from northeast Mexico through southern Mississippi, including Brownsville, Corpus Christi, Houston, Beaumont, Lake Charles, and Jackson, MS.

We know that historically in setups like this, there often tend to be slower moving, or “training” bands of heavier rainfall that can pop up, dumping anywhere from 2 to 4 inches in an hour over a given location. In fact, if you look at the overnight high resolution ensemble from the Storm Prediction Center, the probabilities of 5 inches or more of rain in a 24 hour period is rather high from tonight through tomorrow night. The key here is not to focus on any one spot, but to accept that there is a strong signal of potentially very heavy rain in a short time over a broad area.

HREF model probability of 5″ or more in 24 hours tonight through Monday night.

Basically, we know that someone is probably going to come out of this with 10 inches of rainfall, but we do not and probably will not know where until the event really gets moving along tomorrow and Tuesday. At this point, folks from Texas through Mississippi and Alabama should prepare for potentially disruptive travel heading into this week at times. Many areas are under a slight risk (2/4) for excessive rainfall this week, and that may get upgraded to a moderate risk (3/4) at some point. Flood Watches are now posted from south of San Antonio through the Houston area. Additional expansion of these watch areas is likely in the next day or so.

Flood watches are posted for the Corpus Christi, Laredo, and Houston areas in Texas as of Sunday midday. (Pivotal Weather)

Another wrinkle in all this is what happens as the disturbance exits mid to late week. A few European ensemble members (and notably the operational Euro model) try to wind this thing up on exit. It doesn’t look purely tropical but rather almost hybrid-like. A number of the European AI ensembles also show this.

The potential exists for a more organized low pressure area with heavy rain on Wednesday or Thursday as this pattern begins to clear out of the system. (Weathernerds.org)

I am doubtful of this being the case but given the ample support on the AI ensemble, it’s a potential risk. This would be unlikely to develop into a tropical entity, but a situation with heavy rain, thunderstorms, and 20 to 30 mph winds can’t be entirely ruled out between Texas and Mississippi on Wednesday or Thursday. Additional flash flooding risk is possible until the pattern begins to break down later this week.

There are no other tropical concerns of note in the Atlantic.

More tomorrow!

Gulf development unlikely, but soaking rain coming for the Gulf Coast

In brief: While formal tropical development seems unlikely from a Gulf disturbance, the combination of surging tropical moisture and elevated moisture pooling ahead of a cold front may setup a pretty significant heavy rain and flash flooding sitWuation from Texas through Alabama later Sunday through Wednesday.

The National Hurricane Center designated an area to watch yesterday morning in the Bay of Campeche. We’ve been talking about this area on again and off again for a little while now, and it’s now firmly in view.

The Gulf disturbance has maybe a 10 percent chance to organize into a depression or so. (NOAA NHC)

On satellite, there’s definitely a disturbance evident, but what is missing is any sort of surface reflection of this. We’re just dealing with a little too much turbulence in the western Gulf right now to think this has a realistic chance to organize. Wind shear quickly builds to 20 to 30 knots north of the system, so it’ll be entering increasingly hostile territory.

Gulf disturbance has a good deal of moisture but lacks much organization at all. (WeatherFront)

So, we don’t expect much of anything formal from this.

That said, this is going to setup a somewhat interesting situation in the Southern U.S. beginning later Sunday and lingering through Tuesday. As tropical moisture from this disturbance surges northward, it’s likely to interact with a somewhat unusually far south cool front for mid-June. The combination of a slowing/stalling front, already high moisture levels, and a surge of tropical moisture straight out of the Gulf and Caribbean is going to fuel a somewhat potent rainfall setup for a couple days.

Surging moisture out of the Gulf will collide with moisture pooling around a cold front in Texas, Louisiana, Mississippi, and Alabama early next week leading to heavy rainfall. (Pivotal Weather)

It’s still a bit difficult to pin down exactly how much rain is expected and where is likeliest to see the highest totals. However, it seems that we’ll see heavier rain focus on Texas, including the Houston area Sunday night and Monday, spreading east into Louisiana Monday and Tuesday, and then east of there toward southeastern Louisiana, southern Mississippi, Alabama, and parts of the Florida Panhandle by Tuesday and Wednesday.

An average of 1-4 inches of rain is likely from Southeast Texas into the Deep South, but there will likely be higher amounts, perhaps up to 4 to 8 inches or so in some areas. (WeatherFront)

We’re already seeing slight risks (level 2/4) issued for flash flooding risk Sunday through Tuesday. It is possible we see that upgraded to moderate risk (3/4) at some point. I would watch the Houston area and southern Mississippi closest right now for more disruptive flooding risks.

That should clear out by mid to late next week, and then hopefully there will be some time to dry out. These areas will need it. More to come probably on Sunday.