Severe Weather, Flash Flood Likelihood Increasing for Monday Afternoon into Early Tuesday

Updated at 7:30 PM:

According to Jeff Lindner, Harris County Meteorologist, a powerful storm will move into Texas over the next 24 hours bringing multiple hazards to the area. The chances of severe weather and heavy rainfall by Monday afternoon and evening continue to increase. They are also expanding over a wider area. Since the original post, Harris County’s Meteorologist, Jeff Lindner has raised concerns about rises on the San Jacinto River West and East Forks to flood stage over the next few days. Rises on other creeks and bayous in Harris County also look likely, especially where we experience cell training and higher rainfall totals. Lindner advises to monitor weather closely on Monday and Monday night.

Higher Likelihood of Severe Weather Including Tornados Starting Monday Afternoon

There were some doubts yesterday about the likelihood for supercells to develop. But as we get closer to the storm’s arrival and certainty increases, supercell formation looks increasingly likely. “All severe modes will be in play including tornadoes, large hail, and damaging winds,” says Lindner. “There could be a few strong tornadoes, especially for locations north of I-10.” Yesterday, the main likelihood was north of SH105.

The National Weather Service Storm Prediction Center has expanded the enhanced risk (3 out of 5) outline to include more of Southeast Texas. The severe threat will begin in the mid-afternoon hours on Monday and continue into the late evening hours.

6-7 Inches, Flash Flooding Possible 

While the heaviest rainfall will likely occur over North Texas, the potential for high-precipitation supercells to develop and train across Southeast Texas is increasing for Monday afternoon and evening. As the front slows over Southeast Texas Monday night, Lindner expects the severe threat to gradually shift toward heavy rainfall and possible flash flooding throughout the night.

The greatest threat will generally be along and north of I-10. A slow-moving line of supercells will raise the flash-flood threat. If you get caught under one that’s training across your area as we saw back in January, be prepared.

Lindner has virtually doubled his rainfall predictions since yesterday. Instead of widespread 0.5-2 inches across the area, he now sees widespread 3-4 inches. And whereas yesterday he saw isolated rainfall totals up to 4 inches, today he estimates up to 6-7 inches.

Hourly rainfall rates of 2-3 inches will be possible leading to rapid onset flash flooding over urban areas. Street flooding will be the primary threat, but under corridors of excessive rainfall, significant rises on creeks and bayous will be possible.

Jeff Lindner, Harris County Meteorologist

In an update at 7:30 PM Sunday night, Lindner specifically mentioned the possibility of the East and West Forks of the San Jacinto rising to flood stage if we receive the higher rainfall totals in the forecast.

The NWS Weather Prediction Center has upgraded the area north of the I-10 corridor to a moderate risk for flash flooding.

Monday afternoon and evening will be active over the area. So have multiple ways to receive warnings. Make sure you have fresh batteries in your weather radio and flashlights; it could be a long night.

Putting Forecast in Perspective

To put this in perspective:

• The supercells that spawned tornadoes over Kingwood in January dumped approximately 5 inches of rain. I talked with a lady on Facebook this morning whose home was destroyed by a tornado in that storm. She said she received warnings seconds before the tornado struck. She barely had enough time to get to an interior hallway before her home started crumbling around her.
• The May 7th, 2019, storm that flooded more than 200 homes in Elm Grove dumped 7 inches of rain. But less than 20% of the floodwater detention capacity on Woodridge Village had been built at that point.
• The City announced at 5:15 this afternoon that it will lower Lake Houston by 1 foot starting tonight. A forecast greater than 3 inches triggers the Lake Houston lowering protocol.

How To Get Warnings

NOAA broadcasts warnings on weather radio in a continuous loop during emergencies.

The National Weather Service lets you sign up for watches and warnings for your address.

Harris County’s Flood Warning System also lets you sign up to receive rainfall or flooding alerts for your location. The site also contains maps that show real-time rainfall, and river-channel monitoring and forecasting at gages throughout the region.

USGS has a web app called Water On the Go that shows water elevations at flood gages wherever you go in Texas.

Harris County Flood Control District’s Storm Center can connect you to a wide variety of preparedness articles and ways to summon help in an emergency.

A number of companies offer good apps for cell phones that offer warnings. I especially like one called Dark Skies that bills itself as “hyper-local” weather. It frequently tells me to the minute when a storm will arrive at my exact location…wherever I am.

You can also find links to dozens of other weather related apps and sites on my Links Page. Check them out before the storm arrives. You never know when a storm will knock out a web site, a cell tower, or power. So be prepared with multiple backups.

Posted by Bob Rehak on 3/20/2022 based on input from the NWS, HCFCD and City of Houston

1664 Days since Hurricane Harvey