Tonight could be more active than anticipated, so we’re issuing a Stage 1 flood alert for the region’s northern half

Good evening. Just a quick update to say that we’re expecting shower and thunderstorm activity during the overnight hours to be more widespread than previously thought, and that this threat will persist into Tuesday. The greatest risk for heavy rainfall continues to be north of Interstate 10, so we’re issuing a Stage 1 flood alert for parts of the metro area along and north of this freeway. Areas south and west of Houston may also see some heavy rain, but the biggest threat appears to be further inland, to the north.

The problem is that a slow-moving boundary is sagging into the region from the northwest this evening, and it’s finding an environment fairly conducive for additional showers and thunderstorms tonight. In meteorology speak, we’re likely to see the convergence of boundaries that efficiently produce upward motion in the atmosphere. Given the overall tropical air mass, some storms could produce rainfall rates of 2 inches per hour, or higher, which will quickly back up streets. Some parts of the Houston metro area could see an additional 2 to 4 inches of rain overnight, into Tuesday morning, with higher isolated totals. The potential for heavy rainfall, again focused north of Interstate 10, will likely continue on Tuesday.

Here’s the truth: We’re not entirely sure what will happen. We know the ingredients are there for heavy rainfall tonight. It could be a bust, or some location in San Jacinto County could pick up 6 or 8 inches. What we can say for sure is that the atmosphere has potential for heavy rains tonight, and we wanted to call your attention to it. We’ll be back with a full update in the morning.