heavy rainfall

Heavy Rainfall Threat Approaching

Last week, I posted about the possibility of heavy rain early this week. Last night, Dallas experienced torrential rains and they’re headed this way. One amateur weather gage on Londonderry Lane reported more than 14″ of rain! Dallas/Fort Worth officially received 9.46 inches of rainfall in 6 hours and 7.8 inches in 3-hours. Significant flash flooding has resulted. A 1-hour storm total of 3.01 inches was recorded at DFW with a storm total of 6.54 inches. That wiped out 67% of the area’s 2022 rainfall deficit in a few hours.

National Weather Service map as of 12:41 pm Houston time. Purple boxes represent flash flood warnings. Bright green = Flood warnings. Dark green = flood watch.

Threat Will Increase From North to South During Next 24 Hours

According to Jeff Lindner, Harris County Meteorologist, the frontal boundary over north Texas will slowly move southward today and approach the northern portions of southeast Texas by mid- to late afternoon. Numerous showers and thunderstorms will develop along the boundary along with scattered showers developing northward along the seabreeze and Gulf inflow.

The air mass will become extremely moist and unstable. When combined with slow moving/stalled boundaries, excessive rainfall can result. Lindner says areas north of HWY 105 have the first potential for heavy rainfall in early afternoon. Then the front will slowly sink southward toward I-10 tonight into early Tuesday. Expect slow storm motions, cell training, and back-building of cells to the west and northwest. Everything points to heavy rainfall.

While grounds are dry, the local air mass will be capable of some impressive short duration rainfall amounts of 2-4 inches in an hour.

Jeff Lindner, Harris County Meteorologist

This was clearly seen overnight in north Texas. The local air mass will not be much different over southeast Texas. Especially N of I-10. These rainfall rates can lead to rapid flash flooding especially in urban areas.

Widespread rainfall amounts of 2-4 inches are expected over much of southeast Texas through mid week. But Lindner also expects isolated higher totals of 6+ inches. And where these higher totals occur, flash flooding will be possible, he says.

Confidence in rainfall is high. But confidence in rainfall amounts and location of the heaviest rainfall is low.

Street flooding will be the primary threat with the heavy rainfall rates. Rises on area creeks and bayous will be possible if some of the heavier storms train or move slowly over any watershed.

Overall, this wet pattern will linger into late week. But a slightly drier air mass will eventually push through and we should transition back toward a more “normal” cycle of showers and thunderstorms driven mostly by the seabreeze front.

See the National Weather Services predictions below.

Posted by Bob Rehak on 8/22/22 based on information from HCFCD and NWS

1819 Days since Hurricane Harvey