Widespread heavy rainfall along and north of I-10 over the last 24 hours has resulted in rainfall amounts of 2-3 inches over much of that area. Pockets have received 4-5 inches. Those include northern Waller and western Montgomery Counties. Portions of Walker County received 4-6 inches.
Ongoing flooding through much of today closed several roads in low lying areas of northern Waller and Walker Counties. Run-off continues to progress down creeks and into mainstem rivers. Rises will continue along upper Spring Creek into tonight and Saturday. However, at the moment forecasters expect no significant flooding. See attached graphics for 24-hr rainfall totals and current channel status.
First Round Kicks Off Overnight
NWS satellite imagery shows moisture streaming up out of Mexico as of 7PM Friday. The area along the middle Texas coast from the coastal bend up to to about Wharton looks favorable for the formation of another round of heavy to excessive rainfall late tonight and early tomorrow. Models indicate this activity will occur mostly west of I-45 and south of I-10 into Saturday morning before it begins to weaken. Exactly how far northeast rain and heavy rain may spread is still in question. But according to Jeff Lindner, Harris County’s meteorologist, “The latest thinking indicates it will remain southwest of the areas hard hit today.”
Second Round of Storms Saturday Night into Sunday
Lindner predicts a weakening of the storm Saturday afternoon. But he warns to expect numerous showers and thunderstorms Saturday evening. He says they will invade the region from the southwest to northeast. Moisture levels will support heavy to excessive rainfall rates within any organized thunderstorms.
Expect additional rainfall amounts of 1-3 inches over the weekend with isolated totals reaching 4-6 inches…especially around the coastal bend and Matagorda Bay tonight into early Saturday.
Area Soils Now Saturated
I received 3.07 inches in my rain gage today and have standing water in my yard. Soils have become nearly saturated in areas that saw the greatest rainfall today, while areas around Galveston Bay have experienced little rainfall thus far. Heavy run-off in many areas north of I-10 will cause rises in several channels. Keep an eye on the East Fork of the San Jacinto River at FM 1485 into the weekend. The forecast there currently exceeds flood stage.
A good amount of water is routing into the West Fork of the San Jacinto also. But current forecasts keep the river from Conroe to Humble below flood stage. The SJRA is releasing water from Lake Conroe at almost 6000 cubic feet per second. Despite that, the lake level has risen almost a foot and a half today above its normal pool level.
The areas north of the lake received some of the highest rainfall totals this morning. This lake is now 3.5 feet above where it was when the SJRA stopped the seasonal lowering last week. Had they now lowered the lake a foot, it would be even higher now. We can all learn from this experience.
Minor flooding will also be possible this evening along upper Spring Creek west of Hegar Rd with rural low lands near the creek inundated.
Additional rainfall over the weekend may change some of the current forecasts.
Posted by Bob Rehak on 4/30/21 at 8PM based on info from the NWS and Harris County Meteorologist Jeff Lindner
1340 Days since Hurricane Harvey