Lake Houston Area Wednesday Evening River, Lake Report

Here is a river, lake report for the Lake Houston area on the Wednesday evening of Imelda. Top line: West Fork, no problems. East Fork, expect some flooding. Lakefront residents: no problem. Details below.

Storm Did Not Behave as Predicted

On Wednesday, as Imelda became more disorganized and lifted north, the Lake Houston Area remained lucky for the most part. A predicted rain band along US 59 never materialized. Instead, the storm seemed to shift slightly east as you can see in this radar image from 7:52 p.m.

Heavy Rain Mostly to South and East At This Hour

Source: RadarScope/KHGX

Despite nearly 8 inches of rain that fell near the Lake Houston Dam…

Source: USGS via Coastal Water Authority

…the lake level itself is still half a foot below normal (actual 41.85 vs. normal 42.38).

Source: Coastal Water Authority

Not Much Action on West Fork

The gage at US 59 received about 4 inches of rain.

Source: Harris County Flood Warning System

The gage at West Lake Houston Parkway received a little more than 5 inches.

For the most part, as you can see from the bar graphs above, the rainfall, while heavy at times, was also spread out.

The real news for West Fork residents (Humble, Kingwood, Spring, Atascocita) is that areas further west and north received even less rain.

Source: Harris County Flood Warning System: All gages selected.

In fact, every gage around Lake Conroe received less than an inch of rain.

Lake Conroe Still Far Below Normal Level

As a result, Lake Conroe is still 2.2 feet below normal and not releasing any water.

And that means, the West Fork is far from flooding tonight.

West Fork remains 7 full feet below flood stage, despite a slight rise of about a foot and a half today.

East Fork at FM1485 in Danger of Flooding

The East Fork, however, is a different story. The heavy band of rains that fell over Lake Houston itself also extended up the East Fork. Areas like New Caney, Splendora and Patton Village received 8 to 10 inches. And as a consequence, the East Fork at FM1485 is about to come out of its banks. Compare the graph below to the one just a couple hours ago. The river has risen another foot during that time.

Source: Harris County Flood Warning System

The National Weather Service expects the East Fork to crest in the New Caney area at 63.1 feet late tomorrow and Friday.

If it reaches that, it will be about a ten-year flood.

Source: USGS

What Next?

The big question remaining is, “What will happen with Imelda tonight and tomorrow?”

For Downtown Houston and points north and west (including The Woodlands, Conroe, Katy, Sugar Land, Kingwood, and Humble), Matt Lanza of Space City Weather predicts: “Periods of heavy rain through the night. It may be more dry than wet in many locations, and at this point, I don’t see much reason to be too worried about things in those areas. We will watch late tonight for some heavier rain perhaps in the city of Houston or up toward Spring, Kingwood, and Humble.”

Jeff Lindner, Harris County Meteorologist, says, “Some of the high resolution models continue to suggest additional banding will develop and impact the region into the evening and overnight hours, but confidence remains low on where any sustained banding may develop. The most likely outcome is the potential for more sustained banding over the eastern portions of Harris County generally along and east of I-45 and SH 288.”

“Additional rainfall amounts of 2-4 inches with isolated amounts up to 6 inches will be possible in this area with totals west of I-45 generally less than 2 inches,” says Lindner.

Given wet grounds east of I-45, the expected rainfall would likely lead to significant amounts of run-off and rises on the East Fork of the San Jacinto River.

Comparing Today to May 7 on East Fork

Someone on FaceBook asked me, “What does this mean for East Fork Kingwood residents?” The answer is, “If you didn’t flood on May 7, you probably don’t have to worry now.”

We received an almost identical amount of rain on May 7 at that FM1485 gage, 9.4 inches then vs. 9.48 today.

Source: Harris County FWS

During the May 7th event, the East Fork also crested at 63 feet. So use that as your go-by. If you did not flood then, you will probably not flood this week…unless…we get much more rain. Stay tuned to Mother Nature.

Posted by Bob Rehak at 8:30 p.m. on 9/18/2019

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