Flash Flood Watch Issued from Friday Noon to Saturday Noon For All SE Texas

Council Member Dave Martin’s office says that the City of Houston has been lowering Lake Houston water levels since late last night.

Property owners should expect a lowering of up to 18 inches. Should additional lowering be necessary, Council Member Martin will work with Houston Public Works to make sure that everything possible is done to secure life and property in the Lake Houston area.

As of 1:30 a.m. Thursday afternoon, the Coastal Water Authority reported the level of Lake Houston at 41.54 ft. That’s about 12 inches below normal. Pre-releasing water from the Lake creates extra capacity for incoming floodwater to reduce the risk of flooding.

Harris County Meteorologist Discusses Local Impacts

Jeff Lindner, the Harris County meteorologist, also issued a special report this morning warning that, “Flash Flooding of streets along with significant rises on area bayous, creeks, and rivers to flood levels is possible.

Says Lindner, “Powerful upper level storm system moving into S CA and NW MX this morning will track generally eastward and into TX over the next 48 hours. Activity will increase today from the coastal bend northward along the I-35 corridor. Some of this activity will likely affect our far western and southwestern counties later this morning into the afternoon hours.”

Friday-Saturday

Lindner warns, “An excessive rainfall event is likely Friday afternoon-Saturday morning, resulting in flooding.”

“Models continue to suggest near record/record moisture levels will be in place by Friday afternoon. Forecast soundings show little instability, but loaded with plentiful moisture form the surface into the upper levels indicating convection will be very effective at heavy rainfall production. Unfortunately it appears the slow moving surface front will be nearing the US 59 corridor around the time that maximum parameters for heavy rainfall focus over SE TX. This includes a very strong 45-55kt low level jet which will transport copious moisture into the frontals slope. Add in a slow moving surface boundary and a nearly “tropical air mass” and you pretty much have everything needed for excessive rainfall rates.”

Widespread Rainfall of 3-6″, 8-10″ in Places

According to Lindner, widespread rainfall amounts of 3-6 inches appear likely over nearly all of the area with isolated totals of 8-10 inches. It is still somewhat uncertain where those higher isolated totals may occur, but areas along and NW of US 59 may have a slightly greater risk than areas S of US 59. Much of the higher totals will tend to focus closely with the surface front and where it slows at times as it crosses the region. In addition to the overall totals, high hourly rainfall rates of 2-3 inches per hour will be possible which will lead to rapid urban flooding of street systems.”

River Forecast

The National Weather Service predicts significant rises in area watersheds. They say most basins can handle 6 hour totals of 3-4 inches, but anything greater than about 4 inches in 6 hours is going to likely be cause for concern. For Harris County, all of the creeks and bayous will likely see significant rises and exceeding of flood stage levels is possible. Greatest concern at the moment is for the watersheds over the northern half of Harris County. Some structure flooding will be possible if watersheds exceed their banks or intense rainfall rates overwhelm street systems.

They made the following predictions at 12:46 p.m., Thursday.

San Jacinto: minor to moderate flooding expected on the West Fork. Minor flooding on the East Fork

Cypress Creek: minor flooding forecast from Katy Hockley to West Fork of the San Jacinto River

Trinity: minor to moderate flooding expected along the entire river below Riverside

Brazos: Minor flooding expected at Hempstead and Bryan and will likely see at least minor at Richmond and Rosharon

Summary

Timing: Friday morning College Station area, mid to late afternoon Houston area through Saturday morning

Amounts: 3-6 inches widespread isolated 8-10 inches. US59 corridor may get the worst.

Watersheds: flooding of creeks, bayous, and rivers probable

Street Flooding: high threat for street flooding

Severe: a few storms late Friday night may become severe near the coast with a tornado threat.