Thanksgiving storms. Outlook for excessive rainfall

Powerful Thanksgiving Storms Could Bring Flooding

Rainfall predictions associated with approaching Thanksgiving storms keep increasing. Jeff Lindner, Harris County’s meteorologist now says approaching storms will bring widespread impacts from Thursday through Saturday. He also warns that heavy rainfall may lead to street flooding and rises on area creeks/bayous. Models now show a band of 5-7 inches of rain in places.

Thursday

Lindner says a surface warm front will approach the upper TX coast early Thursday and move inland. He expects showers to increase in coverage and intensity near the front, which may approach the US 59 corridor by midday before slowing and potentially stalling Thursday afternoon.

Along and south of the warm front be prepared for isolated severe storms and excessive rainfall with inflow off the Gulf. All the elements are in place for flash flooding “and warm fronts are notorious in these sort of setups for producing excessive rainfall,” says Lindner.

The best case for inland areas is that the warm front is held closer to the coast.

Friday – Saturday

Models have now slowed down the movement of an upper level low to our west. Lindner now predicts a break in the rainfall Friday morning, before another round of widespread, heavy rains move back into the area Friday afternoon and evening.

Expect grounds to become increasingly saturated and runoff to increase. Showers may linger into midday Saturday, before this system finally exits to the east.

Rainfall Amounts

Predicted rainfall associated with the Thanksgiving storms has increased compared to earlier forecasts. That’s because of the potential for slow moving and training thunderstorms Thursday afternoon and the longer duration of rainfall now expected into Friday and Saturday.

Widespread amounts of 1-3 inches can be expected on Thursday afternoon with isolated totals upwards of 5-6 inches.

Some models show a band of 5-7 inches near the warm front Thursday afternoon and this is concerning.

Hourly rainfall rates of 2-3 inches may be possible Thursday afternoon and this will lead to rapid street flooding and significant rises on creeks and bayous.

Jeff Lindner, Harris County Meteorologist

Additional rainfall amounts of 1-3 inches can be expected Friday/Saturday on top of what falls on Thursday and this will only worsen ongoing run-off from the Thursday rainfall.

Runoff 

Soils are primed for run-off with recent wetting rainfall over the region. Our main concern is street flooding, but Lindner cautions us about the potential for significant rises on area watersheds, especially if the higher totals are realized in portions of Harris County.

His greatest concern is for the southern and southeastern portions of Harris County where soils are the wettest and potential rainfall the highest. But he still isn’t confident enough to pinpoint the exact locations of the highest rainfall.

He says most watersheds can handle 3-4 inches. But if we start to exceed 5 inches, the concern for flooding from the bayous and creeks listed below will increase.

IF 5-7 inches, streams most in danger of flooding will be:

  • Clear Creek and its tributaries
  • Armand Bayou
  • Hunting Bayou
  • Halls Bayou (upper around I-45)
  • Little Cypress Creek
  • Willow Creek
  • South Mayde Creek (lower near Greenhouse)
  • Keegans Bayou (lower near Beltway 8/US 59/Wilcrest area)
  • Willow Waterhole
  • Brickhouse Gully
  • Spring Branch Creeks (Spring Branch, Buttermilk, Briar Branch)

Thursday’s Excessive Rainfall Potential

If you’re out and about over the holidays, remember. Be wary of underpasses and bridges. If you can’t see the roadway, you don’t know how deep the water is. Turn around and don’t drown.

Also remember. Seven inches was the amount of rain Woodridge Village received on May 7, 2019. Woodridge now has much more stormwater detention capacity. But there are plenty of other clearcut areas around the area that don’t have much if any yet.


Friday’s Excessive Rainfall Potential

Keep your eye on the sky if you head out the door this holiday. Don’t let the Thanksgiving storms ruin your holidays.

Posted by Bob Rehak on 11/23/22 based on a forecast by HCFCD

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