NWS Says Chance of San Jacinto River Flooding in Next Three Months is Minor

The National Weather Service (NWS) predicts only minor flood risk for both the West and East Forks of the San Jacinto through the end of May. That’s the good news.

NWS predicts only minor long range flood risk for the East (38.85%) and West Forks (26.22%) of the San Jacinto.

Drought Conditions Expanding Across Texas

But there is a downside: potential drought.

The reason for the low risk has to do with a below-average rainfall pattern across much of Texas. The Texas Water Development board posted two stories in the Texas Water Newsroom last week about the potential for drought. Large parts of the state are already severely behind on rainfall for the year and the pattern is expected to continue through May when weakening La Niña conditions could return us to normal.

Source: Texas Water Development Board as of end of February 2021.

The map above shows that most of the Houston area has received about 90% of expected rainfall year to date. But large parts of the state have received less than 20%. TWDB predicts those dark areas on the map will expand at least through May. At that point, TWDB predicts only the extreme eastern part of the state will not be in some kind of drought condition.

At the end of February, drought covered just over half the state, according to the TWDB. Statewide storage in our water-supply reservoirs is at 82 percent of capacity, about three and a half percentage points less than normal for this time of year. 

Drought Relief Could Come as La Niña Fades

Says Dr. Mark Wentzel, Texas Water Development Board Hydrologist, “The National Weather Service anticipates drought expansion across all but the eastern edge of the state by the end of May. Looking a little farther out there is some good news. La Niña conditions, that are at least partially responsible for drought in Texas, are expected to dissipate after April.”

So, the river flooding outlook could be very different by Hurricane season this year.

Did snow in February not help? Not really. Wentzel points out that snow is mostly air. It takes up to a foot of snow to equal and inch of rain.

Posted by Bob Rehak on 3/14/2021

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