Summer outlook: Will Central Texas lakes fill with rain?

The First Warning Weather Team examines the summer rainfall forecast and what it could take to fill the lakes.

AUSTIN (KXAN) -- As Central Texas' wettest month of the year (May) draws to a close, some will see this as a missed opportunity for beneficial rain leading into the summer months. This May, though, has brought significant positives with drought improvement throughout much of the area, as well as significant rises in Lake Buchanan.

However, Lake Travis continues to experience "one of its record low periods," according to Vice President of Water for the Lower Colorado River Authority John Hofmann.

Here we'll look ahead to the summer forecast for rain and what it would take to fill our lakes.

Summer: Our second driest season

The official summer rainfall forecast from the Climate Prediction Center is for "equal chances" wet vs. dry, meaning that odds don't lean wetter or drier for most of Central Texas. That generally means near-normal precipitation should be expected. Head into our eastern counties and the odds tilt wetter.

Bottom line, there's no clear signal suggesting wetter or drier weather this summer compared to normal.

Summer isn't usually a wet season for us. After winter, summer is our second driest season of the year. We don't usually expect much rain in summer and when we do get wet weather, it's typically from thunderstorms that are usually hit or miss in coverage.

The one exception to that: the tropics.

Filling the lakes

This season's repeated storms over the upper Highland Lakes saturated soils near and north of San Saba and Lampasas Counties and allowed for sufficient runoff into the Colorado River and into Lake Buchanan. Lake Buchanan is up more than 11 feet in the last month and only sits 6 feet below average as of this report.

Those storms have positioned themselves too far north to bring much rain into the Lake LBJ Watershed or Lake Travis Watershed, which feeds water into Lake Travis.

In order for Lake Travis to see a significant rise, we need rain to fall in those two watersheds. Both watersheds feed the Colorado River downstream of Lake Buchanan, but west of Austin.

Specifically, rain in the following counties should help: Mason, Llano, Gillespie, southern Burnet, northern Blanco and western Travis.

According to LCRA's John Hofmann, there are two distinct ways that the lakes could fill.

"That could take the form of something that happens very quickly, like a tropical event, or it could take the form of something that happens over a number of different rain events over a period of days and weeks," Hofmann said.

The tropics will be key

The higher odds of rain in our eastern counties and along much of the Gulf Coast this summer is largely due to the expectations for a busier season ahead in the tropics.

Former Chief Forecaster Jim Spencer looked back on one such incident when Lake Travis rose quickly from a tropical system several decades ago, in 1952.

"We had a decaying tropical system that dumped 26 inches of rain and Lake Travis filled overnight -- literally. It rose 50 feet in 18 hours and it was about the level that it is right now. And by the next day, it was at 681 [feet]. Full lake! Incredible. So it can happen quickly. People begin to think that 'oh my gosh, the lake is so low, it's never going to fill up.' But that's not necessarily the case," Spencer said.

He added "about our only hope for a really wet summertime" will be a tropical system that moves inland and stalls over our area, like Hurricane Harvey did in 2017.

Aside from rare moments when the lakes have filled gradually, usually, flooding is our way out of drought.

You can see the back-and-forth between drought and flood since 1940 when looking at the combined storage of Lakes Buchanan and Travis.

Impacts of less rain

Less rain typically means more irrigation. Landscape irrigation is responsible for the vast majority of water usage in the summertime in Central Texas. Do your part to use less water, while complying with local watering restrictions to keep as much water in our lakes as possible.

If you're heading out on the lakes for play, they might look different from last summer as water levels on Lake Travis are lower than this time last year, leaving underwater obstacles more exposed. Always wear a life jacket when out on the water and make sure that everyone else on the boat with you also has a life jacket on.