National Weather Service explains why Monday's thunderstorms caused so much damage

Thousands of Evansville residents are still without power Wednesday morning following a series of thunderstorms that rolled through the Tri-State Monday night and Tuesday − and there's no timetable for when they might get it back.

CenterPoint Energy's outage map reported 4,000 customers in the Evansville area were without power Wednesday morning, down from the nearly 15,000 that were reported Tuesday and 30,000 at its peak on Monday. Some of those people have haven't been able to turn the lights on for nearly two days.

And it's not just homes going without electricity. Two major traffic stoplights in town, U.S. 41 at St. George Road and U.S. 41 at Lynch Road, are still out of service and without an estimated time for when they'll be blinking again, according to Gary Brian, public relations director for INDOT Southwest.

Brian said his agency reported the traffic light outages to CenterPoint and are monitoring the situation.

A spokeswoman with CenterPoint said the company doesn't know when power will be completely restored across Evansville but that they're working to to make it happen as quickly as possible. The problem CenterPoint crews are facing, she said, is the sheer amount of downed trees they're having to cut through just to get to the power lines in need of maintenance.

"They've (CenterPoint) been working around the clock trying to get everything restored, but there's so many trees and poles and wires down," the spokeswoman said. "They have to reset the poles in the ground, (install) new poles, but first they have to cut through all of the trees and the vegetation to even get to the wires that are on the ground − so it's taking some time."

The cause of all this damage? Sustained severe winds that came along with the thunderstorms.

A wind gust totaling 68 mph was reported at the Evansville Airport, but preceding it and following it were multiple minutes of wind gusts in the low-60s, said Andy Lesage, a meteorologist with NWS Paducah. And those types of sustained winds helped bring down trees and powerlines.

The storm produced about 1.45 inches of rainfall in Evansville, Lesage said, which he classified as "not a whole lot." Parts of Posey County had reported four inches of rain by 10 a.m. Tuesday.

More:Here's how a Courier & Press photographer got that lightning picture Monday night

Lesage said the storm, to the weather agency's knowledge, only produced straight-line winds and none of the kind that indicate possible tornadoes. He said a significant "downdraft" combined with sustained wind gusts lasting several minutes at a time were the main culprits behind the damage.

"68 mph at (Evansville) Airport, right next to the population center," Lesage said. "(You can) see what those winds did as they moved through the rest of the city."

According to the National Weather Service, a downdraft often happens when rising air can no longer support the increase in condensation that occurs as it rises higher in the atmosphere. Water vapor forms into water droplets, which then begin forming into larger droplets as the air rises, until the rising air reaches the point where it can no longer support the size of the water droplets and collapses on itself, releasing cold air that descends into the middle and upper levels of a thunderstorm.

This article originally appeared on Evansville Courier & Press: Evansville, Indiana power outages affecting thousands of residents