The Rio Grande Valley has been blessed with a good amount of rainfall between Wednesday, June 22 until Friday, June 24. If you’re wanting to know why and how much it has rained, then I have those answers for you.
On Tuesday, June 21st, a deep surface low pressure system made its way from the Central Plains to the Northern Plains/Midwest regions. A cold front, associated with this low pressure system draped across northern Texas, where it later stalled. Daytime heating and plentiful low level moisture at the surface allowed rain and even severe thunderstorms to form along the stalled frontal boundary in northern Texas.
The storms fired off around 6 or 7 pm CDT and pushed south. Initially, these storms were supposed to subside and die around central Texas, due to the fact that it had little support from daytime heating (as the sun was setting) and because the front had stalled in northern Texas. The storms did weaken after sunset, however, they did manage to have enough energy to make it all the way to the RGV by Wednesday morning.
In addition to the outflow boundary that pushed south from northern Texas, tropical moisture from the Gulf of Mexico had also made its way to south Texas Wednesday morning/afternoon. The combination of both created a very unstable atmosphere. Thus, lots of rain and thunderstorms were generated, as a result.
By Thursday, June 23, the tropical moisture was still present over the Rio Grande Valley, but not nearly as spread out as the rains from June 22nd occurred. Some areas that did see rain Thursday, got their share. Urbanized flooding issues were the main threat for many small towns in the Valley, other than the lightning. Rain is good, but a lot of rain can be deadly, especially coming off of so many day without a drop of rain.
Below is radar ESTIMATED precipitation amounts from Wednesday through Friday afternoon (6/22/2011-6/24/2011) in the Rio Grande Valley (measured in inches):