Temperatures Could Peak on Thursday. Why?
The Upper Valley hit the triple-digits on Tuesday and Wednesday, but Thursday may end up being the hottest day of the week.
A ridge of high pressure has built up over northern Mexico. That ridge spills over into south Texas as well. Add to that some moderate and warm southeast winds at 10-35 mph, and you have the perfect combination for a hot day. Expect 104 in Ranch Country, 102 in McAllen, and 97 in Brownsville.
How does a ridge of high pressure have an effect on heat? By its definition, high pressure in the mid level of the atmosphere is a collecting of dense air... or a bubble of "extra air." It can't float out into space, so that mass of dense air has only one place to go: down. A ridge causes sinking air. When air sinks, it compresses even more as it gets toward the surface. The temperature of that compressed air goes up. It heats as it sinks.
So if you walk out to your car in McAllen or Edinburg on Thursday and notice how rediculously hot it is inside, just look up! It's that sinking, compressing, heating air.
For my detailed forecast for the holiday weekend ahead, click here.. http://www.kveo.com/weather/weather-talk