From Sean Bellafiore:
The first heat advisory of the summer has been issued and runs through 8 PM Thursday as heat index values today and tomorrow may climb as high as 109°. In addition to the heat and humidity today, we'll also have a good chance of seeing rain and potentially strong storms late this afternoon but especially this evening. With mostly sunny skies early and partly cloudy skies later in the day, highs today range from 94° to 98° while heat index values range from 101°-109°. Outside of isolated morning rain (20% chance), we'll stay dry for nearly the entire day. Showers and thunderstorms may form both to our north and west and should push into Central Texas near or shortly before sunset. Some storms may be strong, especially with all of the heat and humidity we'll have in place today. Strong storms may contain high wind gusts as high as 70 MPH, large hail, and frequent lightning. The threat for a tornado is very low but not zero. Overall rain chances are near 50%.
Scattered rain and storms during the early/mid evening hours should start to move out during the overnight hours. We'll likely be dry by Thursday morning. Morning lows, thanks in part to the rain, should settle in the low/mid 70s. Any lingering morning clouds left from overnight rain should dissipate by late-morning. Expect full sunshine Thursday with heat and humidity sticking around. Highs Thursday range from 96°-100° with heat index values again climbing as high as 109°. Similar weather is in the forecast Friday. Mostly sunny skies allow highs to reach the upper 90s with heat index values climbing as high as 107°.
The upper-air pattern for the remainder of the work-week is characterize by weak flow aloft and small disturbances moving through. This weekend, an upper-level trough will dig into the Central Plains. As disturbances rotate around this trough, we'll have to be on the watch for scattered storms during the afternoon and evening from Saturday through Tuesday. Rain chances are only between 20% and 30% at the current time, but those will likely need to be adjusted more as time goes on. As of now, Sunday may bring the best chance for rain and storms. Any storms that form Saturday through Tuesday may potentially be strong since highs climb into the low/mid 90s.