From Sean Bellafiore:
Temperatures were again in the triple-digits Sunday, the fifth day in a row of triple-digit heat and 43rd this summer, but a drop in temperatures (albeit slight) is coming with a cold front arriving Monday. Out ahead of the front Sunday evening, a prefrontal trough has sparked a broken line of showers and storms from the Metroplex through Central Texas to the Big Bend. Scattered showers and a few rumbles of thunder will slowly drift eastward and may provide scattered rain and storms to a few areas through the early evening hours. Late afternoon and early evening rain chances are only near 30%, but any storms that form may contain frequent lightning, heavy rain, and strong wind gusts.
Although the late afternoon rain should come to an end slowly post-sunset, the approach of the front may aid in sparking a few more scattered showers overnight tonight into Monday morning. Overnight rain chances remain near 30% before dropping to near 20% come sunrise as overnight lows fall only into the upper 70s. Rain chances remain near 20% Monday morning but jump to 30% Monday afternoon as the front finally creeps into the area. Expect a broken line of showers and storms to form along the front in Central Texas with any storms that form potentially producing strong winds and heavy rain. Despite the front's arrival, highs Monday will still likely climb into the upper 90s to near 100° with partly cloudy skies.
The front will only slowly move through Central Texas Monday night and could potentially spark a few more scattered showers or thunderstorms. Rain chances, however, will drop to near 20% Monday night into Tuesday with rain chances falling out of the forecast Tuesday morning. Since the cold front will take its time to push through the area, the airmass behind the front will not be as cool as previously thought. Temperatures will not be in the triple-digits Tuesday or Wednesday, but they'll remain in the middle and upper 90s. Fortunately, the front should allow for lower afternoon dew points, so heat index values may only climb as high as 100° and not as high as 106° like we saw this weekend.
The ridge of high pressure to our west is now likely going to reassert itself over Central Texas late next week. The ridge will not be nearly as strong as it was earlier this summer, but it'll be strong enough to squash rain chances, keep skies clear, and keep high temperatures above average. Highs Thursday through Sunday will climb slightly into the upper 90s and low 100s with mostly sunny skies each and every afternoon. The long range forecast doesn't show much of a break from the heat either since the ridge is forecasted to remain near the Southern Plains or Southeastern U.S. potentially through the end of the month.