Rain chances for Kerr County now trending toward Thursday, with flash flood risk on forecasters’ radar

KERRVILLE — The setup for next week’s potential rain event over Kerr County is coming into sharper focus, with the National Weather Service now saying the heaviest rain chances are trending later in the week and flagging a risk of flash flooding as tropical moisture streams into the region.

In its Saturday forecast discussion, the NWS’s Austin/San Antonio office said Kerr County will start next week with more of the same summer-like heat and mostly dry weather under a lingering upper-level ridge. But that ridge is expected to weaken as a trough and an accompanying Pacific cold front push in from the west, setting up what forecasters described as a shift away from the “regionally monotonous summer weather” of recent weeks — with the potential for widespread rain and cooler temperatures by the latter half of the week.

Trough now trending slower, pushing rain chances later

The trough responsible for the potential rain event was still taking shape over the northern Pacific as of Saturday and won’t reach the Pacific coast until sometime Sunday, when forecasters can begin sampling it more directly. Models have grown more consistent on the trough’s timing as it crosses the southwestern U.S., though its behavior once it reaches Texas remains a key uncertainty.

Forecasters said ensemble trends now favor a slower-moving trough than earlier model runs suggested, which has pushed the most likely window for widespread rain slightly later. The rain chances still span roughly Wednesday through Friday, but the highest probabilities in longer-range ensemble guidance have shifted to center on Thursday.

Flash flood potential now on the table

The Weather Service said rain chances should build ahead of the cold front itself, as moist southerly flow strengthens in advance of its arrival, with the front then acting as a focus for the heaviest rain. Because the trough is expected to slow and weaken over the Central Plains late in the week, the front could become slow-moving and potentially linger over the area, which could extend rain chances into Saturday.

Precipitable water values — a measure of the moisture available for rain — are forecast to climb to around 1.8 to 2.1 inches, at or above the 95th percentile for the region, underscoring how much moisture the trough could tap from the Pacific. The Weather Prediction Center has already begun highlighting the potential for rain heavy enough to cause flash flooding sometime in the middle to latter part of next week across South-Central Texas, according to the discussion.

Temperatures: a gradual cool-down, not a sharp one

Forecasters said the trough’s sluggish movement and continued moist inflow mean Kerr County likely won’t see a sharp temperature drop typical of a strong cold front. But the combination of cloud cover, rain and post-frontal air should still push highs toward near-normal territory, with current model blends suggesting highs in the mid-80s to low 90s by late next week. The Weather Service cautioned that confidence in that temperature forecast remains low given uncertainty over the front’s timing and strength. Overnight lows are expected to drop only modestly, since humid air will linger.