Thunderstorms rolled across Galveston County yesterday afternoon into this morning. Rainfall amounts varied quite widely from less than an inch on Galveston Island to 3-4 inches across northern parts of the County, where some localized flooding was reported.
If this were the end to the heavy rain threat, all might be well. However, the chances of more heavy rain are increasing for the end of this week into Saturday or Sunday. Given the already saturated soil, additional flooding can be expected, especially in those areas that receive another 5-8 inches more over the coming 3-4 days.
The rains will be caused by a combination of deep tropical moisture, an upper-level low pressure trough slowly shifting east into West Texas and a weak frontal boundary due to stall near the coast by Saturday.
This is prompting the Weather Prediction Center to assess a moderate risk of excessive rainfall for parts of Southeast Texas including Galveston County.
As mentioned on my blog on Monday, pinpointing the area of highest rainfall will be difficult as it will depend in part on where the front stalls out (serving as a focus for storm activity) and how various outflow boundaries from existing storms set up and interact. In other words, the atmosphere will be very unstable, resulting in multiple rounds of precipitation over the next few days and with rainfall amounts varying greatly from locale to locale across the region.
My advice is to pay close attention to local conditions and heed warnings from the National Weather Service Office.