An upper-level disturbance moving northeastward out of Mexico, combined with a stalled frontal boundary along the lower Texas coast, will bring a good chance of showers or thunderstorms to Galveston County later tonight into Tuesday with rain chances increasing tomorrow as the front drifts back to the upper-Texas coast. Precipitation amounts over the coming 36-hours are generally expected to match those early Saturday morning, which saw League City receiving 1.18 inch of rain and Galveston 0.87 inch.
A bigger concern, however, arises later this week into this weekend. Parts of Texas, possibly even Galveston County, will receive excessive rains later this week into this weekend. The culprits this time will be an upper-level trough to the west with embedded disturbances tracking across Texas, a weak cold front expected to stall near the coast (lingering for several days) and a surge of deep tropical moisture along the coast. All told, rains in excess of 5 inches will be possible over significant parts of East and Southeast Texas.
The problem is that the heaviest amounts of rain and the greatest chance of severe weather will be along and near where the stalled frontal boundary persists. This is difficult to predict this far out in time and the forecast is made even more complicated by the fact that the front is expected to wobble some over the weekend. As a result, currently locating the areas with the greatest probability of excess rain is nearly impossible.
Needless to say, this is a situation we want to monitor closely over the course of this week!