The ongoing deluge in Houston, Texas, is the product of a stalled cold front in East Texas and a "blocking high" over the eastern U.S. The latter dome of high pressure has caused the cold front to become stationary and, at the same time, is funneling a plume of Gulf moisture into the area. In the Northern Hemisphere, winds flow clockwise around high pressure domes and, in this case, are sweeping across the Gulf of Mexico and into Metro Houston; there, the cold front lifts the moisture-laden air, producing copious precipitation.
In northwest Houston, more than 15 inches of rain have fallen, 5 inches more than the previous record for the entire month of April. As one might expect, severe flooding is widespread, snarling traffic, damaging structures and threatening lives. As I write this post, the dome and its moisture plume are slowly shifting eastward and rain is beginning to dissipate in the city.
Indeed, the western edge of the high pressure dome is now entering Louisiana and Gulf moisture is streaming northward along the cold front. Here in central Missouri, the band of heavy rain and its imbedded thunderstorms are nearing Columbia and should arrive by early evening; two days of rain are forecast before the dome and the front move on to the east.