Proceed with caution. That should be the words of warning all Houstonians should keep in mind if they have to be on the roads Friday night. The combination of a cold front mixed with a strong low pressure system to the west of the area will combine overnight Friday and into Saturday to create ideal conditions for heavy rainfall and potentially strong thunderstorms. There is already a Flash Flood Watch in effect for the entire area and will remain that way until Saturday. That will likely lead to street flooding in a number of areas throughout southeast Texas. The big questions are where and when?
The when part is a pretty easy one. Light to moderate showers will be found around the city during the day on Friday, but the real action won't begin until sundown. Rainfall should begin to get more steady and heavier as the night goes on. The heaviest showers should come through with the front in between midnight and 5 a.m. West of the city will be earlier and areas east later.
Where the heaviest rains will fall is a bit trickier to predict. Forecast models are suggesting the strongest thunderstorms will likely be south of I-10 and west of downtown. This is due to the path of the oncoming low. But, the largest rainfall total will be from an area roughly covering downtown and areas north and west of there stretching out from Huntsville over to College Station and down to the Wharton area.
Rainfall totals throughout the day on Friday should be modest, perhaps 1-2 inches. But an additional 2-3 inches will fall overnight and some isolated areas could get totals reaching 8-10 inches. It is impossible to say exactly where, but most forecasts suggest those higher numbers will be well west of Houston.
Fortunately, the front will blow all of that mess out of here by Saturday around sunrise and we should have nicer weather the rest of the weekend. Also, the bayous are low, so they should have no problem containing all the rain we get and delivering it to the Gulf fairly quickly. But, if you don't have to be out Friday night, particularly late, you're better off staying home. And if you do have to be on the roads, don't risk driving into any flood waters.