Rains have already begun to develop and spread across the region. Rains this morning of 1/10 to 1/2″ will be common and will start priming the already moist soils to become saturated. Shifting into the afternoon hours more widespread showers and thunderstorms develop and move northeast through the area. Heavy rains possible this afternoon through Saturday morning. A round of heavy rain is expected to move through by mid-evening as the front slowly sags southward helping to focus the rainfall followed by a second wave of heavy rainfall coming in from the southwest in the Midnight to 9 am Saturday window. The second wave may focus the heavy rains over the southern half of the region close to the front as an area of low pressure develops along the cold near the stalled cold front.
A second and lesser threat is for isolated strong to severe thunderstorms mainly impacting the Upper Texas Coastal waters and coastal counties. A brief window in the coastal counties this afternoon if we can warm up into the lower to mid-70s. followed by a break then the second shot of severe storms possible focused right near the coast around midnight through 6 am. Isolated tornadoes and damaging winds should comprise the severe threat.
The storms should depart the area Saturday between 8 AM and 1 PM clearing out from west to east.
Here is a summary of the threats and how we see them at this time:
Flash Flooding – Though rain rates may not be as high as usual to trigger the typical flash flooding threat, we may see enough rain over time to overwhelm drainage flooding roads and eventually the creeks, bayous and rivers. This is greatest threat of the event.
River Flooding – Moderate stage flooding is expected and even isolated Major stage flooding is possible. Several area rivers have been in flood or running high recently, and an additional bout of heavy rain will not be helpful. West Gulf RFC is expecting minor to moderate river flooding across Southeast Texas, with isolated major flooding. Where flooding is worst will depend on exactly where the most rain falls, but given recent flooding, the Trinity River is of particular concern.
Urban Flash Flood Messaging
Heavy rainfall is forecast for portions of Southeast Texas, including highly urbanized areas like the Houston metropolitan area. Based on forecast conditions, NWS Houston will be utilizing the following urban flash flood messaging for this event:
“Turn Around, Don’t Drown” Flash Flooding (Select if Anticipating High Rainfall Rates; 2-4″/hour)
– Turn Around, Don’t Drown. Isolated underpasses or low-water crossings may be life-threatening.
– Monitor the NWS, your local media, HCFCD and other official weather information sources.