ESFTAE Multiple waves of rain and storms, locally heavy, is expected across the area beginning Thursday and lasting at least into the first part of next week. This is all thanks to an area of low pressure that will meander in the northern Gulf and central Gulf Coast region for several days. While confidence is increasing in the threat of heavy rain and flash flooding, the exact placement and rainfall totals are still relatively low confidence. The current most likely forecast calls for a widespread 4 to 8 inches across the forecast area from Thursday through Monday. This does lie on the higher side of ensemble guidance, but still well below the extreme high end. There is a 10% chance of exceeding 10 inches in localized spots during that time frame. The heaviest of the rainfall and the period of greatest concern is Saturday through Monday. Conditions across the area have been fairly dry with abnormally dry to moderate drought (D0 to D1) conditions observed on the US Drought Monitor. Flash flood guidance is currently around 5-7 inches within a 6 hour period or 6-8 inches within a 12 hour period. However, it is important to note that as rain falls ahead of the main event, these flash flood guidance values may come down. The waves of rain over the next few days will help moisten the ground and prime us for the potential of flash flooding this weekend. Given low confidence in the exact placement of heavy rain, the Weather Prediction Center (WPC) has outlined the entire forecast area in a Marginal Risk of excessive rainfall (level 1 of 4) for each day from Thursday through Saturday, which is as far out as the outlooks go. This means there is a 5-14% chance of exceeding flash flood guidance each day. As confidence increases, an increase in risk level is likely closer to the event. With the antecedent dry conditions, rivers are running low across the area, and it will take a substantial amount of rain to result in even minor riverine flooding. In most cases, the rivers can take 6 to 9 inches before minor flooding occurs. Chances for minor flooding are rather low (generally less than 10%), but we will continue to monitor. Remember the river forecasts locally only account for 48 hours worth of rainfall forecast. If confidence increases in where the heaviest rainfall sets up and/or if the rainfall forecast continues to the increase, a Flood Watch may be needed for parts of the area in the coming days. Keep in mind we are still about 2 to 3 days out from when the bulk of the rainfall is expected, and the forecast can and probably will change between now and then. Keep up to date with the latest forecasts over the coming days. Additional updates to this outlook will be issued if the forecast changes significantly.
