Heavy rain threat continues, some rivers to reach flood stage
Along and north of I-10, multiple locations received 3-6 inches of rain on Thursday. This created numerous areas of flooding and will make it easier for issues to develop as additional rain falls through the weekend. A FLASH FLOOD WATCH is in effect for the entire WBRZ Weather Forecast Area through Saturday morning and could be extended. This means rain could lead to rising and moving water. Please avoid driving on flooded roads as doing so risks stalling or floating vehicles and puts a strain on our first responders to make a rescue. One of the biggest questions is always, timing on the batches of rain. That has been extremely challenging in this particular event and will be through Sunday. Extended dry time may be difficult to find for weekend events.
Today and Tonight: Friday will bring more showers and thunderstorms to the region. Any storm will be capable of dropping a lot of rain quickly as well as frequent lightning and gusty wind. A constant rain is not expected but check the radar frequently if you have outdoor plans. It looks as through a morning batch and another round during the afternoon/evening is the most likely scenario. This could result in an additional inch or two of rain. Temperatures will be held in check, in the upper 70s. Overnight will stay muggy with lows in the low 70s and a scattered showers and thunderstorms remain possible, but should offer some dry time as well.
Up Next: Another round or two of rain and storms will occur on Saturday and Sunday. By the end of the weekend, an additional 1-3 inches of rain is expected, but as we commonly see, some locally higher totals could result in areas of street and poor drainage flooding. By virtue of clouds and precipitation, low temperatures should remain above average while high temperatures are near or just below average. Some drier weather will likely emerge Monday and Tuesday.
All told, we are likely to see event totals from last Wednesday to Sunday of 4-6 inches with locally higher amounts, which is in-line with the forecast issued earlier this week. But, the forecast also called for rain totals to be spaced out over four or five days making runoff manageable for area rivers. However, the Thursday deluge nixed out that possibility and our larger local rivers now are expected to rise above bankfull. Many local rivers are expected to reach minor flood stage, barring another event like Thursday. We will continue to update these levels as additional rounds of rain occur.
The Mississippi River: At Baton Rouge, major flood stage continues with a level of 42.0’ as of Friday morning. Peaking at 44.1’ on March 19, the river set its 7th highest recorded crest at Baton Rouge. In addition, at 125 days this marks the second longest period above flood stage. Heavy rain that fell north of the area will keep the river high through Mid-May. At about 44’, an updated forecast now suggests this second crest could challenge the first earlier this year. Still, the high water is primarily an issue for river traffic and river islands, although some inundation will continue unprotected low-lying areas. The city of Baton Rouge and the main LSU campus are protected by levees up to 47 feet. Some soggy areas and seepage may be noted due to the long duration of high water placing pressure on the levees. As some of the Mississippi River diverts into the Atchafalaya River, gauges at Krotz Springs and Morgan City will stay high as well. This creates backwater flooding in parts of Assumption Parish in areas such as Stephensville and around Lake Palourde. Like Big Muddy, this is expected to be a prolonged event but is not uncommon for the time of year.
A weak cold front is stalling and becoming more diffuse across the area. A broad upper level trough over the western two-thirds of the country has put the local area under deep, southwest wind flow, which is a setup that favors rounds of rain and thunderstorms—especially with a forcing mechanism present in the form of a stalled front. The overall pattern will likely be steady into the weekend. As subtle upper level disturbances ride over the stalled front, we can expect additional rounds of showers and thunderstorms. A more defined shortwave trough will cross the area on Sunday and this trough axis will likely be enough to set off one more round of action but also be strong enough to give the cold front a kick south. Some drier conditions may take hold early next week—especially away from the coast. We are expecting an additional 2-4 inches of rain over the area through Sunday, but in our area, an event like this often leads to isolated amounts that are quite a bit higher. Similar to Thursday, the spots that experience those higher amounts can expect street and poor drainage flooding, rises on smaller streams and bayous and thanks to Thursday’s rain overachieving, we also expect some of the larger rivers such as the Amite, Tickfaw and Tangipahoa to reach minor flood stage at some sites.
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