A stretch of unsettled weather is ahead for Louisiana and Mississippi. Scattered to widespread showers and thunderstorms are anticipated over the next couple of afternoons.

THE FORECAST:

Today and Tonight: Compared to Wednesday, Thursday will be much more active in terms of showers and thunderstorms. Coverage will ramp up from “scattered and mainly west of I-55” yesterday to widespread today. After highs reach the upper 70s and low 80s during the late morning hours, precipitation will develop and drift from south to north across the area. Thunderstorms will be capable of gusty wind and downpours. Some areas, especially from the I-10/12 corridor south to the coast, could receive a few inches of rain leading to street and poor drainage flooding. Please remember to find an alternate route if you encounter a flooded road. Activity will be slow to wane during the evening hours but will gradually translate to the coast by morning as lows barely dip into the upper 60s.

Up Next: Through the weekend, highs will be in the mid 80s and lows will be near 70. Daytime warming and availability of Gulf moisture will allow scattered afternoon showers and thunderstorms Friday and to a lesser extent Saturday and Sunday. Overall, the weekend rain forecast is tricky. In addition to that typical “pop-up” activity, an upper level storm system could drive a line of storms through the area on Saturday or Sunday, but the timing or strength of that feature is not yet clear. Stay tuned for updates. A cold front will pass through the region early next week, restoring drier conditions and near average temperatures.   

It has been a while since we talked about those rain chances, or percentages on the forecast board often seen during the warm season. Here is a quick reminder about what those mean for the WBRZ Weather 13 Parish, 3 County forecast area.

10-30% - Isolated: a few locations receive measurable rain

30-60% - Scattered: part to half of the area receives measurable rain

60-100% - Widespread: almost all of the area receives measurable rain 

Keep in mind, those chances tell nothing about timing. For instance, 100% DOES NOT mean it will rain all day. We will be sure to provide information in our forecasts as to when you can expect rain when chances are on the board. MORE: https://www.wbrz.com/news/a-chance-to-remember

The Tropics: An area of low pressure is expected to develop this weekend northeast of the Bahamas. By that time, the environment is expected to be favorable for some gradual development, and a subtropical depression or storm is likely to form. The system will move northeastward over the western Atlantic from there. Pre-season storms are not that unusual. In fact, the last 5 season have all had a named storm before June 1. If this system gets a name, it will be Arthur.

The Mississippi River: At Baton Rouge, The Mississippi River has fallen into moderate flood stage with a level of 38.6’ as of Thursday morning. The river is expected to continue falling over the next two weeks. The high water is primarily an issue for river traffic and industry on the west side of the river, although some river island inundation will continue as well. The city of Baton Rouge and the main LSU campus are protected by levees at these levels.

THE EXPLANATION:

On Thursday and Friday, persistent onshore flow and cooler temperatures aloft will lead to an active marine breeze and daytime warming cycle of showers and thunderstorms. As you know, these thunderstorms are rarely “severe” but can be attention getting with downpours, frequent lightning and gusty wind. Especially on Thursday, the atmosphere will have above average moisture and ample instability so that thunderstorms can develop earlier, become heavy and persist through the day. Due to these ingredients and support from high-resolution models for widespread heavy storms, the Weather Prediction Center has mentioned a 1 out of 4 risk for excessive rainfall Thursday. By the weekend, the atmosphere is expected to warm a bit, creating more stability, and therefore more difficulty for showers and thunderstorms to develop. Still, isolated coverage is still expected during the afternoon hours as thermometers warm into the upper 80s and the sea breeze kicks into gear. We had been monitoring the potential for a stalling upper level low pressure system to create a concentrated area of unsettled weather along portions of the central or western Gulf Coast Sunday and Monday. However, the latest information suggests that system will actually become more progressive and instead drive a line of convection across portions of the Gulf Coast over the weekend. Forecast models are having difficulty resolving when that happens, but the late Saturday, Sunday time period is being monitored. Beyond Sunday, there is now a good chance that the area will receive a punch of drier air thanks to the aforementioned upper level low driving a cold front through the region.
--Josh

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