Today will be the onset of an unsettled stretch of weather.

Today and Tonight: Showers and thunderstorms are expected to increase during the afternoon hours. Action will be more widespread than Monday and Tuesday. Beneath otherwise mostly cloudy skies, high temperatures may reach about 90 degrees before any rain begin to cool things down. The more active pattern taking hold will mean that showers and storms remain possible at overnight with lows in the mid 70s.     

Up Next:  Much of the forecast 3-6” of rain is likely to occur on Thursday and Friday. Widespread showers and thunderstorms are anticipated each day. Timing is the most difficult aspect of the forecast as daytime heat alone will not be responsible for producing the action. Really, off and on rounds of rain and storms are possible through Friday meaning umbrellas should stay close while outdoor activities should keep the WBRZ WX App. handy. Humidity will remain oppressive but clouds and rain will at least keep air temperatures in the mid 80s—below average.  

Timing: Showers and thunderstorms won’t necessarily follow the standard pattern of flaring up in the afternoon. Daytime heating will certainly help but as waves of energy move overhead, some nighttime action is possible as well.

Threats: Downpours will be the main concern with pockets of heavier showers and storms creating localized street flooding. A FLASH FLOOD WATCH is in effect for locations south and east of Baton Rouge and that could be extended northwestward in the coming days. Also, as is normal with summer storms, frequent lightning will be a danger as well.

From the National Weather Service: The areas of greater concern at this time appear to be the Mississippi Gulf Coast counties...the New Orleans Metro area and the rivers that drain into Lake Pontchartrain. To a lesser extent...the heavy rain threat may spread farther west later in the week to include the Amite/Comite Basin and the streams in East-Central Louisiana.

What should I do? There are factors that bring some uncertainty to this forecast—particularly with exactly where the heaviest rain will occur. Monitor forecasts from the WBRZ Weather Team. We’ll provide the latest alerts in the Baton Rouge area on Facebook and Twitter. If you live in a flood prone area, it would be a good idea to take the normal precautions now, just in case. Finally, always remember not to drive on a flooded road. Not only can a few inches of water float a car when moving, but even standing water can get into an engine causing thousands of dollars in damage.

THE SCIENCE:

Forecast Discussion: An upper level low pressure continues to chug westward along the Gulf Coast. Areas of positive vorticity advection circulating around this low will enhance shower and thunderstorm development through Friday. While daytime heating is one factor that will aid shower and storm development, waves of energy will also play a part making the timing aspect of this forecast period more difficult than usual. At this time, there seems to be forecast model agreement on a couple of particularly active periods. The first wave of energy is progged for Wednesday Afternoon and Evening which should account for the first widespread and heavy episode of rain. Another wave lasts through much of Thursday and into Friday—though this could come in 2 or 3 as the upper wave pulses. Over the weekend, the upper low should open up into move of a trough in the mean flow, however the axis should still be oriented such that higher than average shower and thunderstorm activity continues into early next week. With regard to rain amounts, a water loaded atmosphere with very high dew points and precipitable water value means that thunderstorms will be very efficient rain makers. With fairly weak low level steering winds, any storm could quickly dump an inch or two of rain before dissipating or moving away. The will make areal and potentially flash flooding a concern. By the end of the weekend, a general 3-6” of rain is expected. That forecast range comes from a blend of the more conservative GFS model and the aggressive ECMWF model. Higher amounts are expected south and east of Baton Rouge with lower amounts to the north and west. To this note, depending on the exact placement of the highest rain totals—area rivers will need to be monitored for rapid rises.    

--Josh

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