A front is expected to move into the area Saturday morning bringing a line of showers and storms. Isolated strong to severe storms within the main line are possible. The greatest risk for severe weather, including tornados and damaging winds, is in Northeast Texas, Southeast Oklahoma, Southwest Arkansas, and Northwest Louisiana.
The Baton Rouge viewing area is under a marginal risk (1/5) for severe weather Saturday morning into the afternoon. Severe weather is not expected to be widespread; however, the threat is still present for isolated to scatted strong to severe storms. Areas west of I-55 have a better chance for severe storms before the line weakens as it moves eastward.
Threats: Gusty to severe wind gusts are possible with bowing segments in the main line. A brief spin up tornado cannot be ruled out. Flash flooding and heavy rainfall is also a possibility if storms begin to train as the front slows down.
Timing: Model guidance is in general agreement with the main line moving into the area early Saturday morning. Showers and storms should move through between 3 am and 10 am.
Discussion: An upper-level trough is forecasted to traverse northeastward across the Southern Plains towards the Great Lakes. As it does so, it brings a moderate risk (4/5) for severe weather into Northeast Texas and the surrounding states. The main line of showers and storms will move into Louisiana late Friday night into Saturday morning and begin to weaken. There is a chance of severe weather in Southeast Louisiana based on some favorable atmospheric parameters.
Looking at those parameters, there will be some decent instability available for storms to get stronger. CAPE values across the region range from 500 to 1250 J/kg. Dewpoints will be increasing ahead of the front reaching into the 60s and low 70s due to southeasterly winds from the Gulf. These winds will also allow for warm air advection to get temperatures into the 70s in the overnight to morning hours. Because the main line will be moving in before sunrise, daytime heating will not play a factor in the area leaving instability limited. High dewpoints and warm temperatures contribute to the marginal levels of instability.
Over in the wind department, there looks to be a good amount of wind shear available. Bulk shear between the surface and 1 km is around 30 kts (35 mph) and helicity values north of 200 m2/s2. Brief, spin up tornados are possible as discrete cells move northeast with the line or within the main squall line itself.
One limitation to the severe threat is that the upper and surface lows will be pretty far north of the area and moving northeast throughout the day. This displaces the the jet streaks, and the more favorable atmospheric dynamical forcing, to the north.
Another threat will be that of flash flooding and heavy rainfall. Precipitable water values will be around 2″ with dewpoints into the 70s, so there is plenty of moisture for efficient rainfall. As the overall line moves eastward, it will begin to slow down a touch. Individual storm motion will be towards the northeast allowing the possibility of storms to train, or storms moving over repeated areas of rainfall, to allow high rain totals. Rainfall totals across the area will range from 1″ to 2″ with locally higher amounts possible.
The front will move through the viewing area by the late afternoon and begin to stall into Sunday. Mostly cloudy skies will linger with the stalled front as rain moves eastward and weakens. Moisture will remain behind the front allowing for the possibility of some isolated showers into Sunday.
How to Prepare: Be sure you have ways to receive weather alerts. Secure any loose outdoor furniture and decor. Be cautious when driving in rain and storms during the early morning commute. Late afternoon and evening plans should be clear.
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