5/17 – The Chief’s “Heavy Rain Potential” Wednesday Afternoon Forecast

Light westerly flow ahead of the weak surface front will favor initiation of thunderstorm activity on the eastern side of Lake Pontchartrain and coastal MS earlier in the afternoon before cold pool collisions cause outward expansion of thunderstorm coverage across much of the area. The primary hazards associated with the thunderstorms will be frequent lightning, gusty winds, small hail, and heavy downpours causing street flooding. More specifically, the environment will be similar to previous days…therefore, while some afternoon thunderstorms can be expected to be strong, any severe thunderstorms will be isolated and short-lived in nature.

The weak surface front will gradually work its way through the area causing the flow to pivot from westerly to northerly Wednesday night and also favor any lingering thunderstorm activity to move offshore like it has been doing each night. Post-frontal low stratus will build in over northern areas during the overnight hours and then quickly lift out and dissipate as surface heating takes over after daybreak. Strong upper-level high pressure expanding over the western Gulf of Mexico on Thursday into Friday will cause heights to rapidly rise. Surface high pressure will also mitigate afternoon thunderstorm coverage allowing high temperatures to climb into the low 90s across most areas by Friday. Saturday’s high temperature forecast is less straightforward with the approaching of another weak front. Current timing in forecast guidance indicates the frontal passage will be slower and temperatures will still be able to reach the 90s once again, especially along and south of I-10.

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