Threat of Heavy Rain Continues

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- a rough and exceptionally wet first half of the day

- more rain on the way tonight and into Thursday, stays wet into Friday  

What a way to start the day: widespread rains of 4” to 6” with localized totals of 10” to 12” … Flash Flood Watches and Warnings … confirmed tornado damage in St. John the Baptist Parish …and a Tornado Watch extending from the morning into the late afternoon.

What’s next?

Simple: we’re not done with the wet weather.  The upper-low we’ve mentioned the past couple of days continues to spin -- and remain almost stationary - - to our north and northwest.  As long as it remains intact and in the region, we’ve got the potential for more rounds of storms.  As a matter of fact, models are hinting that we could see another round of activity begin to develop late overnight and into early Thursday morning.  We don’t anticipate anything as wild as what we experienced earlier today but we can’t entirely rule that out either.

There are three ingredients working together that should make for continued wet weather.  First, we begin with our warm-and-moist Gulf air mass at the surface: the steady inflow of Gulf air is a primary fuel for storms.  Then we return to the upper-low: it is generating a steady mid-level flow across our area from the south-southwest while creating vertical shear (increasing wind speeds with altitude) at the same time.  The vertical shear generates lift (of our warm, moist surface air) as well as provides some potential for tornadic development like we saw earlier this morning in St. John the Baptist Parish.  In addition, the upper-low has a cool core which further enhances the vertical transport (lift) of the warm, moist Gulf air.  Rapidly-rising unstable (warm, moist) air means a better chance for strong to severe t-storms.  Add to that the fact that the pocket of cool-air aloft (associated with the upper low) also means a better opportunity for active lightning.

With the upper-low not going anywhere quickly we’re keeping elevated rain chances in the forecast for the next few days: 70% to 80% for Thursday, 60% to 70% for Friday, and 50% to 60% for Saturday.  We don’t expect another round of 5” to 10” rains, but many neighborhoods should be preparing for at least a couple more inches of rain between now and the weekend.  That will not only be a problem for communities along our local rivers but also means standing water problems for places far from traditional river flooding concerns.

By the weekend, we expect the upper low to weaken and that should reduce the rain chances headed into next week.  As a result, our forecasts for Monday into the mid-week call for only limited rain chances - - something typical of early June.

So here we are, with “tropical like” rains without a tropical system.  Let’s just hope that this is not a dress rehearsal by Mother Nature for the upcoming Hurricane Season!

And our sincerest sympathies to those that sustained flood damage today.