Tuesday, June 9, 2015

More Storms Ahead This Week

By Jay Grymes & Steve Caparotta

June 9th WAFB First Alert Quickcast:

- the weather turned active early today, prompting mid-day Flash Flood Warnings for metro BR
- the WAFB First Alert forecast remains “wet” for the rest of the week and the weekend

Heavy downpours at mid-day, with reports of 2” or more falling in less than an hour in spots, produced street flooding for a number of WAFB neighborhoods. By 3:00pm, Doppler radar estimates around Baton Rouge were showing widespread totals of 2” to 3”, with radar estimates of 4” to 5” or more for locations in the northeast corner of EBR Parish and extending into St. Helena Parish.

Also during the afternoon a cluster of powerful storms prompted the NWS to issue a Severe T-Storm Warning for St. Mary, Iberia and lower St. Martin parish areas.

The storms were generally moving from north-to-south (or NNE-to-SSW in some cases), tracking along the eastern periphery of the upper-air ridge that had kept us dry for so many days. However, with the ridge shifting to the west-southwest, we fell under the influence of disturbances riding around the outer edge of that high-pressure dome. 

As we’ve mentioned before, storms moving from north-to-south at this time of year are often a bit more energetic and “electrified” (elevated lightning frequency) than our traditional summer storms, in part because the air aloft tends to be a bit cooler (since it is also traveling from north-to-south around the clockwise flow of the upper ridge). With this upper-level circulation, the air aloft ends up cooler compared to the more typical upper-level temperatures when the flow is from the west or southwest. 

Through the afternoon, there has been one recurring question for the First Alert team: Can we expect more of this kind of action through the rest of the week?

The jury is still out on that question.

While widespread rains like we saw today are far from common, the pattern for the next two or three days will not be substantially different from today. The ridge will remain offset to the southwest, keeping an upper-level north-to-south flow pattern in effect for the lower Mississippi Valley. Now that configuration alone does not mean more big storms in the coming days, but we should remain vigilant for that potential, especially since our latest forecast keeps rain chances at 50% to 60% through Sunday.

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