Monday, March 30, 2015

Staying Warm, Limited Rain Chances

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:

- above-normal temps through Friday
- modest rain chances through the 7-day outlook

We’ve definitely hit a warm spell, with highs in the 80°s that started on Sunday and are expected to persist through Friday. By comparison, normal (i.e., the 30-year average based on 1981-2010) highs at this time of year are in the mid to upper 70°s for the Red Stick. Lows each day look to stay in the 60°s, compared to normal lows in the low to mid 50°s.

The warmer air is accompanied by more moisture (higher humidity), setting the stage for low-end rain chances -- at 20% or less -- for the next couple of days. As we get to Thursday, a weak upper-air disturbance from the west may offer a slight nudge to our local rain chances. Then comes our next front, scheduled for arrival late Friday or very early Saturday. That front should deliver scattered showers and t-storms, but for now at least, the front doesn’t look especially potent, so we see little threat from severe weather associated with its arrival.

It’s still way down the forecast road, but the current outlook for the weekend is not the greatest. While Friday’s front should clear the coast by Saturday late morning, it may stall over the coastal waters rather than sweep south quickly and “cleanly.” Add in another upper-level disturbance from the west and we have modest rain chances for Easter Sunday. We’ve got rain chances for Sunday at 30%, but more importantly for some, any rain that does fall looks to be the afternoon variety: all looks good for Sunrise Services.

On a different track for weather and climate news, the Mississippi River at Baton Rouge is now above flood stage, having risen above stage of 35.0 feet this past Thursday. The current forecast calls for the Baton Rouge gage to crest in the next couple of days just over 36 feet. 

We’ve had some inquiries in recent weeks about this, a lot of it motivated by the memories of the mega-flood back in 2011.

First and foremost, the river will not get anywhere near as high as it did in 2011 (45.0 feet) … for the time being it doesn’t look like the river will even get to 40.0 feet, at least not this spring. In addition, flood stage on the Mississippi River for Baton Rouge fails to include the height of the levee (45 feet or more) for the stretch of river running beside the Capital City. To put it all in perspective, the Mississippi River at Baton Rouge has risen above flood stage 11 times since 2001, including 3 times above 40.0 feet (2008, 2009 & 2011).

The bottom line: we’re just fine.

However, the river is high enough now to start the usual seepage and “sand boils” that we usually see this time of year in the Baton Rouge metro area, mainly along the ‘natural’ river floodplain that extends from the western foot of Baton Rouge’s South Boulevard downriver beyond the L'Auberge Casino. (Boils occur on the west side too.)

That 2011 reading is the 4th highest on record, and the second highest (behind 45.2 feet during April 1945) since the start of construction of a single "consolidated" levee system as mandated by the 1928 Flood Control Act. The 2011 Flood prompted the opening of the Morganza Spillway .. only the second time ever that the Corps of Engineers has opened it, and the only time the Corps opened it due to excessively high water along the river. (The other time was 1973 to reduce pressure on the River Control Structure upriver.)

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