Tuesday, February 21, 2012

Feeling Like Spring!

By Jay Grymes & Steve Caparotta

Happy Mardi Gras!  Mother Nature certainly did her job as the day was just about perfect for area parades!

Florida Parish Rivers Update: The Amite River at Denham Springs has begun a slow fall and should be back below flood stage (29.0 ft) later this evening.  The Amite at Bayou Manchac Point still has another couple of inches to go before cresting somewhere close to 10.5 ft later tonight or early Wednesday -- that gage should be back below flood stage by Wednesday evening.  Farther down the Amite, neither Port Vincent nor French Settlement will reach flood stage, but a number of local roads and cul-de-sacs have standing water.  Elsewhere, only the Tangipahoa at Robert remains above flood stage at about 17.5 ft (as of Tuesday afternoon).  Robert has begun a slow, steady fall today, and should drop below flood stage by early Thursday.

We’re dropping the chances for rain out of the Wednesday forecast, leaving just a spotty shower or two for the afternoon.  Likewise, we’re posting only spotty showers (less than a 20% chance) in the Thursday afternoon forecast.  Great news for those young’uns that have the better part of the week off from school!  Wednesday’s high will climb into the upper 70°s for metro Baton Rouge with highs approaching 80° for Thursday.  Both days will be partly-to-mostly cloudy -- not the prettiest of days but certainly not bad for getting outdoors during February!

A Pacific front rolls into Louisiana early Friday, giving us a decent chance of rain, especially during the first half of the day.  Admittedly, we’re getting some mixed signals from our computer guidance regarding Friday’s rain chances, with our in-house Titan9 model looking rather dry through the day on Friday.  We’re going to go with a 40% to 50% chance of rain for the time being.  For now, this frontal system looks like it will be a “quick-mover” and will race out into the central and southern Gulf by early Saturday.  The cooler air behind Friday’s front will keep highs in the 60°s for Friday and Saturday.

The uncertainty in Friday's forecast stems from how the computer models handle an upper-low currently near Baja California. Some of the guidance keeps the low meandering well to our west on Friday, while other projections have the system moving along the Gulf Coast, implying a more active scenario.

The GFS model keeps an upper-low over northern Mexico on Friday, resulting in little severe weather threat along the Gulf Coast. The ECMWF ('European') model tracks the system right along the Gulf Coast Friday, implying a significant severe weather threat.
We'll continue to monitor model trends, but if we were to lean in a certain direction, it would probably be toward the European model which has shown a bit more consistency the last couple of days. The Storm Prediction Center is leaning that way as well, putting us under a slight risk of severe weather early on Friday.

Current NWS rainfall projections suggest that we could see upwards of 1” of rain from Friday’s frontal passage.  That seems like it may be a tad high given some of the forecast uncertainty, and certainly that would not be great news for folks living along our local rivers.  But the good news is that regardless of Friday’s forecast, all of the gaging sites along the Florida Parish rivers (the Amite, Tangipahoa and others) will be well-below flood stage before rains arrive.  If we can keep Friday’s storm totals around 1” (or less), there shouldn’t be any real concerns.

NOAA/HPC rain projection from 6 p.m. Thursday through 6 p.m. Friday

For now, we’re going with a mainly dry weekend ahead: fair skies on Saturday and partly-cloudy skies with spotty afternoon showers for Sunday.  One of our guidance models is hinting at the potential development of an upper-level disturbance that slides across the northern Gulf -- if that were to occur, we would expect clouds over the weekend and our Saturday and Sunday rain chances would jump-up!  But at least for now, we’re not biting on that weather “solution” for the weekend just yet.

In the extended outlook, we bring slight rain chances (about 20%) into the Monday forecast, with our next frontal passage on Tuesday generating showers and t-storms.

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