Tuesday, January 8, 2013

Flash Flood Watch Into Thursday

By Jay Grymes & Steve Caparotta

As of 5PM, much of the Baton Rouge metro area had already received upwards of one-half-inch of rain, with generally light-but-steady rains continuing to fall over the ‘Red Stick.’  The rain through the overnight is expected to remain fairly constant as well, and falling at slightly higher rates than we’ve seen this afternoon.
A FLASH FLOOD WATCH has been in effect for areas west of the Atchafalaya Basin, and a new FLASH FLOOD WATCH -- which includes most of the WAFB viewing area - - was issued this afternoon and remains in effect until 6PM Thursday.

We’re still awaiting the passage of the anticipated warm front that we described yesterday.  That likely occurs tomorrow morning, which means rain likely not only through the night but through the morning hours too.  Looks like a very wet morning commute.  Lows tonight likely remain in the 60°s for many of us, with highs on Wednesday climbing into the 70°s as we move into the “warm sector” (the south side of the warm front).
While we think there will be breaks in the rain during Wednesday afternoon, we still expect showers and possibly a few t-storms through the day.  As we head into Wednesday night and early Thursday, our attention will turn to the west with the approach of a cold front.
As we noted yesterday, the advancing cold front does not look like it will be an especially fast-moving boundary, so the timing through Thursday is still a bit in question.  For now, we’ll call for scattered showers and t-storms Wednesday night, with “showers and t-storms likely” for Thursday morning.  For the time being, it looks like rains will slowly end from west-to-east during the afternoon and evening.
The NWS Storm Prediction Center still has most of the viewing area under a “SLIGHT RISK” for severe weather for Wednesday into Thursday morning. The primary threat will come as a cool front approaches from the west on Thursday.
Models continue to show differences, but it appears as though 2” to 4” for much of the WAFB viewing area between now and Thursday is very reasonable, with locally higher totals.  Not only is this range sufficient to warrant a WATCH, but we’ll need to monitor rainfall trends closely: 4” of rain could become problematic for area rivers.
Projected rainfall totals through Thursday afternoon from the RPM model (left) and GFS model (right). The RPM seems to be running a bit high, but isolated rain totals of 6" to 8" are possible.
It looks like we’ll get a short reprieve from the rains on Friday, but we’ve got our next frontal system moving into the area late Saturday into Sunday, with the system potentially stalling along the coast, keeping rains in the forecast through the early part of next week.

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