Monday, November 26, 2012

Morning Rains, Turning Cooler Tuesday

By Jay Grymes & Steve Caparotta

The long-advertised rain is just around the corner, with the cold front currently (as of 4PM) extending from southern Arkansas into east-central Texas, all linked to a surface low positioned near the ArkLaTex.

Our forecast brings the cold front -- and the surface low -- through the WAFB viewing area around the 3AM - 6AM Tuesday morning, with the frontal complex continuing to the east through the day. Showers and t-storms are expected ahead of and during the frontal passage. A few t-storms may be on the strong side, with gusting winds and pockets of hail, but this is not looking like it has the dynamics to become a severe-weather event for WAFB communities. 

The timing of the front’s arrival and passage may shift a bit, it looks like most of the more active t-storms and heavier rains will be to the south and east of metro BR during the peak morning commute hours (7AM - 9AM), but that does not mean that the rains will have ended for the entire metro area. Definitely allow a little extra time and plan on a weather-impacted Tuesday morning drive.

Current guidance suggests that rain totals will likely run in the 0.5” to 1.0” range.

We think that the rains will end during the morning for BR and points north, with the clouds slowly thinning through the afternoon. Sunrise temps for metro baton Rouge will be in the low 60°s, but with cooler air filtering in behind the morning front, Tuesday’s highs will top-out in the mid 60°s -- maybe even struggle to make the low to mid 60°s north up along the state line.

Yes, the air behind the cold front will be cooler, but not “winter” cold. The northern jet stream (sometimes called the Polar Jet Stream) will remain locked up over the northern states, serving as a blockade for southbound Canadian air. Look for lows on Wednesday and Thursday morning to only dip into the low 40°s for Baton Rouge (upper 30°s along the state line). In addition, the core of high pressure behind Tuesday’s front will quickly shift to the east, re-establishing “return flow” off the Gulf by Wednesday -- that means highs back into the 70°s by Thursday for many of us, with 70°s for Friday and right the rule right through the weekend.

The southeasterly “return flow” and return of the Gulf air mass will mean increasing low-level moisture through the end of the week: we’ll post slight chances for mainly-afternoon showers for Friday, Saturday and Sunday. For the time being we’ll call it a 20% chance for each day, but that may prove to be a little generous.

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