Thursday, January 9, 2014

Increasing Rains Late Friday

By Jay Grymes & Steve Caparotta

With this morning’s start in the upper 30°s and afternoon readings in the 60°s, you might think that spring has arrived early, especially when compared to the record and near-record lows just a couple of days ago. And it gets even warmer over the next two days, with highs in the mid to upper 60°s for Friday and highs approaching 70° for Saturday afternoon.

We admit, there were fewer clouds today than we expected but we doubt anyone is complaining. The clouds will start to work their way into our viewing area tonight. And if you’ve looked at regional Titan9 Doppler radar today, you’ve probably seen the band of showers that has persisted over western and north-central Louisiana for much of the day. But we expect those rains to fizzle out later this evening.

Most WAFB neighborhoods will see Friday sun-up temperatures in the upper 40°s to low 50°s under mostly cloudy skies. Be on the watch for a little light fog for Friday’s wake-up too, but not enough to be a problem for morning commuters.

While this afternoon’s rains to our northwest will dissipate, we still expect a Pacific cold front to slide through the lower Mississippi Valley late Friday into early Saturday. Rain chances will slowly rise during the latter half of Friday -- plan on scattered showers for Friday evening’s rush hour. By Friday night, rain is likely with those rains extending into early Saturday morning as the front passes. Models suggest that the rains are out of the Baton Rouge metro area before sunrise.

What do we mean by a “Pacific front?” The air mass behind Saturday’s cold front comes from the Pacific Ocean rather than being of Canadian or even polar origin (like the frigid air earlier this week). Pacific air masses can be quite cool at times but are generally not bitterly-cold. And in this case, while we will get a little cooler on Sunday, temperatures for Sunday and early next week will still be near- to above-normal for this time of year.

The latest runs of computer rain projections are delivering a mixed bag. The leading American model (GFS) and the European model (ECMWF) still suggest that most WAFB communities get under 1” of rain, with most coming in at under one-half-inch. On the other hand, our in-house RPM model is much wetter; it also hints at the more widespread rains arriving sooner in the afternoon. For now we’ll lean towards the numbers from the GFS and ECMWF, but we’ll take another look at this later tonight and early Friday.

Guidance from our reliable models points to a fairly rapid frontal passage. While there will be rumbles of thunder overnight, few if any storms are expected to become strong to severe. The “quick mover” should allow for clearing skies by lunchtime on Saturday if not sooner. So Saturday afternoon looks like a winner and Sunday should be a fine South Louisiana winter day with plenty of sunshine.

Another Pacific cold front arrives Monday. Based on what we see right now, Monday’s front will also be a relatively fast-mover. In addition, the current guidance suggests that severe weather will not be an issue with Monday’s front and rain totals are likely to come in at under one-half-inch across the viewing area. While we do expect another modest cool-down following Monday’s front, it won’t be all that significant -- our forecast keeps Red Stick lows will stay well-above freezing through the work week with highs in the 50°s and 60°s right into Friday.

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