Monday, September 29, 2014

Staying Warm & Muggy on Tuesday

By Jay Grymes & Steve Caparotta

WAFB First Alert Quickcast:
- isolated showers on Tuesday, isolated-to-scattered rains for Wednesday
- humidity stays elevated with highs in the upper 80°s for Tuesday thru Thursday
- waiting for a cold front to arrive on Friday

As we had anticipated on Sunday, today was a muggy day but many WAFB communities stayed dry. Dew point temperatures in the low 70°s gave it almost a summer feel in terms of humidity … but the clouds kept afternoon high temperatures in the mid 80°s for most WAFB communities. For many of us, passing mid-day and afternoon showers were little more than a nuisance where they did develop.

A weak trough of low pressure still lingers along the northern Gulf Coast: the National Weather Service is “painting” it as a quasi-stationary front. Regardless of how you label it, the air is muggy on both sides. Pockets of rain continue to develop along and near the boundary: motion on the north side is mainly from ENE to WSW while rains on the south side are generally moving west-to-east. But the main story here is that the more significant rains have moved well to our east with only isolated showers impacting southern Louisiana and SW Mississippi.

The trough/front will stay in place for Tuesday and Wednesday. Like today, the primary action will be far to our east but we can’t rule out a few showers over the course of the next two days. We’ll go with spotty to isolated showers for Tuesday (rain chances under 20%) and then call for a 20% to 30% rain chance for Wednesday. Morning starts for both days will be around 70° to the low 70°s for metro Baton Rouge with afternoon highs in the upper 80°s under partly-cloudy to partly-sunny skies.

Headed into Thursday, the air mass over us becomes a little more unstable as we await the arrival of a cold front on Friday. Set rain chances on Thursday at 50% or better for the afternoon and evening with rain likely through the overnight and into Friday morning. Our latest guidance suggests that Friday’s front arrives in the WAFB viewing area sometime close to sunrise on Friday but should steadily push to the south and southeast through the middle of the day. That could mean a rather wet and messy morning commute for Friday; however, if that timing pans out, we can expect some improvement by/before the evening drive home. At this point we are not anticipating a significant severe weather event but we could see a few stronger storms develop just ahead of the advancing front. Frankly, it’s still a little too early to assess the overall severe weather threat, so we’ll keep an eye on the potential as the week progresses.

The payoff arrives by Saturday morning with all indicators pointing to a fine weekend: cooler mornings, low humidity during the day and plenty of sunshine for Saturday and Sunday. Those along and north of the I-10/12 could see lows close to 60° or so for Saturday’s sunrise with Sunday morning lows falling into the mid to upper 50°s for most WAFB neighborhoods. Highs for both days look like the low 80°s for metro Baton Rouge -- fine early fall weather.

In the tropics, an area of low pressure west of Bermuda -- labeled as Invest 97L -- has a good spin and solid organization based on satellite presentation but remains short on convection. Given 97L’s current lack of thunderstorm activity and the expectation for enhanced shear in the coming days, the system is given only a slight chance (about 20%) of becoming a sub-tropical or tropical storm in the next couple of days according to the National Hurricane Center. Still, Bermuda residents need to keep an eye on the situation; but for the U.S., regardless of what becomes of 97L, it appears destined to stay out over the Atlantic and head north and then northeast towards ever-cooler waters. Elsewhere in the basin, all remains relatively quiet.

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