Severe weather risk now centered on Baton Rouge
With a 2pm update, the National Weather Service Storm Prediction center has included the entire WBRZ Weather Forecast area in an "enhanced risk" for severe storms. The city of Baton Rouge is in the center of the greatest threat area.
Today through Tomorrow: The week will end on a partly sunny and mild note as high temperatures again reach for 80 degrees. Conditions are virtually unchanged after Thursday’s rain event and south winds of 5-10mph as well as unseasonably high humidity will continue. The warmth and humidity, though welcome by some, will cause problems overnight. Ample fuel will be in place for a wave of thunderstorms expected to cross the region. A few storms may be severe with damaging wind gusts, hail and even an isolated tornado. Temperatures will stay in the mid 60s.
Moving into Saturday temperatures will return to the upper 70s and humidity will stick. The environment will become increasingly favorable for severe weather. However, confidence is low in the threat materializing as ongoing morning storms and lack of an afternoon trigger when ingredients are most favorable serve as limiting factors. In any case, those that do spawn may quickly become severe with damaging wind, large hail and tornadoes possible.
The SPC has placed the entire WBRZ Weather Forecast area in an "enhanced risk" for severe storms. This means that numerous severe storms are possible in the risk area, making the threat a 3 out of 5. In other words, there is a 30 percent chance of experiencing severe weather within 25 miles of a given point in the risk area. There is a 30 percent chance of damaging wind and a 15 percent chance of large, possibly very large, hail.
1) Gusty Wind – in storms that turn severe, wind gusts could exceed 58mph.
2) Hail – much colder air aloft and strong updrafts will allow some hail to form.
3) Tornadoes – plenty of low level wind shear will give storms that do develop the ability to rotate.
4) More rain – downpours could bring another 1” or so of rain.
Estimated Timeline: Looking at this event in two parts, confidence is high for the first half and low for the second half with regard to timing. For the first part, a cluster or even squall line is expected to cross South Central Louisiana overnight between 10pm Friday – 4am Saturday. This part will bring a higher risk for damaging wind and hail but an isolated tornado is also possible. For the second part, isolated showers and thunderstorms may flare up on Saturday Afternoon and Evening, however this is not a certainty. The below image shows our RPM forecast model at 8pm with virtually no precipitation. Still though, conditions would allow any storms that can flare up to turn severe with large hail, damaging wind and an isolated tornado remains possible. The threat for severe weather will end Saturday Night. Scattered showers may linger into Sunday.
Impacts: Those venturing out Late Friday Night or Early Saturday Morning should pay very close attention to the weather and make sure shelter is nearby as thunderstorms approach. For outdoor plans on Saturday, it isn’t time to cancel yet. Monitor the forecast and have an indoor contingency in case. With hail bring a a possibility, it might be a good idea to move cars and outdoor vaulables under cover.
Actions: Monitor the forecast. Overnight weather threats are particularly dicey because we can’t see outside and many are asleep. Be sure you have a way to get alerts such as a NOAA Weather Radio or from the WBRZ Weather Team on Facebook and Twitter. Additionally, the *free* WBRZ WX App. sends push notifications to mobile devices if a watch or warning is issued for your location. Remember, a watch means “conditions are favorable, and a particular threat could develop” and a warning means that “threat is happening and you should take action immediately.” In a tornado warning, seek shelter in a low-level interior room and avoid mobile homes is possible. In a severe thunderstorm warning, get inside of any sturdy structure.
Up Next: Sunday will be mostly cloudy with isolated showers. Highs will back off a bit, topping out in the mid 60s. A more significant cool down will occur overnight with lows into the mid 40s. Monday and Tuesday will be dry and seasonable to slightly above average before a stronger shot of cool air arrives by Thursday.
THE SCIENCE: Friday will be briefly quieter and still mild before a deepening trough sends another cold front toward the area on Friday Night sand Saturday. This go around, models peg much higher instability and shear for the area and thus the severe risk is considerably higher. A warm front positioned along the Gulf Coast and strong vorticity at 500mb moving from west to east across the Coastal Plain sets up an environment favorable for a gusty squall line. Lift and shear created by the boundary will allow storms to continue propagating forward. Current forecast models run the key ingredients and precipitation field through the area between 6z and 12z Saturday meaning a pre-dawn to mid-morning timeframe appears most likely at this point. There is some model uncertainty as to how the second half of the weekend will unfold. The environment will remain conditionally favorable for severe storms meaning while some ingredients will be impressive, they may not overlap. Instability will be highest on Saturday Afternoon, but that point, shear will be weaker. Once to best lift arrives on Saturday Evening, instability will begin to drop. Know that minor adjustments in the timing and positons of any of these elements could lead to a quickly developing severe weather scenario on Saturday Afternoon and Evening with all modes possible—particular gusty wind and tornadoes. The upper level trough axis will cross the area on Sunday allowing some clouds and lingering showers, especially early. As the trough moves across the Southeastern United States, sunshine and cooler temperatures are expected through Monday. A brief warmup may occur Tuesday and Wednesday before a more significant and longer lasting cool spell arrives by the end of next week.