The week will end quiet though some changes will be noted Friday ahead of stormy weather into Saturday.
Today and Tonight: Friday will bring more clouds than sun with high temperatures still climbing into the low 80s. It will be breezy with southeast winds of 10-20mph and occasionally higher gusts. With those winds out of the south, a bit more moisture in the air may support a brief, isolated shower but most locations will likely stay dry.
The National Weather Service Storm Prediction Center (SPC) has issued a “slight risk” for severe weather on Saturday. This means scattered severe storms are possible within the forecast area. An isolated intense thunderstorm is possible. On a scale of 1 (lowest) to 5 (highest) severe weather threat, this event is a 2. Another way of describing the threat is that there is a 15 percent chance of experiencing severe weather within 25 miles of a given point in the risk area.
The area has certainy faced much greater risks for severe weather, but even with low chances, we never want to turn our backs when the environment is capable of producing strong storms. Here is the breakdown:
1) Gusty Wind – in storms that turn severe, wind gusts could exceed 58mph.
2) Hail—in the most intense storms, some marginally severe hail (1” in diameter) could occur.
Precipitation: Generally, less than a half inch of rain is expected, though a locally higher amount may be found within the 13 Parish, 3 County Forecast Area—especially where the heaviest storms occur.
Estimated Timeline: Showers and thunderstorms are expected to arrive in the form of a weakening squall line, likely reaching the Atchafalaya Basin around 2am Saturday, the Mississippi River around dawn and I-55 by about 8am. Some showers and thunderstorms may linger into the late morning and early afternoon hours, but impact weather will wrap up soon after that.
Impacts: Saturday Morning outdoor events in the area will certainly want to monitor the radar. Even without severe weather, rain and thunderstorms (lightning) would force activity inside. Have access to weather alerts in case additional action is necessary.
Actions: Get watches and warnings with a NOAA Weather Radio or from the WBRZ Weather Team on Facebook and Twitter. Additionally, the newly updated and *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.” Remember, in the event of a severe thunderstorm warning, get inside of a sturdy, enclosed building and move away from windows.
Up Next: Saturday will begin stormy (see above) with temperatures in the mid 60s. Some clearing is expected for the second half of the day and a few peeks of sunshine are even possible. Once the showers end, thermometers will take a run at 80 degrees. Sunday will be mostly sunny with highs in the low 80s. Another scattering of showers and thunderstorms is possible Monday Evening. Warmer than average temperatures will continue through next week.
THE SCIENCE: Clouds will increase ahead of an approaching upper level trough and an isolated shower can’t be ruled out, but any activity would be short-lived. That trough will have an associated surface low and a cold front stretching from Kansas to Texas on Friday. As the upper trough moves from the Midwest to Mid-Mississippi River Valley into Saturday, the surface storm will begin to occlude. A weakening cold front will then slide into western Louisiana on Saturday Morning as an area of positive vorticity advection moves across the Gulf Coast. Like the surface low, the upper trough basin will remain north of the area. Helicity (rotation) will be between 200 and 300—on the low end what is typically needed for tornadoes to develop. CAPE (instability) will be in the 1,000 range, which is sufficient for a few stronger thunderstorms. There should be enough uplift generated by the upper trough and outflow ahead of the squall for an isolated strong to severe storm but high resolution radar simulations show a weakening squall line moving into the area around daybreak Saturday. Given this, damaging wind gusts appear to be the primary threat on Saturday Morning as that line crosses the area. Because the front never fully clears the region, some instability could hang on Saturday Morning meaning that despite weakening wind finds, an isolated strong storm will still be possible through about midday. The Storm Prediction Center does highlight much of the WBRZ Weather forecast area with a “slight risk” for severe weather. Some clearing is anticipated beyond the storm system with a break for the second half of the weekend. Above average temperatures will continue. An active upper level pattern with several troughs spinning across the country will lend to several chances for showers and thunderstorms next week. Forecast models continue to hint at a particularly impressive trough toward the end of next week which, in the early going, has characteristics of another severe weather event. But of course, this is beyond the short term outlook where confidence is considerably lower and the forecast often changes.