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March 26, 2009 From NWS Shreveport (Doug Butts) ...ISOLATED SEVERE STORMS ARE EXPECTED TONIGHT... ...A SEVERE WEATHER OUTBREAK IS POSSIBLE FRIDAY... I originally wanted to conduct a webinar this afternoon, but got so far behind was unable to do so. In an effort to keep everyone informed, I'm sending this rather quick email in its place. If you have any questions, feel free to send me an email. I'll do my best to answer any questions. Warning, though, because of the long-term nature of the severe weather risk, this email could be somewhat long-winded. TONIGHT: Main Risks -- Large hail, damaging winds, especially north of Interstate 20. Isolated tornadoes cannot be ruled out, though. Time of main concern -- 6 pm to midnight. Discussion -- Honestly, tonight's severe weather potential is not quite as clear cut as we would hope. We're still trying to fine tune the forecast details, but here's what we know. There will likely be two "bullseyes" over our region. Clearing across Central Louisiana this afternoon has allowed a warm front to start moving northward across the region. The clearing has allowed destabilization to occur across much of North Louisiana/East Texas. Meanwhile, we see evidence of an upper-level disturbance swinging into North Texas. As these features interact, we expect thunderstorms to develop along this boundary this evening and move toward the east, along and north of the IH-20 corridor. Right now, it looks like the storms will initially develop across Northeast Texas around 6 pm, then move into the Arklamiss Region toward midnight. Light to moderate rain will likely continue several hours behind the initial storms. This is the northern "bullseye." Area radars show a convective complex moving from the Texas Hill Country into Southeast Texas. This complex is expected to move east, affecting communities mainly south of a Jacksonville, TX to Clarks, LA line. Even though there is a possibility of some isolated severe storms, we feel the greater risk of severe storms from the southern "bullseye" will remain south of a Lufkin, TX to Jena, LA line. Forecast tonight has high probabilities for showers and storms through midnight, then gradually tapering from the west between midnight-6 am. FRIDAY: Main Risks -- Tornadoes, damaging wind, large hail Time of main concern -- 10 am to 10 pm Discussion -- We might get a brief break in the action before the "main event" unfolds. A powerful upper-level storm system is forecast to move into the Texas Panhandle tomorrow morning. This will push a dryline east of IH-35 between 10 am and 1 pm. When this occurs, thunderstorms are expected to develop near the dryline across Southeast Oklahoma and East Texas. Additional thunderstorms are expected to rapidly develop during the early afternoon as the storm system moves further east into Louisiana. The combination of low-level wind shear, moisture, forcing, and instability is impressive, especially to the right of a Columbia, AR to Jonesboro and Monroe, LA line. There is a risk for a few strong, possibly long-track tornadoes in this region. The Storm Prediction Center has placed this area (South Arkansas/Northeast Louisiana) in a moderate risk for severe storms. The remainder of the Four State Region remains in a slight risk for severe storms as of 2:30 PM Thursday. We will continue to monitor the latest forecasts and make adjustments to the moderate risk area as the event draws near. After 6 pm, the storms are expected to evolve into a squall line and move east, bringing the possibility of tornadoes, damaging downburst winds, and large hail to most of the Four State Region. We expect the squall line of storms to move east of the El Dorado, AR to Jena, LA line between 10 and 11 pm and east of the Mississippi River toward midnight. Individual storms will likely move east/northeast at speeds up to 50 miles per hour Friday. Regardless, tornado/severe thunderstorm watches will likely be issued tomorrow morning for most of the Four State Region by the Storm Prediction Center. Severe thunderstorm and/or tornado warnings will also likely be issued from your National Weather Service in Shreveport. Now is the time to prepare for the possibility of severe weather over much of the region. If you have any questions, feel free to ask. Tomorrow will likely be quite a busy day. Take care and stay safe! Doug |
