SPC Mar 28, 2018 0600 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 28 Mar 2018

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1155 PM CDT Tue Mar 27 2018 Valid 281200Z - 291200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS NORTHEASTWARD INTO THE ARKLATEX AND LOWER TO MID MISSISSIPPI VALLEY... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN PLAINS...ARKLATEX AND LOWER TO MID MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms with isolated large hail and wind damage are possible today from parts of south and east Texas into the lower Mississippi Valley. A couple tornadoes may occur from east Texas into northern Louisiana and southern Arkansas. ...Arklatex/Lower Mississippi Valley... An upper-level trough will move into the southern High Plains today as southwest mid-level flow remains in place from the southern Plains eastward into the Mississippi Valley. At the surface, a cold front will advance southeastward across eastern Texas extending northeastward into the Arklatex by afternoon. A moist airmass is forecast ahead of the front with surface dewpoints in the mid to upper 60s F. This should result in a corridor of moderate instability from east Texas into northern Louisiana by early to mid afternoon. Thunderstorms during the day should be focused along and behind the front from the Texas Hill Country into northeast Texas. This convection is forecast to expand in coverage moving across the Arklatex late this afternoon and into the lower to mid Mississippi Valley early this evening. At mid-levels, a speed max is forecast to move across the Arklatex this afternoon and evening. This will create favorable shear profiles for severe storm development. RAP and NAM forecast soundings at Shreveport maintain 0-6 km shear in the 70 to 80 kt range and have long looped hodographs. This should support supercells with the potential for a couple tornadoes late this afternoon into this evening. The most favorable area for tornadoes is forecast from east Texas northeastward to near the Mississippi River along the track of a strengthening 40 to 50 kt low-level jet. Supercells and bowing line segments should be associated with hail and damaging wind gusts. The severe threat is forecast to peak in the early evening but an isolated severe threat may linger into the late evening and overnight period. ...Southwest and East-central Texas... An upper-level trough will move across the southern High Plains as southwest mid-level flow remains in place over much of Texas. At the surface, a cold front is forecast to advance southeastward into southern parts of the southern Plains. Ahead of the front, surface dewpoints will be near 70 F resulting in a large area of moderate instability across south-central and east-central Texas. The airmass across south-central Texas is forecast to remain mostly undisturbed today as thunderstorms move away from the area. However, increasing low-level convergence late this afternoon and large-scale ascent associated with the upper-level trough will aid convective initiation along the front. Convective coverage should expand early this evening as thunderstorms move east-northeastward across the Texas Coastal Plains. RAP forecast soundings in this area at 00Z show MLCAPE values in the 2000 to 2500 J/kg range with 0-6 km shear of 50 to 60 kt. This combined with steep lapse rate should be favorable for supercells with large hail. The moist airmass along with steep low-level lapse rates will make damaging wet downbursts possible as well. ..Broyles/Leitman.. 03/28/2018 Read more



[D] [Digg] [FB] [R] [SU] [Tweet] [G]