Severe Weather Threatens A Large Part of the Central US for Thursday


Still shaping up to be a major severe weather outbreak for tomorrow. Storms will form on the dryline along or just west of I-35. Any storm will quickly go severe with the chances for damaging winds, destructive hail & long-track tornadoes. Here’s more from the Storm Prediction Center

Day 2 Convective Outlook
National Weather Service/Storm Prediction Center Norman OK
1226 PM CDT Wednesday Apr 13 2011

Valid 141200z – 151200z

There is a moderate risk of severe thunderstorms southeastern Kansas, eastern Oklahoma and extreme northwestern
Arkansas & southwestern Missouri.

There is a slight risk of severe thunderstorms southern-Central Plains/Ozarks/lower Missouri valley.

A significant severe weather episode is possible Thursday afternoon & evening across southeastern Kansas, eastern Oklahoma and extreme northwestern Arkansas/southwestern Missouri –this threat will include very large hail and a few damaging tornadoes…

Southern & Central Plains/Ozarks/mid Missouri valley. A vigorous shortwave trough over Colorado/New Mexico at the start of the period will quickly translate eastward and continue to amplify and evolve into a negatively tilted trough and close off in vicinity of Oklahoma/Kansas border by Thursday evening. Strong diffluent upper tropospheric flow will
overspread portions of the Central Plains/lower Missouri valley southward to the Ark/LA/Tex creating wind profiles very favorable for organized severe storms. In the low levels, a cyclone will deepen as it moves east-northeastward
from the southern High Plains towards Kansas/Missouri border by 12z Friday. Rapid mass adjustment will be ongoing across the area concurrent with boundary layer destabilization in advance of strong height falls moving towards the region. This will occur as an influx of low level moisture returns northward into the central-Southern Plains along and east of
a north-south oriented dryline forecast to be near the I-35 corridor in Oklahoma and south-central Kansas Thursday afternoon. Steep lapse rates due in part to cold middle level temperatures aloft /-16 to -20 degree c at 500 mb/ will overspread northern Oklahoma which will lead to a destabilizing warm sector from eastern Texas northward through Oklahoma/southeastern Kansas, arcing northwestwd to the north of the surface low over central Kansas.

Current indications are lower 60s degree f surface dewpoints will advect as far north as northestern Oklahoma. Strong low level convergence in vicinity of the deepening surface low over Kansas and steepening low level lapse rates should result in surface-based thunderstorm development by early afternoon in wake of warm advection storms in the morning hours across central-eastern Kansas. Severe storms are expected to develop first near the low and then southward along the dryline by middle-late afternoon in southeastern Kansas into eastern Oklahoma. A narrow tongue of middle 50s boundary layer dewpoints as far north as central Kansas and steep lapse rate profiles /yielding 500-1500 SBCAPE/ will likely result in supercells capable of large hail/damaging winds and isolated tornadoes in backed low level flow north and east of the
surface low over Kansas. Forecast soundings farther south along the dryline indicate a more volatile thermodynamic environment with moderate to strong instability developing by middle-late afternoon. Strong heating will result in MLCAPE values climbing into the 1500-3000 j/kg range as middle level lapse rates /8 degree c per km/ overspread the warm
sector. A north-south band of scattered initially discrete supercells capable of very large hail will move east off the dryline. Low level shear is forecast to increase towards evening as large clockwise curved hodographs /300-450 effective srh/ will support the possibility of strong tornadoes, in addition to very large hail/damaging winds, with the more intense supercells. This activity is forecast to continue eastward during the overnight hours into the Ozarks and Ark/LA/Tex maintaining a severe risk as the upper pv anomaly surges eastward into the Ozarks. It is likely that storms will
consolidate based on the magnitude of forcing and lead to eventual upscale growth into an mesoscale convective system. This may act to temper tornado potential some but continue the severe threat that may extend as far east as the lower MS River Valley by daybreak Friday. Farther S into northestern Texas…storm coverage is expected to remain more isolated and be delayed until the evening hours as forced ascent erodes remaining cinh. Any storms that develop will be capable of large hail/damaging winds and an isolated tornado.

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