Severe Weather Targets the Same Areas Today As It Did on Saturday (4/24/2011)


Severe weather looks possible in the same areas that had severe weather on Saturday. Portions of Texas, Oklahoma, Missouri, Arkansas, Illinois, Indiana, Ohio, Kentucky, Tennessee, West Virginia, Virginia, Maryland, Delaware, Pennsylvania & New Jersey could see severe weather today & tonight. Here is what the Storm Prediction Center is saying on the risk of severe weather for this afternoon & tonight.

Day 1 Convective Outlook
National Weather Service/Storm Prediction Center Norman OK
1058 AM CDT, Sun Apr 24 2011

Valid 241630z – 251200z

There is a slight risk of severe thunderstorms from central Texas across the middle MS and Ohio valleys into the Delaware-Maryland-Virginia region.

Broad cyclonic flow is present today over the western states, while a strong trough digs southeastward into the Pacific coast region. On the east side of the trough, southwest flow aloft will once again affect the central/eastern states. The primary focus for strong/severe thunderstorms will once again be along a convectively reinforced surface boundary from Texas/Oklahoma into the Middle Atlantic States.

A rather complex forecast scenario is unfolding today over this region. A large mesoscale convective system is currently affecting central/eastern Oklahoma, but is expected to drift eastward across northwest Arkansas/southern Missouri today.
In the wake of this activity, weak low level cyclogenesis is occurring over the Southern Plains. This will help to lift the
surface boundary northward into eastern Oklahoma and western/northern Arkansas by evening. Southerly low level winds are also forecast to strengthen through the evening as the western trough slowly approaches. This will result in a corridor of severe weather potential from southeast Oklahoma into southern Missouri.

Present indications are that the ongoing mesoscale convective system may reintensify later this afternoon over northeast Arkansas, spreading across the middle Mississippi Valley with a risk of damaging winds and hail. However, the
primary severe threat today should be near the surface boundary over eastern Oklahoma/western Arkansas/southwest Missouri. NAM/RUC forecast soundings for this evening show effective helicity values of 300-500 m2/s2 in this
area, along with moderate instability and steep middle level lapse rates. Conditions appear favorable for supercell thunderstorm development with a risk of very large hail, damaging winds, and a few tornadoes. The primary forecast uncertainty involves whether the storms will be surface-based. The pattern suggests that many of the storms may be on the cold side of the boundary and could be elevated, limiting the wind/tornado risk.

Ohio Valley into Middle Atlantic States: Large scale forcing mechanisms are hard to identify today east of the Mississippi River. However, several clusters of thunderstorms are ongoing this morning along the surface boundary. All model guidance suggests that a few of these clusters may intensify this afternoon with a risk of locally damaging winds. This threat will likely be modulated by the extent of local heating/destabilization. As such, the cluster moving across West Virginia may have the best potential for rejuvenation as it cross the mountains and approaches the Delaware-Maryland-Virginia region.

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