Another Severe Weather Day on Tap for the South

It’s going to be another day for a severe weather outbreak. I hope we don’t hear about another tragic scene like in Tushka, OK. So far with that 2 people have died with over 25 injuries reported, numerous buildings destroyed including a school where students are concerned that they won’t graduate on time due to the tornado.

Let’s hope for a better day today. Here is the latest on the severe weather. It’s already been active with numerous severe weather warnings and reports during the overnight.

Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0756 am CDT Friday Apr 15 2011

Valid 151300z – 161200z

There is a moderate risk of severe thunderstorms over parts of Alabama and Mississippi.

There is a slight risk of severe thunderstorms surrounding the moderate risk area…from the central Gulf Coast into the middle Mississippi and lower Ohio valleys…

Potent central Kansas upper low expected to move slowly east into central Missouri this evening before continuing east into central/northern Illinois early Saturday. As this occurs…band of 75+ knots 500 mb flow on the south side of system expected to
spread east across the lower Mississippi valley later today…and northeast across the Tennessee Valley/southern Appalachians early Saturday.

At the surface…strong low now centered near ktop should move north-northeast to near kmke by 12z Sat as associated cold front sweeps east across the Ozarks and middle/lower MS valley later today…and east-northeast across the Ohio and Tennessee
valleys early Saturday. Ahead of the front…a NE-SW squall line that evolved from storms over OK and Arkansas yesterday will be accompanied by a significant outflow boundary that should become quasistationary from la northeastward into central Mississippi/Alabama by afternoon. At the same time…a weak front marking the leading edge of relatively rich return flow will advance
east-northeast across MS this morning…across Alabama later today…and into Georgia tonight/early Sat.

Southeastern states: Southerly flow ahead of cold front and decelerating squall line outflow boundary will allow increasingly rich /pw at or above 1.25 inches/ moisture to spread northward across the central Gulf CST region. Coupled with modest daytime heating…this should yield moderate instability with MLCAPE of 1500-2000 j/kg likely by afternoon from eastern Louisiana and central/southern Mississippi and Alabama.

Ongoing squall line now in northern/western Mississippi should continue generally east-northeastward through midday. The northern part may somewhat weaken and become slightly elevated upon encountering partly modified polar air in northern Alabama. But storms in the southern part may intensify and become somewhat more discrete as they encounter destabilizing boundary layer over
eastern Louisiana and central/southern Mississippi. Additional storms may form ahead of this activity in moistening warm sector eastward into Alabama.

While the strongest low-level flow is still expected to shift northward into the Tennessee and Ohio valleys today ahead of Kansas/Missouri upper low…ample /40-50 knots/ confluent low-level flow will remain/over MS/Alabama to maintain long…hooked hodographs…especially as stronger middle/upper level flow overspreads region a toward midday. Potential will therefore exist
for supercells and broken line segments/lewps posing a threat for tornadoes…damaging wind…and hail. One or two of the tornadoes could be strong and long-lived given the likelihood that one or two discrete storms will evolve in the moisture-rich/strongly-sheared environment over parts of Mississippi and Alabama. The severe threat likely will persist…albeit in a somewhat diminished form…through early Saturday as the band of confluent low-level flow and moisture return progresses east into Georgia and the western Carolinas.

Tennessee into the middle Mississippi and Ohio valleys: Partial clearing should spread northeastward from across eastern Missouri and eastern Arkansas into parts of Illinois…western Kentucky…and western Tennessee in wake of overnight squall line.
Daytime heating and middle-level cooling /500 mb temperatures at or below minus 15c/ atop low-level moist axis /with upper 50s to low 60s f dewpoints/ should yield a relatively narrow corridor of moderate instability…with MLCAPE at or above 1000 j/kg.

Forcing for ascent associated with upper vorticity now over northeastern Oklahoma will overspread region around time of maximum heating. This should foster storm development along and perhaps ahead of eastward-moving cold front from far eastern Missouri/northeast Arkansas into western Tennessee…western Kentucky and southern/central Illinois by afternoon. Ample deep south-southwesterly shear will exist for supercells…with profiles expected to be most favorable for broken line segments. Embedded supercells could yield large hail in addition to tornadoes. The storms should move east across parts of the Tennessee and Ohio valleys before weakening during the evening.


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