U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus03 kwns 040648 
Storm Prediction Center ac 040647 

Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0147 am CDT Tuesday Aug 04 2015 

Valid 061200z - 071200z 

..there is a marginal risk of severe thunderstorms over portions of the middle south 
from eastern Arkansas to northern Alabama... 

..there is a marginal risk of severe thunderstorms over portions of the northern plains 
from eastern South Dakota into MN/IA... 

Isolated strong thunderstorms will be most likely from portions of 
Lower-Middle Mississippi River valley east to the central 
Appalachians and middle-Atlantic on Thursday. Another area with the 
likelihood for isolated strong storms will be across the northern 
plains and upper Mississippi Valley. 

Westerly/northwesterly midlevel flow at or below 40kt will exist from the northern High Plains 
east-southeastward across the middle MS valley and east to middle-Atlantic coast. A 
few disturbances are forecast to be embedded within this belt of 
weak to modest flow. The strongest of these will be a shortwave 
trough ejecting east across Montana during the day. Downstream from this 
stronger impulse...an elongated shortwave trough...partly resulting 
from a number of mesoscale convective vortex mergers...will move east across the central to 
northern plains from Thursday afternoon through Friday morning. Another 
mesoscale convective vortex/shortwave impulse over the middle/lower MS valley will spread east 
to the Tennessee Valley during the day. Generally weak forcing for ascent 
with these disturbances will combine with diurnal destabilization to 
promote strong to isolated severe weather during Thursday afternoon 
and evening. 

..mid south... 
Expect strong destabilization to occur along the southwestern flank of 
decaying mesoscale convective system from eastern Arkansas to adjacent areas of northern MS during the 
morning/early afternoon. Strong capping persisting across these 
areas may prohibit more widespread storm development. However... 
degree of instability in the presence of persistent and focused low 
level convergence...in combination with modest to locally strong 
speed/directional shear...suggest at least a marginal and 
conditional risk of severe storms. 

..nrn/Central Plains... 
Warm advection and increasing deep-layer forcing for ascent will 
develop across these areas through the period as a leading/weak 
shortwave trough moves east and is quickly followed by a stronger 
impulse spreading east from Montana through Thursday night. Strong 
destabilization should occur on the flank of residual mesoscale convective system 
outflow/developing warm front from eastern South Dakota into Minnesota during the day. 
Lift across the region will then increase into the evening as the 
next system moves east and height falls induce surface wave 
development on the front across eastern South Dakota. Severe weather risk should 
evolve and persist into the evening given the developing surface low 
and strengthening flow/shear across the region. 

.Carbin.. 08/04/2015