U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 130723 


Day 3 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0223 am CDT sun Oct 13 2019 


Valid 151200z - 161200z 


..no severe thunderstorm areas forecast... 


... 
thunderstorms are expected across portions of the central and 
southern U.S. On Tuesday. Severe potential is uncertain, but could 
develop across parts of East Texas toward the lower Mississippi 
Valley. 


... 
A somewhat complex forecast is in store for Tuesday with regard to 
severe weather potential from eastern Texas toward the lower MS valley 
vicinity. A seasonally strong mid/upper shortwave trough over the 
northern plains will track eastward and deepen over the central U.S. 
Meanwhile, weak perturbations will migrate through westerly 
southern-stream flow across the southern U.S. Ahead of a weak 
mid/upper trough ejecting eastward from the southern High Plains. 
These two troughs will merge over the southern U.S. By the end of 
the period. A cold front associated with a strengthening surface low 
pressure system over the upper Great Lakes/Midwest will surge 
eastward across the Southern Plains and mid-MS valley through the 
evening, and become oriented from lower Michigan to the Tennessee Valley 
southwestward to the Upper Texas coast by Wednesday morning. 


Strong warm advection will occur ahead of the cold front from the 
Southern Plains to the deep south, with a warm front lifting as far 
north as northern Alabama/Georgia Tuesday night. Deep southerly boundary-layer 
flow beneath strong mid/upper level westerlies will produce 
effective shear values capable of sustaining strong to severe 
thunderstorms. However, instability will generally be weak due to 
abundant cloud cover, and lapse rates will remain poor. 
Additionally, thunderstorms will likely be ongoing Tuesday morning 
along/north of the warm front due to this strong warm advection 
regime. This may overall preclude severe convective development 
through peak heating across much of the southern U.S. In favor of 
mainly heavy, training rainfall. 


There may be a greater opportunity for isolated strong/severe storms 
during the late afternoon/evening across the arklatex/East Texas/Sabine 
valley vicinity where some guidance suggests stronger heating will 
occur and more favorable instability may align with favorable shear 
ahead of the southeastward-surging cold front. Other guidance shows 
a less favorable scenario with convection become undercut by the 
fast-moving front. As such, uncertainty remains too high to include 
severe probabilities at this time, but may become necessary in 
subsequent outlooks depending on guidance trends. 


.Leitman.. 10/13/2019 


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