U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 280559 
Storm Prediction Center ac 280558 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1258 am CDT Fri Apr 28 2017 

Valid 291200z - 301200z 

..there is an enhanced risk of severe thunderstorms from central 
Texas northeast to the Ozarks... 

..there is a slight risk of severe thunderstorms from the Texas 
Hill country northeast to parts of the Ohio Valley... 

..there is a marginal risk of severe thunderstorms from south Texas 
to parts of the mid-Atlantic... 

Severe thunderstorms are expected from parts of central Texas 
northeastward to portions of the Ohio Valley Saturday into Saturday 
night. These storms will be capable of large hail, damaging winds, 
and perhaps a few tornadoes. 

A mid-level trough across the western US will continue to amplify on 
Saturday, as an impulse rotates around its periphery from the lower 
Colorado valley towards the Rio Grande. In response, downstream 
ridging will amplify over parts of the mid-Atlantic and Ohio Valley. 

..Southern Plains to the Ozarks... 
Convection is forecast to be ongoing from portions of the Southern 
Plains northeastward to the Midwest at the beginning of the period, 
maintaining a considerable amount of uncertainty with this forecast. 
Nonetheless, a cold front is expected to extend south/southwestward 
from parts of western/central Oklahoma to west-central Texas, where 
it will intersect a dryline extending farther south. Farther north, 
a frontal boundary will stretch from northern Oklahoma northeastward 
towards the mid Mississippi Valley. Convection during the first half 
of the day near/north of this boundary may pose a threat for large 
hail and some strong/damaging gusts. 

As the cold front accelerates eastward later in the day, convection 
is expected re-develop/intensify from central Texas northeastward 
into the Ozarks by late afternoon into the evening. Ample 
surface-based buoyancy and strong south/southwesterly mid-level flow 
should favor large hail and damaging winds initially, with an 
eventual transition to primarily damaging winds as storms grow 
upscale. The extent of the tornado threat remains unclear, as linear 
forcing may preclude a greater threat. However, strong low-level 
shear may favor occasional line-embedded circulations through the 
night. Additionally, more discrete development ahead of the front 
would pose a larger threat; however, capping around 700-800mb may 
keep any stronger storms sparse in coverage until the front arrives 
during the evening/overnight. 

..mid Mississippi and Ohio valleys... 
A front will stretch from the mid Mississippi Valley eastward to 
parts of Pennsylvania through the period. Similar to points farther 
southwest, convection will likely be ongoing Saturday morning, in 
turn affecting the location of the front. Along and north of this 
boundary, strong effective shear and modestly steep mid-level lapse 
rates will likely support a threat for large hail. Through the day 
farther south, warm/moist advection and pockets of modest heating 
are forecast to support sufficient destabilization of the warm 
sector. While the predictability/timing of forcing mechanisms 
remains challenging at this range, the potential exists for one or 
more rounds of storms to develop within the warm sector near/just 
south of the front during the morning/afternoon hours. As these 
storms spread east from the mid Mississippi Valley towards Indiana 
through the day, an attendant threat for damaging winds and perhaps 
a couple of tornadoes is forecast. 

.Picca.. 04/28/2017