- 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.