U.S. Severe Weather Forecast (Convective Outlook)

Today
Tomorrow
Day Three

000 
acus02 kwns 210558 
swody2 
Storm Prediction Center ac 210557 


Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1257 am CDT Tue may 21 2019 


Valid 221200z - 231200z 


..there is a slight risk of severe thunderstorms over a portion of 
the Central Plains and middle Mississippi Valley... 


... 
Thunderstorms capable of mainly large hail are possible Wednesday 
night into early Thursday morning from the Central Plains into the 
middle Mississippi Valley and possibly the southern High Plains. A 
few strong storms with gusty winds and hail will also be possible 
over a portion of the Ohio Valley. 


... 


In wake of a significant shortwave trough lifting northward through 
the northern plains and upper MS valley, an upper ridge over the 
southeast U.S. Will build northwestward into the plains Wednesday. 
Farther upstream an upper trough will amplify across Southern California 
into the Great Basin region. Surface low attending the northern 
stream shortwave trough will occlude over the northern plains and 
further weaken as it moves into the upper MS valley. Trailing front 
will extend south into eastern NE and Kansas then southwestward into the 
southern High Plains. A warm front will extend southeast from the 
low into the Ohio Valley and reach the southern Great Lakes Wednesday 
night. Dryline will retreat through western Texas during the afternoon 
and evening. 


..Kansas through northern Missouri... 


Richer low-level moisture with low-mid 60s f dewpoints will return 
through the pre-frontal warm sector, contributing to moderate 
instability (2000-2500 j/kg mucape) in frontal zone by early 
evening. With building upper ridge and presence of a cap, surface 
based storm initiation still appears unlikely. The most probable 
scenario is for storms to develop during the evening within zone of 
increasing isentropic ascent north of the front associated with a 
strengthening low-level jet. These storms will likely be elevated, 
but effective bulk shear will support potential for updraft 
rotation, and the thermodynamic environment with up to 2500 j/kg 
MUCAPE and 7 c/km mid-level lapse rates should promote some risk for 
large hail. 


..southern High Plains... 


Mid-upper 60s f dewpoints will advect rapidly northwestward through 
the Southern Plains warm sector beneath modest mid-level lapse 
rates, contributing to moderate to strong instability (2000-3000 
j/kg mlcape) during the afternoon. However, significant height rises 
associated with a building upper ridge along with limited forcing 
for ascent should limit thunderstorm development over this region 
most of the period. The dryline will retreat westward with limited 
convergence. While the parameter space will favor severe storms with 
strong instability and 45-50 kt effective bulk shear, confidence is 
low that storms will initiate during the afternoon. Overnight a 
speed Max is forecast to rotate through the base of the upper trough 
and approach the southern High Plains late. Forcing for ascent with 
this feature and the strengthening low-level jet might become 
sufficient for thunderstorm initiation very late from eastern nm 
into West Texas. However, greater confidence exists that initiation 
will wait until after 12z. Given the conditional nature of the 
threat in this region will maintain low severe probabilities this 
update. 


..Ohio Valley... 


Warm front will retreat northward during the day and likely extend 
from the southern Great Lakes into a portion of Ohio by mid-late 
afternoon. Low-level moisture with 60s dewpoints will return through 
the warm sector resulting in moderate instability, and effective 
shear from 40-45 kt will remain sufficient for a few organized 
storms. However, subsidence associated with building upper ridge 
will result in poor mid-level lapse rates. A few storms may develop 
in vicinity of the warm front during the afternoon and pose some 
risk for gusty winds and hail, but overall threat should remain 
marginal. 


..maximum risk by hazard... 
Tornado: 2% - marginal 
wind: 5% - marginal 
hail: 15% - slight 


.Dial.. 05/21/2019 


$$