U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus02 kwns 271725 
Storm Prediction Center ac 271724 

Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1224 PM CDT sun may 27 2018 

Valid 281200z - 291200z 

..there is a slight risk of severe thunderstorms across parts of 
the Great Plains... 

Severe thunderstorms with isolated large hail, wind damage and 
perhaps a tornado threat are expected across parts of the Great 
Plains. A couple of brief tornadoes will also be possible in the 
southeast, in conjunction with Alberto. 

..Great Plains... 
An upper-level low will move slowly northeastward into the northern 
rockies on Monday as an upper-level ridge amplifies across the upper 
Mississippi Valley. At the surface, a trough will deepen across 
eastern Colorado as a slow moving front moves across northern parts 
of the Central Plains. Surface dewpoints to the southeast of the 
front should be in the 55 to 60 f range allowing for moderate 
destabilization across parts of the Central Plains by afternoon. 
Convection is forecast to initiate on the western edge of the 
stronger instability during the mid to late afternoon from 
east-central Colorado northward into eastern Wyoming. Thunderstorm 
development should take place as this convection moves 
east-northeastward into the central and northern High Plains during 
the late afternoon and early evening. Other thunderstorms may also 
develop further east across parts of the Dakotas and Nebraska. 

NAM and GFS forecast soundings are in reasonable agreement across 
the central and northern High Plains during the late afternoon 
showing MLCAPE values mostly in the 2000 to 3500 j/kg range across 
the moist sector. In addition, low to mid-level lapse rates are 
forecast to be quite steep exceeding 8.0 c/km in some areas. This 
combined with moderate deep-layer shear will be favorable for 
supercells with large hail. The strongest deep-layer shear is 
forecast early Monday evening over western Nebraska and northeast 
Colorado due to the influence of a strengthening low-level jet. This 
area appears to have the strongest potential for tornadoes. Model 
forecasts markedly increase convective coverage across the Central 
Plains during the mid to late evening as a shortwave trough moves 
out. As a result, the wind damage potential may increase especially 
if storms can consolidate into an organized multicell line segment. 

Further south across western Kansas into the Texas Panhandle, 700 mb 
temperatures are expected to be above 12 celsius which will 
contribute to a capping inversion. By late afternoon, increasing 
low-level convergence around a surface low in southeast Colorado 
along with a weakening cap, should allow for isolated convective 
initiation. Moderate instability and deep-layer shear combined with 
steep low to mid-level lapse rates should be favorable for isolated 
large hail and a few strong wind gusts. 

..southeast U.S. And Florida... 
the National Hurricane Center is forecasting subtropical storm 
Alberto to move across the northeast Gulf of Mexico and approach the 
coast of the Florida Panhandle around daybreak on Monday. Rainbands 
should spread northward across much of the Florida Peninsula into 
parts of Georgia and South Carolina during the day. Forecast 
soundings from central Florida northward into Georgia show speed 
shear and some directional shear in the lowest 3 km above ground level suggesting a 
tornado threat will be possible with discrete rotating storms. The 
greatest potential for tornadoes could exist from the eastern 
Florida Panhandle northward into central Georgia where the 
combination of instability and low-level shear is forecast to be the 

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

.Broyles.. 05/27/2018