SPC AC 271724
Day 2 Convective Outlook
NWS 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.
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 AGL 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
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