SPC AC 260600
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Fri May 26 2017
Valid 271200Z - 281200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN AND CENTRAL PLAINS EAST-NORTHEASTWARD INTO THE MID
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
ENHANCED RISK AREA ACROSS PARTS OF THE SOUTHERN AND CENTRAL PLAINS
EAST-NORTHEASTWARD INTO THE MID MISSISSIPPI VALLEY...CENTRAL
APPALACHIAN MOUNTAINS AND MID-ATLANTIC...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OUTSIDE OF THE
SLIGHT RISK AREA FROM PARTS OF THE OUTSIDE OF THE ENHANCED RISK AREA
ACROSS PARTS OF THE SOUTHERN AND CENTRAL PLAINS EAST-NORTHEASTWARD
INTO THE MID MISSISSIPPI VALLEY...CENTRAL APPALACHIAN MOUNTAINS AND
Widespread severe thunderstorms with wind damage, large hail and a
few tornadoes are expected Saturday and Saturday night from parts of
the southern and central Plains east-northeastward into the mid
Mississippi Valley and Mid-Atlantic.
...Southern and Central Plains/Mid Mississippi Valley...
An upper-level trough is forecast to move east-southeastward across
the northern Plains and central Rockies on Saturday as
west-southwesterly flow remains located across the southern and
central Plains east-northeastward into the mid Mississippi Valley.
At the surface, a cold front is forecast to advance southeastward
across the central Plains and southern High Plains. A very moist and
unstable airmass should be in place Saturday from eastern parts of
the southern Plains northeastward into the mid Mississippi Valley.
Surface dewpoints are forecast to be in the lower to mid 70s F
across much of this corridor contributing to moderate to strong
instability by afternoon. Deterministic and high-res solutions
suggest that a complex of thunderstorms will first develop across
the central Plains around midday with this complex growing in size
and moving east-southeastward into the mid Mississippi Valley during
the afternoon. The development of a linear MCS will be possible by
early evening across the enhanced risk area.
GFS forecast soundings on Saturday along the northern edge of the
strongest instability from southeast Kansas into southern Missouri
show a capping inversion in place for much of the day. This cap is
forecast to weaken by late afternoon. Forecast soundings also show
an impressive thermodynamic environment with MLCAPE values around
4000 J/kg across much of northeast Texas, eastern Oklahoma and
southern Missouri. In addition, 40 to 50 kt of 0-6 km shear is
forecast along this corridor suggesting thunderstorms will have no
problem organizing. The main question is what mode will be favored.
Some high-res solutions show two bowing line segments moving
east-southeastward across the enhanced risk area. This would be more
favorable for a wind-damage threat. If the storms can form into
clusters instead of lines, then supercells with large hail and
isolated wind damage will be favored. Hailstones of greater than 2
inches in diameter will be possible with supercells mainly from
southwest Missouri into northeast Texas. A tornado threat should
occur across parts of the region especially as low-level flow
strengthens across the region. The severe threat should be more
isolated with southwestward extent across parts of northeast and
...Ohio and Tennessee Valleys/Mid-Atlantic...
An upper-level ridge is forecast to move eastward across the Ohio
and Tennessee Valleys on Saturday as a warm front advances
northeastward into the southern Great Lakes and upper Ohio Valley.
Thunderstorms are forecast to develop along the warm front with this
convection moving east-southeastward across the region during the
afternoon. Forecast soundings at 21Z on Saturday along and to the
south of the warm front in eastern Kentucky, southern Ohio and West
Virginia show moderate instability with MLCAPE values of 1000 to
2000 J/kg, 0-6 km shear values around 30 kts and steep low-level
lapse rates. This environment should support a wind-damage threat
with multicell line segments that can become organized. Hail will
also be possible with the stronger updrafts.
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