Severe Weather Threat Continues Sunday

The threat for severe weather shifts eastward for Sunday. Sure, Oklahoma City could see severe weather overnight Saturday night, but a large area from the Great Lakes to northeast Texas is under the gun for more severe weather, including a moderate risk for severe with long-track tornadoes setting up for Wisconsin into the northern parts of Illinois. Below is what the Storm Prediction Center is saying on this potentially serious severe weather outbreak.

Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
0100 am CDT Sat Apr 09 2011

Valid 101200z – 111200z

..there is a MDT risk of severe thunderstorms across parts of Iowa… Minnesota
and northwest Illinois…

..there is a slight risk of severe thunderstorms across parts of the upper to
middle-MS valley…Great Lakes…Ozarks and Southern Plains…

..tornado outbreak possible Sunday afternoon and evening across the
upper MS valley…

..upper MS valley…
An impressive upper-level trough will move into the Great Plains
Sunday as a powerful 90 to 110 knots middle-level jet ejects northeastward across
the central states. At the surface…a strong low will move northeastward into Iowa
Sunday afternoon with surface dewpoints reaching the lower to middle 60s f
south of a warm front across much of the upper Midwest. The exit
region of the jet will overspread the upper MS valley Sunday
afternoon creating strong deep layer shear profiles very favorable
for severe storms. This combined with strong instability will result
in a significant possibility for supercells and tornadoes across the
moderate risk area. An upgrade to high risk appears likely across a
portion of the upper MS valley in later outlooks.

The current thinking is that cells will first develop in northern Iowa and
southeast Minnesota and move into northern WI during the afternoon ahead of the track
of a surface low and along a warm front. Forecast soundings at 21z near
the warm front show MLCAPE values around 2000 j/kg…0-6 km shear
values near 60 knots and 0-3 storm relative helicities of 250 to 350
m2/s2. Low-level shear should increase with time as a low-level jet
strengthens and approaches from the south. This environment should
support the development of tornadic supercells with a potential for
long-track tornadoes with cells that track east-northeastward along the warm
front. Additional severe storm development should occur southward across
the warm sector from eastern Iowa northeastward into southern and central WI by early
evening. This activity should also rapidly become supercellular with
tornadoes and large hail likely with the more dominant cells. A
threat for strong tornadoes should continue through much of the
evening as a cluster of supercells moves east-northeastward across WI. Severe
storms should also develop southward into northern and western Illinois where the
stronger cells should have a tornado…wind damage and large threat
during the evening.

..Ozarks/Southern Plains…
An impressive upper-level trough will move into the Great Plains
Sunday as a well-developed 90 to 110 knots middle-level jet ejects northeastward
across the Southern Plains and Ozarks. The jet will create strong deep
layer shear profiles across much of the region as a cold front
advances southeastward. Thunderstorm development should occur late Sunday
afternoon from north central MO southwestward across northwest Arkansas into eastern OK and ecntrl Texas
along an axis of moderate instability. The shear environment should
support supercell development but the favored Mode could be
linear…forced by convergence along the cold front. Storms that
remain discrete could become supercells with a threat for isolated
large hail. Wind damage may be the favored threat with line-segments
that persist through the evening with the threat greatest from northwest Arkansas
northeastward into west-central Illinois where a 30 percent probability is located. If a
squall-line develops on the southeastern side of the middle-level jet then an
enhanced wind damage threat could exist across eastern and southern MO.

..ern Great Lakes and upper Ohio Valley…
An upper-level ridge is forecast to be located across the southern
Appalachian Mountains extending northward into the upper Ohio Valley Sunday. An
axis of moderate instability is forecast from lower Michigan southeastward across
Ohio into WV. Thunderstorm development may occur beneath the
upper-level ridge as surface temperatures warm during the day. However…a lack
of large-scale ascent should keep any convection isolated. Strong
deep layer shear and increasing low-level flow may result in a
marginal wind damage threat during the afternoon when low-level
lapse rates should be steep.


2 thoughts on “Severe Weather Threat Continues Sunday

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