Moderate Risk of Severe Weather in the Upper Midwest Sunday

The Storm Prediction Center is making a bold statement by issuing a moderate risk of severe weather over four states in the Upper Midwest on Sunday. Here is the latest information from the Storm Prediction Center concerning this potential outbreak.

Day 3 convective outlook corr 1
National Weather Service Storm Prediction Center Norman OK
0246 am CDT Friday Apr 08 2011

Valid 101200z – 111200z

..there is a MDT risk of severe thunderstorms across parts of southeast
Minnesota…WI…ecntrl Iowa…northwest Illinois and far NE MO…

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

Corrected to extend MDT risk area further into southeast Minnesota and northern Iowa to
match probabilities

..upper MS valley/western Great Lakes…
An impressive upper-level trough is forecast to move into the Central
Plains Sunday with an upper-level low closing off over the northern
plains. Ahead of the system…a powerful 55 to 70 knots jet will
transport low-level moisture quickly northward into the upper MS valley
where surface dewpoints should reach the lower to middle 60s f. This should
allow moderate instability to develop across much of the upper
Midwest by Sunday afternoon where numerous thunderstorms appear
likely to develop as large-scale ascent increases during the
afternoon. Thunderstorms should first develop during the afternoon
along a warm front across Iowa…WI and southern Minnesota with additional
convection initiating along the cold front during the early evening
extending southward into northwest MO. This is expected as the exit region of the
an impressive 80 to 100 knots middle-level jet spreads across the
upper-Midwest creating strong deep layer shear and very favorable
conditions for severe storms. This combined with strong low-level
shear profiles should be favorable for supercells and tornadoes
especially in eastern Iowa…northwest Illinois…southeast Minnesota and SW WI where a moderate risk
has been placed. A few strong tornadoes could occur either near the
warm front in the afternoon or along the cold front as the low-level
jet strengthens during the early evening.

At this point…the models appear to be in good agreement concerning
the timing and strength of the system. Although this is the
case…am expecting the upper-level trough to be a bit slower into
the plains so have nudged the moderate risk a bit southwestward to account
for this.

..srn and Central Plains…
An impressive upper-level trough will move into the Great Plains
Sunday. Thunderstorm development will be probable ahead of the
trough along a cold front from eastern Kansas southward into eastern OK and ecntrl Texas
where moderate instability and strong deep layer shear is forecast.
Due the potential for supercell development…an enhanced threat for
tornadoes…large hail and wind damage could occur during the early
evening from west-central MO southward into northwest Arkansas and NE OK. The threat should
be more isolated in southeast OK and ecntrl Texas but the environment should
still support hail and wind damage.

..upper Ohio Valley and central Appalachian Mountains…
Isolated thunderstorm development also may occur just to the east of
an upper-level ridge in the upper Ohio Valley and central Appalachian
Mountains in this region…models forecast an axis of moderate
instability with enough deep layer shear for a marginal severe
threat mainly Sunday afternoon.

.Broyles.. 04/08/2011


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