Violent Weather Day on Tap for Sunday

Tomorrow is shaping up for what could be a high end severe weather outbreak. Chicago, Milwaukee, Green Bay, Dubuque, just to name a few towns, could see a high risk for severe weather. The potential is there for violent, long-track tornadoes with damaging straight-line winds & destructive large hail. I would urge people in these areas to be on heightened alert.

I will be posting tornado warnings only tomorrow starting at 4 am ET. This is a very serious situation! Below is what the Storm Prediction Center is saying for tomorrow:

Day 2 convective outlook
National Weather Service Storm Prediction Center Norman OK
1233 PM CDT Sat Apr 09 2011

Valid 101200z – 111200z

..there is a MDT risk of severe thunderstorms across parts of far southeast Minnesota…eastern Iowa…northern Illinois and the southern two-thirds of Wisconsin…

..there is a slight risk of severe thunderstorms from the upper MS valley/upper Great Lakes region southwestward into northestern Texas…

…Powerful upper trough is prognosticated to continue eastward across the central third of the Continental U.S. This period…accompanied by a very strong southwesterly jet on the eastern fringe.

This trough will support surface low development across the upper Midwest…with a trailing cold front forecast to shift eastward across the plains. This front will be a focus for a widespread and potentially significant severe weather event this period.

..upper Midwest/upper MS valley/western upper Great Lakes region… Potentially-significant severe weather event — including the potential for a few strong tornadoes — appears to be unfolding for Sunday afternoon and evening.

As the large upper trough approaches…airmass will continue moistening/destabilizing with time. The boundary layer will likely remain capped through middle afternoon…but forcing along the advancing cold front — and in vicinity of the surface low/warm front across southeastern Minnesota/eastern Iowa/southern WI — should allow storms to initiate by 20-22z. Strong low-level flow beneath 80-plus knots middle-level swlys will provide shear very supportive of supercells — and thus storms will rapidly become severe as they increase and spread quickly eastward across the upper MS valley area…fueled by moderate instability. Greatest tornado threat will likely exist across eastern Iowa and into southern WI/northern Illinois…near the surface low and warm front where low-level shear will be maximized. Very large hail and damaging winds are also expected — with the damaging wind threat expected to increase with time as storms likely become more linearly organized with time.

More isolated storms will likely develop southward along the front from MO into northestern Texas. While tornado threat will not be as great…large hail and damaging winds will be possible.

Storms will shift eastward overnight — but should weaken with time with the loss of heating. Severe potential is most likely to linger across the upper Great Lakes/upper Midwest…where strongest forcing — and thus greatest cape/shear combination — is forecast.

..lower Great Lakes region…
While weaker instability is expected across western New York/western PA…afternoon convection cresting the upper ridge and crossing southern Ontario may cross the lakes and bring a limited threat for damaging winds and marginal hail to this region. Any threat should diminish during the evening with the onset of diurnal cooling.


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