U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 260544 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1244 am CDT Monday Sep 26 2016 


Valid 261200z - 271200z 


..there is a marginal risk of severe thunderstorms across parts of the upper Ohio 
Valley and central Appalachian Mountains... 


... 
A few strong to severe thunderstorms may occur this afternoon across 
parts of the upper Ohio River valley and in the nearby Appalachians. 


..upper Ohio Valley... 
An upper-level low will move across Lake Superior today as an 
upper-level trough extending southward from the low moves across the western 
Great Lakes region and lower Ohio Valley. At the surface...a cold front 
will move eastward across the lower Great Lakes and central Appalachians 
with an axis of instability developing just ahead of the front. The 
strongest instability is forecast to develop across eastern Kentucky and WV 
where surface dewpoints should be in the middle 60 S f. In response to surface 
heating and enhanced low-level convergence...thunderstorm 
development will be likely along the front during the afternoon. Rap 
forecast soundings near the instability axis at Charleston WV for 
21z show unidirectional wind profiles with 30 to 40 knots of flow in 
the low to mid-levels. This combined with a moist layer from the surface 
to 700 mb may be enough for a couple marginally severe wind gusts 
with the stronger multicells. 


.Broyles/Cook.. 09/26/2016 


$$ 




Mesoscale Discussion


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Storm Prediction Center mesoscale discussion 251938 
inz000-wiz000-ilz000-252145- 


Mesoscale discussion 1735 
National Weather Service Storm Prediction Center Norman OK 
0238 PM CDT sun Sep 25 2016 


Areas affected...southeastern WI/northern Illinois 


Concerning...severe potential...watch unlikely 


Valid 251938z - 252145z 


Probability of watch issuance...20 percent 


Summary...an increase in showers and thunderstorms and corresponding 
uptick in severe risk is ongoing across parts of southern WI and northern Illinois. 
Ww not expected. 


Discussion...latest visible satellite and radar loops show 
convection increasing along and ahead of an advancing cold 
front...with the stronger convection indicated just ahead of the 
boundary over S central WI at this time. With the pre-frontal environment 
having heated into the 80s above modest middle-level lapse 
rates...mixed-layer cape of 500 to 1000 j/kg is indicated. This 
will continue to fuel a convective increase...as the front focuses 
large-scale ascent /occurring ahead of the advancing middle-level 
trough/. 


Latest vwps show moderate/weekly veering flow with height -- 
sufficient to support a few organized/stronger storms and or/bands 
of convection. While overall severe risk should remain limited 
isolated due to an only modestly supportive background 
environment...hail approaching 1" in diameter or a localized 
damaging gust will be possible...before storms diminish after 
sunset. 


.Goss/Hart.. 09/25/2016 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...grb...lot...ilx...mkx...dvn... 


Latitude...Lon 44448910 44718839 43938762 42288786 41128722 40608835 
40578989 41089028 42818938 44448910