- Day Three
acus03 kwns 180732
Storm Prediction Center ac 180731
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0231 am CDT Thursday Sep 18 2014
Valid 201200z - 211200z
..no severe thunderstorm areas forecast...
thunderstorm development is expected on Saturday from the
intermountain west eastward to the Great Plains and northeastward to
the Great Lakes region. Some marginally severe wind gusts and hail
will be possible with the stronger thunderstorms from the Central
Plains northeastward to lower Michigan. Other storms are expected to
develop across parts of the Gulf Coast states and along southern
parts of the Atlantic Seaboard.
..cntrl plains/middle to upper MS valley/Great Lakes...
A low-amplitude upper-level trough is forecast to amplify across the
upper MS valley on Saturday as a shortwave trough moves into the
base of the larger-scale trough. At the surface...a cold front is
forecast to advance southeastward across the Central Plains and upper MS
valley. Ahead of the front...surface dewpoints should be in the middle to
upper 60s f and moderate instability should be in place by late
afternoon. Surface heating and increasing low-level convergence along
the front should result in thunderstorm initiation by late
Forecast soundings at 00z/Sunday for Chicago Illinois and Alpena Michigan show
0-6 shear of 45 to 50 knots and steep low-level lapse rates.
However...model forecasts are in disagreement concerning the amount
of instability that will be present. If moderate instability can
develop as some models suggest...then a wind damage and hail threat
would be possible late Saturday afternoon. Further to the southwest
from NE Kansas into southeast Iowa...deep-layer shear is forecast to be less than
in the Great Lakes region. In spite of this...stronger instability
and higher surface dewpoints could help compensate for the weakness in
shear...making a marginal wind damage threat possible as well.