Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 192356
SPC MCD 192355
Mesoscale Discussion 0521
NWS Storm Prediction Center Norman OK
0655 PM CDT Wed Apr 19 2017
Areas affected...Northern/Central Iowa
Concerning...Severe potential...Watch possible
Valid 192355Z - 200130Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorms are expected to increase in areal coverage
across much of central and northern Iowa over the next few hours.
Marginally severe hail is the primary risk with convection north of
the warm front.
DISCUSSION...Low-level warm advection should aid areal expansion of
convection across much of central and northern IA over the next few
hours. Latest surface analysis suggests the primary warm front has
advanced into southern Crawford/Carroll counties, just north of
current Tornado Watch 148. A marked increase in thunderstorm
activity has been noted along the cold front extending from
northwest IA into southeast NE. Activity north of I-80 has yet to
exhibit very large hail, possibly due to unfavorable storm mode and
significant clustering. Unless discrete supercells evolve near the
warm front it appears much of the elevated convection may struggle
to generate large hail. For these reasons will continue to monitor
for possible ww.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 41959583 43379452 43549296 43019257 41999348 41959583