Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 242007
SPC MCD 242007
Mesoscale Discussion 0204
NWS Storm Prediction Center Norman OK
0207 PM CST Fri Feb 24 2017
Areas affected...Far eastern Illinois...much of Indiana...southern
Lower Michigan...northwest Ohio
Concerning...Severe potential...Watch possible
Valid 242007Z - 242230Z
Probability of Watch Issuance...60 percent
SUMMARY...Scattered thunderstorms are likely to develop ahead of a
developing low and cold front from near the Illinois/Indiana border
into southern Lower Michigan where a warm front may also focus
development. Storms may eventually affect western Ohio. Hail, wind,
and an isolated tornado are all possible.
DISCUSSION...A pre-frontal line of midlevel convection continues to
move across Indiana and into southeastern Lower Michigan creating
widespread clouds which is hampering destabilization. The northern
end of this line is now interacting with the warm front over
southeastern Lower Michigan, where damaging winds, hail, and perhaps
a brief tornado could occur around the Detroit area. For more
information on this area see MCD 203.
To the west, a cold front continues eastward across eastern
Illinois, with a surface low near southern Lake Michigan as of 20Z.
Ahead of this front, only a narrow zone of mid 50s dewpoints exists,
resulting in around 500 j/kg MUCAPE. Also noted in recent surface
analyses are veering winds, which is reducing low-level shear.
With time, scattered storms are likely to form along the front, and
also near the surface low which will track from northwest Indiana
across southern Lower Michigan. The warm frontal portion of the
threat area will have the greatest conditional tornado threat with
enhanced low-level shear and effective SRH around 200 m2/s2.
However, only elevated hail is likely north of the warm front. To
the south, strong mixing over the warm sector as a whole combined
with the veering winds and a capping inversion suggest a somewhat
mixed storm mode, with mainly hail and wind.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 39258686 38868772 38918809 39258829 39878794 40448769
41158755 41608713 42208612 42608460 42638404 42408385
41918382 41458396 40678503 39258686