Severe Storm Outlook Narrative (AC)
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ACUS11 KWNS 181129
SWOMCD
SPC MCD 181129
INZ000-ILZ000-MOZ000-181400-

Mesoscale Discussion 1768
NWS Storm Prediction Center Norman OK
0529 AM CST Sat Nov 18 2017

Areas affected...Parts of northeast MO into central IL and central
IN

Concerning...Severe potential...Watch unlikely

Valid 181129Z - 181400Z

Probability of Watch Issuance...20 percent

SUMMARY...The potential for storms producing hail will increase some
this morning across northeast Missouri through central Illinois into
central and perhaps northern Indiana.  Most of the hail should be
sub-severe, though a marginal risk does exist for a couple to exceed
1 inch in diameter.

DISCUSSION...Trends in early morning radar imagery indicated an
increase in thunderstorm development across west-central into
central IL near and just north of a warm front that was analyzed at
11Z extending to the east-northeast from a surface low in central MO
through central IL to central IN.  Forcing attendant to
strengthening deep-layer ascent with the approach of a progressive
trough moving east from the Plains today should promote a further
increase in thunderstorm development near the warm front, as the
surface low tracks east-northeast along this boundary.  Additional
forcing for ascent will be attendant to the exit region of a strong
(110-140 kt) 250-mb jet nosing into to the mid MS and lower OH
Valleys this morning to the afternoon.  10Z RAP soundings are in
good agreement with surface temperatures/dewpoints near the warm
front, and the forecast suggests the stable layer should persist
such that storms remain rooted in the 900-850 mb layer.  Steep
midlevel lapse rates atop the shallow inversion combined with
sufficient bulk shear suggest stronger storms could produce isolated
hail, with a couple exceeding 1 inch in diameter.

..Peters/Thompson.. 11/18/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...IWX...IND...LOT...ILX...LSX...DVN...EAX...

LAT...LON   39719040 39379195 39559285 39819326 40239232 40419057
            40628937 40768796 40858655 40878567 40518549 40238566
            40088732 39719040




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