Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 210611
SWOMCD
SPC MCD 210611
INZ000-ILZ000-210745-

Mesoscale Discussion 1375
NWS Storm Prediction Center Norman OK
0111 AM CDT Fri Jul 21 2017

Areas affected...northern IL/IN

Concerning...Severe potential...Watch unlikely

Valid 210611Z - 210745Z

Probability of Watch Issuance...5 percent

SUMMARY...Marginal wind/hail threat will persist for the next couple
of hours across northern IL/IN, but ww is unlikely.

DISCUSSION...Multicell clusters, with radar signatures suggesting
isolated wind damage potential, will persist for the next few hours
while moving along a stalled front from northern IL into northern
IN.  The convection will propagate along the buoyancy gradient
coincident with the front, and the stronger storms may favor the
immediate cool side of the boundary where a weak near-surface
easterly wind component will augment storm inflow.  Background
midlevel flow is roughly 30 kt from the west-northwest and there is
some support for strong downdrafts (i.e., DCAPE at or above 1000
J/kg).  Thus, isolated strong/damaging gusts could occur, but the
overall disorganized nature of the convection will tend to limit any
persistent threat for damaging winds.  The strongest updrafts may
produced some hail, but that threat will likewise be limited by
modest vertical shear and an environment marginal for supercells.

..Thompson/Edwards.. 07/21/2017

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

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

LAT...LON   40328783 40468862 40618923 40728975 40939015 41209004
            41358966 41548925 41598829 41438708 41318634 41178588
            40748557 40448580 40258602 40268699 40328783




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