SPC MD 243

MD 0243 CONCERNING SEVERE POTENTIAL…WATCH POSSIBLE FOR CENTRAL ILLINOIS


Mesoscale Discussion 0243
NWS Storm Prediction Center Norman OK
1121 AM CDT Wed Mar 19 2025

Areas affected...central Illinois

Concerning...Severe potential...Watch possible 

Valid 191621Z - 191845Z

Probability of Watch Issuance...60 percent

SUMMARY...A gradual intensification of thunderstorm activity is
likely across parts of southeastern Iowa into west central into
central Illinois through 1-3 PM CDT.  This may include increasing
potential for a couple of tornadoes, severe hail and locally strong
surface gusts.  Trends are being monitored for the possibility of a
watch, which appears more probable across parts of central/eastern
Illinois later this afternoon.

DISCUSSION...Scattered, modest convective development has been
occurring to the east-northeast of a deep, occluding cyclone now
centered north of Kansas City.  This has been focused along a
dryline, which may continue to become better defined into early
afternoon, as the Rapid Refresh suggests that the trailing cold
front may not quite overtake it.  The leading edge of the primary
cooling at mid-levels is contributing to steepening lapse rates
along the dryline and, with a gradual moistening (surface dew points
increasing through the lower 50s) of the boundary-layer ahead of it,
appreciable further destabilization is expected.  It appears that
this may include mixed-layer CAPE increasing to 500-1000 j/kg in a
corridor from near the triple point across the southeastern Iowa
vicinity into central Illinois.

As this occurs, initially scattered, low-topped thunderstorm
development is likely to undergo a gradual intensification, beneath
an intense south-southwesterly mid/upper jet.  Low-level hodographs
remain rather modest to weak, and Rapid Refresh forecast soundings
suggest that this may not change much until later this afternoon
across parts of east central Illinois (roughly near/east of the
Bloomington and Decatur vicinities).   However, it is possible that
ambient vertical vorticity and steepening low-level lapse rates
along the dryline, near the triple point, may support potential for
at least a couple of generally brief/weak tornadoes, in addition to
severe hail and locally strong surface gusts.

..Kerr/Leitman.. 03/19/2025

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

ATTN...WFO...LOT...ILX...LSX...DVN...

LAT...LON   41469066 41088906 38938848 38998954 39438987 39639122
            40889185 41469066

StormPrep