<pre>ACUS11 KWNS 271750
SWOMCD
Mesoscale Discussion 0831
NWS Storm Prediction Center Norman OK
1250 PM CDT Mon May 27 2019
Areas affected...portions of eastern IA...northern and central IL
and northern IN
Concerning...Severe potential...Tornado Watch likely
Valid 271750Z - 271915Z
Probability of Watch Issuance...95 percent
SUMMARY...Severe thunderstorms with a threat of tornadoes (some
potentially strong), large hail and damaging winds will increase
over the next couple of hours. Watch issuance is likely.
DISCUSSION...A warm front is rapidly lifting northward and draped
across northern IL into southern/central IN as of 17z. Dewpoints
will continue to climb into the mid and upper 60s this afternoon and
MLCAPE values will steadily increase to around 1500-2000 J/kg over
the next 2-4 hours. A shortwave trough currently migrating
east/northeast across IA/MO will provide large-scale forcing, while
a couple of MCVs from morning convection will result in more subtle
forcing across the region. Areas downstream of these MCVs as well as
along the warm front will be a focus for thunderstorm development
and organization in the next 1-2 hours from eastern IA into northern
and central IL. Additional storms are expected to develop along the
northward advancing warm front across central into northern IN. The
timing of convective initiation further east across IN is a bit more
uncertain, but severe storms are expected by 21-22z.
18z RAOB from DVN showed capping just below 850mb. With the incoming
shortwave, temperatures aloft are expected to cool and with
continued heating and moist advection, this cap is expected to
quickly erode by mid afternoon. In fact, 18z RAOB from ILX is
uncapped with steep midlevel lapse rates noted in addition to steep
low level lapse rates and a mean mixing ratio approaching 14 g/kg.
This thermodynamic environment combined with favorable vertical
shear will support supercells. The very moist boundary layer
combined with ideal low level hodographs (noted in DVN RAOB) should
lead to tornado potential supportive of at least a couple of strong
tornadoes.
A tornado watch will likely be needed by 19z across parts of far
eastern IA into northern/central IL. Uncertainty in timing further
east into IN may result in later tornado watch issuance, but expect
additional watch issuance by 21z.
..Leitman/Thompson.. 05/27/2019
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...IWX...IND...LOT...ILX...DVN...
LAT...LON 41429186 41809160 42429102 42499038 42428937 42258765
41978615 41648572 41158534 40738531 40418534 40108563
39918599 39768652 39898758 40128930 40419085 40849194
41279188 41429186 </pre>
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