ACUS11 KWNS 122006
SWOMCD
SPC MCD 122005=20
INZ000-ILZ000-WIZ000-122130-
Mesoscale Discussion 1506
NWS Storm Prediction Center Norman OK
0305 PM CDT Wed Jul 12 2023
Areas affected...Northern Illinois and far southern Wisconsin
Concerning...Severe potential...Tornado Watch likely=20
Valid 122005Z - 122130Z
Probability of Watch Issuance...95 percent
SUMMARY...A tornado watch is likely across northern Illinois and
possibly southern Wisconsin by 21Z.
DISCUSSION...The air mass is recovering rapidly across northern
Illinois in the wake of the morning MCS. An EML, advecting eastward
amid 40-50 knots of mid-level flow has cleared out cloud cover and
allowed for surface heating across eastern Iowa and northwest
Illinois. Temperatures in this area have warmed into the low 80s
with dewpoints remaining steady, or even climbing slightly, into the
low 70s. Temperatures remain in the 60s across northern Illinois,
but expect this warm front to lift quickly northeast through the
evening as a result of surface heating north of this front and
strengthening low-level flow in response to the deepening surface
cyclone across eastern Iowa.
Additional heating, combined with cooling temperatures aloft ahead
of the approaching shortwave trough should result in 1500 to 2000
J/kg MLCAPE by this evening across northern and northeast Illinois.
This instability will be co-located with a strong, veering wind
profile (sampled by the 20Z LOT VWP). Expect a similar wind profile
(featuring 200+ m2/s2 0-500m SRH) to remain along the outflow boundary/composite front through the evening. Supercells are
expected to form along this boundary as ascent increases ahead of a
digging mid-level shortwave trough and within the left-exit region
of the upper-level jet. Southerly winds ahead of the surface low
will provide sufficient low-level streamwise vorticity for a tornado
threat. However, any storms which remain along or slightly
north/east of the boundary, where more backed surface winds will be
present, should ingest much higher SRH and will pose a greater
tornado threat and even the potential for a strong tornado. In
addition, large hail and damaging wind gusts will be possible.
A tornado watch is likely by 4pm to cover this threat.
..Bentley.. 07/12/2023
...Please see
https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!9yYnkhGk3WdQwhTRXgulxwkX__Y4DCGvAaG1Bsi90GdnH_wbWZaGwtOSA1-kjmwLc-7squCFJ= mKjK_w9rwffItgZFMI$ for graphic product...
ATTN...WFO...LOT...MKX...DVN...
LAT...LON 40998855 41538984 41929004 42299010 42539006 42618930
42578790 42318761 41768749 41248754 40998855=20
=3D =3D =3D
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