Alert archive / Illinois / Mesoscale Discussions in 2018

Mesoscale Discussion 1663

November 25, 20188 counties in Illinois; 5 counties in Missouri

The Storm Prediction Center issued this mesoscale discussion at Nov 25, 2018, 4:36 PM CST for 8 counties in Illinois; 5 counties in Missouri. It was in force for 84 min.

The area

The outline as issued.

The facts

Issued: Nov 25, 2018, 4:36 PM CST (22:36 UTC)
Expired: Nov 25, 2018, 6:00 PM CST
In force: 84 min
Issued by: the Storm Prediction Center
Chance of a watch: 5%

Counties Calhoun County, IL, Greene County, IL, Jersey County, IL, Macoupin County, IL, Madison County, IL, Montgomery County, IL, Morgan County, IL, Scott County, IL, City of Saint Louis, MO, Lincoln County, MO, Pike County, MO, Saint Charles County, MO, Saint Louis County, MO

The radar

The St Louis radar (KLSX), 46 km from the middle of the area, began a volume at 22:39 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Lincoln, IL (KILX), launched 12:00Z, 10.6 hours before the alert went out and 199 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1517 m above ground
0-6 km bulk shear: 59 kt
0-1 km storm-relative helicity: 166 m²/s²
0-3 km storm-relative helicity: 409 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

810 
ACUS11 KWNS 252236
SWOMCD
SPC MCD 252236 
ILZ000-MOZ000-260000-

Mesoscale Discussion 1663
NWS Storm Prediction Center Norman OK
0436 PM CST Sun Nov 25 2018

Areas affected...east-central MO into west-central IL

Concerning...Severe potential...Watch unlikely 

Valid 252236Z - 260000Z

Probability of Watch Issuance...5 percent

SUMMARY...A line of strong storms near St. Louis will continue to
quickly shift northeast late this afternoon. Strong surface winds
and small hail will be possible with the storms for the next few
hours as they track into west-central IL.

DISCUSSION...A line of strong thunderstorms near STL will continue
to quickly lift northeast late this afternoon. Instability is
limited across the region, generally less than 250 J/kg MLCAPE.
However, strong forcing for ascent along the cold front and beneath
the exit region of the midlevel jet streak, coupled with strong
vertical shear and low level winds approaching 40kt just off the
surface, will allow for some strong surface gusts. Additionally,
midlevel lapse rates between 6.5-7 C/km will be sufficient for small
hail, which has already been reported west of STL. While conditions
are not overly favorable for tornadoes, backed low level flow ahead
of the line of convection and 0-1km SRH greater than 150 m2/s2
cannot be ignored and a brief/weak spin-up is possible. These storms
are expected to continue for a few more hours into west-central IL.

..Leitman/Hart.. 11/25/2018

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

ATTN...WFO...ILX...LSX...

LAT...LON   39219142 39639062 39779026 39778982 39528943 39198939
            38948955 38718981 38409040 38279072 38519093 38869123
            39059143 39219142

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 25, 11:54 AM CST	Mesoscale Discussion	SPC	Boone, Bureau, Carroll, Cook, DeKalb, DuPage and 10 more	6 hr
Nov 25, 3:57 PM CST	Mesoscale Discussion	SPC	Adams, Brown, Cass, Fulton, Hancock, Henderson and 12 more	4 hr
Nov 25, 3:54 AM CST	Mesoscale Discussion	SPC	Andrew, Atchison, Buchanan, Gentry, Harrison, Holt and 2 more	6 hr
Nov 25, 10:59 AM CST	Mesoscale Discussion	SPC	Adair, Andrew, Atchison, Buchanan, Caldwell, Carroll and 25 more	5 hr

Nearby

Mesoscale Discussions in Illinois, 2018 Mesoscale Discussions in Missouri, 2018 Every mesoscale discussion in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.