Mesoscale Discussion 310

Issued

Apr 8, 2020, 1:46 PM CDT (18:46 UTC)

Expired

Apr 8, 2020, 3:45 PM CDT

In force

119 min

Issued by

the Storm Prediction Center

Chance of a watch

95%

The Lincoln radar (KILX), 88 km from the middle of the area, began a volume at 18:51 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.

• Severe Thunderstorm Watch 89Apr 8, 3:05 PM CDT
• Tornado Watch 90Apr 8, 4:25 PM CDT

566 
ACUS11 KWNS 081847
SWOMCD
SPC MCD 081846 
ILZ000-MOZ000-IAZ000-082045-

Mesoscale Discussion 0310
NWS Storm Prediction Center Norman OK
0146 PM CDT Wed Apr 08 2020

Areas affected...souteast IA...northeast MO...and much of western
and central IL

Concerning...Severe potential...Watch likely 

Valid 081846Z - 082045Z

Probability of Watch Issuance...95 percent

SUMMARY...Thunderstorm development is expected in the next couple of
hours near southeast IA/northeast MO/west-central IL. Very large
hail and damaging winds will be the main threat associated with
these storms.

DISCUSSION...Strong heating across southeast IA into MO/IL ahead of
a surface low and cold front has resulted in weak to moderate
destabilization this afternoon. Strong boundary layer mixing has
been noted across IL, where morning dewpoints had been in the mid
50s F, generally are now in the mid 40s to low 50s F. Further south
across MO toward southern IL, dewpoints from the low 60s to upper
50s F were being maintained. Aloft, a plume of very steep midlevel
lapse rates has continued to spread eastward across the mid-MS
Valley, with 18z regional RAOBs showing 8-9 C/km lapse rates in
place. Cumulus development near a quasi-stationary boundary from
southeast IA into IL has been increasing, while additional deepening
of midlevel CU near the MO/IA border continues. Stronger height
falls have been noted recently across SD/NE into southern MN and
western IA as a lead shortwave impulse begins to eject across the
area ahead of the main upper trough. This is expected to provide
adequate forcing for thunderstorm development in the next couple of
hours. 

Initial development is expected to be semi-discrete, higher-based
supercells. Forecast hodographs continue to indicate long, straight
hodographs with speed shear increasing with height. In conjunction
with very steep lapse rates, large hail (some greater than 2 inches
in diameter) is expected. Low level lapse rates also are steep
across the region due to ample heating and mixing. This should act
to enhance downdrafts, and damaging wind gusts also are expected. As
frontal forcing increases later this evening, and through storm
outflow interactions, upscale growth into one or more bowing
segments is expected across parts of southeast MO into central IL,
further enhancing the damaging wind threat. Given generally dry low
levels resulting in higher-based storms, at least initially, the
tornado threat is expected to be rather marginal.

..Leitman/Guyer.. 04/08/2020

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

ATTN...WFO...LOT...ILX...LSX...DVN...SGF...DMX...EAX...

LAT...LON   41029220 41159207 41289159 41359108 41259048 41128995
            40938931 40628849 40138781 39788757 39568758 39328769
            38838828 38358943 38019044 37879151 37949201 38459236
            39509241 40759227 41029220

Mesoscale Discussions in Illinois, 2020Mesoscale Discussions in Missouri, 2020Mesoscale Discussions in Iowa, 2020Every mesoscale discussion in 2020

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.