Mesoscale Discussion 239

Issued

Mar 23, 2021, 12:44 PM CDT (17:44 UTC)

Expired

Mar 23, 2021, 2:45 PM CDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Pleasant Hill radar (KEAX), 151 km from the middle of the area, began a volume at 17:44 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

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342 
ACUS11 KWNS 231745
SWOMCD
SPC MCD 231744 
MOZ000-ILZ000-IAZ000-KSZ000-NEZ000-231945-

Mesoscale Discussion 0239
NWS Storm Prediction Center Norman OK
1244 PM CDT Tue Mar 23 2021

Areas affected...Northern Missouri...southern Iowa...and far western
Illinois

Concerning...Severe potential...Watch unlikely 

Valid 231744Z - 231945Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated to scattered thunderstorm development is expected
through the afternoon hours across northern Missouri and into
portions of southern Iowa and far western Illinois. Damaging winds
and hail will be the primary threats, though a tornado threat may
evolve later this afternoon and evening.

DISCUSSION...Visible satellite trends through the late morning and
early afternoon have shown partial clearing within a mid-level dry
slot on the eastern periphery of a stacked surface/upper-level low.
This clearing has been sufficient for temperatures to warm into the
low to mid 60s ahead of a surface trough/dryline. Despite a marginal
influx of low-level moisture (dewpoints have climbed into the
low/mid 50s), recent RAP mesoanalysis suggests around 500 J/kg
MLCAPE is in place across central/northern MO. Deepening cumulus and
a few lightning strikes support this idea and indicate buoyancy is
sufficient to support at least transient updrafts. Instability
should increase to some degree into the late afternoon as
temperatures continue to warm. 

Recent analyses also reveal marginal, but sufficient, effective bulk
wind shear orthogonal to the surface trough to support discrete,
organized convection. As low-level lapse rates continue to steep via
diurnal heating, a wind and hail threat should materialize. Given
southeasterly surface flow within the narrow warm sector (per
regional VWPs), a tornado or two will be possible with the more
robust storms. Convection is most likely to develop across northern
MO into southern IL this afternoon. There is some uncertainty
regarding convective coverage further east into IL. However, this
location may see the highest tornado potential later this afternoon
and evening as an increase in the low-level jet augments effective
SRH. A watch is not anticipated at this time, but conditions will
continue to be monitored.

..Moore/Hart.. 03/23/2021

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

ATTN...WFO...ILX...LSX...DVN...SGF...DMX...EAX...OAX...TOP...

LAT...LON   38009235 38659336 39399432 39579526 40049569 40539550
            40869480 41029345 41049208 40699104 40049074 39439049
            38739024 38179082 37939162 38009235

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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.