Mesoscale Discussion 1693

Issued

Sep 4, 2021, 2:20 PM CDT (19:20 UTC)

Expired

Sep 4, 2021, 4:15 PM CDT

In force

115 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

Counties Carter County, MO, Dent County, MO, Iron County, MO, Madison County, MO, Reynolds County, MO, Shannon County, MO, Texas County, MO

The Springfield radar (KSGF), 163 km from the middle of the area, began a volume at 19:21 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.

039 
ACUS11 KWNS 041921
SWOMCD
SPC MCD 041920 
MOZ000-042115-

Mesoscale Discussion 1693
NWS Storm Prediction Center Norman OK
0220 PM CDT Sat Sep 04 2021

Areas affected...Parts of south central into southeastern Missouri

Concerning...Severe potential...Watch unlikely 

Valid 041920Z - 042115Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms may continue to intensify and develop into a
small organizing cluster across south central into southeastern
Missouri this afternoon, possibly accompanied by increasing
potential for strong to severe wind gusts while approaching the
Farmington, Poplar Bluff and Cape Girardeau areas through 4-6 PM
CDT.  It not clear that a severe weather watch is needed, but trends
will continue to be monitored.

DISCUSSION...There has been some recent intensification of
convection and initiation of thunderstorms to the south/southeast of
Lebanon, MO.  This appears to be occurring near the intersection of
a weak southward advancing surface front (enhanced to some degree by
convective outflow) and a zone of strengthening differential surface
heating along the southern fringe of remnant early day convective
cloud cover and rainfall.  This also appears immediately ahead of
weak mid-level troughing migrating across the lower Missouri/middle
Mississippi Valleys.

The zone of differential surface heating coincides with a corridor
of moderate deep-layer vertical shear, beneath 30-50 kt westerly
flow in the 700-500 mb layer, and extends across southern Missouri,
toward the Cape Girardeau area.  Warm advection along and to the
immediate cool side of this surface boundary will contribute to
large-scale ascent, and may support continuing upscale convective
growth through this afternoon.  

With modest southerly system-relative low-level wind fields
contributing to inflow of seasonably moist air boundary-layer air
(characterized by CAPE of 1000-2000 J/kg) from along and south of
the front, the evolution of a small increasingly organized
convective system appears possible.  Although lower/mid tropospheric
lapse rates are generally modest to weak, precipitation loading
coupled with downward momentum transfer may gradually contribute to
the risk for strong surface gusts approaching or briefly exceeding
severe limits.

..Kerr/Bunting.. 09/04/2021

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

ATTN...WFO...PAH...LSX...SGF...

LAT...LON   37379214 37979155 37698990 36929093 37009276 37379214

Mesoscale Discussions in Missouri, 2021Every mesoscale discussion in 2021

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.