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SPC MD 1390

MD 1390 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PARTS OF SOUTHEASTERN IOWA...NORTHEASTERN MISSOURI...CENTRAL ILLINOIS AND INDIANA
MD 1390 Image


Mesoscale Discussion 1390
NWS Storm Prediction Center Norman OK
0219 PM CDT Thu Jul 29 2021

Areas affected...Parts of southeastern Iowa...northeastern
Missouri...central Illinois and Indiana

Concerning...Severe potential...Watch possible 

Valid 291919Z - 292115Z

Probability of Watch Issuance...60 percent

SUMMARY...Scattered strengthening thunderstorm development through
5-7 PM CDT may gradually pose increasing risk for locally damaging
wind gusts.  The potential for activity to consolidate into a larger
cluster that would require a severe weather watch remains uncertain,
and appears relatively low, but trends are being monitored for this
possibility.

DISCUSSION...Forcing for ascent along a stalled outflow boundary has
remained sufficient to maintain sustained modest thunderstorm
development along a corridor near the Burlington, IA through Peoria,
IL vicinities.  Associated outflow and anvil cloud cover and light
precipitation continue to impact the environment to the southeast of
this activity, but the influence may be waning with a corridor of
recent stronger surface pressure falls evident in observations
across the Springfield and Mattoon, IL vicinities.  Additionally,
scattered new thunderstorm development is underway in closer
proximity to the outflow boundary, near/north of the Interstate 74
corridor, into central Indiana.

The newer thunderstorm development coincides with a corridor
seasonably high precipitable water on the order of 2 inches, in the
presence of modest shear beneath 20-40 kt northwesterly flow around
the 500 mb level.  Gradually, with increasing inflow of a very moist
boundary layer characterized by mid/upper 70s surface dew points,
and large CAPE growing in excess of 3000-4000 J/kg with increasing
insolation, substantive further intensification appears probable
through 22-00Z.  This may include the evolution of isolated
supercells and small organizing clusters, with at least modestly
steep lower/mid tropospheric lapse rates and heavy precipitation
loading contributing to the risk for potentially damaging wind
gusts.

..Kerr/Hart.. 07/29/2021

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

ATTN...WFO...ILN...IND...LOT...ILX...LSX...DVN...DMX...EAX...

LAT...LON   40809250 40869094 40858985 40788911 40548762 39848493
            38838683 39058987 39789180 40809250 

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SPC MD 1389

MD 1389 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR SOUTHERN OH
        
MD 1389 Image

Mesoscale Discussion 1389
NWS Storm Prediction Center Norman OK
0148 PM CDT Thu Jul 29 2021

Areas affected...Southern OH

Concerning...Severe potential...Watch possible 

Valid 291848Z - 292045Z

Probability of Watch Issuance...60 percent

SUMMARY...Increasing thunderstorm coverage is anticipated this
afternoon. Environmental conditions support severe storms and trends
are being monitored for watch issuance.

DISCUSSION...Air mass across southern OH continues to destabilize
amid clear skies and strong heating. Large-scale ascent across the
region is modest, but still strong enough to initiate convection
given the lack of convective inhibition. The warm and moist
conditions in place support moderate to strong instability, and
recent mesoanalysis estimates MLCAPE over 2000 J/kg. This region is
also on the southern edge of the stronger mid-level flow, with
resulting effective bulk shear of 40 to 50 kt. Minimal forcing
should result in mostly cellular convection, with the overall
environment supporting robust updrafts capable of isolated hail and
damaging downburst winds. Storm coverage may be high enough to merit
watch issuance, and convective trends are being monitored closely.

..Mosier/Hart.. 07/29/2021

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

ATTN...WFO...PBZ...RLX...CLE...ILN...

LAT...LON   40388470 40378283 40258115 39758097 38988178 38638246
            38698327 39208468 40388470 

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