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SPC MD 1540

MD 1540 CONCERNING SEVERE THUNDERSTORM WATCH 528... FOR PORTIONS EASTERN SD INTO SOUTHERN MN AND NORTHERN IA
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Mesoscale Discussion 1540
NWS Storm Prediction Center Norman OK
0740 AM CDT Sat Jul 20 2019

Areas affected...Portions eastern SD into southern MN and northern
IA

Concerning...Severe Thunderstorm Watch 528...

Valid 201240Z - 201415Z

The severe weather threat for Severe Thunderstorm Watch 528
continues.

SUMMARY...Damaging, severe wind gusts will remain possible with
storms moving from eastern South Dakota into southern Minnesota and
northern IA. Downstream watch issuance is possible (60% chance).

DISCUSSION...A long-lived convective line has produced multiple
severe and damaging wind gusts across central/eastern SD this
morning. Strong inbound velocities have been observed with this line
from the KFSD radar. A surface front lies generally southwest to
northeast from southeastern SD into southern MN and northern IA. As
this line begins to encounter greater surface-based instability, its
potential to produce damaging winds may increase. Northerly
low-level winds quickly veer to southwesterly while also
strengthening through mid levels. Resultant effective bulk shear
values of 40-55 kt will easily support continued organization within
the line this morning. A downstream Severe Thunderstorm Watch is
possible across parts of southern MN into northern IA to address
mainly the severe/damaging wind threat. 

Farther east, a band of elevated thunderstorms associated with warm
air advection centered in the 850-700 mb layer has developed over
southern MN the past couple of hours. Modestly steepened mid-level
lapse rates were observed on the 12Z sounding from MPX, with around
2250 J/kg of MUCAPE present. Even greater instability (MUCAPE up to
4000 J/kg) is being estimated by mesoanalysis feeding into the
southern flank of the ongoing band of storms. Strong effective shear
of 45-55+ kt in addition to the plentiful instability has fostered
robust updrafts embedded within the overall band. Marginally severe
hail will remain possible this morning with the strongest cores,
although predominant cluster storm mode may tend to limit a greater
hail threat.

..Gleason/Grams.. 07/20/2019

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

ATTN...WFO...ARX...MPX...DMX...FSD...ABR...

LAT...LON   43489749 43699765 44019743 44419711 44999678 44979602
            44799504 44549416 44719286 44419223 44039178 43289167
            42919186 42919294 42929497 43029643 43149701 43489749 

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