Mesoscale Discussion 0585
NWS Storm Prediction Center Norman OK
1041 AM CDT Mon Apr 28 2025
Areas affected...far eastern SD...southwest MN...northwest IA...far
northeast NE
Concerning...Severe potential...Watch possible
Valid 281541Z - 281745Z
Probability of Watch Issuance...60 percent
SUMMARY...Isolated convection may develop over the next couple of
hours from far eastern South Dakota into southwest Minnesota,
northwest Iowa, and possibly northeast Nebraska. Large hail and
damaging gusts would be initial risk, though a tornado risk also
could increase with time/eastern extent. Area is being monitored for
possible watch issuance.
DISCUSSION...Latest visible satellite/Day Cloud Phase RGB shows
deepening cumulus developing along the surface boundary extending
southward across eastern SD into northeast NE. Ahead of this
boundary, broken cloudiness has allowed for filtered heating, and
temperatures have warmed into the upper 60s to low 70s F. Meanwhile,
a corridor of mid 60s F surface dewpoints is overspreading the
region. Latest SPC Mesoanalysis and modified RAP forecast soundings
suggest MLCIN has eroded, though warmer temperatures at 700 mb
remain, which may limit instability through the 850-700 mb layer in
the short term. Initial convection may tend to be somewhat elevated,
though could become surface-based with time and eastward extent.
Hi-Res CAMs are fairly inconsistent this morning, but generally
suggest that convection will increase ahead of the surface
low/southward trailing boundary in the next couple of hours. Given
favorable shear, with enlarged and favorable curved low-level
hodographs already in place amid moderate MLCAPE, convection could
develop rapidly once large-scale ascent increases toward
midday/early afternoon. Initial activity may favor large hail and
damaging gusts early in convective evolution, with an increasing
tornado risk with time/eastward extent. Timing for convective
initiation and initial coverage is a bit uncertain, but trends are
being monitored and a watch may need to be issued in the next 1-2
hours.
..Leitman/Hart.. 04/28/2025
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MPX...DMX...FSD...OAX...ABR...
LAT...LON 43099782 44979694 45249674 45369652 45479614 45479576
45269532 44909523 44219503 43319488 42859504 42519536
42269607 42219634 42159708 42189767 42339802 42619804
43099782
MOST PROBABLE PEAK TORNADO INTENSITY...120-150 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN
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