SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 PM CDT Tue Jul 30 2024
Valid 311200Z - 011200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS FAR
SOUTHEAST SD...FAR EASTERN NE...AND WESTERN IA...
...SUMMARY...
Scattered strong to severe storms are possible from the Plains to
the southern Great Lakes and the Appalachians to portions of New
England. Highest severe potential is expected across IA Wednesday
evening.
...Synopsis...
Expansive upper ridging is forecast to persist across much of the
southern CONUS on Wednesday, with modestly enhanced westerly flow
north of this ridging across the northern CONUS. Several shortwave
troughs will be embedded within this westerly flow, with the
easternmost shortwave expected to progress eastward across the
Northeast and Mid-Atlantic. Another shortwave trough, likely
enhanced by ongoing deep convection, is forecast to move across the
Upper Great Lakes and OH Valley. The most well-defined shortwave
trough in the series will likely move into the northern/central
Plains during the early afternoon, continuing into MN/IA late
Wednesday night/early Thursday morning.
General expectation is for the surface pattern Wednesday morning to
be characterized by troughing across the Plains, with several
embedded surface lows, and extensive ridging centered over the
northwest Gulf of Mexico and covering much of the Southeast. Primary
surface low attendant to the shortwave trough progressing into the
northern/central Plains is expected to begin the period over the
central NE/SD border vicinity before then tracking into the NE/SD/IA
border region by Wednesday evening. A cold front will extend
southwestward from this low, and will gradually move southeastward
as the parent low moves east.
Surface pattern east of the Plains into the Mid MS and OH Valleys
will be complicated by the evolution of preceding thunderstorm
clusters (and associated outflow) as well as by any thunderstorms
generated by these shortwave troughs. Even with this uncertainty, a
sharpening, warm-front-like boundary will likely extend from the low
over NE/SD southeastward into southern IL, with the eastern portion
over southern IL potentially modulated by ongoing storms.
...Mid MS/OH Valleys into the central/southern Appalachians
Wednesday morning through the afternoon and evening...
Showers and thunderstorms will likely be ongoing in the southeastern
IA/northern IL/northeast MO vicinity early Wednesday morning as
storms which are expected to develop across IA late Tuesday night
continue southeastward. Most likely scenario is for these storms to
gradually weaken throughout the morning as the low-level jet weakens
and the storms become increasingly displaced eastward. However,
there is a low-probability scenario where this cluster is organized
enough to maintain its intensity throughout the morning. Given the
low-probability and general forecast uncertainty, only Marginal/5%
wind probabilities will be maintained for this region with this
outlook.
Additional thunderstorm development is anticipated downstream from
the upper OH Valley into the central and southern Appalachians as
the remnants from the early morning storms move into a moist, and
diurnally destabilized airmass. Shear will be weak, with a
multicellular, pulse mode anticipated. Damaging gusts will be the
primary severe risk.
...Upper Midwest/Mid MS Valley into the central/southern Plains...
Southerly flow will continue to advect ample low-level moisture into
the warm sector ahead of the cold front associated with the
shortwave trough moving into the northern/central Plains, with low
70s dewpoints likely reaching southern MN by early Wednesday
afternoon. Robust heating amid this high low-level moisture will
support airmass destabilization and very strong buoyancy, with over
3000 J/kg of MLCAPE throughout much of the warm sector. Thunderstorm
development is expected to begin across SD and MN during the
afternoon, with the environmental conditions supporting strong to
severe storms. Large to very large hail is possible initially,
particularly across eastern SD and southern MN where buoyancy is
highest. Thunderstorm development is then expected to expand
southwestward along the front, from SD into KS (potentially even the
TX/OK Panhandles). A more outflow-dominant storm character is
anticipated with southern extend as weaker shear preclude updraft
organization.
Organization into a forward-propagating MCS appears likely Wednesday
evening, with the potential for significant-severe gusts stretching
into IA. This MCS will likely still be ongoing early Thursday
morning across IL, although the strength and organization of the MCS
at that time is uncertain. Enough buoyancy should still be in place
to support severe if the MCS remains organized.
..Mosier.. 07/30/2024
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