LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1252 AM CDT Wed Apr 05 2023
Valid 051200Z - 061200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM LOWER MI
ACROSS THE MIDDLE/LOWER OH VALLEY INTO THE MID-SOUTH...
...SUMMARY...
Scattered severe storms posing a risk for tornadoes and large hail
are expected in a corridor across eastern Illinois through Lower
Michigan today. Additional thunderstorms accompanied by potentially
damaging wind gusts, hail, and a few tornadoes are possible from
Ohio Valley into the Lower Mississippi Valley.
...Synopsis...
Current satellite imagery shows deep upper troughing across the
western CONUS, with a strong shortwave trough moving through the
northern/central Plains. This shortwave is expected to continue
northeastward into western Ontario while maturing into a deep
mid-latitude cyclone. A large area of enhanced southwesterly flow
aloft will accompany this cyclone, stretching from the southern
Plains into the Upper Great Lakes/OH Valley.
Surface low associated with this cyclone is currently over central
IA. Expectation is for this low to progress quickly
north-northeastward into WI while occluding. An additional
triple-point low is forecast to progress more northeastward, taking
it across northern Lower MI and into northeastern Ontario. An
associated cold front, which will likely extend from southern WI
southwestward through the TX Hill Country during the early morning,
will progress eastward/southeastward. As it does, it will interact
with a broad warm sector that extends across much the MS and OH
Valleys, supporting numerous thunderstorms throughout the day.
...IL to OH and Lower MI...
Thunderstorms will likely be ongoing ahead of a composite outflow
boundary at the start of the period, which is expected to extend
from northern Lower MI southwestward into northern IL. An early
morning hail risk is possible ahead of this boundary from eastern IL
into southern Lower MI, where prefrontal storms should encounter an
environment characterized by steep mid-level lapse rates and strong
vertical shear. Some tornado risk would exist with these storms as
well, particularly if a semi-discrete mode can be realized later
into the morning when surface temperatures should be slightly
warmer. Strong low- to mid-level flow will support a damaging wind
gust potential with both the prefrontal storms and more linear
development along the composite outflow.
Some additional development is possible over this region later in
the afternoon as the primary cold front pushes through. Strong wind
fields will be in place, leading to some potential for damaging
gusts. However, only limited air-mass recovery is expected, and
mid-level temperatures will likely be relatively warm from the
preceding convection. These factors are currently expected to keep
storm coverage limited.
...Mid/Lower MS Valley...East/Southeast TX...
Large-scale forcing for ascent will become increasingly displaced
north of the region, with storm outflow becoming the primary
mechanism pushing the front eastward. Buoyancy will be greater here
than areas farther north, and shear will remain moderate. As a
result, the potential for severe thunderstorms still exists despite
the weaker large-scale forcing. Damaging gusts are the primary
severe risk, although lapse rates will be steep enough to support
hail, particularly if cell mergers result in brief updraft
intensification. Low-level shear is strong enough to support a
low-probability tornado threat as well, although the linear,
outflow-dominant storm mode will mitigate the overall potential.
...Middle/Upper TX Coast into the Lower MS Valley...
Thunderstorms are expected to develop during the evening and
overnight as modest warm-air advection occurs along the stalled
front from the middle TX Coast into the Mid-South. Steep mid-level
lapse rates may still be in place, supporting enough buoyancy for
isolated hail.
..Mosier/Thornton.. 04/05/2023
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