RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0233 PM CDT Fri Jul 03 2026
Valid 032000Z - 041200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
EASTERN NEBRASKA INTO WESTERN IOWA AND SOUTHERN LOWER MICHIGAN...
...SUMMARY...
A swath of damaging to severe gusts is expected across southern
Lower Michigan over the next few hours. Scattered damaging gusts are
also likely over portions of the Mid Atlantic. Otherwise, scattered
wind damage and large hail are still expected from parts of Nebraska
into Iowa today. Isolated to scattered severe storms remain possible
extending eastward from the northern/central Plains into the Midwest
and Tennessee Valley.
...20Z Update...
The main change made to this outlook was to upgrade southern Lower
MI to a Category 3/Enhanced Risk, driven by 30 percent/CIG1 wind
probabilities. A cold-pool-driven MCS, with some bowing tendencies
and a history of producing numerous measured gusts in the 60-70 mph,
is rapidly approaching southern Lower MI. KGRR inbound velocity data
shows a rear-inflow jet exists with this MCS, and surface
observations/latest mesoanalysis show a favorable environment in
place for bow-echo persistence. Surface temperatures are exceeding
90 F in spots, amid 70-75 F surface dewpoints, yielding a gradient
of 1500-3500 J/kg MLCAPE. Up to 30 kts of effective bulk shear
coincides with this buoyancy gradient, with vectors oriented normal
to the MCS leading-line orientation. Therefore, the expectation is
for a damaging wind swath to occur over southern Lower MI with the
passage of this MCS. At least scattered gusts will likely exceed 50
kts in intensity, and a few of these gusts may exceed 75 mph.
30 percent wind-driven probabilities were also added over portions
of eastern PA into far southeastern NY and NJ, where surface
temperatures are exceeding 100 F in spots ahead of a developing
multicellular cluster. While vertical wind shear is modest, the
well-mixed boundary layer is yielding low-level lapse rates well
over 8 C/km on a widespread basis, with corresponding DCAPE
approaching 1500 J/kg. As such, several of the stronger storm cores
may produce wet downbursts capable of at least tree/wire damage on a
scattered basis, and a few severe gusts are also possible.
Otherwise, the previous forecast (see below) remains on track.
..Squitieri.. 07/03/2026
.PREV DISCUSSION... /ISSUED 1100 AM CDT Fri Jul 03 2026/
...SD/NE...
Water vapor loop shows a weak shortwave trough over central WY
approaching the Black Hills region. This, along with remnant
outflow boundaries from recent convection, will aid in the
development of scattered thunderstorms over western SD/NE by
mid/late afternoon. Steep mid-level lapse rates and supercell
structures will promote the risk of very large hail in the initial
storms over the Black Hills. Activity is expected to organized into
a bowing MCS during the evening and track roughly along the NE/SD
border with a risk of severe wind and hail.
...NE/IA/Northwest MO...
Moderately strong southerly low-level winds over KS will maintain a
hot/humid air mass across southeast NE today. Thunderstorms are
expected to intensify along pre-existing outflow boundaries by late
afternoon and develop/move into IA. Large CAPE in this region
(MLCAPE > 4000 J/kg) and sufficient westerly flow aloft will pose a
risk of supercells capable of large hail and damaging winds through
the evening hours.
...IA/IL/IN/MI/OH...
A remnant outflow boundary is also tracking eastward across the MS
river into northern IL. The air mass ahead of this boundary is very
moist and unstable with dewpoints in the mid 70s and peak diurnal
CAPE values expected to exceed 3500 J/kg. Models differ on
convective evolution of storms that form in this regime, but there
is potential for an upscale-growing MCS producing a swath of wind
damage from northern IL into parts of IN/MI and northwest OH this
evening.
...NY/PA/NJ...
Hot and humid conditions are present across much of the northeast
states today, with full sunshine leading to steep low-level lapse
rates and moderate CAPE. It is unclear how many thunderstorms will
form in this region today given weak forcing. However, the
environment is conditionally favorable for damaging winds in any
convective clusters that can persist.
...TN Valley/Southern Appalachians...
A widespread moist and unstable air mass will aid in the development
of disorganized and slow-moving thunderstorms again this afternoon
and early evening. Weak winds aloft suggest chaotic storm
evolutions, but the strongest cells will pose a risk of locally
damaging winds gusts and small hail throughout the area.
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