Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0750 AM CDT Sun May 17 2026

Valid 171300Z - 181200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS AND MID MISSOURI VALLEY...

...SUMMARY...
Severe thunderstorms are expected this afternoon into tonight across
parts of the southern/central Plains to the Upper Midwest.
Supercells with very large hail and strong tornadoes are possible
initially this afternoon, before one or more bowing clusters leads
to a greater threat for severe/damaging winds this evening.

...Synopsis...
Large-scale upper troughing over the western CONUS should further
amplify today as an embedded mid-level jet and associated shortwave
trough move from the West Coast to the Four Corners region through
the period. A broad zone of around 40-50 kt southwesterly mid-level
flow will persist today from the southern/central High Plains to the
Upper Midwest, with multiple small-scale perturbations forecast to
advance northeastward across these regions. At the surface, a low
over western KS this morning is expected to gradually develop
northeastward towards the KS/NE border vicinity this evening. A
dryline trailing from this low will mix eastward through late
afternoon peak heating across the southern/central High Plains. A
warm front will attempt to lift northward today across NE/IA into
southeast SD and parts of southern MN, while a cold front is
forecast to gradually advance southeastward across the
northern/central Plains through the period.

...Southern/Central Plains into the Upper Midwest...
Initial thunderstorm development appears likely across eastern CO
this afternoon in a low-level upslope flow regime. This activity
will likely become supercellular and capable of producing large to
very large hail given the presence of steep mid-level lapse rates,
strong deep-layer shear, and moderate instability. By 20-22Z,
additional robust convection is expected to develop along/near the
cold front across north-central NE/south-central SD in a rapidly
destabilizing airmass. There is still some uncertainty with how far
north the warm front and related rich low-level moisture will reach
across the northern Plains/Upper Midwest, especially given ongoing
convection and related outflow this morning across NE/IA.

Still, an increasing large hail threat remains evident with any
convection that develops along/near the cold front this afternoon,
as ample MUCAPE and strong deep-layer shear will support organized
updrafts, including supercells initially. A strong tornado threat
will exist with any of these supercells that can become/remain
surface based, as low-level shear strengthens through the late
afternoon/early evening. A greater threat for severe/damaging winds
should develop as convection quickly grows upscale into bowing
clusters this evening. The northeastward extent of this severe wind
threat remains a bit uncertain, especially into southern/central MN
where the warm front is forecast to reach. A risk for embedded QLCS
tornadoes may continue with the surface-based portion of the
cluster.

Thunderstorm initiation farther south along the length of the
dryline appears somewhat conditional given modest large-scale
ascent. But, most guidance continues to show at least isolated
high-based convection developing by late afternoon across parts of
north-central KS southward into the eastern TX Panhandle/western OK.
Any thunderstorms which can be sustained will pose a threat for
large to very large hail and tornadoes, especially across KS where a
40-50 kt southerly low-level jet will enhance 0-1 km shear. A strong
tornado appears possible this evening with any supercell that can
persist, although there should be a tendency for upscale growth into
a severe wind producing cluster with time as the cold front
overtakes the dryline.

...Great Lakes/Lower Michigan...
Recent radar and visible satellite imagery show an MCV associated
with earlier convection across the central Plains is present over IA
this morning. This feature is forecast to track east-northeastward
today, and should approach eastern WI and Lower MI by late
afternoon/early evening. Modest enhancement to the low/mid-level
wind field should exist in close proximity to this MCV, and the
surface warm front is expected to gradually develop northward across
these regions through the day. Some intensification of convection is
possible this afternoon/evening along and near the warm front, with
sufficient instability and shear to support a mix of supercells and
multicell clusters capable of producing damaging winds, hail, and
perhaps a tornado. A Slight Risk has been added for parts of Lower
MI given increased confidence in this scenario occurring.

...Southeast...
On the western periphery of a surface high centered over the western
Atlantic, diurnally maximized thunderstorm development should focus
from the southern Appalachians across GA and the interior/western FL
Peninsula. Even though deep-layer shear will remain weak, a
favorable thermodynamic environment with steepened low-level lapse
rates should support strong to pulse-severe type convection capable
of producing isolated wind damage/downbursts and perhaps marginally
severe hail.

...Central and North Texas/ArkLaTex/Lower Mississippi Valley...
A fairly robust cap is expected to remain across the southern extent
of the warm sector today, with minimal/nebulous large-scale ascent
over the southern Plains. Still, some guidance suggests elevated
thunderstorms may develop through peak afternoon heating across
parts of northeast TX into the ArkLaTex/lower MS Valley in a
persistent low-level warm advection regime. If this occurs, then
isolated severe hail and damaging winds would be possible given the
strong MUCAPE forecast.

...Mid-Atlantic...
Mid-level ridging should build over the Mid-Atlantic through the
afternoon, which should tend to suppress most convection. However, a
weak mid-level perturbation noted in water vapor imagery this
morning over OH may support isolated convective development this
afternoon across parts of MD/PA and vicinity. The overall
environment does not appear overly favorable for organized severe
thunderstorms, but gusty winds could occur with any of the stronger
cores that may develop.

..Gleason/Marsh.. 05/17/2026