LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0255 PM CDT Tue Jun 16 2026
Valid 162000Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
EASTERN ILLINOIS...INDIANA AND LOWER MICHIGAN THROUGH THIS EVENING
AND IOWA TONIGHT...
...SUMMARY...
Severe thunderstorms remain possible this afternoon and tonight
across multiple parts of the Midwest, as well as on a more isolated
basis across the Gulf Coast, south-central Plains and northern
Plains.
...20z Update Wisconsin and Michigan to Illinois and Indiana...
Beneath the cold core of the clipper, steep mid-level lapse rates
and weak buoyancy are supporting scattered thunderstorms. While
available MUCAPE is somewhat limited (500-750 J/kg) 500 mb temps
near -20C are supportive of marginally severe hail with the stronger
cores. This threat should end by evening as buoyancy declines with
the loss of diurnal heating. Have expanded the 5% hail across Lake
Michigan into the UP and eastern WI shores.
Southern portions of the Level 2 Slight risk were also expanded into
eastern IL where robust convection is expected along the cold front
this afternoon and evening. Hail, damaging gusts and a couple of
tornadoes remain possible.
...MT and northern Plains into the Midwest tonight...
Ahead of the strong belt of mid-level flow ahead of the upper trough
moving out of Canada, afternoon model guidance remains bullish on
several rounds of strong and occasionally severe storms late tonight
into early Wed. However, CAPE will be rather weak, which should
limit overall convective organization. Isolated severe gusts remain
possible.
The upstream convection will eventually intersect with a rapidly
moistening air mass across parts of IA and the Midwest. This will
likely result in a cluster of more robust severe storms near
daybreak across SD, IA and MN at the nose of a 50+ kt 850 mb jet.
Increasingly strong vertical shear from the upstream trough/jet will
support supercells or elevated bowing segments capable of hail and
severe wind gusts by 12z Wed. Have connected the MRGL areas over the
northern Plains into the Midwest.
...Southern and central Plains...
Strong heating along the stalled front initially over the southern
and central Plains could result in isolated to widely scattered
thunderstorms late this afternoon and early evening. Increasing
vertical shear and low-level moisture advection could favor some
risk for hail with supercells. However, warm temperatures aloft and
only modest large-scale forcing for ascent casts considerable
uncertainty on storm development/maintenance this evening. Should a
supercell or two become established, large hail and damaging gusts
would be possible before ending overnight.
..Lyons.. 06/16/2026
.PREV DISCUSSION... /ISSUED 1113 AM CDT Tue Jun 16 2026/
...IN/Lower MI...
Morning water vapor loop shows a strong and progressive Clipper
system tracking southeastward across MN/WI. A band of clouds and
isolated thunderstorms precedes this system, extending from southern
Lower MI into central IL. While a few strong storms are possible to
develop in this band, the greater risk for severe storms appears to
be associated with a period of heating in the wake of these clouds.
Steep lapse rates and cold temperatures aloft will combine with
dewpoints around 60F to result in sufficient afternoon/evening CAPE
for widely scattered strong/severe storm development. Large hail
will be the initial main concern, along with some risk of a tornado
or two. By early evening, damaging winds will be the main concern.
...IA Overnight...
The next in a series of fast-moving upper-level features will move
across the Dakotas tonight, with large-scale forcing for ascent
spreading into parts of MN/IA before 12z. This ascent will begin
interacting with a plume of returning moisture, leading to scattered
thunderstorm development in the pre-dawn hours. Elevated supercells
capable of large hail will be the main risk through 12z.
...MT/ND...
The aforementioned upper feature will affect northeast MT and the
Dakotas this afternoon and evening. A deeply-mixed boundary layer
will develop over this area with temperatures in the 80s and 35-45F
t-td spreads. CAPE will be rather weak, which should limit overall
convective organization. Nevertheless, fast-moving high-based
showers and thunderstorms capable of gusty and occasionally severe
wind gusts are expected.
...Gulf Coast...
The tropical system (PTC 1) along the south TX coast is expected to
slowly organize today, with widespread showers and thunderstorms
from east TX into the central Gulf coast. Low-level winds are not
particularly strong and forecast hodographs are only marginally
favorable for updraft rotation. Nevertheless with such a broad area
of risk, a tornado or two is certainly possible this afternoon
through tonight.
Read more CHECK UPDATE ZOOM GRAPHIC
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