MD 0445 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EASTERN NEBRASKA INTO MUCH OF IOWA


Mesoscale Discussion 0445
NWS Storm Prediction Center Norman OK
1022 AM CDT Wed Apr 15 2026

Areas affected...Eastern Nebraska into much of Iowa

Concerning...Severe potential...Watch possible 

Valid 151522Z - 151745Z

Probability of Watch Issuance...40 percent

SUMMARY...The severe risk will gradually increase and spread
eastward into this afternoon. A few instances of severe hail is the
main concern for the next few hours. While timing is uncertain, a
watch may eventually be needed for parts of the area.

DISCUSSION...Water-vapor imagery indicates a midlevel trough moving
eastward across the central Plains, preceded by around 50 kt of
southwesterly midlevel flow (per regional VWP data). An accompanying
surface low, currently analyzed over southeast NE, will track
eastward along a composite outflow/stationary front draped across
southern IA into this afternoon. Isolated elevated thunderstorms are
already evolving to the northeast of the surface low and to the
north of the boundary in eastern NE, which will pose a risk of
isolated severe hail in the near term. This activity will generally
spread/develop eastward along/north of the surface boundary in
tandem with the surface low and deep-layer ascent accompanying the
midlevel trough into this afternoon. Despite the expected elevated
nature of these storms for the next several hours,
elongated/straight hodographs (40-50 kt of effective shear) and
steep midlevel lapse rates/modest buoyancy atop the boundary layer
will support transient elevated supercell structures capable of
producing severe hail.

With time, the low-level mass response accompanying the midlevel
trough and surface low will draw lower/middle 60s dewpoints
northward into central IA in the wake of ongoing convection.
Depending on the degree of diurnal heating in cloud breaks, this may
support a transition to surface-based storms into the afternoon,
with an associated risk for damaging wind gusts and large hail with
organized clusters and supercells. It is unclear if the
ongoing/morning and early-afternoon elevated storms will warrant a
watch, though current thinking is that a watch may eventually be
needed for parts of the area.

..Weinman/Gleason.. 04/15/2026

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DVN...ARX...DMX...FSD...OAX...

LAT...LON   40829616 41109669 41539692 42079675 42439631 42739541
            43059318 43079208 42849135 42369096 41799105 41349153
            41089232 40909421 40829616 

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

SPC 1300Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0746 AM CDT Wed Apr 15 2026

Valid 151300Z - 161200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN
PLAINS INTO THE MIDWEST AND SOUTHERN GREAT LAKES...

...SUMMARY...
Severe thunderstorms posing a risk for large hail to very large
hail, severe gusts, and a couple of tornadoes will be possible
across portions of the southern Plains toward the Great Lakes this
afternoon and evening.

...Synopsis...
Water-vapor imagery this morning shows an upper trough from the
eastern Dakotas south-southwestward into the southern Rockies.  A
few disturbances will migrate eastward coincident with the trough
with the most notable being over the central High Plains this
morning.  The aforementioned disturbance will move east reaching the
mid-upper MS Valley with the trailing southern extent of the wave
moving into the MO Ozarks and OK by daybreak Thursday.  A weak
diffuse low will move from northern KS to the southwest Great Lakes
by late tonight.  Farther east, an MCV near MO-IL will translate
east and become perhaps a focus for storm activity later this
afternoon across OH-PA.  A rather complex forecast is apparent due
in large part to considerable convection and related outflow
permeating the warm sector overnight across much of the Slight-Risk
area.  

...Iowa into the mid MS Valley...
In the wake of showers/storms this morning from IA southward into
MO, a moist and weakly capped airmass will destabilize through early
afternoon.  The eastward approach of the mid-level disturbance will
likely contribute towards scattered thunderstorms developing 19-21z
from near the weak low eastward along the composite outflow/frontal
zone into IL-WI and southward into MO within a weakly capped warm
sector.  Forecast soundings show straight-line hodographs over IA
with sizable CAPE in the hail growth zone.  The potential for
splitting supercells appears evident with the stronger storms
capable of very large hail and perhaps some tornado risk across IA
and northern MO.  

...Ozarks into Oklahoma and north Texas...
Morning raobs showed steep 700-500 mb lapse rates (7.5-8 deg C/km)
atop a seasonably very moist return-flow airmass.  Models generally
show storm development near the dryline by mid afternoon with
initial development becoming supercellular.  Large to very large
hail will be possible with the stronger updrafts.  Residual outflow
from overnight convection moving into the Ozarks may play a role in
enhancing low-level shear later today.  Forecast soundings show
somewhat limited low-level hodographs with a tendency for a
veer-back-veer signature.  Additional storms will favor some
clustering and upscale growth with time due in part to the forecast
hodographs.  Nonetheless, all hazards will be possible at least
through the early convective life cycle before the possibility for
wind damage and linear structures perhaps evolve during the evening.
 
...Southern Great Lakes into the Northeast...
The remnants of an overnight squall line are moving east across
NY-PA this morning with a trailing outflow boundary extending
westward into OH and northeast IN.  Moist low levels and the
eastward advection of steeper mid-level lapse rates will act to
destabilize the southern Great Lakes into western PA through midday
and into the afternoon.  Forcing for ascent and enhancement of flow
associated with the MCV will potentially focus thunderstorms and aid
in their organization potential beginning this afternoon. 
Considerable uncertainty remains regarding this scenario and whether
a mesoscale corridor of higher tornado probabilities is needed
(i.e., northeast OH).  Will defer to later outlooks to where perhaps
mesoscale corridors of greater wind/hail threat and an isolated risk
for a couple of tornadoes could develop.

..Smith/Dean.. 04/15/2026