Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1247 AM CDT Mon Apr 20 2026

Valid 211200Z - 221200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms will be possible across the western CONUS, the
south-central CONUS, and the southern Great Lakes on Tuesday.
Potential for severe weather appears low.

... Synopsis ...

Midlevel ridging will be in place from the eastern Great Basin into
the Plains at the start of the forecast period, while persistent
northwesterly flow aloft continues across the Upper Midwest and Ohio
Valley. Farther west, an upper trough will gradually advanced inland
across California into the Great Basin by the end of the period. 

At the surface, a broad area of high pressure centered over the
Southeast and adjacent Atlantic will maintain southerly flow across
the central US. This will promote a gradual moisture recovery across
the central Plains into the southern Great Lakes. A weak frontal
boundary pushing south through portions of the central Plains and
Great Lakes will denote the northern edge of the moisture return.

... Lower Great Lakes ...

Thunderstorm development along the frontal zone may be delayed until
later in the day or evening as moisture slowly returns northward.
While relatively cold temperatures aloft should support steep lapse
rates, the quality and depth of the boundary-layer moisture is
expected to be the biggest unknown. The NAM is the most aggressive
with the depth and quality of the moisture return, and if moisture
quality is close to what is shown in the NAM, enough instability
should materialize to take advantage of the stronger vertical shear
to support a few organized cells capable of gusty winds or small
hail. However, most model guidance is less aggressive with the
quality of the moisture return so no probabilities have been added
at this time. 

... South-central US ...

Convection will likely be ongoing at the start of the forecast
period. Modest vertical shear and elevated instability may support a
couple strong thunderstorms capable of hail and gusty winds.
However, overall thunderstorm intensity should wane through much of
the period as upper ridging overspreads the region.

... Western US ...

As the upper trough moves inland, ascent will increase across the
Pacific Northwest, northern California, and portions of the Great
Basin. Within the Central Valley and nearby terrain, pockets of
diurnal heating, combined with cool midlevel temperatures may
support isolated thunderstorm development during the afternoon.
Despite this modest instability, weak vertical shear should limit
any organized severe potential.

..Marsh.. 04/20/2026

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0227 AM CDT Mon Apr 20 2026

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE HIGH PLAINS OF NEBRASKA SOUTH INTO THE TEXAS PANHANDLE...

...SUMMARY...
Severe thunderstorms capable of hail and gusty winds may develop
during the late afternoon and evening across portions of the High
Plains. Elsewhere, thunderstorms will be possible across the
northern Gulf Coast and portions of the Ohio Valley.

... Synopsis ...

A shortwave trough will eject northeast out of the basal region of
the western CONUS trough and into the northern Plains on Wednesday.
As this happens, strengthening southerly/southwesterly midlevel flow
will overspread much of the High Plains. A surface cyclone over
eastern Montana will gradually deepen as it slowly moves east. 

... Central High Plains south into the southern High Plains ...

As the Montana surface cyclone gradually deepens on Wednesday, Gulf
moisture will be drawn northward into the central and northern
Plains. As the upper trough approaches the region during the late
afternoon/evening, modest height falls are expected to overspread a
sharpening dryline across far eastern Colorado or western Nebraska
south into the Texas Panhandle. Kinematic profiles up and down the
dryline show ample vertical shear for supercells capable of
producing hail and gusty winds. However, considerable uncertainty
remains regarding thunderstorm coverage owing to the significant
differences in the depth and quality of the boundary layer moisture
return noted in the 20260420/00Z guidance suite. For example, the
NAM is nearly 5F more moist along the dryline across portions of
Nebraska than global models. 

That said, pattern recognition and 00Z RRFS suggest that at least a
couple of storms should develop along the dryline from Nebraska
south into the eastern Texas Panhandle. Deep-layer flow will largely
parallel the dryline during the afternoon which should preclude much
eastward advancement. A 5% unconditional risk area has been added to
account for this potential.

... Elsewhere Across the CONUS ...

Thunderstorms may be ongoing at the start of the forecast period and
persist into the early afternoon across portions of the northern
Gulf Coast. The thunderstorm potential should wane with time as
increasing midlevel heights suppress large-scale ascent. 

Additionally, modest low-level moisture and weak instability may
support a few lightning strikes within a weak surface boundary
across the Ohio Valley.

..Marsh.. 04/20/2026

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0358 AM CDT Mon Apr 20 2026

Valid 231200Z - 281200Z

...DISCUSSION...
In the days preceding this forecast period, a long-wave trough will
develop across the western US. This feature will persist across the
western and central US through the forecast period supporting a
multi-day severe weather threat across portions of the central US.

On Thursday/Day-4, a lobe of vorticity will rotate around the closed
midlevel low across the northern Rockies. This will reinforce a
surface cyclone as it moves north into Canada. As this low moves
north, a combined dryline/cold front will move east into an
increasingly moist environment across the central Plains. The
airmass ahead of the front should destabilize during the day
Thursday, with MUCAPE values over 1000 J/kg possible into portions
of Minnesota. 

Thunderstorms should develop across portions of northeast Kansas
into Iowa during the late afternoon as height falls overspread the
surface front. These storms should quickly build southward along the
front into portions of Oklahoma and southern Kansas. Kinematic
fields initially should support supercells, but midlevel flow will
increasingly become parallel to the front suggesting that storms
will grow upscale into one or more linear segments.

The surface front, augmented by convective outflows, will continue
to push south and east into the Southern Plains and the greater
ArkLaTex region overnight Thursday into Friday/Day-5 before stalling
out. Forecast soundings along and ahead of the frontal boundary
indicate an unstable, uncapped environment with vertical shear
between 30-40 knots should support additional severe thunderstorms
Friday afternoon into the evening/overnight across portions of
eastern Oklahoma and Arkansas.  

By Saturday/Day-6, the larger-scale flow across the southern Plains
will begin to respond to a low-latitude trough moving into southern
California by once again becoming increasingly southwesterly.
Embedded perturbations within this southwest flow ahead of the main
trough will support an ongoing severe threat across the southern
Plains. However, the location of various surface boundaries
(dryline, outflow, frontal) will be predicated on the evolution of
prior days of convection and the timing of the aforementioned
perturbations in the midlevel flow. Thus, while pattern recognition
suggests severe weather will be possible on Days 6,7, and 8,
certainty as to the location of greatest severe potential on any
given day remains too low to highlight with unconditional
probabilities at this time.