SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0249 PM CDT Mon May 05 2025
Valid 052000Z - 061200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
SOUTHERN PLAINS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE UPPER
OHIO VALLEY/MID-ATLANTIC...AND PARTS OF THE EASTERN FLORIDA
PENINSULA...
...SUMMARY...
Severe thunderstorms are expected across southeast New Mexico into
Texas this afternoon into tonight. Scattered large to very large
hail and severe winds are the primary threats, though a few
tornadoes are also possible. Additional strong to severe
thunderstorms should occur across the upper Ohio Valley/Mid-Atlantic
and the eastern Florida Peninsula this afternoon and evening.
...20z Update...
Minor adjustments were made to the D1 Outlook to extend the Slight
Risk further south and east across portions of south-central Texas
near the Houston Metro. A persistent supercell has been shifting
south and east along a boundary of more favorable CAPE, producing
large hail. Additional thunderstorms may traverse this region
through the afternoon/evening posing some risk for severe wind and
hail.
Additional development across portions of western Texas and
southeastern New Mexico is expected to intensify late
afternoon/evening. The Slight was expanded northwestward to account
for latest trends in storm development. See MCD#696 for more
information.
See previous discussion below for more information.
..Thornton/Gleason.. 05/05/2025
.PREV DISCUSSION... /ISSUED 1130 AM CDT Mon May 05 2025/
...Southern Plains...
Generally elevated convection is ongoing late this morning from
portions of northwest to south-central TX. This activity is largely
being driven by low-level warm/moist advection atop a surface front.
Given the presence of steep mid-level lapse rates and strong
effective bulk shear, some of these thunderstorms should continue to
pose a threat for mainly isolated large hail in the short term. If
the convection across south-central TX can persist through the
afternoon, it will have some chance to become surface based and pose
a greater threat for hail, damaging winds, and perhaps a tornado
with eastward extent towards the Gulf Coast, as the surface front
attempts to lift slowly northward. Severe probabilities have been
expanded eastward some to account for this potential.
Farther west, a closed mid/upper-level low will move slowly eastward
across the Southwest through the period. Difluent flow aloft will
encourage weak lee cyclogenesis across far west TX through this
evening, and low-level moisture will continue to stream
northwestward along/south of a front across south-central/west TX
into southeast NM. Moderate to locally strong instability will
likely be in place by late afternoon along/east of a surface dryline
across far west TX, and south of the front. There is still a fair
amount of uncertainty regarding the timing of robust convective
initiation across the southern High Plains, as stronger mid-level
height falls/ascent attendant to the upper low begin to overspread
the warm sector mainly this evening.
Even with this continued uncertainty, it appears likely that several
supercells will erupt by no later than this evening across southeast
NM into parts of west and south-central TX. Given a rather favorable
thermodynamic and kinematic environment, along with steep mid-level
lapse rates, very large hail will be a concern with these
supercells. A strengthening southeasterly low-level jet through the
evening will also act to increase low-level shear and provide
enhanced boundary-layer hodograph curvature/elongation. The threat
for a few tornadoes with any sustained supercell remains apparent.
The potential for convection to grow upscale into one or more
clusters this evening/overnight remains uncertain. Still, some
threat for severe winds will exist with any supercell or clusters.
Based on latest guidance trends, the Enhanced Risk has been expanded
southeastward towards Del Rio.
...Upper Ohio Valley/Mid-Atlantic to Eastern North Carolina...
A closed upper low will remain centered over the OH Valley today. A
mid-level shortwave trough and attendant jet is forecast to move
northward from the Carolinas to the southern Mid-Atlantic through
the afternoon and evening. Large-scale ascent will likely encourage
scattered thunderstorms to form generally along and west of a
surface front that arcs from southeast VA to western/central PA.
Daytime heating of a modestly moist low-level airmass and cool
temperatures aloft associated with the upper low should aid in the
development of around 500-1500 J/kg of MLCAPE by mid afternoon
across parts of the upper OH Valley into the southern Mid-Atlantic
and eastern NC. Even though low-level flow will tend to remain
fairly muted, southeasterly winds near the surface are forecast to
gradually veer to southerly and strengthen with height at mid/upper
levels. This should support sufficient deep-layer shear for
organized convection. A mix of multicells and supercells are
anticipated, with a threat for scattered large hail and damaging
winds as they spread northward through the afternoon and evening.
Based on latest observational and guidance trends, some westward and
southward expansions have been made to the Slight Risk across these
regions.
...Florida Peninsula...
Much of the FL Peninsula will remain displaced south of the stronger
mid/upper-level flow and forcing associated with an upper low over
the OH Valley today. Still, seasonably cool temperatures aloft
combined with modest enhancement to the mid-level westerlies should
foster adequate instability and deep-layer shear to support modest
updraft organization. Thunderstorms are expected to preferentially
favor the Atlantic Coast sea breeze today, with a stalled front over
the central FL Peninsula also serving as a potential low-level
forcing mechanism. Any convection which does develop may pose a
threat for severe hail and damaging winds before it moves offshore
by early evening. Given increased confidence in scattered to
numerous thunderstorms, along with long/straight hodographs aloft, a
Slight Risk for hail has been added for parts of the eastern FL
Peninsula with this update.
...Western Dakotas...
Even with low-level moisture remaining limited across the northern
Plains today, weak instability should develop by this afternoon in a
narrow zone focused along a front extending across the western
Dakotas. Widely scattered thunderstorms should initiate along this
boundary by this afternoon as glancing large-scale ascent from a
shortwave trough over the Canadian Prairie provinces overspreads the
region. A well-mixed boundary layer and steep lapse rates should
promote efficient momentum transfer with downdrafts, and isolated
strong to severe winds and perhaps some hail may occur with
pulse-type and loosely organized clusters.
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