SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0256 PM CDT Sun May 04 2025
Valid 042000Z - 051200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
EASTERN NEW MEXICO AND WEST TEXAS....
...SUMMARY...
Scattered severe thunderstorms are expected across parts of eastern
New Mexico and west Texas this afternoon and evening. Large to very
large hail, isolated severe wind gusts, and possibly a tornado or
two may occur. Additional sporadic severe storms are possible over
the Ohio Valley and Atlantic Coast.
...20z Update...
Mid afternoon water vapor imagery shows two well-defined upper lows
ongoing across the CONUS. Ascent from these features is supporting
several clusters of strong to severe storms. While buoyancy is
somewhat limited, moderate deep-layer shear will continue to support
a risk for damaging gusts and marginally severe hail with more
organized/persistent clusters across parts of the OH Valley,
Carolinas and parts of FL this afternoon and evening. Probabilities
have been trimmed from the west where storms are moving offshore
across FL.
Across the west, supercells with large to very large hail, damaging
gusts and perhaps a tornado or two will remain likely from parts of
southeastern NM into west TX. Upslope flow is supporting an increase
in storm coverage this afternoon. As destabilization continues,
scattered severe storms are likely into this evening. Have adjusted
severe probabilities slightly farther west to better capture
convective initiation off the higher terrain. See Severe
Thunderstorm Watch 222 for additional information.
...Great Basin and western US...
Beneath the western upper low, scattered thunderstorms have
developed and will likely persist into this evening from the Four
Corners into parts of the Great Basin. Cool mid-level temperatures
are supporting weak, but sufficient buoyancy for occasional stronger
storms. Moderate deep-layer shear may also support occasional storm
organization. While meager surface moisture will limit a more robust
threat, a sporadic damaging gust and/or small hail cannot be ruled
out from any stronger storms/clusters that persist, especially over
northwestern AZ and southern NV where buoyancy and shear may be
locally enhanced beneath the cyclone aloft.
..Lyons.. 05/04/2025
.PREV DISCUSSION... /ISSUED 1125 AM CDT Sun May 04 2025/
...New Mexico and West Texas...
Large-scale ascent will increase this afternoon across NM and the
southern High Plains as strong difluence aloft associated with an
upper low over northwest Mexico and the Southwest moves eastward.
Steep lapse rates aloft atop modest low-level moisture will act in
tandem with daytime heating to foster up to 1000-1250 J/kg of MLCAPE
across eastern NM and far west TX by mid afternoon. While low-level
southeasterly flow will initially be modest, various RAP/NAM
forecast soundings show substantial veering and some strengthening
with height at mid/upper levels. Resultant long/straight hodographs
aloft and strong deep-layer shear will likely support a few
supercells with an attendant threat for large to very large hail (up
to 1.5-2.5 inches in diameter). Isolated severe wind gusts may also
occur as this convection spreads slowly eastward across eastern NM
into parts of west TX through the evening. Although low-level
moisture will remain modest, a southeasterly low-level jet is also
expected to gradually strengthen this evening, which should support
enough 0-1 km SRH for a tornado or two with any sustained supercell.
These thunderstorms will eventually weaken with eastward extent into
west TX as MLCIN gradually increases by mid/late evening.
...Upper Ohio Valley/Mid-Atlantic to the Carolinas...
An expansive closed mid/upper-level low will remain centered over
the OH/TN Valleys today. A belt of stronger south-southwesterly
mid-level winds will overspread parts of the upper OH Valley and
southern Mid-Atlantic through this evening. This enhanced flow along
with upper-level difluence should provide sufficient large-scale
ascent for isolated to scattered convection this afternoon across
parts of OH into WV and western PA. Low-level moisture will remain
somewhat limited across this area, with surface dewpoints generally
in the low to mid 50s. Even with filtered daytime heating, poor
lapse rates aloft should keep any more than weak instability from
developing. Various RAP forecast soundings across this region also
show flow backing with height aloft, which lends considerable
uncertainty regarding convective organization. While an isolated
damaging wind/hail threat may exist, the overall environment should
keep the severe threat fairly marginal.
A somewhat separate area of convection may develop this afternoon
across eastern NC into VA, generally along/ahead of a weak surface
front. While these thunderstorms will have access to greater
low-level moisture, both instability and deep-layer shear are
expected to remain modest. Still, some risk for damaging winds and
hail should exist with any cells or clusters that can develop,
before this activity gradually weakens through the evening with the
loss of daytime heating.
...Florida...
Scattered showers and thunderstorms are ongoing across parts of the
southern/central FL Peninsula. A subtropical upper-level jet should
continue to aid thunderstorm development across the FL Peninsula
through the afternoon. But, persistent cloud cover and poor lapse
rates aloft noted on area 12Z soundings may hinder destabilization
to some degree. Even so, a rather moist low-level airmass exists
along/south of a front over north FL/far southeast GA, and even
modest further heating should support sufficient instability for
surface-based convection. With weak low-level flow gradually veering
to westerly and strengthening at mid/upper levels, this activity
should have enough deep-layer shear for modest updraft organization.
Thunderstorms may preferentially form on/near the Atlantic Coast sea
breeze this afternoon while posing an isolated threat for severe
hail, damaging winds, and perhaps a brief tornado.
...Eastern Idaho into Southern Montana...
As a mid-level trough moves eastward over western Canada and the
northern Rockies, scattered thunderstorms should develop this
afternoon and evening across eastern Idaho into southwest Montana.
This region will have steep mid-level lapse rates and cool
temperatures aloft associated with the shortwave trough. Deep-layer
shear is expected to remain modest, but a couple of stronger cores
with small hail and gusty winds could still occur.
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