SPC May 8, 2025 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1128 AM CDT Thu May 08 2025

Valid 081630Z - 091200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE
MID-SOUTH INTO THE TENNESSEE VALLEY AND SOUTHEAST...AND PARTS OF THE
RIO GRANDE VALLEY IN TEXAS...

...SUMMARY...
Scattered thunderstorms with severe wind gusts and large hail are
expected today over parts of the Tennessee Valley and southern
Appalachians/Southeast, with isolated very large hail possible.
Severe wind gusts and large to very large hail will also be possible
across portions of west/south Texas including the Rio Grande Valley.

...Tennessee Valley/Southeast Appalachians into the Southeast...
A positively tilted upper trough will extend from Ontario and the
Northeast southwestward across the Great Lakes, OH/TN Valley, and
into the Mid-South and southern Plains today. A weak surface low
analyzed this morning over the mid MS Valley is forecast to
gradually fill/lose definition through the afternoon/evening, as a
weak cold front moves slowly south-southeastward through the period.
Areas of at least scattered to broken clouds remain evident on
recent visible satellite imagery from northern MS/western TN to the
southern Appalachians. This will tend to hinder diurnal
destabilization to some extent, but cool temperatures aloft (around
-13 to -16C at 500 mb from area 12Z soundings) and modestly
steepened mid-level lapse rates should compensate to some extent.

Within the broader upper troughing, a weak embedded upper low/trough
will continue to advance slowly eastward from the mid MS Valley to
the TN Valley and southern Appalachians through this evening. Modest
large-scale ascent associated with this feature, along with weak
low-level convergence along the cold front, should be sufficient to
aid in at least scattered convective development across these
regions this afternoon. A combination of moderate instability and
around 30-40 kt of effective bulk shear appear adequate to support
some thunderstorm organization. Multiple supercells and short line
segments/clusters should develop and spread east-southeast this
afternoon/evening across parts of the Mid-South into the TN Valley
and southern Appalachians. Large hail will be possible with
sustained supercells, and isolated very large hail (potentially up
to 2-2.5 inches in diameter) could also occur. Otherwise,
severe/damaging winds will also be a concern with any clusters.
Based on latest observational and guidance trends showing a
favorable environment this afternoon and evening across a broader
portion of the TN Valley/Southeast, the Slight Risk has been
expanded westward some across the Mid-South/lower OH Valley where
convection is initiating, and eastward to include more of
north/central GA, and the western/central Carolinas into
south-central VA.

A somewhat separate area of strong to severe thunderstorms may focus
along/near the Atlantic Coast sea breeze this afternoon from parts
of coastal/southeast GA to the east-central FL Peninsula. Seasonably
cool temperatures aloft combined with moderate to strong instability
and a generally long/straight hodograph at mid/upper-levels should
support some threat for both large hail and damaging winds with any
cells/clusters that can form.

...Rio Grande Valley...
Thunderstorms are ongoing late this morning across parts of west TX,
in association with a weak shortwave trough over northern Mexico and
related modest low-level warm/moist advection. Current expectations
are for this activity to gradually increase in coverage and
intensity across the Big Bend region and vicinity through the
afternoon as daytime heating acts to further destabilize an already
moist low-level airmass. While mid-level winds are not forecast to
be overly strong with the low-amplitude shortwave trough, veering
winds with height will support deep-layer shear around 35-45 kt.
Supercells should be the primary convective mode initially, with a
threat for scattered large to very large hail (generally 1.5-2.5
inches in diameter) and isolated severe winds.

Additional intense convection should develop over the higher terrain
of north-central to northeast Mexico, with some potential for this
activity to spread east-southeastward across the Rio Grande Valley
this afternoon and evening in a moderately to strongly unstable
airmass. Large hail will continue to be a threat with any sustained
supercells, and the threat for severe/damaging winds may also
increase if a small cluster/MCS can develop and spread southeastward
this evening and tonight. Finally, a separate area of strong to
severe thunderstorms may develop through the afternoon along/near
the coast and a stalled front in deep south TX. This activity would
also pose some threat for severe hail/wind given a very
moist/unstable airmass and sufficient deep-layer shear for organized
updrafts.

..Gleason/Thornton.. 05/08/2025

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