Valid 051200Z – 061200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS A SMALL
PORTION OF THE SOUTHEAST CENTERED OVER SOUTHERN GA/NORTHERN FL…
A few severe thunderstorms are possible across portions of the
southeastern United States Thursday.
A progressive upper flow pattern will prevail across the U.S. today,
with the two prominent systems affecting the country. The first —
a short-wave trough initially over the north-central states — is
expected to progress east-southeastward across the Great Lakes and
Midwest, as it gradually strengthens and evolves into a closed low.
The other feature — a southern-stream short-wave trough progged to
be crossing the lower Mississippi Valley during the morning — will
be associated with strong/isolated severe storms over the Southeast
during the day. The system will shift quickly east-northeastward,
moving off the Carolinas/Mid Atlantic coast overnight.
At the surface, a low near the mouth of the Mississippi at the start
of the period is progged to move quickly east-northeastward along a
conglomerate outflow/front, before moving off the Georgia coast
during the afternoon. Showers and scattered thunderstorms are
expected to persist near and ahead of the low, before moving
offshore by early evening.
…Southeast AL/southern GA/northern FL and the FL Panhandle…
As the upper trough advances east-northeastward across the Southeast
and an associated surface low tracks eastward along the west-to-east
front/outflow, a very favorably sheared environment is forecast
ahead of the low — with winds strengthening substantially and
veering with height from southerly to west-southwesterly. This
kinematic environment, and the presence of a west-to-east
vorticity-rich baroclinic zone — aligned roughly parallel to
forecast storm motion — support a risk for supercell storms,
including some tornado potential. While weak low-level lapse
rates/limited CAPE expected to persist through the day will temper
severe potential to some extent, a narrow corridor of more focused
severe risk is expected, in close proximity to the frontal zone.
Exact location of the boundary — and thus northern extent of the
severe risk — remains a bit uncertain at this time, as the front
continues progressing slowly southward at this time, while elevated
storms continue in a zone of warm advection north of the front.
Some northward retreat is expected, though persistent convection in
the cool sector should prevent a more aggressive northward surge.
Given these factors, a relatively narrow zone of SLGT risk —
including 5% tornado potential — is evident, aligned roughly along
the GA/FL border. Though diurnal destabilization should remain
minimal, late morning/early afternoon uptick in severe risk is
expected, as the upper system advances quickly across the Southeast.
Risk will end in most areas as the surface low moves offshore,
though a stronger storm may linger over northeast Florida along the
trailing cold front into early evening.