SPC May 19, 2025 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0751 AM CDT Mon May 19 2025

Valid 191300Z - 201200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FAR NORTH
TEXAS...MUCH OF CENTRAL AND EASTERN OKLAHOMA...SOUTHEAST
KANSAS...AND THE OZARKS...

...SUMMARY...
Significant severe weather is likely from the central/southern
Plains into the the Ozarks today into tonight. All severe weather
hazards are expected, to include tornadoes (some potentially strong
to intense), very large hail, and severe winds.

... Synopsis ...

A large, amplified trough over the Rockies will shift slowly
eastward into the Plains today. Embedded within this longwave
trough, a complex evolution is expected. Downstream of the trough, a
negatively tilted shortwave trough will deepen and close off across
the northern Plains. Meanwhile, upstream, a closed low currently
over Idaho will dig southeastward, open up, and eject into the
central Plains.

As this evolution occurs, strong midlevel flow (in excess of 50
knots) will remain across much of the central and southern Plains
through the forecast period. By late in the afternoon, midlevel flow
will strengthen to perhaps 70 knots in response to the ejecting low
into the central Plains.

At the surface, the main synoptic low will be somewhat
diffuse/elongated over northwest Kansas into southwest Nebraska this
morning. Extending southward from this low, a dryline will stretch
through western Kansas into the Oklahoma and Texas Panhandles,
continuing into west Texas. A warm front will extend eastward near
the Kansas-Nebraska border before curving southeastward into
Missouri into the southern Appalachians. 

The surface low is expected to gradually fill today as it slowly
moves east/northeast into south-central Nebraska, Despite this, rich
Gulf moisture will be maintained across the central and southern
Plains. Dewpoint temperatures at or above 70F will advect northward
from Texas through Oklahoma perhaps to as far north as northeast
Kansas. 

During the afternoon, strong diurnal heating along the dryline may
result in a sub-synoptic low developing across northwest Oklahoma.
This low will slowly progress east along the Oklahoma-Kansas border
during the afternoon, weakening with time.

... Southern and Central Plains into the Ozarks ...

A strongly sheared atmosphere will already be in place at the start
of the forecast period. As diurnal heating commences and 70F
dewpoints advect northward, the atmosphere across much of the
central and southern Plains will become strongly to extremely
unstable as well, with surface-based CAPE values between 3000-5000
J/kg across the region.

Multiple rounds of storms are expected across the region today. One
such initiating mechanism looks to be a subtle shortwave trough
embedded in the larger scale flow currently across eastern New
Mexico. This wave should initiate thunderstorms across eastern
Oklahoma northward into eastern Kansas by midday. It is unclear if
these storms will initially be elevated, but as they move east and
the atmosphere destabilizes further ahead of the line, a transition
to more surface-based convection should occur. At the same time, the
low-level jet is forecast to strengthen/reorganize across eastern
Oklahoma/western Arkansas into western Missouri. This will yield
ample low-level curvature to the hodograph. Thus, given the strongly
sheared environment in place, supercells capable of producing all
severe hazards, including strong tornadoes, will be possible with
this first round of storms. 

By mid-to-late afternoon, 30-60 meter mid-level height falls should
overspread the dryline as it mixes east into central Kansas
southward into western north Texas. Rapid thunderstorm development
is expected along the dryline given the forecast extreme
instability. These thunderstorms should develop west of the better
low-level jet/flow, where the low-level flow is expected to be a
little more veered than across eastern Kansas/Oklahoma. This veered
low-level flow still will result in a strongly sheered environment,
but with more straight hodographs and less low-level curvature. The
result should be another round of supercells, albeit with a tendency
to split. These supercells will be capable of producing very large
hail and tornadoes. The number of supercells across the dryline
combined with a propensity to split, may result in destructive
interference and result in a more episodic hail and tornado threat.

In addition to the hail and tornado threat, the number of expected
thunderstorms in the presence of a very moist and unstable
atmosphere with steep lapse rates may result in strong downdraft
winds. The most likely region for this will be across portions of
northeast Oklahoma, northwest Arkansas, southeast Kansas, and
southwest Missouri. A 45% wind area was included in this outlook.

... Southern Illinois into Southern Appalachians ...

Along the northern periphery of shortwave ridging over the
Southeast, a midlevel jet streak will cross the southern
Appalachians during the afternoon. Here, an influx of steep midlevel
lapse rates atop rich boundary-layer moisture will yield strong
surface-based instability along/south of a warm front draped across
the region. Scattered thunderstorms will spread east-southeastward
along/south of the front from TN into the southern Appalachians,
where the favorable buoyancy and around 40-50 kt of effective shear
will promote organization into clusters and a couple splitting
supercell structures. Damaging winds and large hail will be possible
with the strongest storms.

Overnight, additional thunderstorms may develop across southern
Illinois and western Kentucky in association with warm-air advection
ahead of the main area of thunderstorms to the west. These
thunderstorms will also pose the potential for small hail and
isolated wind damage.

..Marsh/Smith.. 05/19/2025

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