NOAA Storm Prediction Center

Convective Outlooks

Convective Outlooks
The convective outlooks serve as guidance to the local NWS forecast offices and are used by emergency managers, private sector meteorologists, media, and other weather customers concerned with public safety. Three separate risk areas (slight, moderate, and high) are used to describe the expected coverage and intensity for the categorical severe weather threat on days 1-3 along with severe weather probabilities for the potential threat.

Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1200Z Outlook
  
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 Forecast Discussion


000
ACUS01 KWNS 260555
SWODY1
SPC AC 260554

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1254 AM CDT Sun May 26 2019

Valid 261200Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS THE CENTRAL HIGH PLAINS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING ACROSS THE LOWER OHIO VALLEY AND MID ATLANTIC COAST
REGION...

...SUMMARY...
Severe thunderstorms, including a few supercells with a risk for
tornadoes, are expected today across much of the High Plains, into
the central Plains.  Additional severe thunderstorms are possible
across the lower Ohio Valley into the Mid Atlantic Coast region,
accompanied mainly by a risk for severe wind and hail.

...Synopsis...
A large-scale pattern including persistent, prominent subtropical
ridging centered near the eastern Gulf coast, and encompassing much
of the Southeast, and large-scale troughing within the mid-latitude
westerlies across much of the West, will persist through this
period.  Within the Western troughing, the most prominent
perturbation, including a deep mid-level low, is forecast to dig
inland of the California coast, to the south of San Francisco Bay,
through the lower Colorado by 12Z Monday.  As it does, models
indicate that a downstream impulse will pivot northeast of Baja, and
accelerate across the southern Rockies through larger-scale ridging
across the central High Plains.  This likely will be accompanied by
deepening surface troughing across much of the High Plains, and
perhaps modest surface cyclogenesis from eastern Colorado into
Nebraska late this afternoon through tonight, providing a focus for
considerable strong to severe thunderstorm development.

Farther east, several convectively generated or enhanced
perturbations will continue to migrate around the northern periphery
of the subtropical ridging, and are expected to aid convective
development along and south of an initial surface front advancing
southward into/through the Mid Atlantic coast region and Ohio
Valley.

...Plains...
The short wave emerging from Baja is forecast to be substantive
enough to suppress larger-scale mid-level ridging and contribute to
a transition to cyclonic flow across and east of the southern
Rockies late this afternoon and evening.  It appears that this will
be accompanied by a strengthening of southwesterly flow to 40-60 kt
(in the 700-500 mb layer) across the central High Plains, and
strengthening of initially modest southerly 850 mb flow to 30-50+ kt
by late this evening, from the Texas South Plains through the
central Plains by late this evening.

Moisture return to the deepening surface trough across the central
High Plains is already underway beneath north/northeastward
advecting warm elevated mixed-layer air.  Models indicate that this
will contribute to moderate to large CAPE across much of the High
Plains, and into the warm sector of the developing cyclone across
the central Plains.

Various model output does indicate that lower/mid tropospheric warm
advection could contribute to thunderstorm development by early
afternoon across parts of western Kansas.  This probably will be
rooted above the boundary layer, before it has a chance to
substantively destabilize, and it remains at least somewhat unclear
what impact this will have on subsequent thunderstorm development as
it spreads northeastward ahead of the approaching short wave
impulse.

There appears likely to be at least a narrow corridor of moderate to
strong boundary layer destabilization across the Texas/Oklahoma
Panhandles into eastern Colorado by mid to late afternoon, which
should be sufficient to support propagation of thunderstorm activity
off the Rockies into the High Plains.  In the presence of
strengthening shear, the environment is expected to become conducive
to supercells with potential for large to very large hail.  Although
low-level hodographs may be initially weak to modest, a few
tornadoes also appear possible, particularly across the
Colorado/Kansas border area into the Panhandle region.

Tornadic potential eastward across the central Plains this evening,
as the low-level jet strengthens, remains a bit more unclear.  It
appears that large-scale forcing for ascent may support an upscale
growing convective system with primarily a risk for strong wind
gusts along the leading edge of a strengthening surface cold pool,
across parts of western Kansas into south central Nebraska.

...Lower Ohio Valley into the Mid Atlantic Coast region...
Models indicate that seasonably high boundary layer moisture content
ahead of the southward advancing front will become characterized by
moderate CAPE by this afternoon.  This will support potential for
organizing clusters of thunderstorm activity, aided by forcing and
shear associated with the perturbations progressing around the
northern periphery of the subtropical ridge.  Flow including 30-40+
kt in the 700-500 mb layer may be sufficient to support occasional
isolated supercells, but severe hail and wind appear the primary
hazards in the presence of generally weak low-level hodographs.

..Kerr/Squitieri.. 05/26/2019

$$