ACUS01 KWNS 181954
SWODY1
SPC AC 181953

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Thu Apr 18 2024

Valid 182000Z - 191200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
EASTERN MISSOURI INTO SOUTHERN ILLINOIS...EXTREME SOUTHWEST
INDIANA...FAR SOUTHWESTERN KENTUCKY...FAR NORTHWESTERN TENNESSEE...

...SUMMARY...
Damaging gusts to 70 mph, large hail up to 2 inches in diameter, and
a couple of tornadoes remain possible this afternoon into early
tonight across the middle Mississippi and lower Ohio Valleys.
Isolated large hail and damaging winds are also still possible
farther south from northern Mississippi and Arkansas into central
Texas.

...20Z Update...
The only changes made to the ongoing outlook were to trim thunder
and severe probabilities in areas that have been cleared by the
passing surface cold front. Otherwise, the previous forecast (see
below) remains generally on track, with no major changes made.

..Squitieri.. 04/18/2024

.PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Apr 18 2024/

...Mid MS/lower OH Valleys through tonight...
Recent surface analysis places a low just south of MCI along the
KS/MO border vicinity. A warm front extends eastward from this low
across central MO, far southern IL and into KY. Airmass south of
this warm front is moderately moist, with observations sampling mid
60s dewpoints along much of the AR/MO border, with some upper 60s
farther east over the MO Bootheel. Expectation is for this moist
airmass to continue progressing northward throughout the day, likely
reaching the I-70 corridor by the mid-afternoon. A cold front also
extends southwestward from this low through north-central to
southwest OK, continuing through northwest TX and southwest TX. An
outflow boundary from overnight convection precedes this cold front,
although by only about 30-50 miles or so.

General expectation is for thunderstorm intensity and coverage to
increase early this afternoon as these surface boundaries interact
with the increasingly moist and unstable boundary layer downstream.
Overall convective evolution is a bit more uncertain, particularly
regarding when the storms become more balanced with the cold front
and/or outflow no longer undercutting updrafts. Current thinking is
that this occurs during the early afternoon across central MO, with
quick upscale growth promoting an organized convective line. Primary
risk within this line will be damaging wind gusts from 45 to 65 mph.
Large hail from 1 to 2" is also possible, particularly with any more
cellular development ahead of the front and/or outflow.

A similar convective evolution appears likely farther north (from
central MO into central/southern IL and western IN) near the surface
low, but with augmented mesoscale ascent near the low. This
augmented ascent could contribute to more vigorous updrafts and a
somewhat more organized convective structure, despite being
displaced north of the better low-level moisture and buoyancy.
Additionally, the eastward-progressing low will allow storms here to
be more favorably aligned with the deep-layer vertical shear. This
could contribute to a more forward-propagating structure and the
potential for damaging gusts, despite modest thermodynamics. As a
result, the outlook probabilities were shifted a bit northeastward
across IL and IN. Primary threat here is wind gusts, although the
backed low-level flow near the surface low could contribute some
tornado threat as well.

...Much of AR through southeast OK and into North/Central TX this afternoon/evening...
A cold front extends southwestward from a low near the KS/MO border southwestward through north-central to southwest OK, continuing
through northwest TX and southwest TX. Surface heating ahead of this
front is expected to result in strong buoyancy within the moist
airmass that is already in place across the region. Widely scattered
to scattered thunderstorm development is expected by about 21z along
the front from northwest AR across southeast OK into north and
central TX. Deep-layer shear will be strong enough for some
supercell structures capable of producing isolated very large hail
(up to 2.5 inches in diameter), along with damaging outflow gusts
given the potential for strong downdrafts. These storms will last a
few hours into late evening and then weaken as convective inhibition
increases.

...Southeast AR into Northern MS this afternoon/evening...
As mentioned in MCD #480, slightly elevated convection continues to
evolve across the Arkansas/Louisiana border area this morning,
within a zone of QG ascent ahead of a subtle shortwave trough moving
across east Texas. This shortwave is expected to continue
progressing northeastward, with the ongoing storms likely persisting
as they move northeastward as well. General expectation is for this
cluster to maintain its intensity for the next few hours, with some
hail possible, before likely waning thereafter as the low-level jet
weakens and veers. However, that is a fairly low confidence scenario
given that this cluster developed about 4 hours ahead of when much
of the guidance indicated.

Additional development appears probable in the wake of this cluster
over northern LA/southern AR this afternoon. In this area, weak
ascent preceding the shortwave will interact with the unstable warm
sector for widely scattered thunderstorm development this afternoon.
If a few storms do form, the environment will conditionally favor
supercells capable of producing large hail/damaging winds, with the
threat expanding eastward into northern/central MS over time.

$$
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ACUS01 KWNS 251232
SWODY1
SPC AC 251231

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0731 AM CDT Thu Apr 25 2024

Valid 251300Z - 261200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS WESTERN KS AND TONIGHT ACROSS NORTHWEST TX INTO CENTRAL OK...

...SUMMARY...
Very large hail up to 3 inches in diameter and a strong tornado or
two will be possible this evening across western Kansas. Large hail
up to 2.5 inches in diameter, damaging winds to 70 mph and a few
tornadoes will be possible tonight from northwest Texas into central
Oklahoma.

...Synopsis...
A midlevel shortwave trough and associated 70 kt jet will eject
northeastward toward western KS by late tonight and Friday morning.
An associated lee cyclone is expected to deepen this afternoon
across northeast CO, with a sharpening dryline arcing to its south
across western KS and the TX/OK Panhandles. Farther east, a warm
front will continue to move northward from OK into KS, though
northward progress of the front will be slowed by elevated
convection (posing an isolated large hail threat) that will
reinforce the cool side of the boundary during the day. A somewhat
bimodal threat distribution is expected - the warm sector in western
KS and a second corridor overnight from northwest TX into OK.

...Western KS this afternoon/evening...
An unstable warm sector will be present through this evening, with boundary-layer dewpoints in the 60s beneath steep midlevel lapse
rates. The base of the elevated mixed layer will be relatively
warm, suggesting the need for surface temperatures into the 80s on
the immediate moist side of the dryline. The better potential for
storm development this afternoon will be across western KS, where
dryline parcel residence times will be longer and in closer
proximity to the left-exit region of the approaching mid-upper jet.
The initial dryline storms will likely become supercells capable of
producing very large hail of 2-3 inches in diameter, and these
storms could continue northeastward as elevated supercells atop the
warm front. The potential for a strong tornado or two will increase
this evening as the storms encounter richer low-level moisture and
increasing low-level shear. However, the window of opportunity will
not be particularly large given the presence of a rain-reinforced
front to the northeast and increasing convective inhibition by late
evening.

...Northwest TX into OK overnight...
A general consensus of most overnight forecast guidance suggests a
southern corridor of greater hail/wind threat starting early tonight
just off the Caprock and then spreading northeastward over northwest
TX into southwest/central OK early Friday morning. Thunderstorm
initiation will become more probable by 03-06z in association with cooling/moistening at the base of the elevated mixed layer,
coincident with the beginning of eastward movement of the
dryline/Pacific cold front along the trailing influence of the
ejecting midlevel trough. Storm mode will likely trend to
clusters/line segments while spreading northeastward.
Boundary-layer dewpoints approaching the upper 60s beneath steep
midlevel lapse rates will contribute to MUCAPE in excess of 2000
J/kg through the overnight hours, which will favor the potential for
both large hail (especially with any embedded supercells) and
damaging winds of 60-70 mph. A few tornadoes may also occur with
embedded circulations as low-level shear increases tonight.

...TX Panhandle/western OK this afternoon/evening...
A conditionally favorable environment for supercells with very large
hail and tornadoes will exist this afternoon/evening across the
eastern TX Panhandle into western OK. The primary uncertainty here
will be lingering convective inhibition and substantial uncertainty
in storm coverage/location along the dryline. For these reasons,
have lowered the overall severe threat, but maintained some
conditional significant severe potential.

..Thompson/Kerr.. 04/25/2024

$$
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ACUS01 KWNS 281945
SWODY1
SPC AC 281943

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0243 PM CDT Sun Apr 28 2024

Valid 282000Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
EASTERN TEXAS ACROSS THE ARKLATEX AREA...

...SUMMARY...
Clusters of severe storms are possible through early tonight, with
the most concentrated threat for wind damage, large hail and a few
tornadoes from the ArkLaTex southward into east Texas.

...20Z Update...
Little overall change was made to the existing outlook, as
potential, as well as uncertainty, remain over a large region.

An upper trough with cool temperatures aloft remains over the
Plains, with midlevel temperature gradient from IA into eastern OK
and southwestward across northern TX. Satellite imagery as well as
surface observations continue to show gradual heating and
destabilization as clouds thin from the decaying early day MCS.
Given substantial southwest flow aloft and at least a marginally
unstable air mass over most of the region, little change was made to
most of the outlook area. The greatest severe risk looks to be
centered over eastern TX toward the ArkLaTex and toward the Sabine
Valley late, in closer proximity to stronger instability.

Farther north across eastern OK into AR and southern MO, an
increasing low-level jet late this evening and right-entrance region
of the upper jet may yield a more concentrated corridor of strong to
perhaps severe storm potential after 00Z and into the night.

..Jewell.. 04/28/2024

.PREV DISCUSSION... /ISSUED 1125 AM CDT Sun Apr 28 2024/

...East TX/LA/Southern AR...
A long-lived large nocturnal MCS that affected much of TX overnight
has weakened substantially, but remains over parts of east TX.
Ample low-level moisture and moderate instability is present to the
east of this activity, along with deep southerly low-level winds and
little inhibition. This will result in rejuvenation of storms by
mid-afternoon along the remnant outflow boundary. Forecast
soundings in this area show sufficient deep-layer shear for
supercell structures capable of large hail, damaging winds, and a
few tornadoes. This activity will spread eastward through the
evening into LA/southern AR, with a continued risk of damaging wind
gusts and isolated tornadoes.

...OK/AR/MO...
The overnight MCS has significantly affected the air mass across
much of eastern OK/western AR/southern MO, with expansive cloud
cover and surface dewpoints now in the 50s to lower 60s. Many of
the 12z models are insistent that higher theta-e air will return to
this region, resulting in a robust severe threat emerging by late
afternoon - but our confidence in that scenario is rather low at
this time. Redevelopment of afternoon thunderstorms over eastern OK
seems likely, and there remains a risk of hail, damaging winds, and
a tornado or two from this activity. Storms that form will spread
eastward into AR and southern MO during the evening.

$$
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