ACUS01 KWNS 011247
SWODY1
SPC AC 011245

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Mon Apr 01 2024

Valid 011300Z - 021200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS
OF THE SOUTHERN PLAINS TO THE LOWER MISSOURI AND OHIO VALLEY
REGIONS...

...SUMMARY...
Severe thunderstorms are expected today into this evening within a
broad swath from the southern Plains to the lower Missouri and Ohio
Valley regions. Tornadoes (a few strong), destructive hail, and
damaging thunderstorm gusts all are possible.

...Synopsis...
The most important mid/upper-level feature for this forecast will be
a deep, positively tilted, synoptic-scale trough, initially
extending from the northern High Plains across UT to northern Baja.
Several shortwave troughs and vorticity lobes will traverse the
associated cyclonic flow, as the broader trough shifts eastward. By
the end of the period, the synoptic trough should extend from IA
across KS and the southern High Plains to far west TX and
northwestern MX. A lead shortwave perturbation -- evident in
moisture-channel imagery over the eastern AZ/western NM region and
southward into adjoining parts of MX -- will eject across the
southern High Plains today, reaching the TX Panhandle and western OK
by 00Z. This feature should proceed northeastward to parts of
northwestern MO and IA by 12Z tomorrow.

Surface analysis at 11Z showed a frontal-wave low over central KS,
with warm front to near a line from SZL-STL-ILN. The low should
migrate along the slowly northward-moving warm front to MO by 00Z,
with cold front southwestward across northwestern OK and the
northernmost TX Panhandle. A dryline -- drawn initially from the
low to the eastern TX Panhandle, near MAF, then southward into
northern Coahuila -- should shift eastward through the afternoon to west-central/southwestern OK, extending southward across the TX Hill
Country to near LRD. By 00Z, the warm front -- perhaps modulated on
the mesoscale by areas of precip -- should extend across northern
MO, central parts of IL/IN, to southern OH and parts of WV. A
secondary low may form near the front/dryline intersection over
western OK. By 12Z tomorrow, an elongated low-pressure area, with
more than one center, is possible from the main frontal inflection
over northeastern MO to central IN. The main cold front should
reach southwestern MO, southeastern OK, northwest TX, and
southeastern NM. To its southeast, a Pacific front should overtake
the dryline this evening and overnight, reaching western AR, the
Arklatex, east TX, and parts of deep south TX by the end of the
period.

...Southeastern KS and western Ozarks to central TX...
Scattered (OK/KS) to isolated (central TX) thunderstorms are
expected to develop this afternoon along/ahead of the dryline and
front, quickly becoming severe with all hazards possible. The hail
threat will be greatest during the first few hours, while tornado
potential ramps into a probable early-evening peak. Severe
downdraft gusts also are possible, given the strong available
buoyancy and fast cell motions expected.

By late afternoon, much of OK and southeastern KS will reside under
the left-exit region of a cyclonically curving jet streak, above
strong low-level moisture transport accompanying a 50-65-kt LLJ.
Initiation is expected as large-scale ascent preceding the lead
shortwave starts to impinge upon a favorably heated dryline and
moist sector, and the basal EML capping layer erodes. This may
occur earlier over the northern OK/KS part of the outlook near the
front. The environment will be favorable for frequent large hail
and occasional significant to giant hailstones from any sustained
supercells. MLCAPE of 2000-3000 J/kg is possible, amidst 60-75 kt effective-shear magnitudes. Forecast soundings indicate abundant
inflow-layer moisture content to supply the updrafts, long
hodographs commonly associated with significant hail (from right- or left-moving storms), as well as significant to giant hail in both
historic analog soundings and a 2D hail-model.

Though convective coverage may become densest north of the Red
River, the potential for longer-lasting discrete modes near and
south of the Red River conditionally favor isolated extreme hail
sizes even into north TX. Given mesoscale uncertainties and
inconsistent convection-allowing model signals regarding initiation
timing (which influences what low-level shear/hodograph space cells
will enter) and mature storm duration before upscale merging/linear
evolution occur, will hold hail probabilities at previous levels for
now. However, a "hail moderate" may become necessary in this region
if mesoscale trends and post-12Z/today guidance become better
focused on timing/density.

The geometry of the pattern aloft will compel a strong component of mid/upper-level flow parallel to the convective alignment,
encouraging eventual merging, training, and quasi-linear evolution.
How long that process will take is uncertain, and the line
ultimately may backbuild into central TX. Still, with LLJ-expanded
hodographs and surface-based inflow parcels available in the
early/mid evening, tornado potential (some strong) should exist with
any remaining discrete storms, as well as in embedded QLCS
mesocirculations. Severe potential should ramp down late tonight
(after about 06Z) over this region, but persist longer in the next
(below).

...Lower Missouri Valley to Ohio Valley...
Multiple episodes of strong-severe thunderstorm development are
expected this afternoon through tonight, each capable of all severe
hazards. The distribution of severe weather over this corridor may
be quite non-uniform/clustered, as mesoscale convective processes
and boundaries evolve. Strong tornadoes may occur over parts of MO
into central/southern IL while the afternoon/evening CAPE/shear
parameter space and frontal proximity encourage potential
development of at least a couple long-lasting supercells.
Severe to isolated giant hail also is possible, especially from
discrete supercells the western portion over MO/IL containing
steepest lapse rates, greatest CAPE, and similarly favorable
vertical wind profiles as the southern Plains area.

Moist advection should quickly boost boundary-layer mixing ratios
and dewpoints today, with surface dewpoints in the 60s common along
and south of the warm front by midafternoon. Peak/preconvective
MLCAPE should reach 2000-2500 J/kg south of the warm front over
parts of MO/IL/IN, diminishing to 1000-1500 J/kg from the
northeastern KY/southern OH area eastward. Effective-shear
magnitudes should range from near 60 kt over MO to 40-50 kt in
eastern parts of the outlook. An MCS may evolve this evening from
convection over MO and sweep east-northeastward on either side of
the warm front, reaching parts of IN/OH/northern KY late tonight
before weakening. Though moving into an airmass that will be
stabilizing near the surface -- with time and eastward extent --
such a complex may have enough forced ascent and downward momentum
transfer behind that to maintain organized wind-damage potential
over the Ohio Valley tonight.

..Edwards/Leitman.. 04/01/2024

$$
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ACUS01 KWNS 081244
SWODY1
SPC AC 081243

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0743 AM CDT Mon Apr 08 2024

Valid 081300Z - 091200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
NORTHWEST AND NORTH-CENTRAL TEXAS...

...SUMMARY...
Multiple rounds of severe thunderstorms should develop from mid
afternoon through tonight across a large portion of the southern
Plains into the Mississippi Delta region. Large to giant hail is
the main threat, especially over northwest Texas, though a few
tornadoes and severe gusts are also possible in an area extending
east into northern Louisiana.

...Synopsis...
Morning water-vapor imagery shows a positively-tilted mid-level
trough over the Desert Southwest/northwest Mexico. This mid-level
trough will amplify as it moves across the Southwest and northern
Mexico. An associated belt of strong southwesterly flow will extend
from the base of the trough across the southern Great Plains and
into the lower MS Valley. A cyclone will develop in West Texas and
deepen through the period as southerly low-level flow advects rich
moisture into TX/LA [near the record high lowest 100-mb mean mixing
ratio observed this early in the year at the Brownsville raob site
(17.2 g/kg)]. A warm front will advance northward to the Red River
by early evening. A cold front analyzed this morning moving south
through the TX Panhandle/western OK will become stationary later
today.

...Northwest Texas into north-central Texas...
Strong heating on the northwest periphery of rich low-level moisture
will weaken the cap across northwest TX by mid afternoon. Forecast
soundings indicate a moderately unstable airmass (1000-2500 J/kg
MLCAPE) will continue to destabilize into the evening as
south-southeasterly flow strengthens and advects 50s (west) to mid
60s (near I-35) surface dewpoints into the region by early evening.
Veering and strengthening flow with height (100+ kt at 250 mb) will
favor supercells as the initial convective mode. Large to giant
hail (3-4 inches in diameter) is possible in addition to some
tornado risk towards evening. Some consolidation into a cluster/MCS
may occur during the evening across north-central TX with some risk
for all 3 hazards.

...East Texas into the ArkLaTex...
Moderate to strong instability is expected to develop across east
Texas and into western Louisiana this afternoon as upper 60s to near
70s dewpoints advect northward. Despite a solar eclipse across this
region, its impact on the overall severe weather threat will likely
remain minimal. Only moderate warming will be sufficient to erode
inhibition across the region with a gradual strengthening of
southerly 850-mb flow and isentropic ascent as the primary focus for
storm development by mid to late afternoon.

Strong instability and shear is expected and will support
supercells capable of large to very large hail. However, there are
some concerns about storm interference and updraft longevity.
Initially, a warm nose around 700mb is evident on NAM/RAP forecast
soundings which may limit more robust updraft development. This warm
nose is forecast to erode by 23/00Z. However, by that time,
widespread shower/thunderstorm development may be underway which
could be a limiting factor to updraft longevity and a greater
tornado/large hail threat.

Some guidance suggests a MCS may develop out of the
northwest/north-central Texas convection and move through northeast
Texas during the overnight hours. This solution will greatly depend
on the evolution of earlier convection and position of the
convectively enhanced warm front by late evening.

...Texas Hill Country overnight...
Increasing forcing for ascent via stronger mid-level height falls
will overspread much of western/central Texas tonight. Continued
moistening with mid-upper 60s deg F dewpoints beneath steep 700-500
lapse rates (8 deg C/km) will result in 2500 to 3000 J/kg MUCAPE.
Elongated hodographs with 60-kt effective shear will promote
supercells and mainly a risk for large to very large hail.
Southerly 850-mb flow will increase overnight via a LLJ and act to
augment initially limited hodographs. If a cluster organizes
overnight (06-12z), a risk for severe gusts and perhaps a tornado
could develop. Have extended Slight Risk equivalent wind/tornado
probabilities southward for this potential scenario.

...West Texas early Tuesday...
The dryline is expected to retreat into West Texas overnight with
strong instability building back to near Midland early Tuesday
morning. As strong upper forcing overspreads this region, at least
isolated to scattered storms will probably develop on the western
periphery of a strongly unstable/sheared environment. Have adjusted
the some of the severe probabilities farther west where the progged
western edge of moisture/buoyancy will be located.

..Smith/Mosier.. 04/08/2024

$$
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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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