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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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