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ACUS01 KWNS 271246

SWODY1

SPC AC 271244



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0744 AM CDT Wed Mar 27 2024



Valid 271300Z - 281200Z



...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF

THE NEAR-COASTAL SOUTHEAST...AS WELL AS PORTIONS OF CENTRAL AND

NORTH TEXAS...



...SUMMARY...

Isolated severe hail and damaging winds are possible over parts of

the near-coastal Southeast, as well as portions of central and north

Texas.



...Synopsis...

A vast area of the CONUS begins the period with cyclonic mid/upper-

level flow, thanks to nearly phased northern- and southern-stream

synoptic troughs.  The southern one is apparent in moisture-channel

imagery from eastern NM to the Big Bend region of west TX, then over

Coahuila, and should move eastward to AR, east TX and the

northwestern Gulf by 00Z.  The northern one is anchored by a 500-mb

cyclone centered initially over northwestern MN, forecast to pivot

to near Thunder Bay, ON, by 00Z, then northeastward to between Lake

Superior and James Bay around 12Z. By then, phased troughing will

extend from there across Lake Michigan and the lower Ohio Valley to

the southern-stream perturbation over parts of AL, southeastern LA

and the north-central/west-central Gulf.



At the surface, 11Z analysis depicted an occluded low over northern

ON, with an occluded/cold front to near BUF, PIT, and BKW, to a

triple-point low near AGS.  A cold front extended from there

southwestward across the AAF area to the central/southwestern Gulf. 

A warm front was drawn from the southern low east-southeastward

between SAV-CHS.  The warm front should shift northeastward across

coastal SC and the Low Country today.  Another frontal-wave low may

form tonight over SC then move offshore.  The cold front should move

slowly southeastward, reaching near an XMR-EYW line by 12Z tomorrow.



...Southeast CONUS...

An ongoing belt of precip, with embedded/scattered thunderstorms,

should continue to shift slowly eastward across the area, in step

with (and near the position of) the front.  The most intense cells

will be capable of damaging gusts -- especially on and ahead of the

boundary -- as well as severe hail.  That includes a semi-organized,

bowing storm cluster moving inland from the FL coastal bend, for

another hour or so until it encounters substantially more stable air

sampled by the 12Z TBW and JAX RAOBs.



The near-surface layer -- initially stable over land from prior

nocturnal cooling -- should undergo both gradual diabatic heating

through anvil-cloud cover, and warm/moist advection through the

afternoon.  This will erode the morning stable layer and support

peak preconvective/prefrontal MLCAPE of 1500-2000 J/Kg over parts of

northern FL, and 1000-1500 J/kg over eastern GA and parts of SC. 

Flow aloft will remain strongly parallel to the front and the

convective plume, continuing a messy convective character with

embedded thunderstorms.  Forecast hodographs support a blend of

sporadic left- and right-moving supercells, and mainly organized

multicells, with stronger shear and buoyancy but somewhat weaker

lift over southern parts of the outlook area.  As the threat appears

sporadic and spatially isolated -- not very well-focused in time or

within the broader precip swath -- probabilities are held at

marginal unconditional thresholds for now.



...Central/north TX...

Widely scattered thunderstorms are possible for a few hours this

afternoon into early evening, moving eastward to southeastward, with

isolated severe hail and strong to marginally severe gusts possible.



An area of surface low pressure over eastern NM -- initially tied to

lee troughing that extends well poleward into AB -- will split off

and move southeastward over northwest/north-central TX this

afternoon in response to the perturbation aloft, with a trough/

convergence zone to the south or south-southeast across central TX. 

These features should provide enough lift for convection, amidst

minimal capping.  As the mid/upper trough shifts toward and over the

area, very cold air aloft (500-mb temperatures at or below -25 deg

C) will contribute to steep midlevel lapse rates exceeding 8 deg

C/km.  Despite being seemingly cool at the surface and well behind

the cold front, diabatic heating and residual moisture (dewpoints

generally mid 30s to mid 40s F) should erode MLCINH by mid/late

afternoon, with 300-700 J/kg MLCAPE possible.  Though low-level flow

will be weak, enough deep shear should exist to support multicells

and at least transient supercell structures, atop a well-mixed

subcloud layer.  The threat should wane by about 03Z as the

near-surface layer stabilizes and coverage/intensity of what had

been mostly diurnally driven convection diminishes.



..Edwards/Leitman.. 03/27/2024



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