• DAY1 4/5 RISK AREA POSTE

    From Mike Powell@618:250/6 to All on Sat Apr 25 13:39:00 2026
    ACUS01 KWNS 251252
    SWODY1
    SPC AC 251250

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0750 AM CDT Sat Apr 25 2026

    Valid 251300Z - 261200Z

    ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL/EASTERN OKLAHOMA AND FAR NORTH TEXAS...

    ...SUMMARY...
    Severe thunderstorms with very large to giant hail (2 to 4+ inches
    in diameter), tornadoes, and scattered damaging winds are expected
    late this afternoon through tonight across parts of the southern
    Plains and ArkLaTex. A couple of strong tornadoes are possible.

    ...Synopsis...
    A closed mid/upper-level low will remain centered over Manitoba and Saskatchewan today, while generally zonal/westerly mid-level winds
    persist over the southern Plains. A weak shortwave trough over the Southwest/southern Rockies this morning is forecast to eject
    eastward over the southern/central Plains by late this afternoon. At
    the surface, a convectively reinforced outflow boundary draped
    across north-central/northeast TX will shift northward into OK as a
    warm front today, while a low gradually deepens over northwest TX by
    late afternoon/early evening. Rich low-level moisture characterized
    by upper 60s to low 70s surface dewpoints will likely advance as far
    north as central into southeast OK through peak diurnal heating,
    with lesser moisture return farther north into northwest OK, KS, and
    southeast NE ahead of a cold front. A dryline will extend
    south-southwestward from the surface low across central into
    south-central TX.

    ...Southern/Central Plains into the ArkLaTex...

    Strong to locally extreme instability (MLCAPE 2500-4000+ J/kg) is
    expected to develop along/east of the dryline in TX and south of the
    warm front in OK by peak afternoon heating. The presence of
    seasonably cool temperatures aloft and 7.5-8.5 C/km mid-level lapse
    rates will also support this very favorable thermodynamic
    environment. While large-scale ascent associated with the ejecting
    mid-level shortwave trough is not expected to be overly robust, it
    should be sufficient for at least isolated thunderstorm initiation
    by mid afternoon to early evening (around 20-23Z), especially near
    the warm front/dryline intersection in south-central OK.

    40-50 kt of generally westerly effective bulk shear will support
    intense supercells, with multiple right/left splits likely. This
    activity will quickly intensify shortly after convective initiation,
    and very large to giant hail appears likely (2-4+ inches in
    diameter). The Enhanced/Moderate Risk areas have been expanded
    slightly in OK and north TX to account for deviant thunderstorm
    motions and the potential for multiple intense supercells to track east-southeastward along/near the warm front. A conditional risk for
    supercells remains apparent farther south along the length of the
    dryline in TX, although confidence in convective initiation remains
    low. Have maintained the Marginal Risk for this potential, with some
    expansion eastward in case isolated thunderstorms do initiate.

    Modest southerly low-level winds (around 20-30 kt at 850 mb) will be
    present through this evening across the southern Plains. Locally
    enhanced 0-1 km SRH will be present near the warm front with backed near-surface winds. This will support a threat for tornadoes with
    any right-split supercells that can remain surface based. A slight
    increase in the low-level jet this evening and presence of very
    strong to locally extreme buoyancy also suggests some threat for a
    couple of EF-2+ tornadoes. With time this evening, convection may
    grow upscale and pose a threat for scattered severe/damaging winds
    as it spreads southeastward into the ArkLaTex.

    Farther north in KS/NE, instability and low-level moisture is
    expected to remain weaker/more limited. But, some supercells/small
    clusters may eventually develop this afternoon and move
    east-northeastward given sufficient deep-layer shear for updraft
    organization. Isolated to scattered severe hail and damaging winds
    should be the main threat with this activity through mid evening
    before it eventually weakens.

    ...Lower Mississippi Valley/Central Gulf Coast...

    A long-lived convective cluster has nearly moved offshore from the
    coast of AL/MS/LA. In its wake, a rain-cooled airmass exists across
    much of the lower MS Valley. This should hinder the development of
    much surface-based instability through early afternoon. Still,
    eventual re-destabilization should occur along/near the remnant
    outflow boundary. Isolated cells that may develop could pose some
    risk for hail and damaging winds.

    ..Gleason/Thompson.. 04/25/2026

    $$

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