• DAY1SVR: Enhanced Risk S

    From Dumas Walker@21:1/175 to All on Tuesday, April 09, 2024 08:22:00
    ACUS01 KWNS 091221
    SPC AC 091220

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0720 AM CDT Tue Apr 09 2024

    Valid 091300Z - 101200Z


    Scattered severe thunderstorms are likely today across much of Texas
    into the lower Mississippi River Valley. Several tornadoes, a
    couple of which may be strong, large to very large hail, and severe
    gusts are forecast.

    A mid- to upper-level low evident in water-vapor imagery near the
    NM/AZ/Mexico border this morning, will move east into northwest TX
    by daybreak Wednesday. Early morning analysis indicates an
    outflow-reinforced effective frontal zone is draped east to west
    from western LA into central TX, with the western portion of the
    boundary intersecting a surface low over the Permian Basin this
    morning. This surface low will gradually develop eastward into the
    TX Hill Country by early evening as the mid- to upper-level
    trough/low encroaches on the southern Great Plains. Little overall
    northward advancement is forecast in the outflow/effective frontal
    zone across central TX eastward into north-central LA during the

    ...TX to Lower MS Valley...
    A multi-scenario severe thunderstorm outlook is lending considerable uncertainty to this forecast. Strong to locally severe
    thunderstorms may continue to develop and increase in coverage over northwest/west TX this morning as the leading edge of stronger upper
    forcing for ascent overspreads a capped but moist/unstable airmass
    near/north of the frontal zone (reference 12z Midland raob). As an
    80-kt 500mb speed max translates through the base of the upper
    trough, additional storm development will likely occur in a
    moist/warm conveyor across portions of central TX eastward into
    western LA. Models maintain the LLJ across east TX into southern AR
    most of the period. As a result, episodic bouts of deep convection
    should be noted across this region. Strong boundary-layer heating
    on the southwestern periphery of active convective clusters (most
    likely to occur over east-central TX and locales farther east) will
    yield a very unstable airmass by mid afternoon. The presence of
    surface dewpoints near 70 deg F beneath steep 700-500 mb lapse rates
    will yield large buoyancy, and the risk for large to very large hail
    with the stronger updrafts. Large low-level hodographs (200-300
    m2/s2 0-1 km SRH) in the warm frontal zone will act to enhance both
    supercell development and a tornado risk with any supercells that
    can develop and move into this moist/strong low-level shear
    corridor. During the evening, large-scale height falls will spread
    east and it seems increasingly probable a squall line will develop.
    A few tornadoes and 60-80 mph gusts are possible with this potential
    linear MCS.

    ...Lower Great Lakes...
    Southern influence of a strong short-wave trough will glance
    northern OH into western NY. Boundary-layer heating is expected to
    contribute to modest instability by mid afternoon as surface
    temperatures warm through the mid 60s to near 70F. Ample deep-layer
    shear will exist for a few robust storms capable of generating gusty
    winds and perhaps isolated severe hail. Greatest risk will be with
    convection that develops along the front as it eases southeast into
    this region.

    ..Smith/Mosier.. 04/09/2024

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