• DAY1SVR: Day 1 Convective

    From Weather Alert to All on Wed Apr 28 14:55:00 2021
    ACUS01 KWNS 281934
    SWODY1
    SPC AC 281933

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0233 PM CDT Wed Apr 28 2021

    Valid 282000Z - 291200Z

    ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
    OF TEXAS...

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM TEXAS INTO
    SOUTHERN IL/WESTERN KY AND ACROSS PARTS OF THE LOWER GREAT LAKES...

    ...SUMMARY...
    Severe thunderstorms are possible across parts of the southern
    Plains to southwest Texas through this evening. Other severe storms
    may develop in parts of the lower Great Lakes region. In both
    areas, the most intense thunderstorms may produce large hail and
    wind damage. A tornado threat also may develop in the southern
    Plains.

    ...20z Update...

    Only minor adjustments have been made to outlook areas with the 20z
    update. The main adjustments have been to trim the Marginal and
    Slight risk areas across parts of northwest OK into northwest TX.
    This is based on the current position of the cold front and where
    persistent precipitation/cloud cover has limited destabilization.
    The Slight risk also was expanded across parts of western KY where
    an ongoing threat for damaging winds will continue the next several
    hours. The Marginal risk has also be adjusted slightly southward
    from MO into OH based on frontal position. Minor adjustments were
    also made to the Enhanced risk/30% SIG Hail area in southwest TX
    based on current position of developing convection. Otherwise,
    overall forecast philosophy remains unchanged from the previous
    outlook.

    ..Leitman.. 04/28/2021

    .PREV DISCUSSION... /ISSUED 1131 AM CDT Wed Apr 28 2021/

    ...TX...
    An upper low is over southeast AZ today, with strong southwesterly
    midlevel winds extending across the southern Plains. At the surface
    widespread moist and at least moderately unstable air is present
    across much of central/east TX. Forecast soundings suggest the cap
    is relatively weak today, which makes the timing/position of
    convective initiation more uncertain. However, it appears the
    primary forcing boundaries will be a remnant outflow boundary
    extending from north of SJT to near MWL, and also the dryline west
    of SJT. Both boundaries are likely to activate by mid/late
    afternoon, with a risk of supercells capable of very large hail,
    damaging winds. While low-level shear is not particularly strong,
    presence of boundaries, ample CAPE, and discrete mode may promote a
    risk of a few tornadoes across the ENH risk area through the
    evening.

    ...West TX into OK...
    Visible satellite imagery shows breaks in the clouds across much of
    west TX into western OK. This overlaps the dryline from SJT
    northward, where most 12z CAM solutions indicate the development of
    scattered afternoon and evening thunderstorms. A few intense cells
    are likely to form in this area, with a primary risk of large hail.

    ...Southern MO into Southern IL...
    A cluster of organized/intense thunderstorms is affecting southern
    MO this morning. This activity may persist through the day and
    eventually track into southern IL/western KY. Shear is quite
    strong, but instability is very limited in this corridor due to
    cloud cover. Nevertheless, persistent convective organization may
    allow for a continued risk of damaging wind gusts and occasional
    tornado spin-ups through the day.

    ...OH/PA/NY...
    A line of showers and thunderstorms is forecast to develop this
    afternoon over Lake Erie and spread southeastward across the region.
    Dewpoints in the mid 50s and relatively strong heating will result
    in MLCAPE values around 1000 J/kg. Deep-layer vertical shear is
    more than sufficient for a few rotating/bowing segments through the
    afternoon posing a risk of hail. Low-level lapse rates will also be
    steep in areas where heating is optimized, aiding in the development
    of strong/damaging wind gusts.

    $$
  • From Weather Alert to All on Fri Dec 31 19:32:00 2021
    ACUS01 KWNS 311936
    SWODY1
    SPC AC 311934

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0134 PM CST Fri Dec 31 2021

    Valid 312000Z - 011200Z

    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MAINLY AFTER
    MIDNIGHT FROM SOUTHEAST OK/NORTHEAST TX TO MIDDLE TN/SOUTHERN KY....

    ...SUMMARY...
    Scattered severe thunderstorms remain possible, mainly from late
    evening into the overnight across parts of the South-Central States
    towards the Tennessee Valley.

    ...Northern AL/Northwest GA...
    There will be a window of opportunity this afternoon for a period of
    isolated strong/severe storms to affect northern AL and northwest
    GA, within a weakly forced but favorably sheared environment. Refer
    to MCD #2089 for further details on this scenario.

    ...Northeast TX/southeast OK to TN/KY...
    The ongoing forecast remains on-track, with no changes made.
    Thunderstorms will begin to develop after 10pm across the SLGT risk
    area, with the primary severe threat mainly after midnight.
    Sporadic hail and wind events may occur overnight in this corridor,
    with the potential for a tornado or two if supercell structures can
    develop.

    ..Hart.. 12/31/2021

    .PREV DISCUSSION... /ISSUED 1020 AM CST Fri Dec 31 2021/

    ...Synopsis...
    Within a large-scale trough over the western CONUS, one shortwave
    trough just off the Baja CA coast will eject east-northeast to the
    southern High Plains tonight, in advance of another shortwave trough
    digging south-southeastward from the Pacific Northwest to the Desert
    Southwest. In response to the ejecting Baja trough, lee cyclogenesis
    is expected across southeast CO and northeast NM. This cyclone will
    begin to develop eastward along a sharp baroclinic zone late in the
    period, as cold air damming occurs across the High Plains.

    ...Northeast TX/southeast OK to TN/KY and the Deep South...
    A broad warm sector has been established for many days from TX into
    the Southeast with mid 60s to low 70s surface dew points, and
    northward spread of this warm sector is expected through tonight
    into southeast OK/AR/TN/southern KY. There is uncertainty regarding
    the potential for open warm sector thunderstorm development with
    minimal forcing for ascent and some lingering convective inhibition.
    However, if a storm or two manage to become sustained later this
    afternoon from central MS to northwest GA, the environment will
    conditionally favor a supercell severe threat.

    Otherwise, increasing low-level moisture along the consolidating
    baroclinic zone and strengthening forcing for ascent primarily
    through low-level warm theta-e advection will lead to increasing
    storm coverage overnight from north TX/southeast OK east-northeast
    across AR/TN/KY. Given deep-layer wind fields largely paralleling
    the baroclinic zone, elevated convection on the cool side of the
    boundary may pose a threat for sporadic severe hail and wind. Any
    surface-based storms along or just south of the front will have the
    potential to develop supercell structures and to produce a few
    damaging gusts, isolated severe hail, and a couple tornadoes from
    about 06-12Z.

    $$
  • From Weather Alert to All on Sat Jan 1 14:14:00 2022
    ACUS01 KWNS 011624
    SWODY1
    SPC AC 011623

    Day 1 Convective Outlook
    NWS Storm Prediction Center Norman OK
    1023 AM CST Sat Jan 01 2022

    Valid 011630Z - 021200Z

    ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS TN...NORTHERN MS/AL...SOUTH-CENTRAL KY...

    ...SUMMARY...
    Tornadoes, a couple of which could be strong, along with damaging
    winds will be possible through tonight, especially across the
    Tennessee Valley.

    ...Ark-La-Tex to the TN Valley...
    Convection has persisted along a baroclinic zone demarcating the
    northwest edge of the richer low-level moisture from the Ark-La-Tex
    into western TN/KY. The convection has reinforced this boundary with
    modest pressure rises behind it, resulting in it receding southeast
    in the Mid-South. It is very unlikely to return north, given the
    lack of appreciable cyclogenesis as a result of an expansive cold
    air mass across the central U.S. that will undercut the stronger
    forcing for ascent in advance of the primary shortwave trough over
    the Four Corners. Even though the main surface cyclone will not be
    intense and will develop farther away from the warm sector (in
    tandem with an ejecting shortwave trough over KS/OK), strong
    deep-layer wind fields and vertical shear will persist through the
    day and into tonight in the warm sector across the TN Valley.

    Given the persistence of the subtropical ridge over FL and only
    glancing/small height falls through the day, much of the convection
    may remain confined to the convection-reinforced frontal zone.
    Still, there will be the potential for embedded supercells within a
    broken band of storms along the front, and a lower chance for a
    few supercells in the open warm sector along diffuse confluence
    zones a little south of the front later this afternoon/evening.
    Effective bulk shear of 60-70 kt and MLCAPE of 500-1500 J/kg will
    conditionally support supercells capable of producing tornadoes,
    damaging winds, and marginally severe hail. The prospects for a
    couple strong tornadoes will likely hinge on pre-frontal supercell
    development that is not entirely undercut by the surface front. This
    is most likely from northern portions of MS/AL into middle TN where
    effective SRH in excess of 300 m2/s2 should be common late this afternoon/evening. The frontal convection will spread southeast
    through the overnight hours, with a gradually lessening severe
    threat and shrinking warm sector centered on AL toward the end of
    the period.

    ..Grams/Karstens.. 01/01/2022

    $$