• MESO: Mesoscale Discussion 0072

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Jan 18 18:31:43 2023
    ACUS11 KWNS 181831
    SWOMCD
    SPC MCD 181830=20
    TNZ000-MSZ000-ARZ000-LAZ000-182000-

    Mesoscale Discussion 0072
    NWS Storm Prediction Center Norman OK
    1230 PM CST Wed Jan 18 2023

    Areas affected...northeast Louisiana...east Arkansas...west/north Mississippi...and far southwest Tennessee

    Concerning...Severe potential...Tornado Watch likely=20

    Valid 181830Z - 182000Z

    Probability of Watch Issuance...80 percent

    SUMMARY...The ongoing severe weather threat is expected to continue
    eastward this afternoon. Downstream watch issuance is likely.

    DISCUSSION...A broken line of convection with embedded supercell
    structures is ongoing across WW 24. These storms are evolving in an
    environment broadly characterized by modest MLCAPE (500-1000 J/kg)
    and favorable bulk shear (50-60 kts). A steadily clearing boundary
    layer ahead of the convection has yielded gradual warming, with
    surface temperatures in the low to mid 70s F across the region. This
    has steepened 0-3-km lapse rates slightly, which have increased to
    around 6 C/km per recent 17z/18z special soundings at SHV and JAN, respectively. Amidst broader moist advection, some boundary-layer
    mixing is evident in northeast Louisiana and west Mississippi with
    dewpoints dropping slightly to the low 60s F. This environmental
    evolution (along with ongoing convective patterns) is expected to
    yield continued, gradual upscale growth as the system progresses
    eastward. The primary threats should include a few tornadoes and
    isolated damaging wind gusts, mainly associated with any embedded
    supercells and/or more intense mesovortices within the broader
    convective line.

    ..Flournoy/Gleason/Grams.. 01/18/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_UW-e5-O9jCRzD8_i0dEi5GTMQAF-M4rYuFNREqNKgAug2zawC4_7C6ZyDU08ipt4I9R6YlK6= sPAl8hS3sKD43jyAHA$ for graphic product...

    ATTN...WFO...MEG...JAN...LZK...SHV...

    LAT...LON 34228948 33228995 32029087 31539164 31509250 31639290
    31999272 32339244 32849216 33279197 33389147 33769119
    34309094 34919100 35369087 35518983 35208938 34228948=20


    =3D =3D =3D
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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Jan 16 08:32:47 2024
    ACUS11 KWNS 160832
    SWOMCD
    SPC MCD 160832=20
    GAZ000-ALZ000-FLZ000-MSZ000-LAZ000-161330-

    Mesoscale Discussion 0072
    NWS Storm Prediction Center Norman OK
    0232 AM CST Tue Jan 16 2024

    Areas affected...Southern MS into central/southern AL and a small
    part of northwest GA

    Concerning...Winter mixed precipitation=20

    Valid 160832Z - 161330Z

    SUMMARY...Winter precipitation will shift eastward early this
    morning. Embedded heavier showers of sleet or freezing rain will be
    possible.

    DISCUSSION...Early this morning, a broad area of post-frontal
    precipitation is ongoing from southern MS into central AL. This area
    of precipitation will continue to spread eastward this morning in
    conjunction with the front and a weak eastward-moving frontal wave
    across the northeast Gulf of Mexico. Weak but nonzero MUCAPE (as
    noted in the 06Z BMX sounding) will continue to support fast-moving
    showers with briefly moderate precip rates embedded in the broader
    light precipitation shield.=20

    A substantial warm nose aloft (also noted on the 06Z BMX sounding)
    atop a shallow subfreezing layer at the surface will continue to
    support freezing rain and sleet as the primary winter precipitation
    types. Strong low-level cold advection will continue to push the
    surface freezing line southeastward with time, with a transition to
    freezing rain expected into parts of south-central AL, southern MS,
    and northwest GA, where temperatures are currently above 32F.
    Deepening cold air beneath the warm nose will support primarily
    sleet across the northwest portion of the precipitation shield. Some oscillation between freezing rain and sleet is possible within the
    transition zone.

    ..Dean.. 01/16/2024

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!5-GM7hl2iI456nMz1JOypMWCUaCdscjt6vJTHg_WaoSKO2rm-G5rdcvOIegZ_q1ehMib1p4PW= ZAc88p3ZRZDSH3u5XM$ for graphic product...

    ATTN...WFO...FFC...BMX...MOB...JAN...LIX...

    LAT...LON 31278928 31908844 32538767 33008710 33768617 34158535
    34148498 33808495 33068514 32898522 32478535 32128557
    31428669 30828792 30178932 30178962 30288978 30528998
    30748983 31278928=20


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