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DEEP SOUTH Severe Weather threat 18-20th

Discussion in 'General Weather' started by Xtreme Weather, Mar 15, 2018.

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  1. Xtreme Weather

    Xtreme Weather Member

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    Looking over the models appears severe weather threat including hail and tornadoes going to be possible for the Mississippi and Alabama area Sunday night into Monday. Front progged to come through the area tomorrow and Saturday will stall and lift northward Sunday/Sunday night resulting in dew points surging into to the low to mid 60's for much of Mississippi and Alabama along with cape around 1500-2000j's. Area of low pressure will form to our W and race off to the E/NE cutting through central TN. SPC had no defined risk at this time for the area but believe this will change over the next 24-36 hrs. if models remain consistent in regards to the last couple runs.

    Edit to say along the warm front could be the focal point for tornados (if system produces)
    F69C7489-EF01-46B9-B7B5-4A8F47B40F6F.jpeg D8FF9B59-987A-4326-9003-8BCBA8DA47FA.jpeg BEE781C9-9355-4254-AF5A-D5B0371B58D6.jpeg

    Carry on...
     
    Last edited: Mar 15, 2018
  2. deltadog03

    deltadog03 Meteorologist Member

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    I think this could be our first real good threat around here.
     
  3. Xtreme Weather

    Xtreme Weather Member

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    Looking more likely disco from Owen at BMX laying out the probs.

    Later Monday morning into the early afternoon, the upper low
    intensifies and the surface low deepens. This will bring a dryline
    boundary across the MS River Valley and through MS by Monday
    afternoon. Ahead of this dryline, models are in decent agreement
    right now with the moisture rebound and afternoon destabilization
    across Central AL. MUCAPE values in both the GFS and ECMWF are 1500-
    2000 J/kg with surface based CAPE exceeding 1500. Surface winds are
    backed to the south for most of the area, with some spots forecast
    to see more southeasterly winds according to the GFS. These backed
    surface winds, coupled with the flow around the deepening upper low
    will result in a fairly deep shear. 0-6km Bulk shear is around 55-
    65kts with 0-3km being 40-50kts. Essentially, the forecast
    hodographs have good curvature and SRH values are greater than 300,
    which would support rotating updrafts. I`m not overly impressed with
    the strength of the LLJ that both the GFS and EC are showing, but
    that wouldn`t prevent a severe threat. The biggest uncertainty right
    now is the Sunday night/Monday morning MCS. Timing and location of
    that MCS will almost fully determine where and what kind of severe
    threat we`ll see on Monday afternoon/evening. The MCS could very
    well cut us off and limit any destabilization, but for now the
    models show moisture and instability building back in. Because of
    that, and with the models now showing more backed surface winds and
    better low level shear, I will change the severe thunderstorm threat
    in the HWO to a tornado threat and increase the confidence slightly
    (to a 2). At this time, all modes of severe weather look possible
    (damaging hail, wind, and tornadoes) for Monday afternoon/evening.
    We`ll need to monitor model trends in the next couple of days to
    determine specifics on timing and location.
     
  4. Xtreme Weather

    Xtreme Weather Member

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    "
    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0400 AM CDT Fri Mar 16 2018

    Valid 191200Z - 241200Z

    ...DISCUSSION...
    Numerical models are in relatively good agreement with the movement
    of a shortwave trough from the southern Plains across the lower MS
    Valley on Monday, with a surface low moving from AR into TN during
    the day or evening. The ECMWF is faster/farther east with the low
    than the GFS, which lends uncertainty. However, the risk area can be
    adjusted in later outlooks.

    On Monday Day 4, a cold front is forecast to stretch roughly from
    middle TN southward across MS by 00Z Tuesday, continuing eastward
    across AL and into GA by Tuesday morning. A warm front will also
    lift north across the region, stretching from northern AL into
    central GA at 00Z. Dewpoints in the 60s F and cool midlevel
    temperatures will result in around 1500 J/kg MUCAPE, with strong
    deep-layer shear profiles supporting organized convection. Low-level
    shear will be maximized near the warm front, and forecast wind
    profiles do support supercells. Conditional on storm mode, a tornado
    threat may exist. The northern threat into TN will depend on
    instability, but otherwise the synoptic setup appears most favorable
    there. To the south, instability will be much greater and one or
    more clusters of storms are expected to spread across AL and GA with
    damaging winds likely given strong mean wind profiles."
     
  5. Darklordsuperstorm

    Darklordsuperstorm Member

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    Woke up to seeing all the local mets in Birmingham sounding the alarm for Monday in unison. That always gets my attention.
     
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  6. Brick Tamland

    Brick Tamland Member

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    Tis the season.

    [​IMG]
     
  7. Arcc

    Arcc Supporter Member

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    Matt Grantham's discussion had me looking at this yesterday. I haven't checked today but yesterday's 18z GFS looks very favorable for Supercells with large hail. Anytime I see 500mb vectors out of the west it sounds alarm bells in my mind.

    The biggest argument against tornadoes is as was low level helicity as was in his discussion. The other thing is shallow boundary layer moisture. Definitely may be our first really legit threat if the GFS is correct.
     
  8. Snowfan

    Snowfan Member

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    Not telling
    Looks like we have our first real threat.
     
  9. Darklordsuperstorm

    Darklordsuperstorm Member

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    12z nam.....
     
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  10. Arcc

    Arcc Supporter Member

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    Yeah the NAM is pretty ridiculous, but even the GFS is getting into very concerning numbers. Here we go into the spring severe season

    Edit: After looking over the soundings on both NAM and GFS, I'd still like to see deeper moisture. I've seen numerous times over the years where shallow moisture in the boundary layer prevented an big event due to the dry air mixing down.
     
    Last edited: Mar 16, 2018
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  11. Millibar-Monster

    Millibar-Monster Member

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    What kind of Torcon number might we be looking at.
     
  12. ForsythSnow

    ForsythSnow Staff Member Moderator

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    Here's what Greg Forbes put out. Looks like the wedge saves some of us.
    [​IMG]
     
  13. Bama Ravens

    Bama Ravens Member

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    From NWS Birmingham:

    [​IMG]
     
  14. RollTide18

    RollTide18 Member

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    Enhanced Risk from BMX this far out is very concerning even without the tornado threat, that hail threat appears to be no joke
     
  15. Arcc

    Arcc Supporter Member

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    Yeah, hail will be a problem with a sounding like this. Helicity increases later as the LLJ strengthens, but based on a blend of the NAM and GFS, monster hail will be the largest threat.

    [​IMG]
     
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  16. StoneMtnWx

    StoneMtnWx Supporter Member

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    Latest from SPC has 15% svr probs with a hatched area in parts of N Al into parts of N/NW GA and S TN
    ...Discussion...
    The timing of a shortwave trough will play a critical role in severe
    potential on Monday across TN, MS, AL and GA. At this time, the NAM
    appears to be too slow and more amplified with this wave over MO
    compared to the ECMWF and GFS which show it over central KY or
    Middle TN at 00Z Tuesday. As a result, severe potential looks quite
    different amongst the models. For example, the latest NAM shows an
    extremely volatile setup over middle TN and northern AL clearly
    favoring strong tornadoes. However, the most likely solution appears
    to be a blend of the ECMWF and GFS, both showing a faster and
    lower-amplitude shortwave, as well as less low-level shear with
    relatively veered 850 mb flow.

    The most probable scenario appears to be for isolated, potentially
    significant severe storms from Middle TN into northern AL and GA,
    dependent on how much destabilization occurs especially in TN.
    Models also indicate substantial storm coverage across much of
    southern GA into northern FL, possibly in the form of an MCS, with
    mainly wind damage potential given unidirectional flow.

    Given the potential for significant severe storms, a categorical
    upgrade is possible in later outlooks once predictability increases
    and the centroid of severe coverage is better established.
     
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  17. Snowfan

    Snowfan Member

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    Not telling
    19482A1B-83A6-4065-8185-94E967C86A61.gif
    Here’s the latest from SPC.
     
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  18. Arcc

    Arcc Supporter Member

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    Looks like the 6z NAM pretty much caved to the GFS regarding more veered and weaker low level wind fields. That said I noticed some of the soundings had the WBZ level around 750mb, yikes. Add in those high lapse rates and the result is lots of insurance claims.
     
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  19. Arcc

    Arcc Supporter Member

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    Looking a little deeper at the 12z NAM, by far the highest threat for tornadoes will be north of I20 and east of I65 in AL. I would say probably in the Fort Payne to Rome area.
     
    Last edited: Mar 17, 2018
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  20. stormcentral

    stormcentral Storm Central Wx Member

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    Southeast TN may get a thump
     
  21. Xtreme Weather

    Xtreme Weather Member

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    NAM if correct down right scary but it is the outlier at this time...
    ANB sounding 12z
    529BAF8A-F803-42B7-B914-4399D9266ADD.jpeg
     
  22. Xtreme Weather

    Xtreme Weather Member

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    GFS says what SVR threat LoL to the North confines greatest risk over Southern portions

    3K NAM was scary as well line fires up along I-65 corridor yikes STP parameters of the charts if correct
     
    Last edited: Mar 17, 2018
  23. PEA_RIDGE

    PEA_RIDGE SKETCHY FLETCHY Member

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    Fort Wayne is East of I65 is it not??


    Sent from my Pixel 2 using Tapatalk
     
  24. Arcc

    Arcc Supporter Member

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    Yes.... :facepalm:

    Thanks for pointing that stupid error of mine out.
     
  25. Arcc

    Arcc Supporter Member

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    The WRFs should be a good indication to which way we should be leaning.

    The 3km NAM would definitely be concerning. I'd like to see a deeper moisture profile, but if we get to what it's showing it may not matter. It has temp of 69 with a dewpoint of 67 across east AL. That would put LCLs on the ground.
     
    Last edited: Mar 17, 2018
  26. Xtreme Weather

    Xtreme Weather Member

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    18z 3km NAM continues to sound the alarm also more of West GA involved
    83EE746E-0E4D-4A4C-A247-924BC877DA65.jpeg
     
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  27. Xtreme Weather

    Xtreme Weather Member

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  28. malak05

    malak05 Member

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    Great it seems Paulding county Ga ia the epicenter tbis year geez
     
  29. Arcc

    Arcc Supporter Member

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    NAM continues to trend more unimpressive.
     
  30. Natedogg25

    Natedogg25 Member

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    So it’s backing off of the threat a bit?
     
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