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    Day 2 Outlook >
Dec 13, 2018 0600 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Thu Dec 13 05:55:07 UTC 2018 (Print Version | 20181213 1200Z Day 1 shapefile | 20181213 1200Z Day 1 KML)
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 Forecast Discussion
   SPC AC 130555

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1155 PM CST Wed Dec 12 2018

   Valid 131200Z - 141200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   EAST TEXAS...

   ...SUMMARY...
   Isolated strong to severe thunderstorms may impact parts of the
   Ark-La-Tex region into the lower Mississippi Valley and central Gulf
   Coast vicinity today and tonight. Large hail should be the main
   threat in parts of east Texas late this afternoon and evening.

   ...Synopsis...
   A lead southern-stream shortwave trough will advance quickly
   eastward over the lower MS Valley into the Southeast today and
   tonight. Meanwhile, a more amplified upper trough will deepen and
   eventually close off over central TX this afternoon and evening. A
   surface low will develop slowly eastward across central/east TX in
   tandem with the upper low, while a weaker secondary low develops
   across the central Gulf Coast tonight into early Friday morning.

   ...East TX into the Lower MS Valley...
   Scattered thunderstorms will likely be ongoing this morning over
   parts of southeast TX as continued low-level warm air advection and
   large-scale lift occurs ahead of the previously mentioned
   southern-stream shortwave trough. Although low-level moisture will
   likely remain limited with dewpoints in the upper 50s/lower 60s,
   modest diurnal heating should support weak instability from
   southeast TX into parts of southern LA through this morning. With
   30-40 kt of effective bulk shear forecast to be present over this
   region, isolated strong/gusty downdraft winds could occur. A tornado
   also cannot be ruled out, mainly near the coast where low-level
   moisture will be somewhat greater.

   As the primary upper trough/low moves across the southern Plains
   this afternoon, a strong mid-level jet of 50-80+ kt will overspread
   much of east TX. There still remains uncertainty regarding the
   degree of destabilization that will develop across this region in
   the wake of morning convection. Still, there will probably be enough
   of a gap through much of the afternoon to allow for some surface
   heating, and mid-level lapse rates will be steepening ahead of the
   upper low as mid/upper-level temperatures decrease. Forecast
   soundings from the NAM/RAP suggest MLCAPE around 1000-1250 J/kg will
   develop in a narrow corridor arcing around the eastern periphery of
   the surface cyclone by 20-21Z. The strong forcing associated with
   the mid-level jet and a cold front attendant to the surface low will
   likely initiate isolated to widely scattered convection by late
   afternoon in parts of east TX. Although not much veering of the
   south-southwesterly winds with height is forecast, they will
   strengthen considerably through the troposphere. Long, nearly
   straight hodographs at mid levels suggest isolated large hail with
   supercells will probably be the main threat, although strong/gusty
   winds could also occur. A tornado or two may also be possible,
   primarily to the northeast of the surface low where low-level winds
   should be locally backed more southeasterly.

   ...Central Gulf Coast...
   The inland advance of a coastal warm front will likely be tempered
   until late tonight across coastal southeastern LA, MS, AL, and the
   western FL Panhandle. Low-level warm/moist air advection will
   gradually increase overnight as the closed upper low over east TX
   slowly approaches from the west and a secondary surface low forms
   and subsequently develops eastward across this region. With low to
   mid 60s dewpoints forecast to move only slightly inland ahead of the
   surface low, a marginal wind/tornado threat should generally remain
   confined along/near the coast where weak surface-based instability
   and strong low-level shear will be present.

   ..Gleason/Cook.. 12/13/2018

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z

        
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Page last modified: December 13, 2018
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