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May 27, 2018 1730 UTC Day 2 Convective Outlook
Updated: Sun May 27 17:24:17 UTC 2018 (Print Version | 20180527 1730Z Day 2 shapefile | 20180527 1730Z Day 2 KML)
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 Forecast Discussion

   SPC AC 271724

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1224 PM CDT Sun May 27 2018

   Valid 281200Z - 291200Z


   Severe thunderstorms with isolated large hail, wind damage and
   perhaps a tornado threat are expected across parts of the Great
   Plains.  A couple of brief tornadoes will also be possible in the
   Southeast, in conjunction with Alberto.

   ...Great Plains...
   An upper-level low will move slowly northeastward into the northern
   Rockies on Monday as an upper-level ridge amplifies across the upper
   Mississippi Valley. At the surface, a trough will deepen across
   eastern Colorado as a slow moving front moves across northern parts
   of the central Plains. Surface dewpoints to the southeast of the
   front should be in the 55 to 60 F range allowing for moderate
   destabilization across parts of the central plains by afternoon.
   Convection is forecast to initiate on the western edge of the
   stronger instability during the mid to late afternoon from
   east-central Colorado northward into eastern Wyoming. Thunderstorm
   development should take place as this convection moves
   east-northeastward into the central and northern high Plains during
   the late afternoon and early evening. Other thunderstorms may also
   develop further east across parts of the Dakotas and Nebraska.

   NAM and GFS forecast soundings are in reasonable agreement across
   the central and northern high Plains during the late afternoon
   showing MLCAPE values mostly in the 2000 to 3500 J/kg range across
   the moist sector. In addition, low to mid-level lapse rates are
   forecast to be quite steep exceeding 8.0 C/km in some areas. This
   combined with moderate deep-layer shear will be favorable for
   supercells with large hail. The strongest deep-layer shear is
   forecast early Monday evening over western Nebraska and northeast
   Colorado due to the influence of a strengthening low-level jet. This
   area appears to have the strongest potential for tornadoes. Model
   forecasts markedly increase convective coverage across the central
   Plains during the mid to late evening as a shortwave trough moves
   out. As a result, the wind damage potential may increase especially
   if storms can consolidate into an organized multicell line segment.

   Further south across western Kansas into the Texas Panhandle, 700 mb
   temperatures are expected to be above 12 Celsius which will
   contribute to a capping inversion. By late afternoon, increasing
   low-level convergence around a surface low in southeast Colorado
   along with a weakening cap, should allow for isolated convective
   initiation. Moderate instability and deep-layer shear combined with
   steep low to mid-level lapse rates should be favorable for isolated
   large hail and a few strong wind gusts.

   ...Southeast U.S. and Florida...
   The National Hurricane Center is forecasting Subtropical Storm
   Alberto to move across the northeast Gulf of Mexico and approach the
   coast of the Florida Panhandle around daybreak on Monday. Rainbands
   should spread northward across much of the Florida Peninsula into
   parts of Georgia and South Carolina during the day. Forecast
   soundings from central Florida northward into Georgia show speed
   shear and some directional shear in the lowest 3 km AGL suggesting a
   tornado threat will be possible with discrete rotating storms. The
   greatest potential for tornadoes could exist from the eastern
   Florida Panhandle northward into central Georgia where the
   combination of instability and low-level shear is forecast to be the

   Tornado:   5%     - Slight
   Wind:     15%     - Slight
   Hail:     15%     - Slight

   ..Broyles.. 05/27/2018



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