SPC AC 161726

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1226 PM CDT Thu May 16 2024

   Valid 171200Z - 181200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
   GULF COAST STATES...

   ...SUMMARY...
   Scattered severe thunderstorms with a few tornadoes, very large
   hail, and damaging winds are possible across parts of the Gulf Coast
   States on Friday through Friday night.

   ...South-central to Southeast States...
   A messy severe weather setup is expected on Friday into Friday night
   amid a series of low-amplitude impulses ejecting within and around
   the positive-tilt, southern-stream shortwave trough across the
   southern Great Plains. Synoptic surface pattern appears nebulous and
   likely driven on the mesoscale by several rounds of convection today
   through the end of D2. Primary changes with this outlook are to
   expand severe probabilities west and east, while reducing
   probabilities across the northern portion of the threat area.

   An MCS or clustered remnants of an early morning one should be
   ongoing at 12Z Friday across parts of the central Gulf Coast region.
   Outflow from this preceding D1 activity will serve as the focus for
   renewed thunderstorm development later in the day. Most guidance
   suggests a separate area of upstream convection may be ongoing or
   will develop by midday across parts of south TX and the TX Gulf
   Coast along and behind the composite outflow/cold front that will
   surge southeast in TX on D1. With the fastest mid-level
   southwesterlies expected to overlie the western to central Gulf
   Coast during the first half of the period, supercells capable of
   very large hail will be possible. This threat should be focused in a
   narrow corridor along the TX Gulf Coast initially, and then develop
   later in the afternoon to evening in the central Gulf Coast. Some of
   this latter activity will have relatively greater potential for
   tornado/wind threats, focused along the outflow in the wake of the
   early-morning MCS. 

   Additional isolated to scattered thunderstorm development should
   occur within the post-frontal/outflow air mass centered on parts of
   the Red River Valley and in south-central TX near the Rio Grande.
   This activity will likely be aided by the embedded low-amplitude
   impulses within the southern-stream shortwave trough. Residual
   buoyancy should be adequate for an isolated hail/wind threat amid
   more muted deep-layer shear closer to the trough axis.

   ...Northern Great Plains...
   A vigorous, northern-stream shortwave trough will move across the
   northern Rockies into the Prairie Provinces and adjacent parts of
   MT/ND through early Saturday. Primary surface cyclone will occlude
   over SK/MB, with secondary cyclogenesis occurring near the SD/WY/MT
   border area along the trailing Pacific cold front. With only
   modified moisture return ahead of the front, MLCAPE will remain
   rather weak. Initial convective development will probably occur
   within the post-frontal upslope flow regime during the early to mid
   afternoon. This activity should spread east and likely expand during
   the late afternoon into the evening. With deeply mixed thermodynamic
   profiles ahead of the front, and steep lapse rates being maintained
   behind it, high-based thunderstorms with amalgamating outflows are
   expected. While the bulk of strong 700-500 mb westerlies will lag
   behind the front, the strengthening flow should support a threat for
   strong to isolated severe surface gusts before convection wanes
   after dusk.

   ..Grams.. 05/16/2024

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z