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Day 1 Outlook Day 2 Outlook Day 3 Outlook Days 4-8 Outlook

Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 2000Z Outlook
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion

ACUS01 KWNS 161950
SPC AC 161948

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0148 PM CST Sat Dec 16 2017

Valid 162000Z - 171200Z


Isolated to scattered thunderstorms should occur from parts of south
Texas to western Mississippi, with the possibility of a few strong
storms near the Texas coast late tonight.

...20Z Update...
No changes have been made to the ongoing forecast. Forecast
soundings from recent RAP/HRRR runs continue to suggest the better
potential for surface-based thunderstorms will remain just offshore
the middle/upper TX Gulf Coast late tonight. Greater low-level
moisture characterized by mid to upper 60s dewpoints remains more
than 100 miles off the middle TX Gulf Coast per 19Z observations,
and some uncertainty remains with the inland extent of mid 60s
dewpoints late tonight. For now, appreciable surface-based
thunderstorm and associated strong/gusty wind and isolated tornado
risk over land still appears too low across any portion of the TX
Gulf Coast to include severe probabilities with this update.

..Gleason.. 12/16/2017

.PREV DISCUSSION... /ISSUED 1028 AM CST Sat Dec 16 2017/

...Coastal Texas to far Southern Louisiana...
In response to an amplifying/kicker shortwave trough along the CA
coast, a closed upper low over northern Mexico at midday will become
more progressive and eventually take on a more negative tilt as it
accelerates northeastward over the eastern half of TX toward eastern
OK/Ark-La-Tex tonight. Weak near-coastal cyclogenesis is expected
along the middle/upper TX coast this evening with gradual air mass
modification occurring over the western Gulf of Mexico.

As this occurs, convection is likely to increase this evening with
widely scattered thunderstorms spreading northeastward through the
overnight. While deep-layer/low-level shear (accentuated by a 40-55
kt low-level jet) will steadily increase this evening, the
likelihood of a surface-based-convection-conducive air mass remains
questionable over inland areas. 

Consistent with late-morning satellite imagery and inland/maritime
observations, latest short-term guidance continues to indicate that
the semi-moisture rich air mass will likely remain just offshore
through tonight. This should limit the potential for surface-based
convection over inland areas with various RAP/12Z NAM forecast
soundings depicting the persistence of a shallow near-surface stable
layer with surface dewpoints generally no higher than 63-64F inland.
While the potential for a tornado and/or damaging winds should
remain very low inland, a few supercells and/or semi-organized bows
may be noted across the offshore waters tonight off the middle/upper
TX coast toward coastal southwest LA.