U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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Storm Prediction Center ac 281741 


Day 2 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1241 PM CDT Tue Mar 28 2017 


Valid 291200z - 301200z 


..there is an enhanced risk of severe thunderstorms Wednesday 
afternoon and night over much of Arkansas...northwest la...East Texas and 
extreme southeast OK... 


..there is a slight risk of severe thunderstorms surrounding the 
enhanced risk from southeast Kansas...southern MO...and southern Illinois to 
the middle Texas coast... 


..there is a marginal risk of severe thunderstorms across portions 
of the Southern Plains to the lower and middle MS valley... 


... 
Severe thunderstorms are expected on Wednesday into Wednesday night 
from parts of East Texas, eastern Oklahoma, and southeast Kansas 
into the lower and middle Mississippi Valley. 


... 
A strong shortwave trough will move steadily east across the 
southern half of the Great Plains on Wednesday into Wednesday night 
toward the lower and middle MS valley, while an embedded closed 
midlevel cyclone tracks from northwest Texas into OK and Kansas. An 
upstream shortwave trough is expected to dig southeastward from the 
southwest states through northern Mexico toward the lower Rio Grande 
Valley late Wednesday night. At the surface, an elongated area of 
low pressure is expected to extend from southwest OK to 
south-central/southeast Kansas at 12z Wednesday, with models suggesting 
low pressure will tend to consolidate and reach southwest MO region 
by 12z Thursday. A cold front/dryline is forecast to extend 
southward through central OK to deep south Texas at the start of day 2. 
This front will shift slowly east into eastern OK and East Texas by 
Wednesday afternoon. A warm front will move north across much of Arkansas 
and the mid-south, reaching southeast KS, southern MO to western Tennessee 
by 30/00z. A secondary cold front surging to the east/southeast 
across the Southern Plains should overtake the lead cold front late 
Wednesday night and extend from western Arkansas to off the Texas coast by 
12z Thursday. 


..Southern Plains to lower-mid MS valley... 
Models continue to indicate the widespread thunderstorms across the 
Southern Plains tonight should diminish in intensity and severe 
threat Wednesday morning over east TX, east OK into southeast Kansas to 
southwest MO. Midlevel impulses translating through the eastern 
periphery of the closed low Wednesday morning and afternoon should 
support renewed storm development/intensification from parts of 
northeast Texas through eastern OK to southeast Kansas along the first cold 
front. Greater destabilization on the northern extent has resulted 
in a little northward expansion of the slight risk area. Although 
strong shear vectors oriented nearly parallel to the cold front 
suggest a linear storm Mode, the strength of the bulk shear /50+ kt/ 
and moderate instability support embedded supercells. Thus, all 
severe hazards will be possible, except farther north into northeast 
Kansas where storms should remain elevated. 


Meanwhile, the next in a series of midlevel shortwave troughs will 
move toward The Ark-la-tex region Wednesday evening and night, and 
strong 500-mb 2-hour height falls of 60-90 meters are expected 
across The Ark-la-tex and eastern OK to the lower and mid MS valley. 
Additional storms will develop across East Texas Wednesday afternoon 
where the environment will be moderately unstable with strengthening 
effective bulk shear resulting in organized storms producing all 
severe hazards. A 50+ southerly low-level jet developing Wednesday 
evening and shifting east after dark will increase the severe- 
weather threat resulting in a risk of supercells and bowing 
structures producing tornadoes (possibly strong), as well as large 
hail and damaging winds. 


..middle Texas coast to deep south Texas... 
The southern extent of the first cold front is expected to move 
offshore Wednesday morning of the middle and southern Texas coast, 
though moisture return in expected Wednesday night with the approach 
of the digging shortwave trough and the approach of the secondary 
cold front. Steep midlevel lapse rates spreading atop the moisture 
return will support moderate instability, with a few strong to 
severe storms possible late Wednesday night/early Thursday morning 
as the cold front reaches the middle and south Texas coastal region. 


.Peters.. 03/28/2017 


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