U.S. Severe Weather Forecast (Convective Outlook)

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swody1 
Storm Prediction Center ac 250055 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0755 PM CDT Fri Mar 24 2017 


Valid 250100z - 251200z 


..there is a slight risk of severe thunderstorms this evening 
across parts of southeast Texas into the Ozark Plateau and lower 
Mississippi Valley... 


..there is a marginal risk of severe thunderstorms across 
surrounding portions of the plains and Mississippi Valley... 


... 
A risk for severe thunderstorms continues, mainly across parts of 
eastern Texas into the Ozark Plateau this evening, perhaps spreading 
into the lower Mississippi Valley overnight. 


..plains/Mississippi Valley... 
Although a significant lower/mid tropospheric cyclone is in the 
process of weakening across the south Central Plains, deep layer 
mean wind fields and vertical shear within/above the surface warm 
sector remain potentially supportive of substantive severe weather 
potential as the center of circulation turns east northeast of 
central Oklahoma toward the Ozarks tonight. The lack of a broad 
deep low-level moisture return off the Gulf of Mexico appears the 
primary factor limiting destabilization and convective potential. 
However, mid-level cooling to the south and east of the circulation 
center has cut off the northeastward advection of elevated 
mixed-layer air from the Mexican plateau region. And a pre-frontal 
band of convective cloud cover and precipitation has stabilized 
boundary layer conditions ahead of the dryline, across much of 
western Arkansas into the Sabine valley. Furthermore, downward 
mixing of dry lower/mid tropospheric air has slowed boundary layer 
moistening across a large portion of the lower Mississippi Valley. 


Still, attempts at vigorous thunderstorm development are underway 
near and just ahead of the dryline, within a narrow corridor of more 
substantive moistening, from near the Oklahoma/Arkansas border 
south/southwestward into parts of southeastern Texas. An 
intensifying line segment northeast/east of Fayetteville and Fort 
Smith Arkansas likely has been aided by stronger forcing for ascent ahead 
of the mid-level low. This is expected to continue to spread 
northeastward across parts of southern Missouri and northern 
Arkansas through this evening, with at least some risk for 
potentially damaging wind gusts, but severe weather potential, in 
general, may be limited by weak boundary layer instability. 


Somewhat better severe weather potential appears to exist from 
portions of eastern/southeastern Texas through central/northern 
Louisiana and southeastern Arkansas. Forcing for ascent associated 
with an impulse pivoting around the southeastern periphery of the 
south Central Plains mid-level low may contribute to consolidation 
of initially discrete storm development into a progressive 
organizing line of storms. This could be aided by some increase in 
low-level moisture off the Gulf of Mexico, but even this is not 
certain. Given sizable clockwise curved low-level hodographs near a 
40-50 kt southerly 850 mb jet, a risk for tornadoes exists, 
particularly this evening across parts of southeast Texas into The 
Ark-la-tex region. However, potentially damaging wind gusts may 
become the more prominent threat, and could continue into the lower 
Mississippi Valley overnight. 


.Kerr.. 03/25/2017 


$$ 

Mesoscale Discussion


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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 250258 
laz000-txz000-250400- 


Mesoscale discussion 0324 
National Weather Service Storm Prediction Center Norman OK 
0958 PM CDT Fri Mar 24 2017 


Areas affected...southwest and central parts of la 


Concerning...severe potential...watch possible 


Valid 250258z - 250400z 


Probability of watch issuance...60 percent 


Summary...in addition to an increasing risk for storms capable of 
damaging winds moving into the area from the west during the 
overnight hours, the potential exists for a tornado or two. 


Discussion...latest subjective surface analysis indicates an 
increase of surface dewpoints (into the mid-upper 60s degrees f) 
over central and southwest la that is probably the result of a 
relaxing in boundary-layer mixing and the northward advection of 
Richer moisture. The kpoe and klch vads show 50-kt and 40-kt from 
the south-southwest at 3km above ground level. According to short-term model data, 
the strongest low-level shear will be located farther north over 
central la compared to the immediate coast. Forecast soundings show 
large looping hodographs with 300-400 m2/s2 of 0-1km srh. As such, 
the greatest conditional risk for a tornado may be in the 
overlapping area of where the stronger low-level shear and the 
northern extent of the Richer low-level moisture. At this point, it 
appears this may be over central la during the overnight hours. 


.Smith/Thompson.. 03/25/2017 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...lch...shv... 


Latitude...Lon 31639368 31469236 31169214 30569222 30249281 30219366 
31639368