U.S. Severe Weather Forecast (Previsione fenomeni)

Tre Giorni

acus01 kwns 291648 
Storm Prediction Center ac 291647 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1147 am CDT Wed Mar 29 2017 

Valid 291630z - 301200z 

..there is an enhanced risk of severe thunderstorms from the 
Ozarks/lower MO valley southward to la/lower MS River Valley... 

..there is a slight risk of severe thunderstorms from the 
Ozarks/lower MO valley southward to la/lower MS River Valley... 

..there is a marginal risk of severe thunderstorms from East 
Texas/south-Central Plains to MS River Valley... 

Severe thunderstorms are expected later today into tonight from 
parts of East Texas, eastern Oklahoma, and southeast Kansas into the 
lower and middle Mississippi Valley. Large hail, tornadoes, and 
damaging winds will be possible especially late this afternoon and 

..Ozarks/lower MO valley to arklatex/lower MS River Valley... 
The closed upper trough currently over the south-Central Plains at 
late morning will continue a slow-general-northeastward advance 
toward the lower MO River Valley through late tonight and early 
Thursday. Ahead of this system, 12z regional observed soundings 
reflected considerable lapse-rate-related impacts from the 
overnight/early morning squall line that continues to move generally 
east-northeastward and decay across the Ozarks and Ark-la-tex 
vicinity. This may have ramifications on the 
extensiveness/likelihood of significant hail potential, for 
instance, although the air mass will recover/gradually moisten and 
destabilize to the south of a northward-moving warm front across the 
Ozarks/lower MO valley, and ahead (east) of a slow-eastward-moving 
cold front. 

Latest thinking is that surface-based storms will develop as early 
as mid-afternoon near the eastern Kansas surface low southward along the 
front, including far eastern portions of Kansas/OK into western portions 
of MO/AR. Moderate low-level hodograph curvature (beneath strong but 
somewhat backed mid-level southwesterly winds) and resultant strong 
low-level shear/srh will support a tornado risk aside from large 
hail and evolving damaging wind risk into this evening. 

Farther south, storms may diurnally be a bit more isolated across 
the remainder of the arklatex vicinity, although an ongoing 
quasi-linear cluster across near-coastal southeast Texas may persist 
east-northeastward into la as it favors a zone of outflow-related 
weak boundary/zone of differential heating. This cluster and other 
peripheral development may pose a damaging wind/tornado risk through 
the afternoon and evening hours. 

Later tonight, storms should increase in coverage/intensity 
initially across portions of Arkansas/la as forcing for ascent/DPVA 
increases related to an east/northeastward-ejecting vorticity maxima 
within the base of the larger-scale trough. Related mass response 
should result in increasingly strong low-level winds/confluence. A 
mixed Mode of storms should be prevalent, with hail initially 
possible prior to a more common damaging wind/embedded tornado risk 
as storms toward/across the MS river late tonight. 

.Guyer.. 03/29/2017 


Mesoscale Discussion

acus11 kwns 291832 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 291831 

Mesoscale discussion 0368 
National Weather Service Storm Prediction Center Norman OK 
0131 PM CDT Wed Mar 29 2017 

Areas affected...southeast Texas into western Louisiana 

Concerning...severe potential...watch possible 

Valid 291831z - 292100z 

Probability of watch issuance...60 percent 

Summary...storms may strengthen later today into the evening with a 
tornado risk along with locally damaging winds. A watch could be 
required later this afternoon. 

Discussion...a leading line of cells approaching the Sabine River is 
currently weakening, while new cells continue to evolve to the west 
near dying/mixing outflow boundaries. Here, the cap is locally 
weaker as well as compared to points east, although the 18z lch 
sounding shows a dramatic increase in low-level moisture and 
weakened capping inversion. 

Strong southwesterly flow aloft will continue to overspread the 
area, with main surface low well to the north. Southerly 850 mb flow 
around 25-35 kt will be maintained, and change little through 00z. 
As the trough approaches, a boost to low-level convergence will 
occur and help to eventually push this cluster of cells eastward 
across la. 

In the short term, it appears the severe threat will be driven by 
the storm scale, with merging cells eventually becoming supercells 
as gradual destabilization occurs and meso lows form, also locally 
backing surface winds and maintaining favorable low-level shear. 
Indeed vwps show better backing at 850 mb in closer proximity to the 
storm cluster, with less favorable shear farther east into la. The 
air mass remains very moist, with impressive lapse rates aloft. 
Although widespread severe is not expected, a small corridor may 
certainly develop a supercell tornado risk this afternoon through 

.Jewell/guyer.. 03/29/2017 

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


Latitude...Lon 28699576 29809541 30549526 31129463 31149395 30959310 
30599297 30169299 29839311 29699330 29629383 29429440 
29049485 28819535 28699576