U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 300602 
Storm Prediction Center ac 300601 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0101 am CDT Thu Mar 30 2017 

Valid 301200z - 311200z 

..there is an enhanced risk of severe thunderstorms from southern 
parts of Illinois and Indiana and southwest Ohio south across the 
Tennessee Valley to central Mississippi... 

..there is a slight risk of severe thunderstorms from the middle and 
lower Mississippi Valley across the Ohio Valley to the 
Appalachians...and south to the Gulf Coast... 

..there is a marginal risk of severe thunderstorms surrounding the 
slight risk area...and extending to the Georgia/South Carolina 
coastal area... 

Severe thunderstorms potentially capable of damaging winds, 
tornadoes, and hail are forecast on Thursday over parts of the 
middle and lower Mississippi Valley into the Ohio and Tennessee 

An upper low crossing eastern Kansas early in the period is forecast 
to accelerate eastward across Missouri and into the Midwest through 
the period -- as a vigorous short-wave over the Pacific northwest at 
the start of the period digs southeastward with time, evolving into 
a deepening closed low with time and reaching the Arizona/Utah 
border region by the end of the period. 

As the eastern upper low is kicked eastward by the digging western 
system, short-wave troughing -- within broader cyclonic flow 
surrounding the low -- will move quickly eastward out of the 
Southern Plains and across the Gulf of Mexico and Gulf coastal 
states. This will facilitate a rather rapid eastward advance of a 
surface cold front across the southeast quarter of the country. 
This front -- trailing southward from a parent low moving across the 
Ohio Valley states through the afternoon and evening -- should 
extend from the southern Appalachians to the Florida Panhandle 
vicinity by 31/12z. 

..the Midwest south to the Gulf Coast, and the Mississippi Valley 
east to the Appalachians... 
a very complex weather scenario continues to unfold -- complicated 
largely by ongoing showers and locally strong to severe storms now 
affecting the middle and lower Mississippi Valley area. Models 
suggest that much of this convection will be contained within two 
distinct clusters at the start of the period -- one crossing the mid 
Mississippi Valley into the lower Ohio Valley area, and a Second 
Crossing southern and eastern Mississippi/eastern Louisiana. The 
Ohio Valley convection is forecast to gradually weaken through the 
morning hours, while the southern cluster of convection may persist 
-- in a locally severe manner -- across the central Gulf coastal 

This convection and associated cloud cover continues to cast 
uncertainty with respect to areas of potentially greater insolation 
and thus destabilization, but it appears that at least modest 
instability will evolve along and ahead of the advancing cold front 
-- which should extend southward from a western Illinois surface low 
roughly along the Mississippi River around midday. With mixed-layer 
cape values likely reaching 500 to 1500 j/kg by early afternoon in 
the wake of prior convection, new storm development should begin. 
Organization of the storms will be augmented by strong lower- and 
middle-tropospheric south-southwesterly flow, and though turning 
with height will remain limited in most areas, speed shear suggests 
both rotating storms and small-scale bowing segments will evolve 
with time. Along with potential for hail, damaging winds are 
expected, and a few tornadoes will be possible as well -- 
particularly over the lower Ohio Valley area where a more 
southeasterly component to the surface flow should exist ahead of 
the low and in the vicinity of the warm front. Convection may 
organize into a broken band, spreading eastward across the Ohio and 
Tennessee valleys and central Gulf coastal states through the 
afternoon and evening, along with attendant severe potential. 

With areas of most concentrated risk difficult to discern, a broad 
enh/level 3 risk area is being included, with slight/level 2 risk 
being expanded eastward at this time -- both across the mid Ohio 
Valley along the mid-level low track, as well as across the southern 
Appalachians region as a rapidly advancing short-wave trough Fosters 
increasing ascent through the evening and overnight hours. 

.Goss/cohen.. 03/30/2017 


Mesoscale Discussion

acus11 kwns 300635 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 300634 

Mesoscale discussion 0376 
National Weather Service Storm Prediction Center Norman OK 
0134 am CDT Thu Mar 30 2017 

Areas affected...south central MS through southeast la 

Concerning...Tornado Watch 101... 

Valid 300634z - 300800z 

The severe weather threat for Tornado Watch 101 continues. 

Summary...tornado risk continues to trend downward as primary threat 
has transitioned to isolated damaging wind across remaining portion 
of Tornado Watch 101. This watch will be allowed to expire at 08z. 
While some risk for mainly a few strong wind gusts may persist from 
southeast la into southern MS for an hour or two beyond 08z, the 
overall threat is expected to remain too marginal for another ww 

Discussion...broken squall line from southern MS into central 
portions of coastal la is moving east at 25-30 kt, while individual 
storms embedded within the line move more rapidly northeast. A few 
loosely organized storms persist within a portion of the line 
including bowing segments across southern and south central MS. Vwp 
data show largely unidirectional wind profiles with modest size 
low-level hodographs. Tendency will be for the low-level jet to 
gradually shift north toward the Tennessee Valley and away from the more 
unstable portion of the warm sector into the early morning. While 
threat for mostly a few strong to damaging wind gusts may persist 
next 2-3 hours as storms continue through the marginally unstable 
environment, overall threat appears too marginal for an additional 
ww issuance. 

.Dial.. 03/30/2017 

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


Latitude...Lon 29769292 30149184 31209075 32369019 32728985 32368949 
30888991 29769050 29379186 29769292