U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 190100 
Storm Prediction Center ac 190059 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0759 PM CDT sun Mar 18 2018 

Valid 190100z - 191200z 

..there is a slight risk of severe thunderstorms from part of 
southeast Texas to the central Gulf Coast through tonight... 

..there is a marginal risk of severe thunderstorms surrounding the 
slight risk to the Southern Plains and Arkansas... 

Severe storms with mainly hail and damaging winds are expected 
through tonight from southeast Texas to the central Gulf Coast 
region, while an isolated hail threat is possible from part of the 
Southern Plains to Arkansas. 

A compact, potent shortwave trough will advance into OK and the 
Central Plains this forecast period with a closed low forming in the 
base of the trough across OK to southeast Kansas by 12z. As this occurs 
the primary surface low will track/redevelop from southeast Colorado into 
central and northeast OK tonight to early Monday morning. An 
attendant cold front will advance east across the Southern Plains, 
reaching eastern OK/Texas into south Texas by 12z. The greatest 
severe-weather threat through tonight is expected to be from 
southeast Texas through southern la to the central Gulf Coast, in 
vicinity of a west-east outflow boundary near the I-10 corridor. 

..southeast Texas to the central Gulf Coast region... 
A cluster of discrete storms will advance to the east, tracking in 
vicinity of an aforementioned outflow boundary through southern la. 
Southerly surface winds and some strengthening of southwesterly 
850-mb winds in response to stronger height falls spreading into 
OK/Kansas tonight will maintain a moist and unstable environment across 
the slight risk area. Forcing for ascent attendant to a weak 
midlevel impulse/jet streak that aided storm development this 
afternoon in central Texas will spread east across la into the central 
Gulf Coast region. This combined with weak low-level warm air 
advection suggests convection will continue to form with eastward 
extent. Strong westerly 500-mb winds and strengthening 
west-southwesterly 850-mb winds from southern la to southwest Alabama 
will result in strong westerly shear favoring linear structures with 
damaging gusts and hail the primary severe threats. 

..eastern Texas/OK panhandles through parts of OK and southern Kansas... 
A strongly forced band of thunderstorms has developed from western 
Kansas into the northern Texas Panhandle per mosaic radar imagery and 
trends in lightning data. These storms should be mainly elevated 
through tonight as they track to the east and northeast across an 
area with a stable boundary layer. Weak instability suggests hail 
will be the primary threat with the stronger cells. 

..south-central OK into Arkansas... 
Operational-hrrr and esrl-hrrr each suggest a short broken band of 
storms may develop over south-central OK (near or just east of 
I-35), as strong height falls spread across this region in tandem 
with the cold front. This activity could produce damaging winds 
and/or hail with storms spreading to Arkansas toward Monday morning. 

.Peters.. 03/19/2018 


Mesoscale Discussion

acus11 kwns 190355 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 190355 

Mesoscale discussion 0138 
National Weather Service Storm Prediction Center Norman OK 
1055 PM CDT sun Mar 18 2018 

Areas affected...southwest through central Louisiana 

Concerning...Severe Thunderstorm Watch 12... 

Valid 190355z - 190530z 

The severe weather threat for Severe Thunderstorm Watch 12 

Summary...a modest for a few instances of damaging wind and hail 
will persist until around 06z, but overall weakening trend should 
continue, and another ww issuance should not be needed. 

Discussion...overall trend has been for storms over central la to 
undergo a gradual weakening trend and become less organized. This 
trend is expected to continue, but occasional semi-organized 
structures will persist. The downstream atmosphere across eastern la 
and southwest MS is only marginally unstable north of a dissipating 
convective outflow boundary. The surface layer has cooled 
substantially with temperatures in the low 60s, suggesting 
convective inhibition will remain a limiting factor and should 
continue to promote a slow but gradual weakening trend. In the 
meantime, the stronger storms will remain capable of producing 
locally strong wind gusts and some hail. 

.Dial.. 03/19/2018 

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


Latitude...Lon 31639184 30799189 30269252 30329344 30589371 31409320 
31869243 31639184