U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 182021 
Storm Prediction Center ac 182019 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0319 PM CDT Wed Sep 18 2019 

Valid 182000z - 191200z 

..there is a marginal risk of severe thunderstorms across parts of 
southeast Minnesota and northern Wisconsin... 

A few strong storms are possible this evening from northern and 
central Wisconsin into southeast Minnesota. 

The only change to the outlook is to remove thunder from parts of 
western and northern Minnesota where dry air advection is reducing 
instability and reducing the chance for thunderstorm development. 

.Broyles.. 09/18/2019 

Previous discussion... /issued 1116 am CDT Wed Sep 18 2019/ 

A strong negatively-tilted shortwave trough is rotating 
northeastward across ND into northern Minnesota. A trailing cold front 
extends across Minnesota into northwest Iowa. Clouds are prevalent along the 
front, but should slowly dissipate by mid afternoon, allowing some 
heating/destabilization to occur. This is expected to result in 
scattered thunderstorm development near the Minnesota/WI border - mainly 
after 00z. Forecast soundings suggest sufficient winds aloft and 
cape to promote a few gusty/damaging wind reports, but organized 
severe activity is not anticipated. 

A broad precipitation shield continues with Imelda, with the only 
areas of more discrete convective elements along the far eastern and 
southern peripheries of the complex. Local VAD profiles show that 
low-level shear is not particularly strong in these outer bands. 
While transient rotation is possible in the strongest cores, the 
tornado threat appears to remain low. 


Mesoscale Discussion

acus11 kwns 182231 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 182231 

Mesoscale discussion 1982 
National Weather Service Storm Prediction Center Norman OK 
0531 PM CDT Wed Sep 18 2019 

Areas affected...portions of southeast Texas 

Concerning...severe potential...watch unlikely 

Valid 182231z - 190000z 

Probability of watch issuance...5 percent 

Summary...a localized tornado threat will persist for the next hour 
or two between Houston and Beaumont. 

Discussion...several mini-supercells have exhibited low-level 
rotation in the past hour with the cluster of storms between Houston 
and Beaumont. One of these cells showed a tight low-level couplet 
and probable dew points in far eastern Harris County around 22z. Daytime 
heating south of this activity has increased temperatures into the 
80s with dewpoints remaining in the mid to upper 70s. This has 
yielded MLCAPE around 1500 to 2000 j/kg. The khgx vwp shows some 
low-level srh, but the low-level shear is more favorable at klch 
with 0-1 srh around 125 m2/s2. However, the environment in southern 
Louisiana is more stable due to ongoing precipitation. Therefore, 
there is a narrow corridor where this better low-level shear and 
instability overlaps where the environment is favorable for a brief 
tornado threat. Given the limited area and the expected short 
duration of this threat, a watch is unlikely. 

.Bentley.. 09/18/2019 

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


Latitude...Lon 29799533 29999502 30099469 29999430 29629428 29469455 
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