U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 190539 
Storm Prediction Center ac 190537 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1237 am CDT Thu Jul 19 2018 

Valid 191200z - 201200z 

..there is a slight risk of severe thunderstorms across the middle MS 

Severe thunderstorms will be possible later today across parts of 
the Mississippi Valley and Central Plains. A few strong storms may 
also be noted near the Canadian border of the northern plains and 
over the southwestern US. 


Early-morning water-vapor imagery depicts a well-defined mid-level 
circulation over South Dakota. This feature is forecast to shift into 
southwest Minnesota as associated 500mb speed Max digs into southwest Iowa by 
mid afternoon. Large-scale high-level diffluence downstream across 
the mid-MS valley will encourage deep convection along the eastern 
edge of plains steep lapse-rate plume. 

While the large-scale pattern favors a focused corridor of potential 
severe, especially across portions of Iowa into northeast MO, pre-dawn 
convection across this region may prove disruptive regarding 
timing/placement of potentially more significant thunderstorm 
development later in the day. Will maintain higher severe probs for 
the more synoptically favorable portion of the upper trough but 
meso-scale features will undoubtedly influence severe development. 

Latest NAM guidance suggests strong heating will develop ahead of a 
surface front from Kansas into southwest Iowa. If this boundary is the 
dominant low-level feature, and forecast buoyancy is as expected, 
then thunderstorms should develop immediately downstream of the 
surface low position, potentially arcing southwest into portions of 
Kansas. There is some concern for supercell development across 
Iowa/northern MO and if discrete storms develop then large hail and 
damaging winds can be expected. While a tornado can not be ruled 
out, low-level shear is not forecast to be particularly strong. This 
activity will propagate southeast during the evening as the 
mid-level jet translates toward southern MO. 

..northern plains... 

Strong surface heating is forecast across eastern Montana into ND ahead 
of a surface front that will sag south of the international border 
during the afternoon. While instability is not forecast to be that 
significant, steep lapse rates and adequate deep-layer flow should 
support a few marginally severe thunderstorms capable of generating 
gusty winds and some hail. This activity will be strongly diurnal in 


Seasonally high-precipitable water air mass will be maintained across northwest 
Mexico into the lower Colorado River valley through the day1 period as the 
center of a mid-level high begins to drift toward the southern 
rockies. While mid-level temperatures are forecast to be somewhat 
warm across AZ, strong surface heating and adequate buoyancy may 
prove sufficient for gusty winds with the strongest convection. 

.Darrow/squitieri.. 07/19/2018 


Mesoscale Discussion

acus11 kwns 190853 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 190852 

Mesoscale discussion 1081 
National Weather Service Storm Prediction Center Norman OK 
0352 am CDT Thu Jul 19 2018 

Areas affected...southeast NE...northeast Kansas...far northwest MO 

Concerning...Severe Thunderstorm Watch 282... 

Valid 190852z - 190945z 

The severe weather threat for Severe Thunderstorm Watch 282 

Summary...hail and strong to severe wind gusts remain possible with 
the thunderstorm cluster moving through southeast NE into far 
northeast Kansas. 

Discussion...convective cluster, anchored by a strong updraft along 
its western periphery, continues to move through southeast NE. 
Updraft intensity has largely remained steady over the past hour or 
so. Given that the downstream airmass is moist and unstable, the 
relatively steady-state trend is expected to continue for at least 
the next hour. Most recent radar imagery suggests a turn from a 
predominately southeasterly motion to more of a south-southeasterly 
motion (into the slightly higher instability) may be occurring 
presently. Hail and strong to severe wind gusts remain possible with 
this cluster. 

.Mosier.. 07/19/2018 

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


Latitude...Lon 39549731 40119733 40539684 40659615 40629562 40289506 
39509491 38769601 39009684 39549731