U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 251604 
Storm Prediction Center ac 251602 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1102 am CDT Tue Jun 25 2019 

Valid 251630z - 261200z 

..there is an enhanced risk of severe thunderstorms over parts of 
southeast Nebraska...northeast Kansas...northern Missouri...and 
southern Iowa... 

..there is a slight risk of severe thunderstorms over parts of the 
northern High Plains... 

The greatest potential for severe thunderstorms today is over parts 
of the Central Plains to northern Missouri and southern Iowa, where 
very large hail and sporadic severe gusts are possible. 

Water vapor imagery shows relatively strong zonal midlevel winds 
extending from the northern Great Basin across the northern plains. 
The southern fringe of the stronger westerlies lies across Colorado/KS/MO, 
where a weak east-west surface boundary is also present. South of the 
boundary, southerly low-level winds are helping to transport very 
moist air northward, with dewpoints expected to approach 70f by late 
afternoon along the border of eastern KS/NE. Strong heating is also 
occurring, which will yield an extremely unstable air mass. Present 
indications are that isolated intense storms will form along the 
boundary in the 19-21z period, with initial supercells capable of 
very large hail and damaging wind gusts. An isolated tornado or two 
is also possible. Activity is expected to build quickly eastward 
during the late afternoon along the boundary into southern Iowa and 
northern MO. Activity may organize into one or more short bowing 
segments with a risk of damaging wind gusts. 

..northern plains... 
The axis of strong midlevel winds extends across southern Montana into 
SD, with a few weak shortwave troughs embedded in the flow. It 
appears likely that widely scattered strong storms will develop over 
the higher terrain of western and southern Montana by late afternoon - 
spreading eastward through the evening. As this activity emerges 
into western South Dakota later today, slightly greater moisture/instability 
profiles may result in sufficient intensification for a few 
organized severe storms capable of large hail and damaging winds. 

..IA/IL/WI into lower Michigan and northern in... 
Morning visible satellite imagery shows a well-defined mesoscale convective vortex over 
eastern Iowa. Strong heating is occurring ahead of this feature, and 
some of the 12z cam guidance suggests that a cluster of 
thunderstorms will intensify this afternoon over southern 
WI/northern Illinois. If this occurs, strong westerly flow aloft, steep 
low-level lapse rates, and sufficient cape would pose a risk of 
damaging wind gusts. Have expanded the risk areas slightly farther 
east/south into lower Michigan and northern Indiana, and will 
monitor the region for further expansions of severe potential in 
later updates. 

.Hart/Goss.. 06/25/2019 


Mesoscale Discussion

acus11 kwns 251811 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 251810 

Mesoscale discussion 1242 
National Weather Service Storm Prediction Center Norman OK 
0110 PM CDT Tue Jun 25 2019 

Areas affected...portions of southern WI...northern 
Illinois...northwestern in...and southwestern lower Michigan 

Concerning...severe potential...watch possible 

Valid 251810z - 252015z 

Probability of watch issuance...40 percent 

Summary...isolated severe thunderstorms with a damaging wind and 
hail risk may develop this afternoon. Severe Thunderstorm Watch 
issuance is possible depending on radar trends. 

Discussion...a well-defined mesoscale convective vortex that originated from convection 
earlier this morning across NE will continue moving quickly eastward 
around 40 kt along the WI/Illinois border this afternoon. Low-level 
airmass recovery is still underway to the east of this MCV, with the 
environment only weakly unstable. But, surface dewpoints have 
generally increased into the upper 50s and lower 60s across 
north-central/northeastern Illinois. Recent vwp profiles from kdvn and 
klot show strong westerly flow around 35-50 kt in the 2-4 km above ground level 
layer in association with the mesoscale convective vortex. There is some concern that as 
low-level lapse rates continue to steepen, some of these enhanced 
winds aloft could reach the surface if a small thunderstorm complex 
can develop. Radar imagery from 18z shows a recent increase in 
reflectivity along the WI/Illinois border, and this could be the first 
attempt at the formation of a bowing segment. Isolated strong to 
damaging winds appear to be the main threat, although hail could 
occur in the strongest updrafts as mid-level lapse rates gradually 
steepen. Although watch issuance is not immediately likely, an 
increase in convective coverage/intensity may warrant a Severe 
Thunderstorm Watch at some point this afternoon. 

.Gleason/Hart.. 06/25/2019 

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


Latitude...Lon 42858952 43098887 43108719 42978577 42568540 41618573 
41198756 41358898 41808996 42498985 42858952