U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 230052 
Storm Prediction Center ac 230051 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0751 PM CDT Thu Jun 22 2017 

Valid 230100z - 231200z 

..there is a slight risk of severe thunderstorms across parts of 
the central Gulf Coast states and Tennessee Valley... 

..there is a slight risk of severe thunderstorms across parts of 
the southern and Central Plains... 

..there is a marginal risk of severe thunderstorms outside of the 
slight risk across parts of the central Gulf Coast states...Georgia 
and the Tennessee Valley... 

..there is a marginal risk of severe thunderstorms outside of the 
slight risk area from parts of the High Plains east-northeastward 
into the southern Great Lakes... 

Thunderstorms will persist across parts of the central Gulf states 
and Tennessee Valley this evening. A few will be capable of 
producing localized damaging wind gusts and a couple of tornadoes. 
Other strong to severe storm with potential for large hail and wind 
damage will be possible from western Kansas southward into the 
northern Texas Panhandle this evening. A marginal severe threat will 
be possible this evening into the overnight period from the Central 
Plains east-northeastward into the southern Great Lakes. 

..central Gulf Coast states/Tennessee Valley... 
The National Hurricane Center has Tropical Depression Cindy in far 
northwest Louisiana at the present time. Several south-to-north 
oriented rainbands are located to the north of the center in eastern 
Arkansas and to the east of the center across the Gulf Coast states 
into Georgia. Regional WSR-88D vwps from Memphis, Tennessee to Birmingham, 
Alabama show strong low-level shear profiles with 0-1 km shear generally 
in the 25 to 35 kt range with veering winds with height in the 
lowest 2 km above ground level. This will be favorable for storm rotation and 
possibly a tornado or two associated with the stronger cells 
embedded in these line segments. 

..southern and Central Plains... 
Water vapor imagery shows cyclonic west-northwesterly flow with a 
subtle shortwave trough located in the Central High plains. 
Scattered thunderstorms are ongoing in the vicinity of a cold front 
just ahead of the shortwave trough in southwestern Kansas. The rap 
is analyzing moderate instability in western Kansas where MLCAPE is 
estimated in the 1500 to 2000 j/kg range. The WSR-88D vwp at Dodge 
City shows veering winds with height with 30 to 40 kt of westerly 
flow in the mid to upper-levels. This along with the moderate 
instability should be enough to continue a severe threat for a few 
more hours. Isolated large hail and wind damage will be primary 

..mid to upper Mississippi Valley/southern Great Lakes... 
Water vapor imagery shows westerly mid-level flow is in place from 
the north-central states eastward into the Great Lakes. At the 
surface, a cold front will advance southward across the mid to upper 
Mississippi Valley and Great Lakes region. Scattered thunderstorms 
are already ongoing in northern Iowa, southern Wisconsin into lower 
Michigan from near the front southward. The airmass along this 
corridor is moderately unstable according to the rap with MLCAPE in 
the 1000 to 2000 j/kg range. In addition, regional WSR-88D vwp shows 
0-6 km shear in the 25 to 35 kt range suggesting the environment 
will be capable of producing marginal severe storms with hail and 
strong wind gusts possible. Storm coverage should gradually increase 
this evening into the overnight period as the front moves southward 
across the region with the marginal severe threat continuing through 
late in the period. 

.Broyles.. 06/23/2017 


Mesoscale Discussion

acus11 kwns 230209 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 230209 

Mesoscale discussion 1129 
National Weather Service Storm Prediction Center Norman OK 
0909 PM CDT Thu Jun 22 2017 

Areas affected...Central/Northeast Iowa 

Concerning...severe potential...watch unlikely 

Valid 230209z - 230415z 

Probability of watch issuance...20 percent 

Summary...isolated hail and damaging wind gusts are possible with 
thunderstorms along the front as it moves across Iowa. A generally 
limited severe threat is anticipated and a watch is not anticipated, 
but convective trends will be monitored closely. 

Discussion...thunderstorms have developed over the past hour along 
the cold front extending from ccy (in northeast ia) southwestward to 
cbf (in southwest ia). Airmass ahead of this cold front is 
characterized by dewpoints in the low 70s, which, when combined with 
steep mid-level lapse rates (i.E. Around 7-7.5 deg c per km per the 
latest mesoanalysis), is supportive of moderate instability. 
Continued southeastward progress of the cold front into this airmass 
is expected to result in continued thunderstorm development along 
the cold front. This region is along the southern periphery of the 
stronger flow aloft but enough shear (i.E. Effective shear around 30 
kt) exists to support some updraft organization and a supercell or 
two, particularly across northern portions of the region where the 
shear is strongest. Hail is possible with these more organized 
storms. Farther south, a more multicellular Mode is anticipated with 
any hail likely a result of brief updraft intensification due to 
cell mergers. Some upscale growth into a more linear system is 
possible but the generally modest mid-level flow (and shear) are 
expected to preclude anything but occasionally damaging winds. As a 
result, a watch is not current expected but trends will be monitored 
for upscale growth and a resulting increase in the damaging wind 

.Mosier/Hart.. 06/23/2017 

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


Latitude...Lon 41529527 42659365 43299270 43409152 42879114 41369267 
41089468 41529527