U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 231309 
Storm Prediction Center ac 231308 

Day 1 convective outlook corr 1 
National Weather Service Storm Prediction Center Norman OK 
0808 am CDT Fri Jun 23 2017 

Valid 231300z - 241200z 

..there is a slight risk of severe thunderstorms from a portion of 
the Gulf Coast states into the Tennessee and Ohio valleys... 

..there is a slight risk of severe thunderstorms over a portion of 
the Southern Plains... 

..there is a marginal risk of severe thunderstorms from a portion 
of the Gulf Coast states into the northeast states... 

..there is a marginal risk of severe thunderstorms over a portion 
of the Southern Plains... 

Corrected for slight risk upgrade over a portion of the Southern 

Thunderstorms may become capable of producing isolated strong to 
damaging wind gusts and a few tornadoes mainly this afternoon from a 
portion of the central Gulf Coast states northeastward into the 
central Appalachians. A few severe storms with strong wind gusts and 
hail will also be possible in the northeast U.S. And Southern 


The remnants of Cindy situated over western Tennessee will become absorbed 
within a belt of stronger westerlies associated with an upper trough 
amplifying over the Great Lakes and Ohio Valley. This feature will 
subsequently accelerate east northeast through the Tennessee Valley and 
into the southern Appalachians this afternoon and tonight before 
reaching the Virginia coast by the end of this period. At the surface a 
cold front stretching from the Great Lakes into the southern High 
Plains will continue southeastward and likely extend from New 
England into southwest Texas by 12z Saturday. 

..central Gulf Coast states and Tennessee Valley through the 
central Appalachians... 

Remnants of Cindy are transitioning to extratropical and will 
accelerate through the Tennessee Valley and southern Appalachians today. 
Belt of stronger winds aloft resulting from the strengthening 
gradient between Cindy and the amplifying northern-stream upper 
trough will spread through the Tennessee and Ohio valleys. Immediately 
downstream from the circulation, a pronounced dry slot is evident 
from parts of Tennessee through KY, and this should promote a period of 
boundary-layer destabilization, though MLCAPE will remain marginal 
/aob 500 j/kg/ due to weak mid-level lapse rates. Nevertheless, 
convection within the associated convergence bands will likely 
increase this afternoon in a kinematic environment favorable for 
rotating updrafts. A few bowing segments and low-topped supercells 
are possible and will pose a risk for isolated strong to damaging 
wind gusts and a few tornadoes. The very marginal thermodynamic 
environment will probably remain a limiting factor over much of this 

..northeast states into the Ohio Valley... 

Winds aloft will strengthen over much of this area in association 
with the amplifying upstream trough with 0-6 km shear increasing to 
35-40 kt. Widespread convection is ongoing from New York into New 
England within zone of isentropic ascent north of a warm front. 
Other convection is occurring farther south from Ohio to PA within 
deformation zone northeast of the remnants of Cindy as well as in 
association with a progressive mid-level shortwave trough. The 
atmosphere may undergo some destabilization where cloud breaks occur 
this afternoon, resulting in potential for a few organized strong to 
severe storms with damaging wind the main threat. While potential 
for slight risk may exist over a portion of this region, will 
maintain marginal risk category this update due to widespread clouds 
and uncertainty regarding evolution of the thermodynamic 

..Southern Plains... 

Steep lapse rates and diabatic warming of the boundary layer will 
promote moderate instability in this region. Storms will likely 
develop along southward-advancing cold front as well as over the 
higher terrain from parts of OK, Texas and nm. The warm sector resides 
well south of the stronger winds aloft with weak shear supportive of 
multicells capable of producing a few strong to damaging wind gusts 
and marginally severe hail this afternoon into early evening. 

.Dial/picca.. 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