U.S. Severe Weather Forecast (Конвективни Outlook)

Day Three

acus01 kwns 221633 
Storm Prediction Center ac 221632 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1132 am CDT Fri Jun 22 2018 

Valid 221630z - 231200z 

..there is an enhanced risk of severe thunderstorms this afternoon 
through late evening from eastern Colorado to northwestern OK... 

..there is a slight risk of severe thunderstorms from parts of the 
High Plains to the lower MS/Tennessee valleys and Virginia... 

Scattered severe storms are expected across parts of the 
central/Southern Plains, southeast and mid-Atlantic states today. 

..eastern Colorado this afternoon to OK overnight... 
Remnants of overnight convection persist from southern to 
northwestern OK, though this convection should weaken slowly through 
early afternoon. In the wake of these storms, the low levels will 
modify through surface heating and boundary-layer dewpoints in the 
50s will continue to spread northwestward into eastern Colorado. 
Meanwhile, a midlevel trough is now moving across Utah/WY/northwestern 
co, with ascent downstream from the trough supporting weak 
convection over northern Colorado. Destabilization of the low levels will 
remove convective inhibition, and early arrival of the ascent should 
support storm development by early afternoon across eastern Colorado. 
Moderate-strong buoyancy (mlcape of 2000-3000 j/kg), steep midlevel 
lapse rates, and effective bulk shear near 50 kt are all supportive 
of initial supercells with very large hail. 

The storms should grow upscale through cell/outflow interactions, 
with one or more clusters expected to move southeastward through 
tonight. Damaging winds and hail will be the main threats with 
storms focused along the instability gradient along the modifying 
outflow and residual synoptic front from southwest Kansas and the 
panhandles into western OK. 

..lower MS to Tennessee Valley region today... 
A series of speed maxima are rotating around the southern periphery 
of a midlevel low over southern IL, one of which is associated with 
the ongoing convection from southeastern Arkansas into northern MS. The 
northern portion of this convection should spread eastward toward 
northern Alabama through the afternoon in conjunction with the speed Max 
and surface heating/destabilization, as well as moisture advection 
from the southwest. A mix of multicell clusters and supercells will 
be possible given effective bulk shear near 40 kt and MLCAPE 
increasing to near 2000 j/kg, with an attendant threat for damaging 
gusts and large hail. 

Farther west, storms are ongoing from southeastern Arkansas into 
northeastern la. Surface heating to the immediate south and 
southwest, and boundary-layer dewpoints in the low-mid 70s, will 
drive MLCAPE of 2000-3000 j/kg along the composite front/outflow 
boundary and help maintain the storms through the day. This area 
will remain along the southern fringe of the stronger mid-upper flow 
from the west-northwest, though another possible mid-upper speed Max 
will approach late this afternoon (now associated with the 
convection along the Red River valley of TX/ok). A mix of multicell 
clusters and supercells will be possible, and will likely 
train/back-build through the day across southern Arkansas/northern la and 
west central MS. Damaging winds and large hail will be the main 

..VA area this afternoon/evening... 
A lobe of ascent, as evidenced by the band of weak convection 
ongoing from central WV to southwestern VA, will spread 
east-northeastward today in association with an embedded speed Max 
rotating around the southeastern periphery of the midlevel low over 
southern Illinois. Though midlevel lapse rates are rather poor, surface 
heating from NC into central Virginia will contribute to gradual 
destabilization through the afternoon, and will likely support 
scattered thunderstorm development. As the storms move 
northeastward, they will encounter a slow-moving front from central 
Virginia to the lower Chesapeake area. Low-level shear will be maximized 
along this front, with sufficient hodograph curvature/srh to support 
a threat for rotating storms with a tornado or two and isolated 
damaging gusts later this afternoon through late evening. 

.Thompson/Bentley.. 06/22/2018 


Mesoscale Discussion

acus11 kwns 221857 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 221856 

Mesoscale discussion 0823 
National Weather Service Storm Prediction Center Norman OK 
0156 PM CDT Fri Jun 22 2018 

Areas affected...portions of the central/northern High Plains 

Concerning...severe potential...watch unlikely 

Valid 221856z - 222030z 

Probability of watch issuance...20 percent 

Summary...thunderstorms will increase in coverage through the 
afternoon, and some will pose a damaging wind and large hail threat. 
While a watch is not currently expected, convective trends will be 
monitored for an increase in organization, which could necessitate a 

Discussion...a severe thunderstorm has developed over the Black 
Hills this afternoon, and other cells are developing within 
confluence along a surface trough over the western Dakotas and 
Nebraska Panhandle. As mid-level ascent continues to Foster new 
development within this steep lapse rate environment, storms should 
grow into multicell clusters, with some brief supercell structures 
possible. However, relatively disorganized mid/upper wind profiles 
should Foster more cluster modes that are driven east by merging 
cold pools. Some threat for damaging winds and large hail will 
continue to evolve, but a lack of greater organization casts doubt 
on the need for a watch. 

.Picca/Thompson.. 06/22/2018 

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


Latitude...Lon 41200388 41580401 43550436 45030447 45860458 46340452 
46640428 46720410 46860366 46560318 45280282 43490233 
41570180 41030197 41020304 41200388