U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 190541 
Storm Prediction Center ac 190539 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1239 am CDT Tue Jun 19 2018 

Valid 191200z - 201200z 

..there is a slight risk of severe thunderstorms across the Central 

Severe thunderstorms are expected across the Central Plains Tuesday 
afternoon and evening while marginally severe thunderstorms are 
expected from the Midwest into Virginia. 

..Central Plains... 

Late evening model guidance suggests a significant short-wave trough 
will eject across the Great Basin into western Colorado by 18z then into 
the High Plains of Kansas/Texas Panhandle by 20/12z. A corridor of stronger 
mid-high level flow will translate across Nevada/Utah into the Central 
High plains by peak heating which should enhance convection that 
evolves over the higher terrain from southeast Wyoming to south of the 
Palmer Divide by mid afternoon. Cam guidance supports this scenario 
with scattered supercells evolving over the plains within a 
strengthening shear regime. This activity will be supported by 
large-scale height falls and moist upslope flow that should 
encourage east-southeast propagation toward western Kansas during the 

Latest thinking is pre-dawn convection across the Central Plains 
should gradually wane as it drifts into south-central NE by the 
start of the period. If convective outflow from this activity is not 
too disruptive, the strongest corridor of boundary-layer heating is 
expected to develop from southern Colorado into extreme southeast NE. 
Forecast soundings strongly favor supercells across southeast Wyoming/Colorado 
into western Kansas. Aside from large hail a few tornadoes can be 
expected across this region. 

Thunderstorms that develop downstream along the frontal zone from 
the northern Texas Panhandle into southeast NE will do so within a 
weaker-sheared environment and more clustering is expected. As a 
result, hail/wind will be the primary threats. 

..Midwest to Virginia... 

Upper ridge is expected to be shunted a bit east Tuesday with 
anticyclonic flow forecast across the Midwest/Ohio Valley into the 
middle Atlantic. High precipitable water air mass will necessarily extend along this 
corridor which will coincide with a frontal zone draped from Virginia into 
Illinois. Boundary-layer heating will be instrumental in convective 
development along/south of this wind shift but environmental shear 
is not expected to support more than pulse/multi-cell updrafts. 
Locally damaging winds are the primary threat with this diurnally 
driven convection. 

.Darrow/squitieri.. 06/19/2018 


Mesoscale Discussion

acus11 kwns 190411 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 190411 

Mesoscale discussion 0788 
National Weather Service Storm Prediction Center Norman OK 
1111 PM CDT Mon Jun 18 2018 

Areas affected...northeast Colorado 

Concerning...Severe Thunderstorm Watch 189... 

Valid 190411z - 190615z 

The severe weather threat for Severe Thunderstorm Watch 189 

Summary...severe risk continues across a small portion of northeast 

Discussion...latest radar loop shows a cluster of strong/severe 
storms moving across portions of northeast Colorado, with the most 
intense cell -- which has evolved into a small-scale bowing band -- 
crossing northwest Washington County at this time. In the past 
hour, this storm produced a 62 knot wind gust at ft. Morgan in 
Morgan County, and currently shows radar signatures capable of 
producing very large hail. 

As this convection continues, the boundary layer continues to 
cool/stabilize, with temperatures in most areas now into the mid to 
upper 60s. This continues to suggest that a gradual decrease in 
storm intensity -- and particularly the damaging wind threat -- 
should occur over the next couple of hours. Until then however, 
storms remain locally well organized, and capable of producing large 
hail and a damaging wind gust locally. 

.Goss.. 06/19/2018 

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


Latitude...Lon 40350254 39930366 39860499 40100498 40790413 40940298