U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 272002 
Storm Prediction Center ac 272000 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0300 PM CDT Thu Apr 27 2017 

Valid 272000z - 281200z 

..there is a marginal risk of severe thunderstorms from parts of 
the southeast U.S. Northward into the lower Great Lakes... 

..there is a marginal risk of severe thunderstorms for portions of 
the central and southern High Plains... 

A few storms capable of damaging winds and perhaps hail or a tornado 
will be possible over parts of Georgia and South Carolina. 
Otherwise, isolated severe wind gusts may accompany thunderstorms 
from portions of the lower Great Lakes region to the southeast 
states today into this evening, and across portions of the central 
and southern Great Plains late this afternoon into this evening. 

The only change from the earlier outlook is to reduce wind 
probabilities from 15% to 5% for the Georgia/SC area. As the Great Lakes 
upper system becomes increasingly displaced from the Georgia/SC area, 
weakening upper support will likely lead to less overall risk for 
wind damage due in part to the lack of a linear Mode and stronger 
forcing for ascent. 

Elsewhere, the outlook was not adjusted substantially. 

.Smith.. 04/27/2017 

Previous discussion... /issued 1127 am CDT Thu Apr 27 2017/ 

An ongoing band of strong thunderstorms continues to occasionally 
Show Low/mid level rotation and indications of severe threat. This 
scenario will likely continue through the afternoon as more storms 
form eastward across central Georgia and eventually into western SC. 
Local VAD profiles and forecast soundings suggest that low/deep 
layer shear is favorable for organized thunderstorms including 
supercells and bowing structures. Continued daytime heating and 
destabilization along the southern fringe of cloud cover across the 
risk area would support an upgrade to slight risk. Locally damaging 
wind gusts are probably the main threat in the strongest cells. 
However, an isolated tornado or two, along with some hail, is 

The latest surface analysis shows a cold front sweeping eastward 
across lower Michigan and western Ohio. Only broken cloud cover ahead of the 
front is helping surface temperatures to climb through the mid 70s, 
resulting in steep low-level lapse rates and marginal instability. 
12z cam solutions are relatively consistent that scattered showers 
and thunderstorm development this afternoon along/ahead of the front 
from eastern Ohio into much of WV and western PA. The storms will 
eventually spread into central PA/Virginia and western Maryland this evening. 
Strongly considered an upgrade to slight over parts of this corridor. 
However, forecast soundings suggest very little cape and mid-level 
lapse rate only in the 6.0 c/km range. It is likely that a few 
fast-moving showers and thunderstorms will pose a risk of 
gusty/damaging wind gusts this afternoon. This region will be 
re-evaluated for an upgrade to slight at 20z. 

A few high-based thunderstorms are expected this afternoon and early 
evening over parts of southeast co, southwest KS, and portions of 
the Texas/OK panhandles. Instability will be quite limited. However, 
steep mid level lapse rates and favorable wind fields suggest some 
risk of hail and gusty winds in the strongest cells. 


Mesoscale Discussion

acus11 kwns 272023 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 272023 

Mesoscale discussion 0575 
National Weather Service Storm Prediction Center Norman OK 
0323 PM CDT Thu Apr 27 2017 

Areas affected...central Georgia...far southeast Alabama 

Concerning...Tornado Watch 169... 

Valid 272023z - 272200z 

The severe weather threat for Tornado Watch 169 continues. 

Summary...severe threat across watch 169 persists but is expected to 
continue waning with time. A few isolated strong to severe storms 
are possible across southeast Alabama. 

Discussion...intensity of the thunderstorm cluster stretching from 
mcn to mlj in central Georgia has diminished over the past hour or so, 
likely a result of encountering an airmass characterized by less 
low-level moisture, cooler surface temperatures, and less overall 
instability. In addition to the less-favorable thermodynamics, 
low/mid level flow is gradually decreasing as well, leading to a 
reduction in the low-level and bulk shear. Overall, the airmass is 
becoming increasingly more hostile to robust convection and the 
severe threat, while still non-zero, is waning. 

Outside of the watch across southeast al, a few stronger storms have 
developed where better low-level moisture exists and the overall 
instability is better. Some transient updraft rotation is possible 
across this area with a resulting isolated severe threat. 

.Mosier.. 04/27/2017 

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


Latitude...Lon 33588409 33938318 33878167 32188170 31088561 32668535