Convective Outlook

U.S. Severe Weather Forecast

acus01 kwns 241227 
Storm Prediction Center ac 241226 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0626 am CST Fri Nov 24 2017 

Valid 241300z - 251200z severe thunderstorm areas forecast... 

isolated thunderstorms are possible across portions of the Florida 
Peninsula and Keys. 

In mid/upper levels, mean troughing over the eastern U.S. Will 
persist. Meanwhile western ridging will amplify again, following 
the departure of a positively tilted shortwave now over parts of 
Mt/ID/or. A well-defined/southern-stream shortwave trough -- now 
evident in moisture-channel imagery over the extreme eastern Gulf of 
Mexico -- will cross Florida through the daytime hours. 

At the surface, an elongated frontal-wave low offshore from the Florida 
Atlantic coast is expected to consolidate and ripple northeastward 
along the boundary today, while the trailing cold front proceeds 
southeastward down the remainder of the peninsula and across the 
Keys by late this evening and overnight. 

Thunder coverage today over land looks to be much more limited than 
evident in the previous outlook. Showers and isolated thunderstorms 
are possible primarily over southeastern areas into early afternoon, 
as boundary-layer heating/mixing reduces mlcinh and weak convergence 
supports development, amidst favorable low-level moisture. Modified 
12z mfl radiosonde observation and model forecast soundings suggest 800-1200 j/kg 
MLCAPE is possible. Lack of more robust deep shear, lift and lapse 
rates indicates minimal severe potential. As the afternoon 
progresses, isallobaric forcing related to offshore Atlantic 
cyclogenesis will veer prefrontal surface winds and reduce 
convergence. At the same time, large-scale subsidence behind the 
aforementioned southern-stream perturbation, as evident in 
moisture-channel drying, will spread eastward across the region, 
further disfavoring additional/substantial convective potential. 

.Edwards.. 11/24/2017 


Mesoscale Discussion

acus11 kwns 231824 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 231823 

Mesoscale discussion 1776 
National Weather Service Storm Prediction Center Norman OK 
1223 PM CST Thu Nov 23 2017 

Areas affected...central Florida 

Concerning...severe unlikely 

Valid 231823z - 232030z 

Probability of watch issuance...20 percent 

Summary...threat for a couple of damaging wind events and a brief 
tornado will persist through mid afternoon, primarily in a narrow 
corridor across north central Florida. Overall threat appears too 
marginal for a ww. 

Discussion...storms have undergone some intensification as they 
moved onshore just north of Tampa, possibly due to interaction of 
attendant NE-SW oriented convergence boundary with the seabreeze. 
Stationary front extends from just north of Tampa to north of 
Melbourne, and visible imagery shows thinning cirrus, allowing 
modest diabatic warming of the boundary layer in the warm sector 
where MLCAPE ranges from 500 to 800 j/kg over central Florida. Models 
indicate there should be some tendency for low-level winds to veer 
and weaken as a low-amplitude shortwave trough moves east of the 
peninsula later this afternoon. In the meantime, the more favorable 
low-level hodographs with 150-250 storm-relative helicity will 
persist in vicinity of the stationary front. Storms moving east and 
interacting with this boundary may develop occasional supercell 
structures and bowing segments, posing a risk for locally strong to 
damaging wind gusts and a brief tornado. The marginal thermodynamic 
environment and tendency for the low-level winds to veer and weaken 
later this afternoon suggest overall threat should remain limited. 

.Dial/Hart.. 11/23/2017 

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

Latitude...Lon 28538243 28818191 29178131 29198101 29008096 28628148 
28078248 28538243 

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