Convective Outlook

U.S. Severe Weather Forecast

000 
acus01 kwns 181941 
swody1 
Storm Prediction Center ac 181940 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0240 PM CDT Thu Oct 18 2018 


Valid 182000z - 191200z 


..no severe thunderstorm areas forecast... 


... 
isolated thunderstorms are possible across the Texas coast, 
northeastern Florida, and parts of the central and southern rockies 
through tonight. However, severe storms are not expected. 


..20z outlook update... 
Some changes have been made to categorical (10 percent probability) 
thunderstorm lines, most notably across Florida, in an attempt to 
better account for latest trends in observational data and model 
output. 


Across Florida, where forcing for ascent is generally weak beneath 
mid/upper subtropical ridging, any appreciable risk for 
thunderstorms late this afternoon into tonight now appears generally 
confined to northeastern areas. This is where higher precipitable 
water is focused along/ahead of a slow moving then 
stalling/weakening frontal zone, in the presence of somewhat weaker 
mid-level inhibition (compared to central/southern florida). 


.Kerr.. 10/18/2018 


Previous discussion... /issued 1116 am CDT Thu Oct 18 2018/ 


... 
A closed low over the central rockies will continue eastward and 
begin to phase with an amplifying shortwave trough over the upper 
Midwest tonight. Cool mid-level temperatures, sufficiently steep 
lapse rates, and weak buoyancy will support a threat for isolated 
thunderstorms over the central rockies, while other thunderstorms 
will be possible across southern/eastern nm toward northwest Texas. 
Farther southeast, a weak low-level warm advection regime is 
becoming established across TX, with isolated lightning strikes most 
likely to occur along the coast and offshore waters. Otherwise, 
despite negligible large-scale forcing for ascent, isolated 
thunderstorms will be possible within the lingering tropical air 
mass across FL, primarily along the front across North Florida. 


$$ 

Mesoscale Discussion

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acus11 kwns 162228 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 162228 
ncz000-scz000-170100- 


Mesoscale discussion 1587 
National Weather Service Storm Prediction Center Norman OK 
0528 PM CDT Tue Oct 16 2018 


Areas affected...portions of NC/SC 


Concerning...severe potential...watch unlikely 


Valid 162228z - 170100z 


Probability of watch issuance...5 percent 


Summary...strong/gusty winds may occur on an isolated basis through 
the evening. Watch issuance is unlikely. 


Discussion...glancing influence of large-scale ascent associated 
with an upper-level jet over the mid-Atlantic/northeast coupled with 
modest low-level convergence along a stalled front should support 
isolated to scattered convective development through the evening 
across the southern half of NC and parts of SC. This generally 
east-west oriented front will likely serve as a focus for 
thunderstorms, with a couple attempts at convective initiation noted 
recently near gsp in upstate SC. A meso-low noted on 22z surface 
analysis near Fay may also subtly enhance low-level convergence 
along the front in southern NC. 


Some cloud breaks to the south of the front have contributed to 
temperatures in the low 80s at 2228z. A moist-level airmass is also 
present across the warm sector, with dewpoints generally in the 
upper 60s to lower 70s. Daytime heating and plentiful moisture are 
supporting MLCAPE around 250-1000 j/kg, with poor mid-level lapse 
rates limiting even greater destabilization. 40-50+ kt of 
west-southwesterly mid-level flow is present across much of the 
Carolinas, and a strengthening wind profile with height is 
contributing to around 40-50 kt of effective bulk shear. Mid-level 
rotation within thunderstorm updrafts will likely occur given this 
degree of shear, and a couple transient supercells cannot be ruled 
out. A small line segment or thunderstorm cluster will probably 
consolidate along the front as it moves eastward through the 
evening. 


Even with nocturnal cooling commencing soon, already steepened 
low-level lapse rates should encourage efficient momentum Transfer 
of convective downdrafts to the surface. Isolated strong/gusty winds 
primarily capable of tree damage appear to be the main severe 
threat, but very isolated hail may also occur. Regardless, the 
thermodynamic environment will remain quite marginal, and watch 
issuance is unlikely at this time. 


.Gleason/Edwards.. 10/16/2018 


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


Attention...WFO...mhx...rah...ilm...cae...gsp... 


Latitude...Lon 34358191 34878185 35328123 35558022 35557834 35157592 
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