U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 180558 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1258 am CDT Thu Oct 18 2018 


Valid 181200z - 191200z 


..no severe thunderstorm areas forecast... 


... 
isolated thunderstorms are possible across parts of Texas and the 
Florida Peninsula, and parts of the intermountain west through 
tonight, but severe storms are not anticipated. 


... 
Evolution of the upper pattern is forecast today, as an upper trough 
crossing eastern Canada and New England advances/moves offshore. In 
the wake of this feature, flow will relax/become more westerly 
across the Midwest. 


Meanwhile in the west, the weakening cut-off low over the 
intermountain region will gradually begin to eject eastward, as it 
gets kicked by a trough digging southeast across the Canadian 
prairie. By tonight, these two features should be in the process of 
merging into one larger trough over the plains. 


As these two troughs advance, a surface cold front is progged to be 
shifting southward out of Canada and into the northern 
plains/northern rockies late overnight. Elsewhere, high pressure 
will largely prevail, as the remnant baroclinic zone over Florida 
and the northern Gulf of Mexico region weakens further. 


Severe weather is not expected through the period, given the benign 
pattern. Showers and a few embedded thunderstorms are expected from 
Florida westward across the Gulf to Texas, near the dissipating 
front. Showers and a few lightning strikes are also expected across 
portions of The Rockies -- with greatest thunder risk apparent over 
eastern Utah/western Colorado near the peak-heating position of the 
center of the ejecting/weakening cut-off low. 


.Goss/Gleason.. 10/18/2018 


$$ 

Mesoscale Discussion


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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... 


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