U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 191315 
Storm Prediction Center ac 191313 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0713 am CST Mon Feb 19 2018 

Valid 191300z - 201200z 

..there is a marginal risk of severe thunderstorms across the 
Southern Plains... 

A few strong to severe thunderstorms are possible over a portion of 
the Southern Plains, mainly late this afternoon into tonight. 

..Southern Plains... 
As a large-scale upper-level trough continues to amplify over The 
Rockies, a partially modified Gulf air mass with low to middle 60s f 
warm-sector dewpoints will advect northward across Texas and 
Oklahoma today. At the same time, a modest elevated-mixed layer will 
spread eastward and overlap the western fringe of the moist warm 
sector, contributing to a corridor of 500-1000 j/kg MLCAPE primarily 
from western and central Oklahoma through southwest Texas. 

That said, warmer temperatures aloft will contribute to a capping 
inversion over the more unstable portion of the warm sector during 
the day. Additionally, scattered showers and cloud cover atop this 
increasingly moist air mass provide some uncertainty regarding the 
exact degree of surface-based destabilization and related prospects 
for deep convective development later today, particularly given the 
presence of relatively subtle/weak forcing-for-ascent-related 
influences aloft. 

Will essentially maintain severe risk areas/probabilities largely as 
is with this outlook cycle given some of the aforementioned 
uncertainties and caveats. Heating and mixing in vicinity of the 
southwest/West Texas dryline may contribute to at least isolated 
storms by late afternoon or evening. Other storms may initiate over 
the higher terrain of northern Mexico and spread northeast into 
southwest Texas. Another area of potential surface-based development 
will be near the dryline/cold front intersection across Oklahoma, 
although any storms initiating in this area may have a tendency to 
become elevated as they move northeast and cross the frontal zone. 

If/where more robust storms develop later today, very strong (55+ 
kt) 0-6 km shear will support potential for supercells with any 
storms developing along the dryline or higher terrain from southwest 
Texas into western Oklahoma. Conditional upon storm initiation, a 
small window will exist for a tornado during the early evening, 
mainly from western Oklahoma into northwest Texas as low-level 
hodographs become more favorable due to the strengthening low-level 
jet, and before the boundary layer stabilizes. Otherwise, the 
primary severe threat is expected to be large hail. 

.Guyer/marsh.. 02/19/2018 


Mesoscale Discussion

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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 182147 

Mesoscale discussion 0071 
National Weather Service Storm Prediction Center Norman OK 
0347 PM CST sun Feb 18 2018 

Areas affected...parts of West Texas 

Concerning...severe potential...watch unlikely 

Valid 182147z - 182245z 

Probability of watch issuance...5 percent 

Summary...at least isolated strong to severe storm development 
appears possible during the 4-6 PM CST time frame, with severe hail 
and locally strong wind gusts the primary potential hazards. 

Discussion...weak to moderate destabilization is ongoing near the 
dry line across West Texas, with continued boundary layer heating 
and mixing. Latest rap output suggests cape is now on the order of 
500-1000 j/kg. Low-level convergence appears weak, and mid/upper 
forcing for ascent unclear, but inhibition appears to be in the 
process of becoming increasingly negligible. At least isolated 
thunderstorm development does not appear out of the question within 
the next hour or two, probably near or west/southwest of Midland, 
based on latest visible imagery. 

Given favorable deep layer shear beneath southwesterly mid-level 
flow on the order of 40-50 kt, any sustained convection could take 
on a supercell structures. This probably would be accompanied by at 
least the risk for severe hail and localized strong surface gusts, 
before boundary layer instability wanes after nightfall. 

.Kerr/Thompson.. 02/18/2018 

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


Latitude...Lon 31250339 32360272 33110158 33120058 32100184 31550236 
30670330 30880347 31250339