U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 231934 
Storm Prediction Center ac 231933 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0233 PM CDT Wed may 23 2018 

Valid 232000z - 241200z 

..there is a slight risk of severe thunderstorms across parts of 
the northern and southern High Plains... 

Scattered severe thunderstorms are possible this afternoon and 
evening across the High Plains, and across eastern portions of 
Virginia and North Carolina. 

..southern High Plains update... 
Scattered storms are expected to develop this afternoon as a moist 
air mass continues to heat across the area. Despite weak shear 
profiles, favorable lapse rates aloft and plentiful moisture should 
yield scattered cells capable of severe hail, with an eventual 
merging of outflows and attendant wind threat. As such, have 
upgraded the area to a slight risk for this afternoon into early 
evening. For more information see mesoscale discussion 498. 

.Jewell.. 05/23/2018 

Previous discussion... /issued 1151 am CDT Wed may 23 2018/ 

..northern High Plains... 
Morning water vapor imagery shows a large upper trough over the 
western states, with an embedded shortwave trough lifting 
northeastward through The Four-Corners region. Lift ahead of this 
feature should overspread parts of Wyoming and southeast Montana this 
afternoon and evening, leading to scattered thunderstorm 
development. Strong daytime heating and surface dewpoints in the 
50s, coupled with steep mid level lapse rates and relatively cool 
temperatures aloft will yield afternoon MLCAPE values of 1000-1500 
j/kg and only a weak cap. This, combined with favorable deep-layer 
shear will promote rotating updrafts capable of large hail and 
damaging winds. As storms spread eastward into parts of South Dakota/NE, 
outflow mergers will likely increase the risk of damaging wind gusts 
through the evening. 

..southern High Plains... 
Another round of afternoon/evening thunderstorms are expected to 
affect eastern nm and West Texas. Visible satellite imagery confirms 
that considerable low-level moisture is in place over this area, and 
as the low-clouds burn off this afternoon, a strongly unstable air 
mass should develop. Despite the favorable thermodynamic setup, 
vertical shear profiles are quite weak and steering flow is 5-10 
knots. This will lead to rather disorganized thunderstorms capable 
of locally damaging wind gusts and hail. Through the evening, cam 
solutions suggest that outflows may organize as they spread into 
west TX, with an increased risk of gusty/damaging winds in the more 
intense cores. 

A warm/humid air mass is present today over parts of southern Virginia and 
much of NC, leading to strong afternoon instability (mlcape values 
of around 1500 j/kg). Models are in good agreement that scattered 
thunderstorms will affect this region later this afternoon and 
evening. Forecast soundings suggest low-level wind fields will be 
quite weak with less than 10kt winds expected in the lowest 4-5km. 
This suggests that isolated cells may briefly produce downbursts, 
but the threat of a more organized severe event is rather low. 

Scattered thunderstorms are expected to affect parts of ME as a 
shortwave trough and associated cold front moves through the area. 
Organized severe storms are not expected, but the strongest cells 
could produce locally gusty/damaging wind gusts - especially in the 
eastern parts of the state. 


Mesoscale Discussion

acus11 kwns 232315 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 232315 

Mesoscale discussion 0505 
National Weather Service Storm Prediction Center Norman OK 
0615 PM CDT Wed may 23 2018 

Areas affected...eastern New Mexico and adjacent West Texas 

Concerning...Severe Thunderstorm Watch 118... 

Valid 232315z - 240045z 

The severe weather threat for Severe Thunderstorm Watch 118 

Summary...the severe threat continues across ww 118. A downstream 
ww across the Texas South Plains is not anticipated at this time. 

Discussion...a risk for hail and damaging wind gusts continues 
across the discussion area. A few instances of large hail have been 
noted with isolated, cellular structures over the past hour. 
Meanwhile across southern portions of the area, the first signs of 
upscale growth have been observed in eddy, Lea, and Chaves counties 
in New Mexico. Moderate instability and minimal convective 
inhibition should continue to support the ongoing hail/wind threat, 
and meager low-level wind fields suggest that any tornado threat 
should remain isolated at best. 

With time, upscale growth into linear segments should continue as 
low-level flow increases and cold pools expand beneath ongoing 
storms. Storms in southeastern New Mexico could reach the eastern 
extent of ww 118 and the Texas/New Mexico border over the next 
couple of hours or so, pending specific evolution of these upscale 
growth processes. 

.Cook/grams.. 05/23/2018 

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


Latitude...Lon 36950536 37100502 37140419 37120360 36970317 36580301 
36090296 34660286 33450272 32230247 31330230 30860207 
30290208 29860228 29580257 29260287 28990316 29080347 
29310418 29620479 30460492 31520510 32610551 33560572 
34400579 35070581 35710564 36950536