U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 240553 
Storm Prediction Center ac 240551 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1251 am CDT Thu may 24 2018 

Valid 241200z - 251200z 

..there is a slight risk of severe thunderstorms over a portion of 
the northern and Central Plains... 

Isolated to scattered strong to severe thunderstorms are expected 
across portions of the northern and Central Plains and upper 
Mississippi Valley this afternoon and evening. 


Upper trough currently over the northern High Plains will continue 
east northeast through North Dakota and the upper MS valley region 
today. Associated cold front will move east through the Dakotas, 
while a warm front advances through Minnesota. A Lee trough/dryline will 
reside across the central through southern High Plains. 

..northern plains and upper MS valley region... 

Ascent with mcvs currently moving through the Central High plains 
will contribute to the development of thunderstorms later today over 
portions of Minnesota. Areas of residual clouds will temper boundary layer 
destabilization to some degree with MLCAPE to 1500 j/kg possible, 
but this region will also reside east of steeper lapse rates and 
stronger winds aloft. Weak vertical shear and modest instability 
should limit overall severe threat with this activity, but a few 
isolated strong to damaging wind gusts and marginally severe hail 
are possible. 

Farther west, the pre-frontal warm sector should become moderately 
to strongly unstable over the central and eastern Dakotas where 
eastern fringe of steeper lapse rates will overlap western portion 
of moist axis. Diabatic warming should boost MLCAPE to 2000-2500 
j/kg. The stronger forcing for ascent accompanying the upper trough 
is expected to affect primarily North Dakota where widely scattered 
to scattered storms are expected to develop along and just ahead of 
the cold front, with more isolated activity with southward extent 
into South Dakota. Somewhat stronger (30-40 kt between 700-400 mb) 
flow aloft accompanying the upper trough will contribute to 30-35 kt 
effective bulk shear supporting primarily multicell and possibly 
some marginal supercell structures. Some storms may eventually 
congeal into clusters as they continue east into the evening. 
Damaging wind and large hail should be the main threats. 

..Central High plains region... 

Upstream vorticity maximum currently over northern Arizona is expected to 
move into eastern Colorado this afternoon, and storms are expected to 
develop over the higher terrain and along Lee trough before moving 
into a moderately unstable atmosphere where deeply mixed boundary 
layers will promote strong downdrafts. Storms may eventually congeal 
into an mesoscale convective system as they continue east into better moisture across Kansas 
where a strengthening low-level jet will promote a forward 
propagation through at least early evening before storms begin to 
weaken. Weak vertical shear will favor multicells, but the 
thermodynamic environment will support a risk for damaging wind and 
some hail. 

.Dial/Cook.. 05/24/2018 


Mesoscale Discussion

acus11 kwns 240142 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 240142 

Mesoscale discussion 0507 
National Weather Service Storm Prediction Center Norman OK 
0842 PM CDT Wed may 23 2018 

Areas affected...far eastern New Mexico and portions of West Texas 

Concerning...Severe Thunderstorm Watch 118... 

Valid 240142z - 240245z 

The severe weather threat for Severe Thunderstorm Watch 118 

Summary...a severe threat will linger through the scheduled 
expiration of ww 118 (03z). An isolated hail/wind threat will exist 
just east of the watch during this period as well. 

Discussion...ongoing convection has propagated into the far eastern 
portions of ww 118 at this time, and a few storms have exited ww 118 
into portions of the Texas South Plains. A notable weakening trend 
has commenced with the ongoing activity - likely due to gradually 
weaker lapse rates/buoyancy with eastward extent. Nevertheless, 
forward-propagating clusters/linear segments amidst weak to moderate 
instability (1000-1500 j/kg mucape) will continue to Foster isolated 
hail/wind threat for the next 1-1.5 hours within stronger 
thunderstorm cores. Increasing low-level flow may sustain a few 
storms beyond this time frame, although the stabilizing boundary 
layer is expected to mitigate the overall threat. 

Remaining portions of ww 118 that have stabilized due to prior 
convection may be cancelled early. 

.Cook.. 05/24/2018 

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


Latitude...Lon 36680373 36900329 36720268 35860231 34150225 32080215 
31200210 30440237 29740264 29180289 28980322 29040379 
29330430 29790462 30240470 30540432 31240386 32200371 
33160356 33980356 34730371 35470386 35820383 36680373