A Mesodiscussion is issued by the National Weather Service's Storm Prediction Center when there is a chance of a significant weather event impacting an area. These are routinely issued before weather watches or as updated to weather watches.

SPC MD 507

MD 0507 CONCERNING SEVERE THUNDERSTORM WATCH 118... FOR FAR EASTERN NEW MEXICO AND PORTIONS OF WEST TEXAS
MD 0507 Image

Mesoscale Discussion 0507
NWS 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
continues.

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...

ATTN...WFO...SJT...LUB...AMA...MAF...ABQ...

LAT...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 

Read more

SPC MD 506

MD 0506 CONCERNING SEVERE THUNDERSTORM WATCH 117... FOR NE PANHANDLE....WEST-CENTRAL NE...SOUTHWEST/SOUTH-CENTRAL SD
MD 0506 Image

Mesoscale Discussion 0506
NWS Storm Prediction Center Norman OK
0828 PM CDT Wed May 23 2018

Areas affected...NE Panhandle....West-central
NE...Southwest/South-central SD

Concerning...Severe Thunderstorm Watch 117...

Valid 240128Z - 240300Z

The severe weather threat for Severe Thunderstorm Watch 117
continues.

SUMMARY...Potential for damaging wind gusts and hail will persist
across the remaining portions of Severe Thunderstorm Watch 117.
Convective trends will be monitored closely to determine the need
for a downstream watch.

DISCUSSION...Ongoing supercell in Oglala Lakota county is strongest
storm of day across the region thus far. Recent MRMS MESH suggests
hail around 3 inches possible with this storm. Large hail will
remain possible with this storm during the next hour or so before a
transition to a more linear mode reduces the potential for very
large hail. Recent reflectivity surge northeastward as well as the
influence of the approaching line segment farther southwest and
interaction with an outflow boundary suggest upscale growth is
probable with this currently discrete storm.

To the south/southeast of this storm (i.e. across west-central NE),
convection has recently increased along a residual outflow boundary
in Cherry and Grant counties while the supercell that recently moved
through Garden county appears to have become more outflow dominant.
All of these signs point toward eventual cool pool amalgamation and
eventual upscale growth into a linear MCS. 

However, the downstream airmass will soon experience nocturnal
stabilization and there is some question as to whether or not the
MCS will be strong/mature enough to produce damaging wind gusts in
the resulting stable low-level environment. Even if damaging wind
gusts are not realized, steep mid-level lapse rates, sampled well by
regional 00Z soundings, and increasing low-level flow will remain
supportive of severe hail. Convective trends will be monitored
closely to determine the need for a downstream watch.

..Mosier.. 05/24/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FSD...ABR...LBF...UNR...CYS...

LAT...LON   42240409 43560354 44540104 44329968 42689943 41380102
            41090296 42240409 

Read more