U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 261645 
Storm Prediction Center ac 261644 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1144 am CDT Mon Jun 26 2017 

Valid 261630z - 271200z 

..there is a marginal risk of severe thunderstorms across the 
Pacific northwest and northern rockies... 

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

..there is a marginal risk of severe thunderstorms across northern 
Florida and southeast Georgia... 

Thunderstorms with severe hail and strong wind gusts are possible 
late this afternoon into evening across the Pacific northwest and 
northern rockies in addition to parts of the Great Plains. Other 
strong storms may occur along the coastal southeast states. 

..Pacific northwest/northern rockies... 
Gradually strengthening westerlies aloft are expected over the 
region today. This will be as an upper low just off the coast of 
northern California continues east-northeastward and a trough amplifies over 
British Columbia, while a convectively related disturbance also 
shifts eastward from southeast Washington/northern Idaho into Montana. It seems 
likely that thunderstorms will increase this afternoon especially 
east of the Cascades across central/eastern or into adjacent 
Idaho/southeast WA, in addition to parts of west-central Montana. 
Strengthening winds aloft/vertical shear will help support some 
sustained east/northeastward-moving storms. Isolated instances of 
locally damaging winds will be possible with the strongest storms 
along with some hail, particularly across parts of or into Idaho where 
somewhat greater moisture/destabilization is expected. 

..Central Plains/southern High Plains... 
Under the glancing influence of the upper Midwest/Great Lakes 
upper-level trough, isolated to widely scattered thunderstorms are 
likely to develop by mid/late afternoon within a corridor from 
southern NE southward into Kansas. Although mid-level lapse rates are 
not particularly steep by late-June standards, gradually returning 
moisture, moderate buoyancy, and supercell-favorable wind profiles 
(in the presence of strong northwesterly flow aloft) should allow 
for isolated severe thunderstorms capable of severe hail/locally 
damaging winds as these storms spread southeastward through the late 
afternoon and evening hours. 

Elsewhere, as a moist upslope flow regime persists, other storms are 
likely to develop/intensify across along the southeast Colorado/northeast 
nm Raton Mesa vicinity and higher terrain of interior nm. In the 
presence of moderate buoyancy and 30-35 kt of effective shear, some 
of the stronger storms will be capable of hail. 

Farther south, one or more remnant mcvs may refocus afternoon 
redevelopment, including the possibility of a few stronger storms, 
across parts of the Texas Edwards Plateau and nearby transpecos 

..North Florida/coastal Georgia... 
As weak height falls spread toward the region today, a moist 
environment and sea breeze circulations in vicinity of a 
stalled/slow-moving front may allow for a few stronger storms this 
afternoon capable of downbursts. 

.Guyer/Gleason.. 06/26/2017 


Mesoscale Discussion

acus11 kwns 261904 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 261903 

Mesoscale discussion 1152 
National Weather Service Storm Prediction Center Norman OK 
0203 PM CDT Mon Jun 26 2017 

Areas affected...southern NE...northern Kansas...eastern Colorado 

Concerning...severe potential...watch possible 

Valid 261903z - 262030z 

Probability of watch issuance...40 percent 

Summary...isolated to widely scattered severe thunderstorms are 
possible this afternoon, with a threat of large hail and locally 
damaging wind gusts. 

Discussion...a thunderstorm has recently intensified across 
southwest NE, with additional towering cumulus noted extending into 
far northeast Colorado along a weak cold front. Towering cumulus has also 
recently developed across along a weak surface trough into 
east-central Colorado. While large-scale forcing is subtle at best, slight 
moistening noted on WV imagery is suggestive that modest ascent is 
overspreading the region. Additional storms will likely be focused 
along the weak cold front extending from northeast Colorado into southwest 
NE/north-central KS, and also along a north-northwest-south-southeast oriented outflow 
boundary running from north of Concordia, Kansas to just east of Salina, 

Moderate midlevel northwesterly flow will continue to support 
effective shear of 35-45 kts through the afternoon, which will be 
sufficient to support organized convection, and a few supercells 
will be possible later this afternoon. Buoyancy and midlevel lapse 
rates are greatest across eastern Colorado/northwest Kansas/southwest NE and 
decrease with eastward extent, but MLCAPE of 750-1500 j/kg across 
the mesoscale discussion area will be sufficient for some hail risk with the 
strongest cells. Weak low-level flow will tend to limit the damaging 
wind risk to some extent, but steep low-level lapse rates will 
support some wind gust potential, especially with any upscale growth 
that may occur later this afternoon. 

Some uncertainty remains regarding the coverage of the severe threat 
this afternoon, but watch issuance is possible if multiple organized 
cells/clusters appear imminent. 

.Dean/guyer.. 06/26/2017 

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


Latitude...Lon 40810231 40379938 40129760 39759725 38499624 38379722 
38490112 38610319 39250343 40420306 40810231