U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 150059 
Storm Prediction Center ac 150057 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0757 PM CDT sun Sep 14 2014 

Valid 150100z - 151200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms...a few potentially capable of producing 
severe hail...are possible across parts of the central Great Plains 

Water vapor imagery shows a vigorous shortwave trough moving into 
the western Dakotas this evening and this feature will rapidly translate 
east-southeastward towards the Dakotas/Minnesota border late tonight. A Lee low over 
eastern Colorado/western Kansas will maintain a southerly fetch with low-level moisture 
transport into parts of the Central Plains as a cold front moves southward 
through the Central High plains. 

..cntrl plains this evening and overnight... 
Adequate moisture observed this evening /sfc dewpoints near 60 degree 
f/ has partly resulted in a conditionally unstable airmass across 
this region as a plume of steep to very steep middle-level lapse rates 
remains overhead in advance of the north-central U.S. Upper trough. The 
possibility for additional isolated shower/thunderstorm development 
over this region will become increasingly focused as isentropic lift 
increases in tandem with a strengthening low level jet tonight. Ample 
effective shear would support updraft rotation and hail growth with 
any strong elevated updraft. The paucity of storm coverage in the 
latest model guidance suggests the large hail threat will probably 
remain fairly isolated tonight. 

.Smith.. 09/15/2014 

Mesoscale Discussion

acus11 kwns 142348 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 142348 

Mesoscale discussion 1717 
National Weather Service Storm Prediction Center Norman OK 
0648 PM CDT sun Sep 14 2014 

Areas affected...northestern Colorado...southwestern Nebraska...northwestern Kansas 

Concerning...severe potential...watch unlikely 

Valid 142348z - 150115z 

Probability of watch issuance...20 percent 

Summary...a risk of isolated large hail and perhaps damaging wind 
will continue for at least the short term associated with an intense 
thunderstorm cluster currently over northeastern Colorado. 
Uncertainty regarding the duration and coverage of the severe threat 
makes watch issuance unlikely at this time. 

Discussion...at 2340z...an intense thunderstorm cluster was ongoing across 
extreme northestern Colorado...with baseball-sized hail reported at 2312z in 
Logan County. This activity evolved out of a plume of relatively 
weak high-based convection that intensified as it encountered 
stronger instability...with MUCAPE of 1500-2000 j/kg noted per 
recent mesoanalysis. Effective shear of 40-50 kts is more than 
sufficient to maintain organized storm structures...with very steep 
midlevel lapse rates supporting a continued hail risk. A damaging 
wind risk may also evolve if upscale growth of the cluster 

The longevity of the severe risk associated with this cluster may be 
limited...with lower Theta-E and weaker instability noted with eastward 
extent. The cluster will likely attempt to propagate southeastward along the 
instability gradient...potentially approaching areas near or just 
north of gld between 01-02z if it holds together. Given the 
uncertainty regarding the extent and duration of the threat...ww 
issuance is unlikely at this time. 

.Dean/Hart.. 09/14/2014 

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


Latitude...Lon 40370285 40580273 40840239 40900180 40650115 40180066 
39740048 39160083 38970123 39020169 39170219 39480272 
40210292 40370285