U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 300530 
Storm Prediction Center ac 300529 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1229 am CDT Tuesday Sep 30 2014 

Valid 301200z - 011200z 

..there is a slight risk of severe thunderstorms over portions of South Dakota and northestern 

Isolated severe thunderstorms with hail and perhaps a tornado are 
possible Tuesday from South Dakota into Nebraska. A few strong 
storms with hail may also develop from Kansas southward into 
northwestern Texas by late afternoon into the evening. Isolated hail 
will also be possible across portions of Pennsylvania. 

A negatively-tilted shortwave trough will move across the Dakotas 
with surface low over central South Dakota at 21z. At the same time...a warm 
front will extend eastward from the low along the South Dakota/ND border and southeastward 
into western Iowa with a dryline from east-central South Dakota into eastern Nebraska and southwestward 
into the eastern Texas Panhandle. Low-level moisture will be somewhat 
meager...but will likely support isolated strong to severe storms 
during the afternoon where forcing for ascent is strongest near the 
boundaries and with ample shear in place. 

To the east...a small upper low will shift southeastward across Ohio...PA...WV and 
Virginia with cool air aloft and enhanced shear helping to support a few 
strong daytime thunderstorms. 

..ern South Dakota and Nebraska during the afternoon... 
A north-S oriented zone of non-severe thunderstorms will exist early in 
the day from northern Kansas across Nebraska and South Dakota in association with the warm 
conveyor belt ahead of the low. In the wake of this early 
activity...cooling aloft will persist coincident with strong heating 
west of the dryline across South Dakota and Nebraska. Dewpoints into the middle to upper 
50s f are likely to extend nwwd toward the surface low over central 
South Dakota. By middle/late afternoon...an arc of storms appears 
likely...comprised of relatively low-topped supercells. A tornado or 
two will be possible along with large hail. 
Due to the northward movement of the upper low...forcing for ascent will 
weaken with southward extent into Nebraska...but isolated hail will be possible 
there during the afternoon as well. 

..ern Nebraska...KS...far western OK into northwestern Texas overnight... 
weak forcing along the stalling surface trough/dryline may be sufficient 
for isolated strong storms capable of marginal hail from Kansas into 
northwestern Texas. Temperatures aloft will not be particularly cool...and 
shear will be marginally favorable for a long-lived cell capable of 
hail during the peak heating hours. 

During the evening...warm advection with the southwesterly low-level jet will 
help increase lift across northestern Kansas and vicinity...with perhaps 
marginal hail. 

..cntrl and western PA...Northern WV and southwestern New York during the afternoon... 
a shortwave trough will move southeastward across Michigan and across Ohio/PA/NY 
during day with cooling aloft favorably timed with daytime heating. 
A weak cool front will help focus development across mainly western PA. 
Although middle to upper-level flow will increase across southern areas 
under the jet maximum...winds in the lowest 3km will be relatively weak. 
This should result in little if any tornado threat even with a few 
cells perhaps exhibiting midlevel rotation...and any wind threat 
should be quite localized. Cool temperatures aloft will strongly 
favor hail production...which will be the primary threat. 

.Jewell/Rogers.. 09/30/2014 

Mesoscale Discussion

acus11 kwns 300000 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 300000 

Mesoscale discussion 1777 
National Weather Service Storm Prediction Center Norman OK 
0700 PM CDT Monday Sep 29 2014 

Areas affected...northestern nm...southeastern Colorado...southwestern Kansas...western Texas/OK panhandles 

Concerning...Severe Thunderstorm Watch 509... 

Valid 300000z - 300100z 

The severe weather threat for Severe Thunderstorm Watch 509 

Summary...damaging wind and isolated severe hail potential will persist for 
the next couple across parts of the southern/Central High plains. The damaging 
wind threat may extend slightly east of ww 509 across southwestern Kansas...but a 
new ww does not appear necessary as potential is expected to 
decrease after 02-03z. 

Discussion...radar mosaic imagery shows isolated discrete supercells 
persisting across northestern nm...approaching the northwestern Texas and western OK 
panhandles...posing a threat for damaging wind gusts and locally severe 
hail. Storms across southern portions of the ww in east-central nm have 
exhibited slow weakening trends over the past hour. 

Farther N/W...convection continues to increase along a Pacific cold 
front from southeastern Colorado southwestward into northestern nm...as a midlevel jet streak is 
ejecting northeastward from north-central nm. This activity is progressing eastward into 
a more marginal thermodynamic environment /see 00z Ama 
sounding/...characterized by low 50s f surface dewpoints...with buoyancy 
forecast to decrease further owing to nocturnal boundary layer 
cooling. Forcing for ascent associated with the ejecting jet streak 
should become increasingly focused north of the mesoscale discussion area into northestern Colorado 
over the next couple hours. These factors are expected to limit the 
eastward progression of a convective wind threat to within or just east of 
ww 509...perhaps extending into far southwestern Kansas this evening. A new ww 
is not currently anticipated. 

.Rogers.. 09/30/2014 

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


Latitude...Lon 38170140 37330146 36460212 34490344 33950443 34120521 
34870546 36070493 37350400 38410356 38580321 38600209