Severe Weather Forecast

U.S. Convective Outlook
Mobile & Email Alerts Actualizare:

560 
acus01 kwns 240608 
swody1 
Storm Prediction Center ac 240606 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0106 am CDT Thursday may 24 2012 


Valid 241200z - 251200z 


..there is a slight risk of severe thunderstorms from eastern Kansas/central and northern MO 
northward across Iowa...southeastern Minnesota and much of WI... 


... 
Late night water vapor satellite loop and short term guidance depict a 
vigorous middle/upper level disturbance over Nevada/Utah rounding the base of 
a larger scale upper trough encompassing much of the western U.S. This 
short wave trough and its associated 75-90kt jet streak will emerge 
across the Central Plains later this morning before pivoting across 
the middle Missouri River valley and then ejecting northeastward toward The 
Arrowhead of Minnesota by late evening. 


In response to strengthening deep-layer ascent along an already well 
established frontal zone draped SW-NE across the Great 
Plains...surface cyclogenesis is forecast from Kansas to Iowa through the 
morning. Resulting low pressure center is forecast to track rapidly 
northeastward along the sharp frontal zone...from southeastern Minnesota into northwestern WI 
through late afternoon...while deepening rapidly. Cold front 
trailing from the low center will spread east from Iowa to northern Illinois and 
south into MO through tonight but its advance and intensity should 
gradually diminish over the plains as the primary upper trough moves 
north into Canada and stronger large scale support for lift along 
the front wanes. 


Broad but weakening middle/upper level troughing will persist along the 
eastern Seaboard this period with a band of more modest middle level flow 
constrained to the immediate East Coast and over portions of the middle 
Atlantic. Persistent swath of southerly flow off the Gulf Stream and 
Caribbean Sea will maintain a very moist maritime tropical airmass 
over the southeast and middle Atlantic. 


..upper MS River Valley... 
As has been the case with some of the more recent severe storm 
episodes...limited low level moisture and strong capping will again 
play a role in the evolution of severe weather potential from Iowa and 
Illinois north across eastern WI and much of WI today. Despite these 
limitations...there is considerable agreement amongst the latest 
guidance that substantial shear and forcing will accompany the 
developing low pressure system from Iowa north-northeastward across western WI later 
this afternoon. Greatest concentration of thunderstorms will likely be along 
the cooler side of the surface boundary...at least initially...where 
parcels will be forced to achieve an level of free convection elevated above a stable 
surface layer. Even in this regime...some hail and evening 
occasional stronger wind gusts may occur with cells or line segments 
racing northeastward at 40-50kt. 


Warm sector to the east of the surface low is likely to remain 
capped given plume of very warm air at middle levels streaming northeastward 
ahead of the ejecting upper trough. However...overnight rain and 
continued southerly flow should allow surface dewpoints to climb into the 
low 60s f as far western WI. MLCAPE coincident with the deepening 
surface low may reach into the 500-1000 j per kg range and...given 
magnitude of forced ascent accompanying the intensifying low 
pressure /deepening around 1mb/hour between 18 and 21z per latest 
progs/...expect potentially dangerous and fast-moving storms to 
develop. The window of opportunity for this development will be 
rather small...from about 19-23z and over a relatively confined 
region from extreme eastern Minnesota into western/northwestern WI. Forecast conditions in 
this time and area appear supportive of a couple of possibly strong 
tornadoes and/or fast-moving line segments capable of damaging 
winds. Shear and instability values near the low support the current 
corridor of high tornado probabilities and an upgrade to greater 
probabilities/confidence is possible with the light of day and a 
close inspection of overnight storm-scale guidance. 


Additional surface-based storm development in the form of lines or 
bows may occur through the late afternoon along the advancing cold 
front. Magnitude of middle level flow directed into the developing 
convection suggests that these storms may pose a threat of damaging 
winds as they move east from northestern Iowa into southern WI and portions of northern 
Illinois. 


... 
More isolated to scattered storm development could occur ahead of 
the front spreading into MO from late afternoon into the evening. 
Larger scale support will be waning along the front in this area. 
However...any storms that can develop will do so in a sufficiently 
sheared environment where warm/hot boundary layer will contribute 
damaging wind potential...and perhaps some hail. 


.Carbin/Mosier.. 05/24/2012 






Mesoscale Discussion

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acus11 kwns 240329 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 240329 
nez000-ksz000-240500- 


Mesoscale discussion 0886 
National Weather Service Storm Prediction Center Norman OK 
1029 PM CDT Wednesday may 23 2012 


Areas affected...parts of northern Kansas and central/eastern Nebraska 


Concerning...Severe Thunderstorm Watch 293... 


Valid 240329z - 240500z 


The severe weather threat for Severe Thunderstorm Watch 293 
continues. 


Summary...initial band of storms has weakened...but elevated 
convection continues to expand west of the MO river -- which will 
likely require either new ww or extension in time/area of ww 293. 


Discussion...latest radar loop shows elevated storms increasing 
across the eastern half of Nebraska...to the cool side of the front and near 
the nose of a 60 knots southerly low-level jet. With ample elevated 
instability and strong isentropic lift...expect storms to continue 
increasing in coverage...with embedded/stronger cells likely to 
remain capable of producing marginally severe hail for several 
hours. Thus -- extension of ww 293 or new ww issuance will likely 
be required...pending coordination with affected offices. 


.Goss.. 05/24/2012 


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


Attention...WFO...fsd...oax...top...ict...Gid...lbf...ddc...gld... 


Latitude...Lon 39319817 38689908 39009973 39690041 40830066 41660004 
41809997 42789790 42659690 42039672 40679715 39319817