U.S. Severe Weather Forecast (Convective Outlook)

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Storm Prediction Center ac 300559 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1259 am CDT Tuesday Jun 30 2015 


Valid 301200z - 011200z 


..there is a slight risk of severe thunderstorms Ohio Valley / deep south / 
mid-Atlantic... 


..there is a slight risk of severe thunderstorms northern plains / Black Hills... 


..There is a marginal risk of severe thunderstorms central/eastern states... 


..there is a marginal risk of severe thunderstorms central/southern Arizona... 


... 
scattered severe storms with damaging winds and some hail are most 
probable across the Ohio Valley to the deep south and the 
Middle-Atlantic States this afternoon into early evening. Large hail 
and severe winds are expected with a few severe storms over the 
northern Great Plains and Black Hills in the late afternoon and 
evening. 


... 
Amplified large-scale pattern will persist with an upper trough over 
the east and a Stout anticyclone over the eastern Great Basin. Several 
shortwave impulses will gradually progress within the broad cyclonic 
flow regime from the northern Great Plains across the Midwest to the 
northeast. 


..deep south... 
The greatest concentration of convection today is expected S of 
ongoing thunderstorms across the mid-south/Tennessee Valley along a lead/weak 
front. S of this boundary over the lower MS valley lies a richly 
buoyant air mass characterized by precipitable water values of 1.75-2.00 inch per 
GPS data/evening radiosonde observations. With predominant westerly low-level flow 
supporting eastward transport of this air mass in conjunction with 
advection of moderately steep middle-level lapse rates from the Southern 
Plains...moderate to strong buoyancy should develop by early 
afternoon outside of lingering morning convection. Moderate 700-500 
mb westerlies should Foster several multicell clusters with damaging winds 
and sporadic hail as the primary hazards. 


..OH valley... 
Ascent tied to a minor middle-level vorticity maximum over the upper MS valley 
should reach the Midwest this afternoon with a weak front/surface 
trough aiding in scattered storms in the middle/late afternoon. 
Although mean mixing ratios will largely be only around 10-12 
g/kg...cold temperatures aloft and 25-35 knots effective shear should 
support multicells and transient supercell structures with initial 
severe hail/wind risks evolving into predominantly damaging wind. 


..mid-Atlantic states... 
Low-level moisture will gradually increase but mean mixing ratios 
should hold at 10-12 g/kg. Amidst marginal middle-level lapse 
rates...robust diabatic heating will be necessary for modest 
buoyancy to develop east of the Appalachians. This should occur S of a 
quasi-stationary front expected to lie across parts of the 
northeast. With weak height falls downstream of the Great Lakes 
middle-level trough...scattered storms should develop in the afternoon. 
30-40 knots effective shear might support a few supercells...but 
overall thermodynamic setup suggests these may remain 
weak/transient. 


..nrn Great Plains/Black Hills... 
A shortwave impulse over the southern Canadian rockies should eventually 
become absorbed within the broad cyclonic flow regime associated 
with the eastern trough. This feature should aid in sharpening a Lee 
surface trough across far eastern Montana this afternoon. With a plume of 
1.00-1.25 inch precipitable water values at present across parts of the Dakotas...a 
narrow corridor of moderate buoyancy should develop near the surface 
boundary with cooler surface temperatures suppressing 
destabilization farther east. As isolated thunderstorms form along the trough 
and Black Hills...elongated hodographs will favor splitting 
supercells with large hail and localized severe winds as the main 
hazards. 


..cntrl/southern Arizona... 
25-35 knots middle-level elys will persist across southern Arizona S of the nearly 
stationary anticyclone over the eastern Great Basin. Hot temperatures 
and deep inverted-v profiles will again support a risk for isolated 
severe winds as well as some severe hail given the strength of the 
flow and probable cell/cluster modes. 


..lower MO valley... 
Low-level warm air advection will strengthen substantially early Wednesday and yield 
scattered to widespread elevated thunderstorms. Sufficient effective shear 
should exist for a risk of localized severe hail/wind. 


.Grams/leitman.. 06/30/2015 

Mesoscale Discussion


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sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 300025 
wiz000-iaz000-mnz000-300130- 


Mesoscale discussion 1236 
National Weather Service Storm Prediction Center Norman OK 
0725 PM CDT Monday Jun 29 2015 


Areas affected...portions of southeast Minnesota into southwest WI and 
extreme northeast Iowa 


Concerning...Severe Thunderstorm Watch 370... 


Valid 300025z - 300130z 


The severe weather threat for Severe Thunderstorm Watch 370 
continues. 


Summary...isolated strong to severe thunderstorms may continue for 
another 1-3 hours. As such...Severe Thunderstorm Watch 370 will be 
extended. 


Discussion...a gradual weakening trend has been noted in radar data 
over the last hour or so. The exception is with storms just north of 
msp and further south along the MS river in far northeast 
Iowa/southwest WI. 00z mesoanalysis along with the 00z mpx radiosonde observation 
indicate MLCAPE near 1000-1500 j/kg still exists with steep midlevel 
lapse rates in place. This could result in current strong to severe 
storms to diminish only slowly. New development however may struggle 
to increase...especially as the upper shortwave impulse shifts 
further east of the region. Per collaboration with weather forecast office mpx and 
arx...Severe Thunderstorm Watch 370 will be extended in space/time. 


.Leitman.. 06/30/2015 


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


Attention...WFO...mkx...dvn...arx...mpx...dmx... 


Latitude...Lon 45649293 44009062 43679036 43219029 42709041 42649106 
42669132 43669396 44239448 44849472 45549458 45859431 
45939368 45649293