U.S. Severe Weather Forecast (Convective Outlook)

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Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1254 am CDT Monday Sep 01 2014 


Valid 011200z - 021200z 


..there is a slight risk of severe thunderstorms from lower Michigan and southeastern WI 
through the Midwest...middle MS valley to eastern Kansas and far northestern OK... 


... 
Isolated to scattered severe thunderstorms should develop along and 
ahead of a weak cold front from parts of the southern Great Lakes 
region southwestward across Indiana...Illinois...Missouri into 
eastern Kansas and far northeast Oklahoma. Damaging winds and large 
hail will be possible with the strongest storms...while a tornado 
cannot be ruled out across the southwestern extent of the slight 
risk area. A few strong wind gusts will be possible this afternoon 
across far eastern Wyoming into parts of southern South Dakota and 
northern Nebraska. 


..lower Michigan/southeastern WI to middle MS valley to southeastern Kansas/northestern OK... 
A progressive shortwave trough is expected to track northeastward from the 
upper MS valley through the upper Great Lakes early in the forecast 
period...reaching Ontario and western Quebec by late afternoon/early 
evening. Although the strongest 500-mb height falls /60-90 M/ are 
forecast to spread through the northern extent of the upper Great 
Lakes...30-60 meter falls should occur across the eastern WI and lower 
Michigan portion of the slight risk area. Meanwhile...an upstream 
shortwave trough and attendant speed maximum are expected to move from 
the central rockies through the Central Plains this afternoon to the 
Midwest and southern Great Lakes later Monday night. 


A cold front associated with the lead shortwave trough is expected 
to extend from Western Lake Superior south-southwestward through central Iowa into 
central Kansas at 12z. This boundary will advance to a position from 
eastern Upper Michigan through southeastern Iowa into southeastern Kansas and north central OK to 
the Texas Panhandle by late afternoon. Frontal convection will likely 
be ongoing at the beginning of the period...enhanced primarily by 
ascent ahead of the upper MS valley shortwave trough. Additional 
storms may also be ongoing at daybreak across eastern Kansas into central/ 
southern MO within a low-level warm air advection regime. Gusty winds and isolated hail 
may occur with the early morning activity...though greater thunderstorm 
coverage and severe weather threat will be possible across the 
slight risk area later today. 


Strongest boundary-layer heating should occur across southeastern Kansas/southwestern MO 
and OK where surface temperatures will warm into the 90s. As a 
result...instability is expected to be greatest along the trailing 
portions of the front where the eastern extent of steep lapse rates will 
contribute to moderate-strong instability /MLCAPE 2000-3000 j per 
kg/. Despite weaker midlevel lapse rates and some uncertainty in 
degree of surface heating...due in part to early day convective 
debris...moderate instability should also develop east-northeastward from MO to 
lower Michigan. 


New thunderstorm development should occur from southeastern WI into lower Michigan and eastern 
Iowa to Indiana from late morning into the afternoon in vicinity of 
the cold front and any differential heating boundaries attendant to 
early morning convection. A 50-60 knots southwesterly midlevel jet accompanying 
the lead trough will result in strengthening bulk shear for the 
potential for organized storms producing damaging winds and hail. 
Meanwhile...thunderstorms are expected to back-build southwestward through MO to southeastern 
Kansas during the middle-late afternoon as the cap weakens. Low-level 
winds will remain backed to southerly into southeastern Kansas...northestern OK and southwestern MO 
enhancing convergence into the cold front and potential outflow 
boundary from early morning storms. Strengthening westerly midlevel 
winds across Kansas/MO by late afternoon will result in strong bulk 
shear for organized storms including supercells with the strong 
instability supporting the potential for very large hail and strong 
wind gusts. The aforementioned zone of backed low-level winds will 
enhance low-level shear for a tornado threat into the early evening. 


..ern Wyoming/southwestern South Dakota and western/central Nebraska... 
A fast-moving midlevel impulse is expected to track east-southeastward from the 
northern rockies to this discussion area by late this afternoon. Despite 
surface dew points in the 40s...steep lapse rates...with 500-mb 
temperatures around -15 c accompanying the impulse...will result in 
marginal instability /MLCAPE 500-1000 j per kg/ this afternoon. 
Thunderstorms are expected to develop within this northwest flow regime with 
locally strong wind gusts being the primary threat. 


.Peters/Dean.. 09/01/2014 

Mesoscale Discussion


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Mesoscale discussion 1654 
National Weather Service Storm Prediction Center Norman OK 
1202 am CDT Monday Sep 01 2014 


Areas affected...parts of central and eastern Kansas 


Concerning...Severe Thunderstorm Watch 480... 


Valid 010502z - 010630z 


The severe weather threat for Severe Thunderstorm Watch 480 
continues. 


Summary...it does not appear out of the question that a new severe 
weather watch will be needed before the currently scheduled 06z 
watch expiration. 


Discussion...the Southern Plains southerly low-level jet is reaching 
peak intensity /50-60+/...and enhancement of warm advection...within 
the Lower/Middle tropospheric baroclinic zone on the southern periphery 
of upper troughing spreading across the Central Plains ... 
maintaining vigorous storm development north of Great Bend into 
areas south of Emporia. The rear/western edge of stronger activity 
is expected to continue gradually shifting east southeastward across 
central and portions of southeastern Kansas through the 06-09z time 
frame...as the low-level jet veers. Wdss-ii mesh data suggests that 
stronger activity may still be producing marginally severe 
hail...aided by strong shear in the cloud-bearing layer...and the 
continuing presence of steep middle-level lapse rates. Even though 
activity is generally rooted above a stable surface-based layer to 
the north of the conglomerate outflow boundary/surface front...it 
does not appear out of the question that heavy precipitation loading 
and downward momentum Transfer may still contribute to occasional 
strong surface gusts that could reach severe limits. 


.Kerr.. 09/01/2014 


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


Attention...WFO...sgf...eax...top...ict...ddc... 


Latitude...Lon 38949825 39009710 38789557 38169472 37599508 37309653 
37529784 37699880 38079933 38579938 38949825