U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 011258 
Storm Prediction Center ac 011256 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0756 am CDT Wednesday Apr 01 2015 

Valid 011300z - 021200z 

..there is a slight risk of severe thunderstorms this afternoon/evening from northern 
Kansas northeastward to SW Minnesota... 

..there is a marginal risk of severe thunderstorms surrounding the slight risk and 
extending southward into OK/North Texas/western Arkansas... 

..there is a marginal risk of severe thunderstorms this afternoon for NE Florida/southeast 

A few strong to severe storms...capable of producing large hail and 
damaging winds...are expected this afternoon and evening from 
northern Kansas northeastward to southwest Minnesota. A more 
isolated risk of severe storms will extend southward across Oklahoma 
into western Arkansas and North Texas...with a separate area across 
northeast Florida and southeast Georgia. 

A midlevel trough will progress eastward from the northern rockies to the northern 
plains through tonight...as a surface cyclone near the ND/South Dakota border 
develops northeastward to southeast Manitoba/western Ontario. In response to the 
cyclogenesis...the moist sector will be drawn northward as far as Iowa/southern 
Minnesota. Farther S...a series of embedded speed maxima will move northeastward 
from central/North Texas across eastern OK/western Arkansas in advance of the weak southern 
stream trough exiting NE Mexico...along with an mesoscale convective vortex from overnight 
convection moving northeastward from NE OK toward SW/central MO today. 

..wrn OK/KS/neb/IA/MN this afternoon into early tonight... 
The cold front /trailing the primary northern plains cyclone/ will move 
southeastward across Nebraska/SD/IA/MN today...and across Kansas/MO tonight. 
Low-level moisture will be drawn northward from OK/Texas in advance of the 
front...with the western edge of the moist sector demarcated by a Lee 
trough/dryline extending southward from a secondary/Lee cyclone in western Kansas 
this afternoon. The low-level moisture field has been disrupted 
across OK as a result of overnight convection...so northward moisture 
transport will likely be delayed/reduced some compared to the more 
aggressive model forecasts. This will likewise reduce buoyancy from 
earlier expectations...though MLCAPE of 1000-2000 j/kg is still 
probable given the plume of 8-9 c/km midlevel lapse that has 
overspread the Central Plains. 

Thunderstorm initiation is expected along the cold front by 21-00z 
from SW Minnesota southwestward into Nebraska...within the narrow corridor of moderate 
buoyancy. Given deep-layer shear that will be marginal for 
supercells...and shear vector orientations parallel to the 
boundary...a rather quick upscale growth to linear convection is 
likely. A few damaging gusts and large hail will be possible with 
the stronger embedded storms for a few hours late this afternoon 
through late evening. Farther SW...the degree of storm development 
is unclear along the dryline this afternoon from SW Kansas southward near the 
Texas/western OK border. Deep mixing will probably reduce boundary layer 
dewpoints east of the dryline...and the moisture influx may also be 
interrupted by the ongoing convection in North Texas. Given the likely 
high-based nature of any storms that form...and only 
marginally-favorable wind profiles for supercells...will maintain 
only 5% hail/wind probabilities. 

..TX to eastern OK/western Arkansas/MO today... 
Clusters of thunderstorms should persist and develop northeastward through 
the day in association with the subtle speed maxima and the mesoscale convective vortex 
ejecting northeastward from NE OK. Lapse rates are not as steep as 
yesterday...and vertical shear has also weakened. Still... remnant 
instability and several clusters of storms suggest a marginal 
wind/hail risk with the stronger embedded storms. Areas farther S 
into central Texas may have some risk for strong storms later 
today...though clouds will tend to slow surface heating. This area 
may need to be re-evaluated in later updates. 

..se Georgia/NE Florida this afternoon... 
A shortwave trough over NE Alabama/central Georgia will move east-southeastward through 
this afternoon...brushing the NE Florida/southeast Georgia area. The 12z jax 
sounding shows sufficient vertical shear and potential buoyancy to 
support a risk for isolated damaging gusts and marginally severe 
hail for a few hours this afternoon. 

.Thompson/Mosier.. 04/01/2015 

Mesoscale Discussion

acus11 kwns 010616 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 010616 

Mesoscale discussion 0174 
National Weather Service Storm Prediction Center Norman OK 
0116 am CDT Wednesday Apr 01 2015 

Areas affected...east central Oklahoma 

Concerning...Severe Thunderstorm Watch 14... 

Valid 010616z - 010745z 

The severe weather threat for Severe Thunderstorm Watch 14 

Summary...the risk for severe winds/hail probably is becoming 
focused in an increasingly narrow corridor...but may persist into 
the 08-10z time frame across parts of east central 
Oklahoma...roughly near/ northwest through northeast of 
McAlester...toward areas southwest of Fort Smith. Parts of ww 14 
probably will need to be extended locally another couple of hours. 

Discussion...thermodynamic profiles in areas not yet impacted by 
convection remain characterized by very steep middle-level lapse rates 
and sizable cape...on the order of 1000-2000 j/kg for most unstable 
lifted parcels. And this continues to compensate for rather 
marginal kinematic parameters...to support thunderstorm development 
capable of producing severe hail and surface gusts. It currently 
appears that severe potential could persist another few hours...with 
strongest storms generally focused where outflow ... with 
the evolving ongoing convective cluster...tracks along a weak 
front/low-level convergence zone extending roughly from 
Ardmore/Spencer through areas southwest of Fort Smith...between now 
and 08-10z. 

.Kerr.. 04/01/2015 

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


Latitude...Lon 35529638 35469542 35289474 35089421 34829383 34409427 
34479484 34489552 34399624 34549659 34929637 35529638