U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 250554 
Storm Prediction Center ac 250553 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1253 am CDT Sat may 25 2019 

Valid 251200z - 261200z 

..there is an enhanced risk of severe thunderstorms this afternoon 
and evening across the Texas Panhandle into western Oklahoma and 
adjacent southwest Kansas... 

..there is a slight risk of severe thunderstorms this afternoon and 
evening near the lower Great Lakes into the Allegheny plateau and 
upper Ohio Valley... 

Severe thunderstorms appear likely today across the Texas and 
Oklahoma Panhandle region, northward into Kansas, and also south of 
the lower Great Lakes region into the Allegheny plateau and portions 
of the upper Ohio Valley. 

Mid/upper subtropical ridging centered near the Gulf Coast appears 
likely to remain prominent through this period. However, models do 
indicate flattening of a ridge axis extending to its north, as a 
significant short wave impulse within the mid-latitude westerlies 
turns northeastward then eastward across eastern Ontario and the 
upper Great Lakes region into Quebec and portions of the northeast. 
An associated surface cyclone may continue to deepen as it migrates 
across James Bay into northern Quebec, with a trailing surface cold 
front advancing southeastward across the Great Lakes while stalling 
over the Central Plains. 

Upstream, large-scale troughing will persist within the mid-latitude 
westerlies across much of the west. Within this regime, models 
indicate that a vigorous short wave trough and embedded deep 
mid-level low will continue to dig along the southern Oregon through 
northern California coast. As this occurs, a downstream trough axis 
is forecast to take on a negative tilt orientation while pivoting 
across baja. While downstream ridging may build to the Lee of The 
Rockies through the High Plains, models continue to indicate that a 
short wave perturbation emanating from the western troughing will 
progress through the ridging across the southern High Plains late 
this afternoon into tonight. 

Moderate to strong instability along the northwestern through 
northern periphery of the subtropical ridging appears likely to 
again provide support for considerable strong to severe thunderstorm 
development today. The stalled frontal zone across the Central 
Plains into portions of the mid/lower Missouri Valley is expected to 
provide the general northern limit of any appreciable severe weather 
potential. A convectively generated or reinforced boundary 
preceding it may provide the focus, or northwestern limit, of any 
appreciable severe weather potential across the middle Mississippi 
Valley into the lower Great Lakes region. 

..southern/Central Plains into the lower Missouri Valley... 
Considerable spread exists among the various model output concerning 
possible convective evolution for this period. However, there 
appears general consensus that the evolving mid/upper pattern will 
support an area of strengthening large-scale forcing for ascent 
across the Texas Panhandle region into portions of western Oklahoma 
by late this afternoon. This likely will be associated with 
strengthening lower/mid tropospheric warm advection, beneath a 
focused area of increasingly divergent high level flow. In the 
presence of moderate to strong instability, which probably will 
include a destabilizing boundary layer characterized by cape in 
excess of 2000 j/kg, this is expected to support considerable 
thunderstorm development, perhaps as soon as early afternoon. In 
the presence of continuing strong deep layer shear, convection 
probably will include supercells with a risk for severe hail. 

Subsequent development is more unclear, but there appears potential 
for convection to grow upscale into one or two larger clusters, 
spreading northeastward and eastward into western Oklahoma and 
southern Kansas, accompanied by a risk for strong surface gusts. 
Potential for tornadoes also remains unclear, but it would seem at 
least a bit more favorable if storms remain more discrete in nature. 
As a southerly low-level jet remains focused across the Texas South 
Plains, and strengthens late this afternoon and evening, it is also 
possible that an outflow boundary left by initial convection may 
remain a focus for continuing discrete storm development, including 
a risk for supercells with tornadoes. 

If convection farther south does not become an inhibiting factor, a 
cold front/dryline intersection across northwest Kansas may also 
provide a focus for the initiation of at least isolated late 
afternoon storms, including supercells. 

..lower Great Lakes/Allegheny plateau/upper Ohio Valley region... 
Focus for organized severe weather potential today remains somewhat 
unclear, but models suggest that this may be most probable in 
association with a convectively generated or enhanced perturbation 
migrating around the flatten mid/upper ridge. It appears that this 
feature could help focus thunderstorm development along the lake 
breeze to the south/east of lakes Erie, and perhaps Ontario, by late 
afternoon. In the presence of 30-50+ kt lower/mid tropospheric flow 
and moderate cape, one or two upscale growing convective clusters 
appear possible, accompanied initially by a risk for severe hail, 
then, primarily, a risk for potentially damaging wind gusts. 

.Kerr/squitieri.. 05/25/2019 


Mesoscale Discussion

acus11 kwns 250217 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 250217 

Mesoscale discussion 0784 
National Weather Service Storm Prediction Center Norman OK 
0917 PM CDT Fri may 24 2019 

Areas affected...parts of far northeast Iowa...extreme southeast 
Minnesota...southwest Wisconsin 

Concerning...Tornado Watch 237... 

Valid 250217z - 250415z 

The severe weather threat for Tornado Watch 237 continues. 

Summary...severe potential continues with sustained supercell 
structures currently located across far southwest Wisconsin. Storms 
are progressing eastward into an increasingly stable airmass, and 
are expected to become increasingly elevated with time. 

Discussion...mutliple supercell structures, occasionally exhibiting 
strong low-level rotation, are progressing eastward along a line 
from Monroe to Lafayette counties in far southwest Wisconsin. These 
storms are co-located just north of a quasi-stationary baroclinic 
zone, where up to 1000 j/kg MLCAPE and effective srh approaching 400 
m2/s2 are in place. As such, any storms that remain rooted within 
the boundary layer over the next couple of hours will have the 
potential to ingest the copious amounts of available streamwise 
vorticity to acquire strong low-level rotation/produce tornadoes. 
Otherwise, a stabilizing boundary layer should result in storms 
becoming elevated with time, reducing the overall tornado threat. 

.Squitieri/grams.. 05/25/2019 

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


Latitude...Lon 42559215 44009187 44018969 42558999 42559215