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Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1200Z Outlook
  
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion

  
000
ACUS01 KWNS 250554
SWODY1
SPC AC 250553

Day 1 Convective Outlook  
NWS 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...

...SUMMARY...
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.

...Synopsis...
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

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