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Storm Prediction Center Forecast


RSS Mesoscale Discussions from Storm Prediction Center

SPC - No watches are valid as of Sat Mar 23 13:45:01 UTC 2019

No watches are valid as of Sat Mar 23 13:45:01 UTC 2019.


SPC - No MDs are in effect as of Sat Mar 23 13:45:01 UTC 2019

No Mesoscale Discussions are in effect as of Sat Mar 23 13:45:01 UTC 2019.


SPC Mar 23, 2019 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0755 AM CDT Sat Mar 23 2019

Valid 231300Z - 241200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM
NORTH-CENTRAL TEXAS TO CENTRAL OKLAHOMA...AND OVER A SMALL PART OF
NORTHERN KANSAS AND SOUTHERN NEBRASKA...

...SUMMARY...
At least isolated severe thunderstorms are possible late this
afternoon from north-central Texas across central Oklahoma, and near
the middle portion of the Kansas/Nebraska state line.

...Synopsis...
In mid/upper levels, a well-defined split-flow pattern is evident
across the CONUS.  A belt of nearly zonal flow extends from CA
across the south-central U.S., to a confluence with the southern rim
of a large cyclone centered east of ME.  In that southern-stream
flow field, the main perturbation and influence on severe potential
today will be a cyclone now centered over eastern CO.  The related
500-mb low is forecast to move east-northeastward across
northwestern KS and south-central NE today, crossing the Missouri
River near OMA around the end of the period.

The associated surface low -- analyzed at 11Z between LIC-ITR -- is
expected to track under or just southeast of the mid/upper cyclone
center.  The low should reach the area between MCK-HLC by 00Z, then
move east-northeastward toward the FNB area overnight, with a weak
cold front trailing southwestward across east-central KS,
northwestern OK and the southern TX Panhandle.  A dryline --
analyzed initially from the TX South Plains area south-southwestward
to the Big Bend -- should be overtaken from north to south by a weak
Pacific cold front to its northwest.  The combined boundary -- still
acting as a de facto dryline in the diurnal heating/mixing period --
should reach south-central/southwestern OK, north-central/northwest
TX, the Edwards Plateau, and north-central Coahuila by 00Z.

...Central OK to north-central TX...
Isolated severe hail may occur from elevated thunderstorms this
morning over portions of southern/central OK.  A conditional risk
for severe thunderstorms is also evident along and just east of the
I-35 corridor this afternoon into early evening.  Any sustained
activity that develops may produce severe hail/gusts, and a tornado
is not out of the question.  Some part of this outlook area may need
an upgrade in a subsequent update as mesoscale boundary/
destabilization trends become better-focused.

An extensive area of ongoing precip and embedded thunderstorms has
produced an outflow boundary that extended from northeast OK
southwestward near PVJ and DUC, to between FDR-SPS and south of CDS.
Those portions of this boundary over southern/eastern OK that have
not already stalled should do so in the next few hours, before
retreating northward midday into afternoon.  As the mid/upper-level
cyclone moves across the central Plains, height falls and tightening
height gradients aloft are expected.  Some boost to large-scale lift
also is possible north of about I-40 in OK, related to DCVA from a
basal vorticity lobe crossing the region late this afternoon.  Deep
shear should increase through the afternoon, with effective-shear
magnitudes 45-55 kt possible and even stronger values measured
through the fixed 0-6-km layer.

The mass response related to the deep-layer cyclone should lead to
destabilization at least marginally favorable for severe convection
today, the main questions being how much and how far north. 
Moisture advection should contribute to surface dew points commonly
in the 50s F near and south of the outflow boundary, with a south-
north axis of 1000-1500 J/kg MLCAPE developing.  North of the
boundary, surface-based effective-inflow parcels still will be
possible, but in a narrower corridor of weaker buoyancy (MLCAPE near
500 J/kg).

Considerable uncertainties remain about convective coverage
area-wide, and in the northern parts, airmass recovery following
morning clouds/precip.  Some of the most aggressive CAM progs
develop several short-lived supercells in a south-north chain
between DFW-PNC.  Other CAMs and synoptic models carry very little
convective precip, or weaker storms.  If the more-aggressive
scenarios prove valid, a greater than "marginal" severe threat would
exist in terms both of intensity and coverage, given the favorable
shear.  However, concerns remain about the magnitude and
northward/spatial extent of destabilization in the wake of a rather
extensive area of outflow now spreading across much of central and
northern OK, with reinforcing clouds/precip expected to last through
at least midday.  Subsequent development would be ingesting
reduced-theta-e boundary-layer air recycled from convectively
processed trajectories north of the residual outflow boundary, whose
location also still appears uncertain by mid/late afternoon.

...North-central KS to south-central NE...
Widely scattered to scattered, low-topped showers and thunderstorms
should form this afternoon in an arc just ahead of the cyclone
track, in a zone of relatively maximized low-level convergence.  A
few cells may produce hail near severe limits.  Funnel clouds or a
small/brief tornado cannot be ruled out.  Lack of greater buoyancy
will be the limiting factor for a more robust severe threat. 
However, very cold midlevel temperatures in the cold-core region of
the cyclone (-20 to -23 deg C at 500 mb) are expected, with
steepening low/middle-level lapse rates.  Forecast soundings suggest
surface-based lifted parcels for temperatures only in the low/mid
50s F, with 300-500 J/kg MLCAPE possible.  Backing of near-surface
winds just east and northeast of the low also will enlarge
hodographs, though deep shear should be weak (effective vector
magnitudes generally under 30 kt) so close to the mid/upper low.

..Edwards/Kerr.. 03/23/2019

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