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Mesoscale Discussion 477 |
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Mesoscale Discussion 0477
NWS Storm Prediction Center Norman OK
1141 AM CDT Tue Apr 30 2019
Areas affected...Oklahoma...Far North Texas...Far Northwest
Arkansas...Far Southeast Kansas...Far Southwest Missouri
Concerning...Severe potential...Tornado Watch likely
Valid 301641Z - 301845Z
Probability of Watch Issuance...80 percent
SUMMARY...The severe threat is likely to increase across the region
over the next few hours. A tornado threat, along with wind damage
and large hail will be possible as cells intensify. A tornado watch
will likely be needed relatively soon.
DISCUSSION...The latest surface analysis shows a stationary front
from north-central Oklahoma extending southwestward into northwest
Texas. Along and south of the boundary, surface dewpoints are in the
upper 60s and lower 70s F, which is contributing to a moderately
unstable airmass. The RAP is estimating MLCAPE values across the
warm sector in the 2000 to 3000 J/kg range. Along the instability
gradient, a small cluster of strong to severe thunderstorms is
developing in north-central to northeastern Oklahoma. This activity
is expected to continue to move northeastward across northeast
Oklahoma. The Tulsa WSR-88D VWP shows 0-6 km shear of 35 kt with 0-3
km storm relative helicity near 270 m2/s2. This shear environment
will support supercell development associated with a tornado threat.
The tornado threat will be greatest with cells that track
northeastward along the front. Large hail and wind damage will also
be possible with this activity.
Further to the south across southern Oklahoma, convection is
beginning to initiate in the vicinity of Ardmore. Some uncertainty
exists concerning how fast this activity will ramp up this
afternoon. For this reason, a tornado watch will likely be needed
over the next hour. The current thinking is that cells will
gradually increase in coverage and intensity with a severe threat
developing by 18Z in south-central and east-central Oklahoma. The
deep-layer shear environment will favor supercell development. In
addition, RAP forecast soundings gradually increase low-level shear
this afternoon across east-central Oklahoma, which will become more
favorable for tornadoes. Large hail and wind damage will also be
possible with supercells that develop.
..Broyles/Hart.. 04/30/2019
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...SGF...TSA...ICT...FWD...OUN...
LAT...LON 34069641 33739740 33829807 34229869 35299872 35849811
36799653 36959616 37139511 36889458 36049445 35489455
34749535 34069641
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