SPC MD 587

MD 0587 CONCERNING SEVERE THUNDERSTORM WATCH 173... FOR CENTRAL OKLAHOMA TO NORTHWEST AND WEST-CENTRAL TEXAS

Mesoscale Discussion 0587
NWS Storm Prediction Center Norman OK
0245 AM CDT Sat Apr 29 2017

Areas affected...Central Oklahoma to northwest and west-central
Texas

Concerning...Severe Thunderstorm Watch 173...

Valid 290745Z - 290945Z

The severe weather threat for Severe Thunderstorm Watch 173
continues.

SUMMARY...Severe storms will continue to pose a threat of large
hail, some exceeding 2 inch diameter, and locally strong winds
overnight into early Saturday morning across portions of central and
western Oklahoma, and across northwest Texas.  Given more recent
thunderstorm development within the WFO Lubbock TX forecast area,
several counties have been added to WW 173.

DISCUSSION...Mosaic radar imagery indicated vigorous thunderstorm
development persisting with supercell structures ongoing from
central to southwest OK.  MRMS MESH data suggested hail around 2
inches in diameter was moving into southwest Logan and far northern
Caddo Counties at 0720Z.  Meanwhile, farther west, water vapor
imagery showed a shortwave trough tracking to the east-northeast
across the southern High Plains ahead of a large-scale trough moving
to the east-southeast across the Four Corners region.  Forcing for
ascent attendant to the lead trough and strong low-level warm air
advection within the nose of a 50-60 kt southerly low-level jet are
supporting more recent thunderstorm development across west-central
TX (generally between Terry to Childress Counties).  All of these
storms are located north of a surface boundary that extended to the
northeast from a low near MAF into southwest OK (between LTS and
SPS) to south of CHK and OUN, and eastward to south of FSM in
western AR.

Aforementioned strong low-level warm air advection and forcing for
ascent spreading across west TX into western/central OK overnight
will maintain new, mainly elevated thunderstorm development within a
gradient of MUCAPE ranging from 1500-3000 J/kg.  This instability
combined with strong effective shear exceeding 50 kt will support
supercells, with objectively analyzed midlevel lapse rates around
7.5 C/km further enhancing the threat for very large hail.  Locally
strong wind gusts will also be a severe-weather threat, primarily
with storms that can become surface-based or near surface-based
closer to the surface front.

..Peters.. 04/29/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TSA...OUN...LUB...AMA...

LAT...LON   33370105 33680145 34380143 35280042 36089893 36359734
            36149658 35049649 34849648 34419722 34199792 33929843
            33719947 33470051 33370105 

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