SPC MD 1670


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Mesoscale Discussion 1670
NWS Storm Prediction Center Norman OK
0635 PM CST Fri Nov 30 2018

Areas affected...Central/Eastern OK...North TX

Concerning...Tornado Watch 429...

Valid 010035Z - 010200Z

The severe weather threat for Tornado Watch 429 continues.

SUMMARY...The threat for large hail, damaging winds, and a few
tornadoes will increase this evening along and east of the I-35

DISCUSSION...At 0030Z, scattered thunderstorms have developed along
two bands from north TX into southwest OK; one band is along a
prefrontal confluence axis approaching the I-35 corridor, with the
second band further west along the primary Pacific cold front.
Storms have largely remained subsevere thus far, but an increase in
coverage and intensity is expected this evening in advance of a
powerful negatively tilted trough moving into the southern Plains.
Regional 00Z soundings from OUN and FWD exhibit very steep midlevel
lapse rates and moderate buoyancy (MLCAPE of 1000-1500 J/kg).
Deep-layer shear is quite strong and low-level shear will continue
to increase this evening in advance of the upper trough. Given the
favorable environment, it is possible that storms will become severe
as they approach the I-35 corridor between now and 7 PM CDT, with
maintenance or continued gradual increase in the severe threat
further east as storms encounter more favorable low-level moisture.
The primary initial threat will be large hail, while any sustained
discrete supercell will also eventually pose a tornado threat. Later
this evening as the primary Pacific cold front catches up to the
storms further east, an evolution into more of a linear mode is
expected, with a corresponding damaging wind threat.  

Further east, storms have been increasing within a low-level warm
advection regime across eastern OK. While much of this activity is
likely slightly elevated, thunderstorm clusters may eventually
become rooted near the surface, posing a near-term threat for
damaging winds and perhaps isolated large hail. Very favorable
low-level wind profiles will also result in a tornado threat across
this region if supercell structures can become established.

Some severe threat will likely extend south of Tornado Watch 429
this evening. While coverage further south remains uncertain, some
areal extension of the watch may be required if storms become
established south of the Metroplex.

..Dean.. 12/01/2018

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


LAT...LON   32399924 34149857 35789824 36449765 36889708 36919475
            36229468 35209469 34139529 33049545 32569589 32249614
            31879663 31629736 31659798 31749849 31969930 32399924 

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