Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 280447
SWOMCD
SPC MCD 280447
ARZ000-OKZ000-TXZ000-280545-

Mesoscale Discussion 0890
NWS Storm Prediction Center Norman OK
1147 PM CDT Sat May 27 2017

Areas affected...Southern/eastern OK...North TX...Western AR

Concerning...Tornado Watch 279...

Valid 280447Z - 280545Z

The severe weather threat for Tornado Watch 279 continues.

SUMMARY...The severe threat will likely continue beyond the 05Z
issuance time of WW 279. A new watch and/or local watch extensions
across portions of southern/eastern OK and western AR will be
necessary, with watch issuance into north TX possible within the
hour or two.

DISCUSSION...An intense cluster of thunderstorms is ongoing across
southern OK at 0430Z. This activity is being focused along an
outflow-enhanced cold front that extends into western portions of
north TX, and some backbuilding has recently been noted into
portions of Clay and Wichita Counties in TX. Strong to extreme
buoyancy continues to feed into this cluster, with effective shear
more than sufficient to maintain embedded supercell structures with
a threat of large hail and damaging wind. The increasingly linear
mode is not particularly favorable for tornadoes, but with strong
instability and increasing low-level shear into the overnight hours,
some threat for a tornado or two with embedded circulations will
continue.

With an increasing low-level jet (approaching 50 kts according to
KFWD VWP) and approaching vort max from the west, the thunderstorm
cluster is likely to maintain its intensity well past the 05Z
expiration time of WW 279, with some additional backbuilding
possible into western north TX, and slow southward propagation into
north-central TX overnight. The severe threat will also continue
across eastern OK into northwest AR with ongoing intense storms.
With these factors in mind, a new watch and/or local watch extension
will likely be needed across portions of southern/eastern OK and
western AR shortly, with new watch issuance into north TX possible
in the next 1-2 hours.

..Dean/Guyer.. 05/28/2017

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

ATTN...WFO...LZK...SHV...TSA...FWD...OUN...

LAT...LON   33979875 34339803 35639567 36349475 36289383 35449393
            34409467 33549572 33539679 33579774 33579832 33639864
            33979875



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