Mesoscale Discussion 270

Issued

Mar 7, 2017, 2:58 AM CST (08:58 UTC)

Expired

Mar 7, 2017, 4:30 AM CST

In force

92 min

Issued by

the Storm Prediction Center

The Little Rock radar (KLZK), 106 km from the middle of the area, began a volume at 08:56 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

• Severe Thunderstorm Watch 69Mar 7, 3:35 AM CST

961 
ACUS11 KWNS 070859
SWOMCD
SPC MCD 070858 
KYZ000-ILZ000-TNZ000-MSZ000-MOZ000-ARZ000-LAZ000-TXZ000-071030-

Mesoscale Discussion 0270
NWS Storm Prediction Center Norman OK
0258 AM CST Tue Mar 07 2017

Areas affected...Southern IL...southeast MO...western KY...western
TN...AR...and parts of northern MS to northern LA

Concerning...Tornado Watch 64...66...67...

Valid 070858Z - 071030Z

The severe weather threat for Tornado Watch 64, 66, 67 continues.

SUMMARY...East/southeast-moving squall line will continue to exit
the remaining valid portions of WW 64 and 66, while the
severe-weather threat will progress across WW 67 with a continued
threat for locally strong wind gusts.  And, in the short term, any
remaining tornado threat appears to be across central AR, though
that trend is likely diminishing.

DISCUSSION...At 0825Z, mosaic radar imagery showed an east/
southeast-moving squall line extending from northwest IN into
southern IL, southeast MO, to west-central AR, and southeast OK. 
Strong surface pressure rises continue to be analyzed in the wake of
this line of storms suggesting convective outflows will be dominant,
with an attendant threat for locally strong to severe wind gusts. 
This also suggests the tornado threat should continue to wane, given
the more linear storm mode.  

The threat for damaging wind gusts should be greatest across the
southern extent of the squall line in northeast and central AR where
there remains greater moisture and instability.  07z HRRR suggests
some destabilization should occur into the morning to the east and
south across the remainder of AR to northern LA and the Mid-South
region.  This combined with a strong southwesterly low-level jet of
50-65 kt per WSR-88D VWPs from LZK to MEG/PAH suggests the threat
for damaging winds should persist into the morning across portions
of AR, northern MS, western TN, and perhaps northern LA, where a new
WW is being considered.

Meanwhile, north/northeast from southeast MO, a more stable boundary
layer is expected to limit an additional severe-weather threat, as
the squall line advances east during the remainder of the night and
early morning.

..Peters/Edwards.. 03/07/2017

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

ATTN...WFO...PAH...MEG...JAN...LSX...LZK...SHV...

LAT...LON   34549441 35389287 36119109 37438988 38178907 38588862
            37908815 37248812 36498835 35288878 34088911 33408991
            32599110 32469213 32639326 32949378 33629430 33709437
            34549441

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.