Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 291832
SPC MCD 291831
Mesoscale Discussion 0368
NWS Storm Prediction Center Norman OK
0131 PM CDT Wed Mar 29 2017
Areas affected...Southeast Texas into western Louisiana
Concerning...Severe potential...Watch possible
Valid 291831Z - 292100Z
Probability of Watch Issuance...60 percent
SUMMARY...Storms may strengthen later today into the evening with a
tornado risk along with locally damaging winds. A watch could be
required later this afternoon.
DISCUSSION...A leading line of cells approaching the Sabine river is
currently weakening, while new cells continue to evolve to the west
near dying/mixing outflow boundaries. Here, the cap is locally
weaker as well as compared to points east, although the 18Z LCH
sounding shows a dramatic increase in low-level moisture and
weakened capping inversion.
Strong southwesterly flow aloft will continue to overspread the
area, with main surface low well to the north. Southerly 850 mb flow
around 25-35 kt will be maintained, and change little through 00Z.
As the trough approaches, a boost to low-level convergence will
occur and help to eventually push this cluster of cells eastward
In the short term, it appears the severe threat will be driven by
the storm scale, with merging cells eventually becoming supercells
as gradual destabilization occurs and meso lows form, also locally
backing surface winds and maintaining favorable low-level shear.
Indeed VWPs show better backing at 850 mb in closer proximity to the
storm cluster, with less favorable shear farther east into LA. The
air mass remains very moist, with impressive lapse rates aloft.
Although widespread severe is not expected, a small corridor may
certainly develop a supercell tornado risk this afternoon through
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 28699576 29809541 30549526 31129463 31149395 30959310
30599297 30169299 29839311 29699330 29629383 29429440
29049485 28819535 28699576