The severe weather threat for Severe Thunderstorm Watch 418
continues.
SUMMARY...A damaging bow echo will continue to shift east/southeast
this evening. A new severe thunderstorm watch will be needed across
parts of northeast AR into TN, perhaps replacing portions of
WW 418.
DISCUSSION...A well defined damaging bow echo continue to shift
southeast into far southeast MO toward northeast AR, western KY and
eventually western TN. Most recently, Poplar Bluff measured a severe
gust of 51 kt and Cape Girardeau measured 63 kt. Multiple mPING
reports of wind damage have also been noted over the past 30 minutes
across Cape Girardeau and Scott Counties in MO and Union County in
far southern IL. Regional VAD wind profile data show an intense
rear-inflow jet with 50+ kt winds around 1.5-4 km ARL from the PAH,
SGX and LSX radars. This descending rear-inflow jet is aiding in
producing these damaging gusts, and is evident in reflectivity data
where low returns are noted behind the initial line of convection.
Downstream of the bow echo, outflow from another long-lived bow echo
moving east/southeast toward central KY arcs westward into the apex
of the southeast MO bow echo. There has been re-invigoration of the
convection at this intersection with increasing reflectivity noted
in 5 and 7 km CAPPI. Recent track on this bow gives a motion toward
the east/southeast at nearly 60 kt, which will bring the system to
the edge of
WW 418 between 00-01z. The southeastern flank of the bow
now shifting into northeast AR is a little less organized and not
progressing as quickly as the apex region further north/northeast.
However, given extreme instability and a very warm/moist downstream
environment with surface dewpoints in the mid 70s, a severe threat
will persist into the evening hours to the west of
WW 418. As a
result, a new watch will likely be needed across parts of northeast
AR eastward into TN.
