Valid 111300Z – 121200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
…SUMMARY…
Isolated to widely scattered thunderstorms are expected from the
Gulf Coast to the Great Lakes and parts of Florida.
…Synopsis…
A highly amplified upper-air pattern is expected through the period,
dominated by a large, occluding cyclone now covering most of the
central/northern Plains, and centered near the ND/SD line. The
associated 500-mb low should pivot primarily northeastward across
western/northern MN by 12Z, with associated mid/upper-level cyclonic
flow extending from the northern Rockies across the central Plains
and Missouri Valley to the lower Ohio Valley and upper Great Lakes.
The associated surface occluded/cold front — analyzed at 11Z from
the low across WI and central IL to a triple point near MVN, to
southern AR, south-central TX and northern Chihuahua — should reach
eastern Lower MI, central KY, central MS, and the northwestern Gulf
by 00Z. By 12Z, the front should extend over eastern OH and the
southern Appalachians to near MOB, and across the north-central to
southwestern Gulf. During the period, it will overtake the slow-
moving warm front initially analyzed across the Mid-South and
northeastern Gulf, shrinking an already small warm sector from
north-south across MS and southwestern AL.
…Gulf Coast to Great lakes…
The strongest deep-layer forcing for ascent, as well as greatest
winds aloft, will remain behind the surface front, along with the
great majority of deep convection. Other storms forming along the
front, mainly over the Mid-South region and MS, should be undercut
by the boundary rather quickly. Isolated to widely scattered
warm-sector cells may form over MS, in a broadly confluent
prefrontal boundary layer with rich moisture, but weak deep-layer
lapse rates. Forecast soundings suggest around 1000 J/kg
preconvective MUCAPE is possible, amidst 25-35-kt effective-shear
magnitudes. Strong gusts may occur from the most vigorous
convection; however, severe potential appears too questionable,
isolated and disorganized for an unconditional outlook area.
..Edwards/Goss.. 10/11/2019
$$