Day 1 Severe Weather Outlook

Valid 022000Z – 031200Z

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH THIS
EVENING FROM NORTHERN OK TO NORTHERN MO…AND FROM NORTHEAST PA TO
SOUTHERN NEW ENGLAND…

…SUMMARY…
Isolated damaging gusts will be possible through the evening from
northern Oklahoma to northern Missouri, and from northeast
Pennsylvania to parts of southern New England.

…20z Update…

The previous forecast is on track and no changes have been made this
update cycle other than adjustments to the 10% general thunder line.
Convective initiation has occurred recently ahead of the cold front
over northwest OK. Additional development is expected to spread
northeast along/just ahead of the front into eastern KS and northern
MO over the next few hours. Strong wind gusts continue to be the
main concern with this activity into the evening hours. For the
latest information regarding severe potential across parts of
OK/KS/MO, see MCD 2054.

Further east, isolated showers and storms will continue to pose a
threat for locally strong gusts from northeast PA into southern New
England through this evening.

..Leitman.. 10/02/2019

.PREV DISCUSSION… /ISSUED 1126 AM CDT Wed Oct 02 2019/

…Northern OK to northern MO this afternoon/evening…
A midlevel shortwave trough over the central/northern Rockies will
eject east-northeastward to the upper MS Valley by the end of the
period, around the northwest periphery of the persistent ridge over
the Southeast. A weak surface wave is expected to develop
east-northeastward along a quasi-stationary surface front from
eastern KS later this afternoon to IL/IN overnight. The wave will
remain weak as the stronger large-scale forcing for ascent is
displaced largely to the cool side of the surface front. A broken
band of convection will likely accompany the weak wave along the
front from eastern KS into MO late this afternoon through late
evening.

Multiple days of convection across the southern High Plains have
reduced midlevel lapse rates near the front from the TX Panhandle/OK
to MO. Thus, buoyancy will be rather modest (MLCAPE 500-1500 J/kg),
driven primarily by surface heating and boundary-layer dewpoints
near 70 F. There will be a narrow zone of enhanced deep-layer shear
along the front this afternoon/evening, which could support a few
organized/marginal supercell storms capable of producing isolated
damaging gusts, and perhaps a brief tornado. Still, the rather
modest buoyancy/lapse rates and marginal low-level shear in the warm
sector suggest that only low wind and tornado probabilities are
warranted this afternoon/evening.

…Northeast PA to parts of southern New England this afternoon…
A series of subtle perturbations will move east-southeastward from
the lower Great Lakes to southern New England through this evening,
coincident with surface cold front that will continue moving
southward. Surface heating south of the front, where boundary-layer
dewpoints are in the mid-upper 60s, will contribute to some
destabilization and the potential for convection along the front
this afternoon. However, warm temperatures aloft and poor lapse
rates will limit the depth of buoyancy and updraft intensity.
Still, deep-layer west-northwesterly shear of 35-40 kt and steep
low-level lapse rates will support some potential for low-topped,
organized convection with strong outflow winds.

$$

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