Valid 112000Z – 121200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND EVENING OVER PARTS OF SOUTHEAST WYOMING…NORTHEAST
COLORADO…AND WESTERN NEBRASKA….
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
SOUTHERN WISCONSIN AND CENTRAL/SOUTHERN LOWER MICHIGAN…
Severe thunderstorms are expected over parts of the central High
Plains, where large hail, damaging wind gusts and a few tornadoes
are possible. Other severe storms may also affect portions of
Wisconsin and Lower Michigan.
Forecast outlined in the previous forecast discussion (appended
below) remains valid. Buoyancy continues to build as the air mass
destabilizes and storms are expected to initiate by 21-22Z as the
upper trough approaches. Additional information about this region is
available in MCD 1958.
Severe Thunderstorm Watch 645 remains in effect across
central/southern Lower MI and southern WI until 03Z. Primary threats
include scattered damaging wind gusts to 70 mph and isolated large
…OH/PA into Mid-Atlantic States…
Thunderstorm coverage is beginning to increase along the
northeastern periphery of the large surface high centered over
middle TN/northern AL. Mid-level flow is generally weak and overall
storm strength and organization is expected to remain marginal. More
information about the area is available in MCD 1957.
.PREV DISCUSSION… /ISSUED 1122 AM CDT Wed Sep 11 2019/
An upper trough over the western states will move slowly eastward
today, with midlevel height falls and lift over the High Plains this
afternoon and evening. Visible satellite imagery shows persistent
low clouds over eastern WY/northeast CO/NE Panhandle, where easterly
low-level winds and ample moisture are present. Current indications
are that these clouds will burn off by mid-afternoon, allowing rapid
destabilization and convective initiation. Other storms are likely
to form along the eastern edge of the low clouds over northwest KS
and southwest NE where strong heating will continue. All of this
activity will be is environment of sufficient deep-layer shear for
supercell structures. Large to very large hail will be the main
threat through much of the afternoon and early evening, although an
isolated tornado or two is possible with the more persistent
supercells. As the low-level jet strengthen this evening, a more
focused damaging wind threat may evolve over NE.
A remnant MCV/shortwave trough is moving across western WI this
morning. Strong heating ahead of the feature over southeast WI and
southern Lower MI should aid in the re-development of scattered
strong to severe storms my early afternoon. Forecast soundings show
sufficient CAPE and mid level wind fields to promote damaging winds
and some hail in the strongest cells. A few supercells are also
possible – especially across central Lower MI in the vicinity of a
weak surface boundary. Storms will track southeastward through the
early evening before weakening.
…Western KS into TX Panhandle…
Isolated strong thunderstorms will be possible once again today
along the surface dryline over western KS and parts of the OK/TX
Panhandles. Gusty winds and some hail will be possible for a few
hours this afternoon and evening.
…OH/PA into Mid-Atlantic States…
Strong heating and ample low level moisture will promote moderate
CAPE values over parts of eastern OH, much of PA, and southward
along an axis into parts of VA/NC. Scattered thunderstorms will
affect this region, with a few of the storms posing a transient risk
of gusty/damaging winds.