Valid 301630Z – 311200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE HIGH
PLAINS…MIDWEST…AND SOUTHEAST ARIZONA…
Isolated severe thunderstorms are possible this afternoon and
evening across parts of the High Plains, and also across southeast
Missouri/southern Illinois to southwest Ohio.
Post-frontal upslope flow will be common from northeast New Mexico
to eastern Wyoming today, maintaining upper 40s to mid 50s surface
dewpoints at peak heating. This should support a plume of modest
MLCAPE of 500-1500 J/kg. Stronger/confluent mid-level westerlies
will generally be confined to the Wyoming portion of the region
where 500-mb flow of 35-45 kt is anticipated, with weaker winds
southward along the Front Range.
Isolated to scattered thunderstorms are expected to develop by mid
to late afternoon over the higher terrain. A few of these storms
should become supercellular for a couple hours across eastern
Wyoming to northeast Colorado. Abundant MLCIN with eastward extent
on the plains and lack of stronger forcing for ascent should keep
severe hail and wind coverage low.
…South-central/southeast Missouri to southern Ohio…
An MCV continues to move slowly eastward over west-central Missouri
late this morning. While this MCV may tend to weaken today, a belt
of modestly enhanced low/mid-level winds accompanying the MCV will
coincide with a front across south-central/southeast Missouri into
southern Illinois. There is a risk for a couple supercells capable
of a tornado and isolated damaging winds, particularly along and
south/southeast of I-44 in southeast Missouri, as well as southwest
Illinois. Farther to the east, a weakly convergent surface front
might aid in small multicell clusters capable of locally damaging
wind across southern Indiana/northern Kentucky to southern Ohio.
Composite outflow/effective front continues to progress
south/southwestward across the Texas Panhandle and Red River
vicinity. Surface-based late afternoon redevelopment will probably
be confined to the Texas Panhandle and possibly far western Oklahoma
near the intersection of the composite outflow/front and dryline. A
few severe thunderstorms are possible, but weakening deep-layer
shear across the region will serve to limit the overall risk.
On the immediate southern periphery of an upper ridge, isolated
thunderstorms are expected to develop over/near the mountains of
southeast Arizona and drift west-southwestward with aid of modestly
enhanced easterly mid-level winds. A reservoir of moist/unstable air
may allow for some relatively stout storms, with strong/gusty
outflow winds a possibility as they move across southeast Arizona.