MIL-OSI USA: SPC Jun 12, 2021 0600 UTC Day 2 Convective Outlook

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Source: US National Oceanic and Atmospheric Administration

SPC AC 120531

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1231 AM CDT Sat Jun 12 2021

Valid 131200Z – 141200Z

…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE
SOUTHERN HIGH PLAINS…WEST VIRGINIA INTO PENNSYLVANIA…AND ACROSS
NORTHERN WISCONSIN…

…SUMMARY…
Isolated severe hail or wind is possible Sunday afternoon and
evening over parts of eastern New Mexico and Colorado, northern
Wisconsin, and over parts of West Virginia, Pennsylvania, and
central New York.

…Synopsis…
An upper ridge will build over the Rockies as a shortwave trough
drops south across the upper MS Valley and Great Lakes. The stronger
cyclonic flow aloft will spread into the Mid Atlantic late, with
height falls beginning during the late afternoon. To the west,
strong southwest flow aloft will exist across the Pacific Northwest
as a strong jet max grazes the WA and OR Coasts.

At the surface, high pressure will be centered over the central
Plains, and over the Appalachians. The most robust moisture and
instability will remain over the southern Plains and lower MS
Valley, but plumes of instability will extend around the central
Plains high into the High Plains, as well as across the OH Valley
near a weak surface trough. Weak instability is also expected to
develop over northern MN into WI, where a weak surface low and cold
front will develop out of the northwest.

…Front Range into the southern High Plains…
Low-level winds will increase out of the southeast late in the day,
resulting in moisture advection. Favorable instability will develop
during the peak heating hours, with isolated storms likely forming
along the Front Range. Although winds aloft will be weak out of the
west/northwest, veering winds with height will favor slow-moving
cells capable of marginal hail or wind from late afternoon through
evening.

…WV into PA and central New York…
A broken line of storms is expected to develop by 18Z from western
NY southwestward toward the OH River near a developing front. Strong
heating and 60s F dewpoints will result in up to 1500-2000 J/kg
MUCAPE, with modest deep-layer shear on the order of 40 kt. Weak
low-level winds suggest forward-propagating line segments capable of
strong wind gusts, but the stronger storms may produce marginal hail
as well.

…Northern WI and MN Arrowhead…
Strong heating will lead to deep mixed layers, beneath strong
northwest flow aloft. While moisture will be limited with lower 50s
F dewpoints, sufficient CAPE is expected to develop, supporting a
few strong storms given increasing lift near the low. In addition,
hodographs will become very long, favoring cellular activity.
Marginal hail will be possible, along with a few strong wind gusts.

..Jewell.. 06/12/2021

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