New York, NY...Chicago, IL...Detroit, MI...Milwaukee, WI...Boston, MA...
SPC AC 121736
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 PM CDT Mon Jun 12 2017
Valid 131200Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTH-CENTRAL PLAINS AND UPPER MIDWEST...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHERN/CENTRAL PLAINS AND UPPER MIDWEST...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS
WEST/NORTHWEST TX INTO FAR WESTERN OK...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE HIGH
PLAINS TO THE GREAT LAKES AND NORTHEAST STATES...
Severe thunderstorms are expected especially Tuesday afternoon into
Tuesday night across the north-central Plains and Upper Midwest,
with other strong to severe thunderstorms possible across the
southern High Plains and Northeast States.
...Dakotas/Nebraska to Upper Midwest...
An upper-level trough, which will be centered over the north-central
Rockies and adjacent High Plains early Tuesday morning, will
continue to take on an increasingly negative upper tilt as it
spreads east-northeastward toward the Dakotas and Upper Midwest
through Tuesday night. A moist air mass will exist along and east of
an eastward-moving cold front, and to the south of a
northward-shifting warm front, which could be augmented by the
remnants of an overnight/early Tuesday MCS from the eastern Dakotas
into MN. Relatively rich moisture with plentiful mid/upper 60s F
surface dewpoints beneath very steep mid-level lapse rates will
support strong destabilization (3000+ J per kg MLCAPE) by peak
heating, with initial development by Tuesday mid/late afternoon
focused near the surface low/front across the eastern Dakotas into
While the strongest winds aloft will tend to lag the front somewhat,
backing and strengthening mid/high-level southwesterly winds atop
the frontal zone will nonetheless yield 40+ kt of effective shear,
which will be more than adequate for initial supercells capable of
large hail and a few tornadoes. While storms across far eastern ND
into northern MN will become more elevated as they spread
northeastward Tuesday night, an organized cluster of
near-surface-based storms could evolve and persist from eastern
NE/southeast SD into southern MN Tuesday evening. Accordingly, at
least some continued potential for damaging winds and severe hail
will persist eastward into the overnight, possibly as far east as
west/northwest portions of WI.
...Northeast states/southern New England...
A weak low-amplitude disturbance or two (possibly convectively
related) will approach the region Tuesday while an upper trough
otherwise amplifies north of the region toward the Canadian
Maritimes. Modestly increasing deep-layer shear and a relatively
moist/unstable air mass near and just ahead of the
southeast-advancing front could support some strong to severe
thunderstorms. Localized wind damage and possibly some severe hail
could occur Tuesday afternoon into evening in association with the
stronger updrafts/downdrafts across the region.
...West/northwest TX into far western OK...
The influence of weak height falls, associated with the
central/northern High Plains-centered upper trough, should be
relatively well timed with peak heating Tuesday afternoon. As
compared to today (Monday), it seems likely that there will be a
somewhat greater probability and coverage for some strong to severe
thunderstorms Tuesday late afternoon into evening, initially near
the dryline. Moderate buoyancy in the presence of as much as 35-40
kt of effective shear could yield a few high-based supercells
capable of large hail, with severe-caliber wind gusts also a concern
as storms progress eastward.
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