SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Fri Aug 16 2019
Valid 171200Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH
DAKOTA...NEBRASKA AND KANSAS EASTWARD INTO WESTERN ILLINOIS...
...SUMMARY...
Severe storms are likely over parts of the northern and central
Plains and upper Midwest on Saturday. A few strong storms are also
possible from the Lower Great Lakes into western New England.
...Synopsis...
An upper trough and attendant cold front will move from MT across
the Dakotas during the day on Saturday, providing lift and increased
deep-layer shear. Southerly low-level winds ahead of this front will
support low 60s F dewpoints into this region, fueling scattered
storms.
To the south and east, a belt of moderate mid and high-level
westerlies will remain over the central Plains, extending
cyclonically eastward into New England. Cool midlevel temperatures
will exist throughout this zone, supporting steep lapse rates aloft
especially over the Plains where strong instability will develop due
to 60s and 70s F dewpoints. A belt of 30-40 kt southwest 850 mb
winds will maintain a feed of greater theta-e across the MO Valley,
supporting bouts of severe storms.
Elsewhere, a low-amplitude shortwave trough will move across the
Lower Great Lakes and New England strengthening deep-layer wind
fields and aiding lift via cooling aloft and increased low-level
warm advection out of the southwest.
...Dakotas and northern NE into IA and IL...
Substantial height falls will occur over the Dakotas during the day
with increasing deep-layer shear. Storms will form relatively early
along the cold front over the western Dakotas, and will increase in
intensity as they encounter a destabilizing air mass to the east.
Damaging winds and hail will be possible. Models suggest storms will
make it into western MN by late evening, but likely weaker.
...KS into MO...
Storms are forecast to be ongoing from eastern KS into MO Saturday
morning, possibly in the form of an MCS on the nose of the low-level
jet. Damaging winds will be possible initially, but a weakening
trend is expected after about 18Z.
Behind this initial activity, strong heating of a moist air mass,
beneath cool temperatures aloft will lead to strong to perhaps
extreme instability, with MLCAPE values in excess of 3500-4000 J/kg
over parts of KS, northwest MO, and into NE. There is spread between
the models regarding where afternoon and evening convection will
initiate, and this may depend on modifying outflow boundaries. At
this time, the greatest probability of initiation appears to be
across the KS/MO/NE/IA quad-state area. Supercells will be possible
initially, with all modes of severe. An MCS is likely to evolve out
of this activity by evening as it continues east toward IL.
While significant severe is possible given the parameter space, will
defer potential "sig" severe delineation to later outlooks when
predictability is greater.
...Northeast OH across NY and into western New England...
Southwesterly low-level winds and heating will lead to around 1000
J/kg MUCAPE, with around 35-40 kt of effective shear. Storms are
expected to form near the lake breezes from northern OH into western
NY, with damaging winds or marginal hail possible. While low-level
shear will not be strong, effective SRH of 100-150 m2/s2 may support
a brief supercell.
...MAXIMUM RISK BY HAZARD...
Tornado: 5% - Slight
Wind: 15% - Slight
Hail: 15% - Slight
..Jewell.. 08/16/2019
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