SPC Jun 27, 2017 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0227 AM CDT Tue Jun 27 2017

Valid 291200Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
PLAINS INTO THE MIDWEST...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS INTO THE NORTHEAST...

...SUMMARY...
Scattered severe thunderstorms are most likely on Thursday from the
central Plains into the Midwest, with hail and damaging wind.
Isolated strong storms are also possible across the central High
Plains, and over parts of the Northeast.

...Synopsis...
An upper low will sink southward into ND with a broad area of
cyclonic flow aloft from the central Plains into the Great Lakes. At
the surface, low pressure will deepen over central KS as a cold
front moves southward across the central High Plains. To the east, a
quasi-stationary front will extend from the NE/KS border across IA
and toward Lake Michigan during the day, with a broad area of moist,
southerly winds east of the low across the MS and OH Valleys with
mid to upper 60s F dewpoints. The combination of 30+ kt midlevel
flow, 30-40 kt 850 mb flow, and a broad area of moisture and
instability will lead to a large area of severe weather potential
stretching from the central Plains across the Midwest. 

...Central Plains into the mid MS Valley...
While difficult to be precise due to likely effects of early storms
and outflows, bouts of thunderstorm activity are likely throughout
the day from eastern KS into western PA and NY, with the most
concentrated area of severe weather expected to form after 18Z from
eastern NE/KS across IA and northern MO. Here, instability will be
greatest, with MUCAPE possibly reaching 2500-3000 J/kg. Indications
are that an MCS could form along the stationary front across eastern
NE and KS, with activity moving across IA and northern MO. Damaging
winds are most likely, along with hail. Other storms are expected to
form near the surface low and along the cold front into central KS
near or after 00Z. Some of this activity could be in the form of
supercells briefly before becoming linear, with hail and wind
threat.

...Midwest into the Northeast...
At least isolated strong to severe storms are expected by afternoon
along the front from IL into OH in an elongating plume of
instability supported by strong west-southwest flow. Winds aloft
look to be parallel to the boundary, which should keep activity
within a narrow west-east zone. Strong 850 mb flow, especially into
NY and PA, suggest strong wind gusts will be the main threat as
instability will be weakest there. Potentially, a supercell could
occur as SRH will be maximized along the eastward-moving warm front
into NY.

..Jewell.. 06/27/2017

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