SPC Jun 13, 2018 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1135 AM CDT Wed Jun 13 2018

Valid 131630Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHERN
APPALACHIANS AND PARTS OF THE CENTRAL GREAT PLAINS...

...SUMMARY...
Scattered severe storms are possible, mainly during the late
afternoon and evening across the northern Appalachians and parts of
the central Great Plains. Large hail, damaging winds, and a tornado
or two may occur.

...Northern Appalachians...
A pronounced shortwave trough over the central Great Lakes will
progress east towards ME through Thursday morning. An associated
surface cyclone will track east across southern portions of Ontario
and Quebec, with a cold front trailing southwest across the Lower
Great Lakes, reaching the northern Appalachians this evening.
Ongoing convection near the front across eastern Lower MI should
intensify as it spreads into far southern Ontario before crossing
over the international border and developing south across parts of
NY/PA late this afternoon into the evening. 

Abundant stratus is prevalent from the Upper OH Valley eastward and
this will temper diabatic heating over most of the region. However,
the northeast periphery of mid-level lapse rates near 7 C/km (as
sampled by 12Z APX/DTX soundings should overspread the warm sector,
contributing to a modestly buoyant air mass with MLCAPE of 750-1500
J/kg. Deep-layer shear will become quite strong with increasingly
elongated hodographs with approach of the shortwave trough, as a
swath of 50+ kt 500-mb westerlies progresses east. Given substantial
cross-boundary flow/shear vectors, a few supercells are anticipated
within a broken band of storms along the front. Damaging winds,
severe hail, and a tornado are possible, although the widespread
clouds and late arrival of the cold front relative to peak heating
should modulate a greater severe risk. 

...Central Great Plains...
A couple storm clusters are ongoing in associated with warm
advection across northwest KS and near the SD/NE border. The
southern convection may persist through the afternoon and develop
eastward north of the stalled front in southern KS, where strong
buoyancy along and south of the boundary will support a threat for
isolated strong to severe gusts and marginally severe hail. The
northern convection should persist through much of the afternoon
amid continued robust warm advection, yielding a risk for a confined
area of severe hail. Refer to MCD 721 for additional short-term
information. 

Farther west, a few storms should form late afternoon into early
evening near the dryline/front/outflow intersection in northeast CO
and vicinity. Here, a veering wind profile with height along with
very steep mid-level lapse rates near 9 C/km may support a
conditional risk for a slow-moving supercell or two anchored near
the boundary capable of large hail, severe wind gusts, and a
tornado.

...Mid-MO Valley/IA...
Warm advection will increase late tonight across the Mid-MO Valley
into IA. Scattered to widespread elevated storm development is
expected early Thursday. This area will be monitored for potential
of marginally severe hail, but uncertainty is great enough to
preclude adding any probabilities in this outlook.

..Grams/Nauslar.. 06/13/2018

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