SPC Jun 30, 2017 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0250 PM CDT Fri Jun 30 2017

Valid 302000Z - 011200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING MUCH OF SOUTHERN OKLAHOMA AND ADJACENT
PORTIONS OF NORTHERN TEXAS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SURROUNDING
AREAS OF THE SOUTHERN PLAINS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY AND LOWER GREAT LAKES REGION/NORTHERN MID ATLANTIC
STATES AND WESTERN NEW ENGLAND...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
SURROUNDING AREAS OF THE NORTHEAST...OHIO VALLEY AND SOUTH CENTRAL
PLAINS...

...SUMMARY...
Severe thunderstorms are possible this afternoon over parts of
Oklahoma, spreading into parts of north Texas and western Arkansas
this evening.  A few severe storms may also affect parts of New
York, northeast Pennsylvania, and New England later today.  Finally,
strong to severe storms will be possible over parts of the Ohio
Valley and Lower Great Lakes Region.  Damaging wind gusts and
occasional severe hail are the primary threats.

...20Z Outlook Update...
Adjustments have been made to categorical and probabilistic outlook
lines, in an attempt to account for latest trends concerning ongoing
destabilization and convective potential.  The most notable of these
is to increase severe probabilities  to an enhanced slight risk
categorization across much of southern Oklahoma and adjacent
portions of northern Texas.

Strong destabilization is ongoing across this region, as a
seasonably moist boundary layer continues to warm with insolation,
beneath a remnant plume of  warm elevated mixed layer air on the
southern fringe of larger-scale troughing within the mid-latitude
westerlies.  This may be just south of a belt of modest (30-50 kt)
westerly 500 mb flow,  where deep layer mean wind fields appear on
the order of 20 kts, but veering of winds with height does appear to
be contributing to  moderate deep layer shear supportive of
organized convective development.  This could include a couple of
supercells initially, before increasing convective development,
consolidation and upscale growth leads to the evolution of an
organizing cluster with increasing potential for strong surface
gusts.

Storms may initiate where low-level surface convergence is locally
enhanced across parts of southwest Oklahoma, northeast of a thermal
low.  Low-level convergence also appears locally enhanced near a
weak front, to the northwest of the Oklahoma City area.  Otherwise,
a zone of enhanced lower/mid tropospheric warm advection across much
of southern Oklahoma seems likely to provide the primary
forcing/focus for convective development into this evening, with the
westerly mean flow tending to contribute to an east/southeastward
propagation of any evolving storm clusters.

..Kerr.. 06/30/2017

.PREV DISCUSSION... /ISSUED 1113 AM CDT Fri Jun 30 2017/

...Northeast...
The morning water vapor loop shows a weak shortwave trough moving
across western NY/PA.  This feature will track eastward across New
England today, providing subtle lift and organization for scattered
showers and thunderstorms.  Clouds are thinning ahead of the system
over eastern NY/PA and much of New England, where surface
temperatures are forecast to warm to near 80F with dewpoints in the
60s.  Moderate CAPE values will support vigorous updrafts with 35-45
knots of effective shear helping storm organization.  The stronger
cells in this region will pose a risk of locally damaging wind gusts
and some hail.  

...OK/TX/AR...
A large nocturnal MCS continues to dissipate at it moves
southeastward across AR.  Strong heating along the western flank of
this system will result in a very unstable air mass across central
and southern OK this afternoon, where steep mid level lapse rates
and dewpoints in the 70s are present.  Scattered thunderstorms are
expected to form in this zone, drifting slowly southeastward this
evening into parts of western AR and north TX.  Thermodynamic
parameters will favor the risk of large hail and damaging wind
gusts.  

...OH Valley...
The northeastern flank of the aforementioned dissipating MCS is
moving into southern IL.  Pockets of moderate CAPE will form ahead
of the remnant boundaries, promoting the development of scattered
afternoon strong thunderstorms.  Vertical shear is not particularly
strong in this area, but residual forcing from the
convectively-induced upper feature may be sufficient for a few
severe storms capable of damaging winds and hail.

...Northeast NM...
Most CAM solutions suggest a small cluster of thunderstorms tracking
southeastward across northeast NM this afternoon and evening, posing
a risk of isolated hail and gusty winds.

Read more

from SPC Forecast Products http://ift.tt/u32qoI