LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Thu Jul 13 2023
Valid 132000Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
NORTHERN NEW YORK AND WESTERN VERMONT...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE
PLAINS...PARTS OF THE OHIO VALLEY...AND NORTHEAST...
...SUMMARY...
Numerous severe thunderstorms are likely today across eastern New
York and western Vermont, with scattered severe thunderstorms
possible across parts of the Ohio Valley and portions of the
southern/central Plains. Damaging winds, large hail, and perhaps a
couple of tornadoes are possible in these areas. Isolated very
large hail may occur across parts of the central Plains.
...Northeast...
A line of storms continues to push rapidly east across NY, with
strong wind gusts measured recently. Instability remains favorable
ahead of the line, and heating continues as well. While the primary
threat is for damaging winds, effective SRH over 150 m2/s2 and
deep-layer shear over 30 kt will also favor a few supercells with
hail or brief/weak tornado risk. For more information see mesoscale
discussion 1523.
Farther south, a relative minimum in thunderstorm coverage is
expected over southern PA into MD, and the Slight Risk has been
modified in these areas as the severe risk should remain isolated.
The primary risk farther south is expected to remain over the OH
Valley, WV and western VA.
...Plains...
Extreme moisture and instability is noted into eastern CO where
dewpoints are in the 68-72 F range. The backed/easterly low-level
flow beneath moderate high level flow is resulting in long
hodographs with around 50 kt effective shear. The result should be
very large hail, as well as developing damaging wind threat as
storms increase in coverage and blend outflows through the OK/TX
Panhandles and into western OK. For more information see mesoscale
discussion 1519.
..Jewell.. 07/13/2023
.PREV DISCUSSION... /ISSUED 1119 AM CDT Thu Jul 13 2023/
...NY into New England...
Water vapor loop shows a strong mid-level shortwave trough
moving across southern Ontario, with a surface cold extending
extending from Lake Erie into central/eastern OH. A warm front
extends east from a surface low over southeast Ontario Province to
the coast near Portland, ME. The cold front will move steadily east
this afternoon into NY where thunderstorm development is underway,
with an increase in coverage likely over the next few hours.
Surface dewpoints in the mid 60s and substantial heating will yield
pockets of MLCAPE over 2000 J/kg, along with moderately steep low
and mid-level lapse rates. Shear profiles are also rather strong,
conducive for organized/supercell structures. Thunderstorms are
expected to intensify over eastern NY in the Hudson Valley vicinity
before spreading into western New England. A mixture of discrete
supercell storms and bowing structures is expected, capable of large
hail and damaging wind gusts, and perhaps a tornado or two. Storms
should weaken during the evening while moving into a more stable
environment with time.
See recently issued Mesoscale Discussion 1517 for additional details
on short-term thinking in this area.
...KY/WV/OH...
As the cold front sags southward into the upper OH Valley by
mid-afternoon, scattered thunderstorms are expected to develop.
Sufficient westerly flow aloft and MLCAPE of 1500 to locally 2000
J/kg will promote supercells and organized clusters capable of
damaging winds and severe hail.
...High Plains from SD to TX...
A broad upper-level ridge is present today over the southwest
states, with the southern fringe of stronger westerlies extending
across CO/KS. A surface dryline will become established by late
afternoon extending from the Black Hills vicinity across eastern CO.
Forcing will be subtle, however minimal CINH and ample
moisture/instability will result in widely scattered intense storms
along the dryline, spreading southeastward through the evening.
Supercells capable of very large hail appear possible. Storms over
western SD/NE, and also over southwest KS and adjacent TX/OK
panhandles may persist well into the night and spread eastward
across those states.
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