SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Wed Aug 07 2024
Valid 072000Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL PLAINS...AND COASTAL NC/SC....
...SUMMARY...
Strong to severe thunderstorms capable of damaging gusts are
possible across the central High Plains this afternoon and evening.
A few tornadoes remain possible today and tonight across the coastal
Carolinas.
The only change for this outlook update is to add a small area of
SLGT risk for parts of coastal NC/SC. Isolated tornadoes have
occurred this afternoon over parts of these areas, and the potential
exists for further development of semi-discrete cells offshore that
rotate inland. Shear profiles remain sufficiently strong to support
further tornado risk. Please refer to MCD #1858 and WW #610 for
further details.
..Hart.. 08/07/2024
.PREV DISCUSSION... /ISSUED 1121 AM CDT Wed Aug 07 2024/
...Synopsis...
Expansive upper ridging will continue across the Southeast and
southern Plains today, although some dampening is possible along its
northern/northeastern periphery. This dampening will occur as a
series of shortwave troughs rotate through the base of the upper
troughing extending from the Hudson Bay into the Pacific Northwest.
Lead shortwave trough in this series is currently moving across the
northern Plains, with another shortwave farther west across the
northern Rockies. Eastward progression of the lead shortwave trough
will encourage an associated eastward/southeastward push of the cold
front that currently extends from far northwestern Ontario into
east-central WY. Thunderstorm development is anticipated along this
front from the eastern Dakotas and MN into NE. Low-level upslope
flow into the central High Plains will also support thunderstorms
ahead of this cold front from southwest WY/eastern CO into the
central Plains.
Farther east, Tropical Storm Debby remain centered off the SC Coast.
Steering currents remain weak in its vicinity, with only modest
northwesterly progress anticipated throughout much of the period.
See latest NHC advisories for track/intensity forecasts for Debby,
as well as tropical watches/warnings.
...Central High Plains/Central Plains...
Southeasterly low-level, upslope flow will help maintain at least
moderate low-level moisture amid strong boundary-layer mixing this
afternoon across the central High Plains. General expectation is for
dewpoints to be in the mid/upper 50s by 21Z, which should be
sufficient for air mass destabilization as temperatures warm into
the mid 90s. Glancing ascent from the shortwave trough moving
through northern Rockies coupled with orographic effects is expected
to result in thunderstorm development across the high terrain, with
these storms then moving into the moderately buoyant and sheared
airmass downstream. Given the moderate shear (i.e. 0-6 around 40
kt), some more organized and persistent updrafts are possible. High
cloud bases and steep low-level lapse rates will also support strong
downdrafts with these more persistent storms.
Given the close storm proximity and high coverage, there is some
chance for cold pool amalgamation, with resulting downstream
propagation into more of the central High Plains. Additionally,
interaction with the frontal boundary could augment updrafts while
also providing a corridor of greater severe-wind potential.
Potential for damaging gusts appears high enough to introduce a 15%
area from far northeast CO/NE Panhandle southeastward into southwest
NE and far northwest KS. Some isolated hail is possible, both with
initial development in the vicinity of the high terrain as well as
any post-frontal development across the central High Plains.
Isolated hail is also possible with any initial development along
the front farther east from far southwest MN/southeast SD into
central NE.
...Coastal Carolinas/TS Debby...
As mentioned in MCD #1857, the near-term tornado risk along the
coastal Carolinas associated with Debby is low, owing to limited
destabilization and poor low-level lapse rates. Even so, rain bands
will continue to wrap around the system throughout the day, and,
given the strong low-level shear in place, any deeper, more
persistent convective cores may be able to produce tornadoes. A
relatively greater (but still quite low) threat may be able to
develop across the Outer Banks vicinity if pockets of heating can
occur within any cloud breaks.
As the system gradually moves northwestward tonight, the loss of
daytime heating suggests the tornado threat may become more confined
closer to the center of the system over coastal northeast SC and
coastal southern NC.
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