254
FXUS62 KGSP 071834
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
234 PM EDT Sun Jul 7 2024

.SYNOPSIS...
A weak surface front will increase the chance for thunderstorm
activity across the area this afternoon and evening. An active
pattern of afternoon and evening showers and storms is expected to
continue for the first half of this week. More typical mid-July
weather is expected toward the end of the week.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 207 PM Sunday: The synoptic pattern remains relatively
unchanged with broad longwave troughing draped across much of the
country from the Northern Rockies to the Ohio Valley. Stout upper
ridging remains centered over California along with another upper
ridge over the Atlantic, the western flank of which nudges into the
southeast states. An upper low associated with a tropical upper
tropospheric trough also continues to spin off the Carolina coast,
but will be of no impact through the near term period. At the
surface, very moist southerly onshore flow continues with a
previously stalled frontal boundary having lifted back north into
the foothills north of the I-40 corridor. The boundary is rather
diffuse, however, and nebulous in surface observations with location
being determined by a subtle moisture gradient and weak low-level
surface convergence.

Ample moisture and warming into the upper 80s to low 90s has
resulted in moderate instability this afternoon with convection
blossoming across the mountains and along the boundary across the I-
40 corridor. With time, convection over the mountains is expected to
become loosely organized along composite cold pools with several
linear structures moving out of the mountains and into the Upstate
and foothills and eventually portions of the Piedmont. 2500-3000
J/kg of surface-based CAPE has been realized on area ACARS
soundings, which will be sufficient for several stronger updrafts
and the development of a mature cold pool. Instability profiles are
very tall and skinny, however, with poor lapse rates and limited
DCAPE. A modified 12z Peachtree City, GA sounding supported a
microburst composite value of 3, which combined with aforementioned
parameter space would be supportive of a few isolated severe
thunderstorms with locally damaging winds. The main threat will be
across the southern mountains, northeast Georgia and the Upstate with
this area being placed in a marginal risk for severe storms from the
Storm Prediction Center.

Convection will push out of the area this evening with at least a
few isolated to scattered showers lingering into the late evening
hours. Thereafter, a widespread deck of low stratus clouds is
expected to build in given a rather moist boundary layer with areas
of fog also possible. Heading into tomorrow, extensive morning
clouds will likely delay daytime heating and the atmosphere will
also remain worked over from today`s storms. Thus, the CAMs are not
overly enthused with the coverage of storms, especially outside of
the mountains. Several storms appear likely over the southern
mountains/escarpment with only isolated to scattered showers and
storms elsewhere. Temperatures will be in the upper 80s to low 90s
tomorrow, but could end up a degree or so cooler if morning clouds
take longer to lift and scatter.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 155 pm Sunday: A deep/weak SW flow will remain over the
southern Appalachians and vicinity through the short term...between
an anomalous trough across the central Conus...and a subtropical
ridge nosing into the Southeast from the western Atlantic. Resultant
quiescent, but very moist atmosphere will continue to support
higher-than-normal coverage of diurnal convection...PoPs mainly
60-70% across the mtns and 50-60% across the Piedmont...through the
period. Diurnal instability is forecast to be adequate for isolated
pulse severe storms...perhaps more than adequate on Wed, when a
consensus of short term guidance indicates sbCAPE will peak at
around 3000 J/kg. One change that is expected is that storm motions
should become a bit swifter, especially on Wed afternoon. This will
be a consequence of the acceleration of the mid-level flow as the
upper trough draws a bit closer...as the circulation associated with
the remnants of T.C. Beryl is expected to become absorbed into the
westerlies...and progresses the central Conus trough to the east.
Nevertheless, the very moist conditions, locally poor antecedent
conditions, and the potential for SW=>NE training cells will result
in a continued low-end threat for excessive rainfall. Temps are
forecast to be a couple of degrees above normal through the period.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 210 pm Sunday: The global models continue to trend
(unfortunately) toward a drier extended period, as upper trough is
expected to progress into the eastern states...albeit weakening and
lifting north of our area over the subtropical ridge. It`s looking
increasingly likely that the proximity of the trough will allow the
deeper/subtropical moisture to shunt east of the CWA during the
latter half of this week, resulting in dwindling chances for
convection. Daily instability and moisture should still be adequate
for diurnal showers and storms, but with coverage more typical for
the time of year. Daily PoPs therefore trend closer to climatology
for much of the period, with standard mid-July threats of a pulse
severe storm or three and locally excessive rainfall. Temps are
forecast at near-to-slightly-above normal through much of the
period.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Convection is ongoing across portions of the
area early this afternoon with a band of showers and thunderstorms
along a stalled frontal boundary extending from the mountains to the
I-40 corridor. Temporary restrictions from convection will occur
first in this corridor impacting KAVL and KHKY. With time, storms
are expected to become loosely organized and push east of the
mountains into the Upstate, foothills and Piedmont. With time,
temporary restrictions are expected at KGSP/KGMU, KCLT and KAND. The
strongest storms across the Upstate may contain gusty winds out of
the northwest. Thereafter, showers will likely linger for several
hours into the evening before dissipating with the loss of daytime
heating. A widespread low stratus deck is anticipated to develop
overnight into the morning hours with IFR ceilings common along with
periods of LIFR. In addition, fog will be possible at any given
terminal. Conditions will be slower than normal to improve tomorrow
morning with MVFR ceilings likely hanging on into the late morning
to early afternoon hours before finally lifting and scattering.
Winds will be generally light out of the south through the period,
but will be variable at times with occasional northerly components
possible, especially in the wake of afternoon/evening storms.

Outlook: An active summertime pattern continues for most
of the upcoming week, leading to scattered to numerous
showers/thunderstorms and possible restrictions each
afternoon/evening. Fog or low stratus may develop each morning,
especially over areas that received rain the previous day.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...JDL
NEAR TERM...TW
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...TW