770
FXUS62 KGSP 250253
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1053 PM EDT Tue Jun 24 2025

.SYNOPSIS...
The heat and humidity will remain elevated through Wednesday as
a hot upper ridge dominates the eastern United States. Isolated
showers and thunderstorms are expected this afternoon and evening,
mainly across the mountains. The upper ridge will begin to break
down after Wednesday as an upper disturbance brings increased
shower and thunderstorm chances to the area each day from Wednesday
through the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 10:25 PM EDT Tuesday: One lingering thunderstorm appears to
have finally dissipated just north of Avery and Mitchell Counties
over the past hour or so. Going forward, things should remain mostly
quite overnight and into the morning. The current Heat Advisory looks
good with no changes planned at this time. We can expect some relief
from the heat overnight, however lows will remain well-above normal
with values in the low to mid 70s outside the mtns.

Otherwise, Wednesday is looking like a busy weather day with multiple
hazards in play. The broad upper ridge will begin to weaken and shift
north and west of the area as a tropical upper tropospheric trof and
associated closed upper low slides west and over Florida. This should
enhance upper lvl E/SE flow across our area with slightly lower heights.
Plenty of heat will still be entrenched across the region with temper-
atures quickly rising again after sunrise. Many locations will likely
see temperatures in the mid to upper 90s by early to mid afternoon with
some sites probably reaching the 100 deg mark, especially in the lower
Upstate and Charlotte metro area. Upper 60s to low 70s dewpts will be
common with heat indices reaching Advisory criteria. Thus, the Heat
Advisory will be allowed to continue thru tomorrow afternoon.

Attention quickly shifts to an increasing severe wx threat Wednesday
afternoon and evening. Influence from the TUTT (mentioned above) along
with waning subsidence from the ridge should allow for rapid development
of sct to numerous thunderstorms during the afternoon and evening. The
environment is expected to be primed for damaging microbursts owing to
a very hot and humid airmass. Much like the past few days, dewpts will
likely remain in the upper 60s to low 70s across most of our area. This
will support high-end sfc-based CAPE values of 4000+ J/kg. Deep mixing
up to 800mb with inverted-V profiles and dry mid-lvl air also supports
DCAPE values in excess of 1000 J/kg. In addition, both low and mid-lvl
lapse rates will be anomalously high. This type of environment has the
potential to produce numerous instances of damaging striaght-line winds.
The storm mode will likely start out as traditional pulse convection with
eventual upscale growth into multiple clusters/linear segments organized
along cold pools. Given the favorable environment, cold pools should be
sufficiently deep to lift parcels to their LFCs and generate new updrafts
along surging outflow boundaries. Damaging straight-line winds will be
the main threat, but a few instances of large hail cannot be ruled out.
Locally heavy rainfall and isolated flooding of low-lying/poor drainage
areas will also be possible. Convective activity will slowly wane thru
the evening with the loss of daytime heating and widespread overturning
of the atmosphere, but some activity could linger into the late evening.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
As of 250 PM EDT Tuesday: The broad anticyclone responsible for
this current heatwave will continue to break down as a subtropical
disturbance moves into FL.  This pattern is expected to evolve
into a rex block, resulting in the cutoff low stalling or slowly
drifting northward across the FL peninsula while the high remains
anchored to the north. Models are generally supportive of an
inverted trough extending northwestward from this low toward the
southern Appalachians. This would provide a source of lift for
diurnally-driven showers and storms each day. The greatest coverage
is expected across roughly the western half of the forecast area
during peak heating hours. Accordingly, PoPs taper off from 60-70
percent in the mountains and foothills in the afternoon to 30-40
percent in the eastern/southern/lower Piedmont. Pulse severe storms
are possible given the favorable wet microburst environment.

An increase in cloud cover and rain coverage will offer some modest
relief from the excessive heat. It will still be hot with high
temperatures in the lower to mid 90s and peak heat indices in the
98- 104F range, but not quite as oppressive as today and Wednesday.
Accordingly, the probability of another heat advisory on Thursday
and Friday are low (but not zero). It should be noted that the
NBM 50th percentile was used for dewpoints as it has the best
verification scores in recent days for the short term.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 250 PM EDT Tuesday: The rex block that forms late in the week
is forecast to weaken but not completely break down this weekend
and early next week. This will result a continued unsettled pattern
with daily chances for showers and storms. Convection follows a
diurnal trend with PoPs highest in the afternoon and evening. The
convective mode will mostly be pulse storms with a few isolated
microbursts and an isolated/localized flash flood threat. The
heat and humidity will persist, but heat indices should remain
just shy of advisory criteria.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Expect VFR conditions thru the 00z taf
period at all terminals. The only exception will likely be to-
morrow afternoon/evening when sct to widespread convection is
expected to impact the fcst area. Patchy mtn valley fog will be
possible again overnight, but it`s not expected to reach KAVL.
Otherwise, sct to numerous thunderstorms are expected tomorrow
aftn/evening. The environment will likely support strong to svr
thunderstorms, hence +TSRA was included in the TEMPO group for
each taf site. The most likely window for convective activity
still appears to be in the 20 to 24z timeframe. Winds will be
light and VRB thru much of the period with calm winds likely at
many sites later tonight and thru the morning.

Outlook: Daily chances for at least sct afternoon/evening showers
and thunderstorms will continue into the weekend. Fog and/or low
stratus will be possible each morning in the usual mtn valleys as
well as near lakes and rivers.

&&

.CLIMATE...
RECORDS FOR 06-25

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      96 1952     63 1889     69 1949     45 1972
                                        1943
                                        1891
   KCLT     102 1914     70 1980     75 1952     53 1889
                            1915        1914
                            1889
   KGSP     101 1952     69 1980     75 1931     52 1972
                                        1925



RECORDS FOR 06-26

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      96 1948     65 1961     69 1952     49 1984
                                                    1974
   KCLT     102 1952     68 1965     78 1948     55 1979

   KGSP     100 1952     71 1991     77 1952     55 1979
                1934                                1974
                1914

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 8 PM EDT Wednesday for GAZ018-026-028-029.
NC...Heat Advisory until 8 PM EDT Wednesday for NCZ035>037-056-057-
     068>072-082-501>510.
SC...Heat Advisory until 8 PM EDT Wednesday for SCZ008>014-019-
     101>109.

&&

$$

SYNOPSIS...JK
NEAR TERM...JPT
SHORT TERM...JK
LONG TERM...JK
AVIATION...JPT
CLIMATE...JPT