585
FXUS62 KGSP 230131
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
931 PM EDT Sun Jun 22 2025

.SYNOPSIS...
The heat and humidity will gradually increase through mid-week as a
hot upper ridge builds over the Southeast region of the country.
Isolated showers and thunderstorms remain possible each afternoon
and evening, mainly across the mountains through Tuesday. The heat
and humidity sticks around through the rest of the week with daily
shower and thunderstorm chances expanding east of the mountains
from Wednesday into the weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 920 pm Sunday: Not much change for this update. One or two
showers along the TN/NC border are continuing to weaken. Other than
that and a few lower clouds over the mountains, another quiet night
ahead.

Meanwhile, a stagnant/highly amplified upper air pattern is becoming
established over the Conus...with a major trough over the West...and
a sprawling eastern anticyclone centered over the central
Appalachians. Subsident warming will result in continued hot
conditions across our area through the period, with min temps
tonight expected to be around 5 degrees above normal. While surface
dewpoints are again expected to mix out to the lower/mid 60s across
most of the area...a region of elevated moisture over the northern
zones and down the I-77 corridor will limit the drying potential
from mixing...and forecast soundings indicate dewpoints may linger
in the upper 60s there Monday afternoon. This results in a forecast
of max heat index values in the 100-103 range across a good chunk of
the NC Piedmont...with some spotty areas of 105 possible. This isn`t
quite enough to warrant a Heat Advisory, but it will be the start of
a protracted period of oppressive heat.

Otherwise, large scale subsidence will continue to be the main
hindrance to development of deep convection...and indeed activity
has been slow to get going across the mountains this afternoon.
Nevertheless, isolated to widely scattered showers and a few storms
are expected to initiate across the ridgetops within the next couple
of hours. E/NE cloud-bearing winds will carry any convection toward
TN and GA...and PoPs are therefore limited to the mountains. Having
said that, the HRRR continues to allow for spotty showers outside
the mtns...so can`t rule that out either, but chances southeast of
the Blue Ridge are less than 20%. If anything, forecast profiles are
more hostile to convective development on Monday, with more of a
capping inversion indicated. PoPs are therefore again limited to the
high terrain...with chances mainly in the 10-20% range.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 115 PM EDT Sunday:

Large upper ridge will be in place over the eastern US for the short
term period, with increasing thicknesses and subsident flow leading
to abnormally hot and oppressive conditions for the region.
Afternoon highs on Tuesday look to the warmest of the period, with
some areas topping out around triple digits and a good chunk of the
Piedmont approaching it. Not quite record highs but still around 10
degrees above seasonal normals and 5-8 degrees above for lows, not
really allowing for overnight cooling/recovery and so the cumulative
heat effects will start piling on. Afternoon dewpoint mixing remains
uncertain as NBM dewpoints are running high (even currently,
dewpoint here at GSP is 63 which is more in line with NBM10 rather
than straight NBM, which lines up with trends the past couple of
days). Unsure how much bias trends will catch up so ended up
blending 75% NBM10 as NBM is notoriously too high with dewpoints.
Forecast soundings show deep mixing to 800mb as well so confidence
in not particularly high. Even so, seeing some heat indices of 105+
along extreme southern zones as well as the I-77 corridor, so either
tonight or this time tomorrow may need to start evaluating placement
of potential Heat Advisory. Little improvement Wednesday, but start
to see additional deep moisture off the Atlantic as the upper ridge
begins to retrograde and a suspicious looking mid-level low develops
in the western Atlantic, pushing additional moisture towards the
coast.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 130 PM EDT Sunday:

Heat begins to back off slightly as we move into the extended
Thursday, aided by reduced insolation/increasing cloud cover from
additional moisture from the mid-level low over the western Atlantic
that will be pushing into the Southeast. Increasing diurnal
convection is noted with this forecast package with likely pops
creeping into the mountains Thursday afternoon, and solid chances
across the Piedmont, with higher pops to finish out the period.
Afternoon highs will remain above normal but only a few degrees
above instead of 10ish degrees above, but with plentiful moisture
around heat indices mainly south and east of I-85 will still flirt
with triple digits, so the prolonged heat will be an issue, just
with some relief likely each afternoon in the form of clouds and
enhanced diurnal convection (though admittedly sometimes afternoon
convective activity makes it worse). Weakness will be hovering
around over the Southeast, leading to a wetter pattern as we enter
the weekend.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR conditions prevail as high pressure
remains overhead. Winds are relatively light to calm going into the
overnight hours. Most sites will have VRB winds through Monday
afternoon. KHKY could see a brief MVFR/IFR restriction for BR at
sunrise, so went ahead and kept the TEMPO going from 09z-12z. No
other vsby/cig restrictions are anticipated at this time. A pop-up
shower or TSRA is possible across the mountains Monday afternoon,
but confidence is too low for any mention. Expect SCT/FEW cu again
Monday afternoon as the area heats up.

Outlook: Dry conditions to persist into at least midweek. Fog and/or
low stratus will be possible each morning in the usual mtn valleys
and near lakes and rivers.

&&

.CLIMATE...
RECORDS FOR 06-23

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      93 2016     64 1936     70 2017     47 1947
                1988
   KCLT     100 2015     63 1936     77 2016     53 1947
   KGSP      99 1988     70 1900     75 2016     54 1972
                1944                                1947



RECORDS FOR 06-24

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      94 1952     66 1991     70 2015     48 1947
                            1919                    1918
   KCLT     102 1930     68 1936     76 1998     55 1972
                                        1914        1936
   KGSP     100 1952     64 1936     76 2016     51 1915



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...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...DEO
NEAR TERM...CP/JDL
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...CAC
CLIMATE...