562
FXUS62 KGSP 230538
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
138 AM EDT Mon Jun 23 2025
.SYNOPSIS...
The heat and humidity gradually increase through mid-week as a hot
upper ridge builds over the eastern United States. Isolated showers
and thunderstorms remain possible each afternoon and evening through
Tuesday, mainly across the mountains. The heat and humidity stick
around the rest of the week with daily shower and thunderstorm
chances area-wide Wednesday into the weekend.
&&
.NEAR TERM /THROUGH TODAY/...
As of 130 AM Monday: Fcst remains on track for the 1 AM
update. Clear skies and light wind should support mtn vly fog
development. Overall, muggy conditions thru the overnight, with
temps in the 70s across the lower elevations.
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 /TONIGHT 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 /06Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR conditions and light winds to continue
thru the period as high pressure remains overhead. KHKY could
see a brief MVFR/IFR restriction for BR like the last couple
of nights, so have 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 this afternoon,
but unlikely to affect KAVL. Expect aftn Cu to develop across the
area, then quickly dissipate after sunset..
Outlook: Dry conditions to continue thru Tuesday. Then a return
to more scattered to numerous diurnal showers and storms starting
Wednesday thru the end of the workweek. 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...AR
NEAR TERM...ARK/CP/JDL
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...ARK
CLIMATE...