017
FXUS62 KGSP 171823
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
223 PM EDT Sun May 17 2026

.WHAT HAS CHANGED...
Timing of the cold front mid-week has sped up a bit and is now
expected Wednesday night into early Thursday morning.

Trending slightly cooler for highs on both Thursday and Friday as
cold air damming develops behind the front.

&&

.KEY MESSAGES...
1. A summer-like pattern will continue through mid-week, with
above normal temperatures and spotty diurnal convection expected,
mainly today and on Wednesday. An isolated severe thunderstorm
will be possible this afternoon and evening.
2. A cold front brings better rain chances mid to late week
but rainfall amounts are expected to remain light so any drought
relief will be limited. Above normal highs linger through Thursday
before cold air damming develops behind the front, allowing for
the return of near to below normal highs Friday and Saturday.

&&

.DISCUSSION...
Key message 1: A summer-like pattern will continue through mid-week,
with above normal temperatures and spotty diurnal convection
expected, mainly today and on Wednesday. An isolated severe
thunderstorm will be possible this afternoon and evening.

The latest mesoanalysis depicts a plume of 8+ C/km mid-level lapse
rates associated with remnant elevated mixed layer covering much of
the southern Appalachians and vicinity this afternoon. As a result,
and despite surface dewpoints that have only managed to creep up
into the upper 50s/lower 60s, sbCAPE of 2000+ J/kg is analyzed in
much of the area along/southeast of the I-85 corridor. Associated
cumulus field is steadily getting healthy across north/central GA
and extreme southwest NC. Soundings from high resolution models
depict an air mass that is weakly capped and/or features high levels
of free convection across our forecast area, but conditions become
more hospitable for convective initiation to our west.

A general consensus of high resolution guidance is that showers and
storms will initiate upstream by late afternoon/early evening with
some potential for activity to wander into the upper Savannah River
Valley this evening. Given the absence of any organized areas of
upward vertical velocity, coverage should be widely scattered at
most, but we still feel that 20-30 PoPs are warranted across ~the
western quarter of our area. With an upper ridge quickly building
along the East Coast...shunting the stronger westerlies north and
west of our area, shear parameters are underwhelming to say the
least, but we still can`t rule out a pulse severe storm or two.

In response to the building ridge, low level Bermuda high is
forecast to intensify/expand over the next couple of days...allowing
the surface ridge to build into the Southeast...turning trajectories
off the western Atlantic rather than the Gulf. This will begin to
circulate subsidence-induced drier air into the CWA tonight, with
afternoon dewpoints only expected in the 50s Monday and Tuesday.
Meanwhile, temps will be steadily warming aloft. These factors are
expected to result in much weaker PM instability...and little in the
way of diurnal convection is expected Mon and Tue.

By Wednesday, the upper ridge/Bermuda high is forecast to begin
weakening as a strong short wave trough sweeps across eastern
Canada/the northeast Conus. Moisture and instability profiles are
therefore expected to improve across our areas, especially as the
leading edge of a frontal zone approaches the southern Appalachians
from the west. PoPs for diurnal convection increase to likely across
the mountains by Wed evening. Shear parameters will improve somewhat
during this time, but signals for any organized severe storm threat
area weak at best. Otherwise, temperatures will remain 6-9 degrees
above normal through the first half of the week.


Key message 2: A cold front brings better rain chances mid to late
week but rainfall amounts are expected to remain light so any
drought relief will be limited. Above normal highs linger through
Thursday before cold air damming develops behind the front, allowing
for the return of near to below normal highs Friday and Saturday.

The main change of note is that the timing of the cold front has
sped up a bit compared to this time yesterday and is now expected to
track across the GSP forecast area Wednesday night into early
Thursday morning. As a result of this earlier FROPA timing, highs
have trended down ever so slightly on Thursday compared to the
previous forecast. However, highs are still expected to remain warm
and above normal on Thursday. The front stalls across the Carolinas
Friday into Saturday as weak cold air damming develops behind the
front (per 06Z the GFS), bringing near to below normal highs back to
the area. The front should then reactivate and lift back north as a
warm front over the Carolinas on Sunday. The 06Z GFS depicts the
wedge eroding by Sunday, allowing just above normal highs to return.
This front will bring better rain chances to the area starting
Wednesday evening, with rain chances sticking around through at
least the weekend. Although we are trending more towards a wetter
pattern with higher chances for rain mid to late week, rainfall
amounts appear to remain light at this time (especially considering
how long rain could stick around). Most locations could see rainfall
amounts ~1-1.5" Wednesday evening through Sunday, with some isolated
locations along the Blue Ridge Escarpment possibly seeing 2"+. Will
continue to monitor QPF trends closely in the coming days but for
now it still looks like there would be limited relief from the
drought with these rainfall totals. With the timing of the front
coming through prior to peak heating on Thursday, and with CAD
expected behind front Friday into Saturday, any potential for severe
weather should remain low for most of the period. However, with the
warm sector returning Sunday behind the warm front, better
instability may develop during peak heating, but confidence is low
with this being day 7.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: A cumulus field continues to steadily expand
across the far western part of the Terminal Forecast Area this
afternoon within a moderately unstable air mass. Isolated-to-widely
scattered deep convection may develop west of the area by
late afternoon, and wander into our western areas by this
evening. However, even at KAND and KAVL, the chance of a shower
or storm is only 20%, and a mention will be omitted from those
TAFs for the time being. For the other TAF sites, the chance
is 10% at most. VFR is therefore forecast through the period,
with FEW/SCT clouds in the 045-060 range forecast at most sites
this afternoon/evening. Having said that, there are hints in the
guidance that continued moist southerly flow into the area could
result in low cloud development by daybreak Monday (similar to
Sunday morning.) However, signals in statistical and raw model
guidance remain very mixed at this juncture, and have opted to
handle the potential with FEW/SCT low MVFR clouds at most sites,
except for SCT IFR clouds at KAND. Otherwise, the pattern of SW
winds at 5-10 kts from late morning through the afternoon becoming
light/variable during the evening will continue.

Outlook: VFR to persist through mid-week, except perhaps in mountain
valleys, where patchy morning fog/low stratus may develop each
morning. An active cold front may bring restrictions associated
with convective precip by late week.

&&

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

&&

$$

AR/JDL