Greenville, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

544
FXUS62 KGSP 291442
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1042 AM EDT Thu May 29 2025

.SYNOPSIS...
Low pressure moves along a front crossing our area tonight and
Friday with more showers and thunderstorms expected. A few strong to
severe storms are possible on Friday especially over the Piedmont.
Drier weather moves over our area for the weekend and into next
week. Below normal temperatures through the weekend will warm to a
little above normal next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM EDT Thursday: A strong 500 mb shortwave is currently
crossing AL/MS, and producing an area of light to moderate rain that
extends into the SW part of the forecast area. The mid clouds and
spotty light rain will spread over most of the CWA thru early aftn,
which will keep temps in check and delay better destabilization. The
latest guidance seems to agree on decent coverage of showers,
but perhaps less thunderstorms. So have bumped up PoPs more in the
likely to categorical range, but kept thunder in the isolated to
scattered range. Despite the cloud cover, still may see over 1000
J/kg of sbCAPE across the southern and eastern zones, which may
be enough for a strong storm or two late aftn into early evening.

Otherwise, a large upper low currently centered over the Upper
Midwest will steadily dig southward towards our region. At the
same time, a southern-stream h5 shortwave will lift north from
the Gulf Coast and translate over our area this aftn/evening.
By the end of the near-term period early Friday, the low will
have opened back up into a trof with the its axis just to our
NW. At the surface, we will remain under broad, but weak high
pressure today, yet our area will remain in the warm sector thru
the period. Any morning fog and/or low stratus should mix out more
readily than yesterday, with partly cloudy to bkn skies expected
again by the early aftn. Shower and/or thunderstorm coverage has
been increasing for today based on the most recent CAM guidance.
Fcst soundings continue to show modest amounts of instability
across most of our CWA by mid-aftn. Overall, the CAM guidance
appears to keep the more discrete/stronger cells generally south
of I-85, but there has not been very good run-to-run consistency
over the last several runs. Nonetheless, I increased our PoPs to
high-end chance with some areas of likely for today/tonight. SPC
currently has most of our non-mtn zones in a Day 1 Marginal Risk
area for severe wx. This area probably extends a bit too far to the
north, but it looks warranted across our southern zones. Otherwise,
temperatures return to near-normal, with highs in the 70s in the
mtn valleys and low 80s across the lower terrain.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Key Messages:

1) A few strong-to-severe thunderstorms possible Friday with a cold
front

2) Gusty winds from the WNW behind the front Fri night/Sat

3) Mostly dry weather returns Saturday

As of 300 am Thursday: The axis of a rather deep upper trough will
progress across the region Friday through Saturday, as a strong short
wave passes just north of the forecast area. Associated frontal zone
is forecast to move into the CWA by around noon on Friday, sweeping
rather quickly across the area through the afternoon. Frontal band
of showers and embedded thunderstorms will accompany the boundary
into the area...warranting likely/categorical PoPs across the west
by late morning. Increasing clouds will limit insolation ahead of
the frontal band, but timing will be such that the surface should
have time to warm to near 80 across the Piedmont...with mid-level
lapse rates of 6.5-7 C/km likely supporting sbCAPE values in the
1500-2000 J/kg range by the time the forcing arrives. The
combination of moderate instability and deep forcing will support
numerous/widespread coverage (70-90 PoPs) of convection east of the
mountains during the afternoon. Deep layer shear of 45-55 kts will
be more than adequate to support organized convective structures...
including supercells producing isolated severe weather. The main
threats will be from damaging winds and large hail, but effective
helicity is forecast to become adequate for an isolated tornado
threat across the Piedmont.

Other than the potential for scattered upslope/northwest flow rain
showers across the NC mountains, showers and storms will end by
Friday evening in the wake of the front, with gusty WNW winds
developing in the cold advection flow through Saturday. Northwest
flow showers could get a boost during the daylight hours Saturday,
as another speed max dives SSE from the Great Lakes/Ohio Valley into
the base of the trough across the Mid-Atlantic and Southeast. This
warrants solid chance PoPs across the mountains Sat afternoon... and
some of these could break containment into the Piedmont. Any showers
should taper off during the evening. Temperatures are forecast to be
a category or two below climo through the period.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Key Messages

1) Generally dry, with only scattered mountain showers possible
Sunday

2) Temperatures gradually warm through midweek

As of 320 am Thursday: The axis of an anomalous upper trough will be
centered near the East Coast at the start of the period...with one
last speed max forecast to dive SSE toward our area along the
western periphery of the trough Sunday. This could support another
enhancement to lingering NW flow showers during the afternoon, with
20-4o PoPs warranted across the entire forecast area. Temperatures
will remain a little below climo for the first 36 hours or so of the
extended.

The remainder of the period will see a trend toward drier and warmer
conditions, as ridging builds into the East from the west.
Temperatures will warm to slightly-above normal levels by the middle
of next week. Conditions are expected to be a little too dry and a
little too suppressed to support diurnal deep convection...and PoPs
are less than 20% Mon through Wed.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: MVFR ceilings continue to linger at a handful
of terminals early this morning. In addition, a few sites are already
reporting fog and LIFR cigs. I still expect conditions to deteriorate
over the next few hrs, as another low stratus deck builds in along
with the potential for locally dense fog at more terminals. Improve-
ment may be slow later this morning with VFR conditions finally re-
turning by the late morning into early afternoon. Scattered showers
and thunderstorms are expected this afternoon/evening. Timing remains
somewhat uncertain, but it`s looking like the most active window will
be from roughly 18 to 22z for the bulk of our area. Thus, I converted
the PROB30s for TSRA to TEMPOs for the above timeframe. Also, expect
a period of lingering showers later in the evening, which I accounted
for with PROB30s for -SHRA. Otherwise, winds will remain light to calm
thru the morning and pick up marginally out of the SW to WSW this aftn.
At KAVL, winds will remain light and vrb to calm thru the morning and
favor a NWLY to WLY direction this aftn/evening and remain 5kts or less.

Outlook: Shower and thunderstorm chances and associated restrictions
continue thru the remainder of the work week with drier conditions
expected by the start of the weekend.

&&

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

&&

$$

SYNOPSIS...JDL
NEAR TERM...ARK/JPT
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...JPT