084
FXUS62 KGSP 041746
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
146 PM EDT Sat May 4 2024

.SYNOPSIS...
A front will remain stalled over the region through the weekend
resulting in periodic showers and thunderstorms. A general
summertime pattern sets up early next week, which will keep
scattered thunderstorm chances around each afternoon. Highs will
trend well above normal by Tuesday, remaining well above normal
through at least Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM EDT Saturday: Coverage of showers continues to
increase this morning with isolated storms generally limited to the
I-77 corridor and the Smokies. Expect shower coverage to become
widespread with scattered storms. Areas of heavy rainfall and
isolated flooding expected with PWs in the 90th-99th percentile of
the daily climatology for our area, good moisture convergence, and
lift. A weak backdoor cold front nudging into the CWA from the
northeast will also provide an additional source of lift for
convective initiation, and could be the focus for locally heavy/
perhaps isolated excessive rainfall this afternoon. Deep S/SW flow
will also pose the potential for training cells within persistent
confluent zone. While the severe threat is low, a few strong storms
with very gusty winds are expected with an isolated severe storm
possible. Highs will be below normal with clouds and rain.

As a short wave trough drifts over the forecast area tonight, the
zone of low level confluence and moisture plume will begin to shunt
east of the area. However, this trend will be rather slowly
evolving, so convective chances will remain elevated through at
least the evening, before slowly winding down overnight. The threat
for locally excessive rainfall threat will persist through at least
the evening. Min temps will again be well above normal.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 230 AM EDT Saturday: A stationary front will be draped from
the Ohio Valley to the Southern Plains Sunday into Monday, remaining
well west and north of the western Carolinas. This will allow for
SW`ly flow at 850 mb keeping an influx of rich gulf moisture in
place across the region. Convective chances look to be much lower on
Sunday compared to Saturday thanks to a weak upper trough gradually
pushing east of the western Carolinas throughout the day. However,
isolated to scattered showers and thunderstorms are still expected
to develop throughout Sunday per the 00Z CAMs. Thus, have likely
PoPs in place across the northern zones, with chance PoPs across the
southern zones. Storm movement will continue to be slow on Sunday
with only about 10-15 kts of shear in place so locally heavy
rainfall will be possible, especially for areas that received rain
on Saturday. The majority of guidance shows SBCAPE values ranging
from ~800-1500 J/kg during peak heating Sunday afternoon. Model
soundings from both the NAM and GFS show an inverted-V and mid-level
dry air in place Sunday afternoon. Thus, an isolated severe storm or
two cannot be entirely ruled out, with the main potential impact
being damaging wind gusts. Shower and thunderstorm chances will show
a slight uptick on Monday as upper shortwaves track overhead the
western Carolinas. Went with categorical PoPs across the western
third of the forecast area on Monday, with likely PoPs elsewhere.
The strong to severe storm potential and locally heavy rainfall
threat return again on Monday thanks to continued weak shear and 800-
1500 J/kg of SBCAPE in place. Highs should end up a few degrees
above climo through the period, with lows around 10-13 degrees above
climo.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 200 AM EDT Saturday: Weak upper ridging builds into the
Carolinas on Tuesday while an upper shortwave tracks overhead the
forecast area. This will act to keep shower and thunderstorm chances
around across most of the forecast area. Have the highest PoPs
(likely) confined to the NC/TN border, with chance PoPs elsewhere
(the exception being the far southern tier of the CWA where there
are no mentionable PoPs). With shear values expected to range from
25-35 kts and SBCAPE values around 1500 J/kg on Tuesday afternoon,
isolated strong to severe storms seem plausible. Tuesday night into
Wednesday weak upper ridging will continue building across
Carolinas. This should generally lead to lower convective chances
compared to Tuesday. Thus, capped PoPs to chance across the western
two-thirds of the forecast area. However, since cloud cover is
currently expected to be lower on Wednesday, global models depict
SBCAPE ranging from 1500-2500 J/kg during peak heating, with shear
still generally ranging from 25-35 kts. Thus, diurnal strong to
severe storms will be possible again on Wednesday. At the sfc, a
cold front will slowly progress eastward out of the central US but
will remain well west of the Carolinas. This will lead to W/SW`ly
850 mb flow in place Tuesday into Wednesday, allowing temps will
climb into the mid to upper 80s east of the mts and across the mtn
valleys each afternoon. A few locations along I-77 in the southern
NC Piedmont may even see highs reach 90 degrees on Wednesday. Thus,
highs should end up around 6-12 degrees above climo. Lows Tuesday
night and Wednesday night should end up around 12-15 degrees above
climo thanks to some lingering cloud cover and SW`ly sfc winds.

The aforementioned cold front will continue trekking eastward
Thursday into Friday leading to better shower and thunderstorm
chances for the western Carolinas as well as the potential for
locally heavy rainfall (especially for areas that received rainfall
earlier in the week). Convection will be in place well ahead of the
front Thursday into Friday so have chance PoPs painted across the
entire area. The only exception is the NC mtns where likely PoPs are
in place for Thursday. The actual FROPA itself should track across
the western Carolinas Friday afternoon into early Friday evening.
The front will allow shear values to increase slightly, ranging from
35-45 kts. Guidance shows SBCAPE values ranging from ~1500-2000 J/kg
on Thursday afternoon so the potential for strong to severe storms
will return once again. Depending on how fast activity pushes south
and east on Friday, the potential for strong to severe storms may
return again Friday afternoon (mainly along and east of I-85). Temps
will climb back into the mid to upper 80s Thursday afternoon across
the mtn valleys and east of the mtns. A few locations along I-77 in
the southern NC Piedmont may once again see highs reach 90 degrees.
Slightly cooler temps can be expected on Friday behind the cold
front, with highs only climbing into the lower to mid 80s east of
the mtns. Lows Thursday night will remain ~12-14 degrees above
climo, becoming ~5 degrees above climo Friday night behind the cold
front.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: The very messy aviation forecast continues
with convection over the area and everything from VFR to LIFR.
Expect convection to continue through the afternoon becoming
isolated to scattered SHRA this evening. VFR TEMPO MVFR or IFR in
SHRA and TSRA this afternoon. Conditions deteriorate overnight even
as precip becomes isolated. Expect MVFR to IFR vsby and IFR to LIFR
cigs. Will see a slow improvement after daybreak with vsby becoming
VFR but cigs only slowly rising through MVFR to eventually VFR.
Scattered convection expected to begin developing before the end of
the period, but best chance holds off until after 18Z except KAVL.
Light and variable to S to SE wind this afternoon becomes light and
variable overnight into the morning Sunday.

Outlook: Enhanced moisture will combine with a weak/stalled front
through the middle of next week, resulting in a period of
active/mainly diurnal convective weather each day. There will also
be the potential for restrictions associated with widespread fog
and/or low clouds each morning.

&&

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

&&

$$

SYNOPSIS...AR
NEAR TERM...JDL/RWH
SHORT TERM...AR
LONG TERM...AR
AVIATION...RWH