203
FXUS62 KGSP 150530
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
130 AM EDT Wed May 15 2024

.SYNOPSIS...
Low pressure brings rain and scattered thunderstorms to our region
through Wednesday. Brief high pressure brings a mainly dry day on
Thursday. Showers and scattered thunderstorms return Friday and
continue into the weekend.

&&

.NEAR TERM /THROUGH TODAY/...
Midnight Update...no major changes.  Tapered PoP/PoTs off based
on very low coverage of showers/thunderstorms at this point.
Activity crossing the NC-TN border into the mountains is quickly
losing its steam.  Fog is developing a little faster than
expected at many locations across the Piedmont, especially the
I-77 corridor...and a dense fog product may eventually be needed.
Will hold off for now and re-evaluate with the 3AM update.

As of 225 pm EDT Tuesday: Upper low passes north of the area Wed,
with occluded front/surface trough moving into our CWA by afternoon.
Weak residual cool pool is expected to drain by afternoon, resulting
in good insolation and destabilization...with sbCAPE forecast in the
1500-2000 J/kg range across much of the area. While a decreasing
height gradient will yield more modest shear parameters (25-30
kts in the 0-6km layer), the more robust instability will support
another period of marginal severe storm risk, with large hail and
damaging wind gusts being the primary threats. Locally excessive
rainfall may become a bit more of a concern Wed afternoon/evening,
if any robust convection is able to track over locations that
receive heavy rainfall through this evening.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
As of 200 PM EDT Tuesday: Upper troughing will be overhead the
Carolinas and northeast Georgia Wednesday evening before gradually
pushing east Wednesday night into early Thursday. Upper ridging will
build in behind the departing trough Thursday afternoon and evening,
remaining overhead through early Friday. The ridge will be nudged
eastward Friday afternoon and early evening as another upper trough
approaches out of the west. Showers and thunderstorms will linger
through Wednesday evening as a sfc low pulls away from the area,
with precip pushing south/east of the area by midnight. However,
some isolated activity along the NC/TN border may linger through
Thursday morning thanks to NW flow. Drier conditions are expected on
Thursday as sfc high pressure briefly builds into the region,
although chance PoPs are possible mainly along and north of I-40 as
latest global model guidance shows the potential for some diurnal
convection. Dry conditions return area-wide Thursday night before
shower and thunderstorm chances ramp up again throughout Friday as a
low pressure system lifts northeast across the Midwest. Have PoPs
increasing from west to east, becoming low-end likely across the
western zones, with high-end chance PoPs across the eastern zones by
the afternoon hours. With global models all showing 30-40 kts of
deep shear on Friday and 500-1,000 J/kg of SBCAPE possible east of
the mtns during peak heating, strong to severe storms may be
possible. However, with the NAM and Canadian showing higher
instability compared to the ECMWF and GFS, confidence on the severe
potential remains low at this time. Locally heavy rainfall will be
possible as well on Friday thanks to wet antecedent conditions. Both
highs and lows should remain around 3-6 degrees above climo through
the short term.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 220 PM EDT Tuesday: Shower and thunderstorm chances will
continue Friday evening into Friday night as the upper trough
approaches from the west. The upper trough should track over the
Southeast Saturday into late Sunday, and looks to stall over the
region through early next week. Have likely PoPs Friday night
through Saturday, with high-end chance PoPs Saturday night through
Sunday. Have lower-end chance PoPs Sunday night through early next
week as confidence is lower regarding how long the low will stall
over the area. The locally heavy rainfall threat will continue
through the weekend, especially as rainfall amounts pile up. The
strong to severe storm threat may linger through the long term, but
confidence on this is low with global models not in great agreement
regarding both deep shear and instability. Lows will remain a few to
several degrees above climo throughout the long term forecast
period. Highs over the weekend look to drop a few degrees below
climo to near climo thanks to cloud cover and precip. Highs early
next week should trend a few degrees above climo.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Dreary conditions again tonight as an upper
low pushes out of IL and into the Ohio Valley.  Periodic light rain
will be possible over the coming hours, but coverage is already
low and should continue to get more sparse as time wears on.
Ceilings are expected to lower to IFR or LIFR leading up to
daybreak; already, some sporadic reports of <1SM vis have come from
some TAF sites as well as surrounding METARs.  Expect visibility to
crash before daybreak as well.  Conditions should improve faster
today than they did on Tuesday, becoming VFR sometime around
late morning/early afternoon.  More widespread convection is
then expected as a lobe of upper energy arrives in the afternoon,
coinciding with peak afternoon instability.  All TAFs now include
PROB30s for TSRA and/or VCTS to handle this.  Winds will generally
be out of the S (SE at KAVL, SW everywhere elses) all day after
a period of light and variable winds overnight.  Once convection
lets up Wednesday night, winds will turn around to WNW in the final
hours of the TAF period as a drying cold front slides into the area.

Outlook: Drying will continue Thursday, before convection and
associated flight restrictions return ahead of a cold front over
the weekend.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...JDL/MPR/SBK
SHORT TERM...AR
LONG TERM...AR
AVIATION...MPR