126
FXUS62 KGSP 231850
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
250 PM EDT Sun Jun 23 2024

.SYNOPSIS...
A cold front will cross the area tonight and bring a chance of
showers with isolated thunderstorms. Drier conditions return through
Wednesday, before another active cold front moves in from the
northwest Wednesday night into Thursday.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 245 PM Sunday: The KGSP radar shows that isolated
showers have developed east of the mtns as of mid-afternoon,
in an environment characterized by sfc-based CAPE on the order
of 1000-2000 J/kg. Mid-level lapse rates are unimpressive, but
low level lapse rates are steep and profiles show enough dCAPE,
generally above 1000 J/kg, to suggest that if we manage to get a
strong enough updraft to get a thunderstorm, and then perhaps some
cloud ice, we could get strong enough downdrafts to produce some
brief gusts that could knock down some tree limbs. Will add some
wording about possible wind damage in the HWO. Precip probs will
be kept in the slight chance range mainly over NC and along/N of
I-85. As for the temps, yes it will be seasonally hot, but the
RH looks like it will stay low enough to keep the Heat Index in
check and below criteria. Meanwhile, a band of showers moving off
the Cumberland Plateau was weakening as shown by most of the CAMs.

Recent model trends for tonight and Monday continue in the
latest forecast guidance. The main concern, albeit minor, is the
thunderstorm chances over the mtns tonight. Models continue to show
a vort lobe dropping in from the WNW tonight, digging a broad upper
trof axis over the Mid-Atlantic region. The forcing should help
to develop and bring a broken band of showers and thunderstorms
into the area after dark, with some timing differences between
the various CAMs. The expectations for any strong to severe storms
are low as the timing is poor. A few of the showers might survive
east of the mtns into the pre-dawn hours on Monday, especially
over the NC foothills and NW Piedmont, but altogether no big deal
and most places will stay dry. Low temps will be mild as the weak
sfc reflection of this short wave will not cross the region until
the hours around daybreak. In reality, this isn`t so much a cold
front as it is more of a dry front, which is typical for this
area at this time of year. Behind the boundary, a sfc high will
build in thru Monday afternoon from the NW on the strength of an
upstream ridge. The upshot is that temps Monday afternoon might
ultimately be similar to Sunday afternoon, but the RH should
be noticeably less (and less than we expected a few days ago),
such that apparent temps should stay well below the Heat Index
criteria. Precip chances will also be limited to a slight chance
over the eastern-most zones in the middle part of the day before
the boundary moves off toward the Coastal Plain in the afternoon.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 1230 PM Sunday...Upper heights will begin to rise early Tue
which will support a Canadian sfc high to the north. This high will
dominate the weather into Wed as it becomes reinforced and ridges
down the east coast. Relatively dry and cool air will mix in, but
still expect deep subs to allow for temps in the l90s east of the
mtns and u80s across the mtn valleys. Soundings show mixing into the
drier air aloft which will help keep sfc dwpts in the u50s to l60s
and HI values below adv criteria. The atmos becomes more dynamic
early Wed as a pos tilted h5 s/w pushes in from the west. This wave
will likely produce sct showers and a few general to strong tstms
across the NC mtns with isol activity east thru the day. Rainfall
amts will be modest and wont make much of a dent in the below normal
precip amounts received this month. Surface dewps will bump up in
this environ ahead of the front and along with temps reaching the
mid to upper 90s east of the mtns, heat index values could rise into
advisory levels across the Lakelands. Overnight temps will remain
rather warm with mins held abt 5-7 degrees abv normal.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 205 PM Sunday...An upper trof axis continues to cross the area
Wed night which will likely maintain chance thunder across the NC
mtns and isolated storms east. With high pressure pushing a llvl
convg zone into the area during the afternoon, expect another round
of tstms across the NC mtns. Meanwhile, heights will rise as a
subTrop ridge builds in from the west. This neg forcing will help
keep tstm strength in the general category Thu afternoon and again
Fri afternoon when the llvl flow brings in an upslope e/ly se/ly
flow. The building ridge dominates the pattern into the weekend and
makes for a summertime pattern with PoPs a little below climo and
temps remaining above normal. Expect highs in the m90s each
afternoon and lows likely held a couple cats abv normal. Heat
indices look to remain below adv level Thu and Fri, yet may reach
criteria Sat as dewpts surge ahead of a sfc front approaching from
the northwest Sat night.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Each day the coverage of cu gets a little
better across the region, so once again today we will contend
with temporary VFR ceiling restrictions with a cloud base 040-050
through late afternoon. Radar shows isolated showers across the
area, so most terminals get a VCSH until it looks more like one
would actually impact a terminal, at which point we will amend. Wind
should be SSW to SW through early evening. A better-defined band of
showers and a few storms will move into the NC mtns this evening
but should not make it past the mtns before falling apart. Have
included a PROB30 for the mtn/foothill terminals to account for
this. The showers will be ahead of a weak frontal boundary that is
expected to move across the area in the early morning to daybreak,
and the passage of the boundary should bring the wind around to
W to NW by mid-morning. VFR thereafter.

Outlook: Drying trend now expected to continue Mon-Tue with little
to no diurnal convection those afternoons. Summertime humidity
returns Wed-Thu with SHRA/TSRA chances also returning.

&&

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

&&

$$

SYNOPSIS...SCW
NEAR TERM...PM
SHORT TERM...AR/SBK
LONG TERM...SBK
AVIATION...PM