Cornelius, North Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

451
FXUS62 KGSP 131832
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
232 PM EDT Thu Mar 13 2025

.SYNOPSIS...
Isolated showers expected over the mountains today and tomorrow,
along with above-normal temperatures that will persist into the
weekend.  A powerful storm system will arrive Saturday evening into
Sunday morning, producing widespread heavy rain and thunderstorms,
some of which will become severe.  Dry and seasonable weather will
return early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 212 PM EDT Thursday: Ahead of a short wave, extensive
high-level cloudiness continues to move slowly across the fcst area
early this afternoon, but there was a back edge of sorts coming
into Upstate SC and southwest NC, which should allow for the weak
destabilization depicted in the model guidance later this afternoon
over the srn/central mtns. FWIW, the mesoanalysis already shows a
small amount of sfc-based CAPE developing up into the Smokies at
this time. An isolated thunderstorm has developed in north central
GA as well. Thus, our convective chances look plausible later this
afternoon and will be kept. Won`t rule out an isolated thunderstorm
this far north as well. Otherwise, temps/dewpts look ok for now.

Once the dampening short wave passes to the east and the sun sets,
we should lose the support for the convective activity, thus precip
probs will slowly diminish into the evening. With that, a lull in
the action will begin as upper ridging downstream of the powerful
and dynamic upper low coming east across the southwestern US works
its way in from the west. The remainder of the night should be
fairly quiet with thinning cloudiness. A weak sfc ridge will be
maintained from the northeast into the middle part of the day on
Friday, of which the model guidance is in good agreement. This
low level feature will keep the low level flow more easterly
well into the day, which will not allow any meaningful moisture
return until perhaps the early part of the afternoon as the flow
starts to veer. Previous guidance suggested the return of low level
moisture earlier in the day, thus more extensive upslope clouds and
precip development in the afternoon. The new guidance delays this
development until the mid/late afternoon, while limiting the extent
much closer to the Blue Ridge Escarpment. This seems reasonable
and will be followed. The mild temps of late will continue, with
lows on the order of 5-10 degrees above normal and highs Friday
greater than ten above normal.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
As of 152 PM EDT Thursday: Friday night will feature the slow
onset of a southerly warm advection regime as a compact upper low
lifts out of the central Great Plains into Wisconsin and Minnesota,
leaving in its wake broad, deep troughing that will amplify over
the southern Plains through the day Saturday.  In response, rapid
cyclogenesis should take place over the Plains, resulting in an
incredibly potent surface low which will lift rapidly into the
Midwest Friday night.  This should spur a QLCS over the Ozarks,
which, despite initially looking quite organized, will likely begin
losing steam over the Cumberland Plateau as it outpaces the better
instability and shear overnight.  Though enough moisture will be
present that some showers, and probably even some thunder, may
make it to the NC-TN state line before dawn Saturday, the odds of
any severe weather embedded in this activity remain fairly low.
Rather, we can expect the WAA regime to continue on Saturday,
drawing moisture north from the Gulf into much of the Southeast,
in what will essentially become a region-wide warm sector.
Despite the rapid increase in moisture, there`ll be relatively
little forcing over the Carolinas through the day, so zones outside
the mountains are expected to remain dry, with only the mountains,
and in particular the southern Blue Ridge Escarpment, seeing much
rainfall due solely to mechanical lift. High temperatures should
climb well above normal, in the upper 70s for the low terrain,
and with some spots along the I-77 corridor and across the southern
Upstate reaching the lower 80s.

Saturday night is when the more active weather gets here.  Though
the core of the surface low will pass well to our north, its cold
front will barrel across the Deep South on Saturday, producing a
fair bit of upstream convection and developing a 60-70kt LLJ out
ahead of a robust frontal circulation.  Unlike in some scenarios
in which upstream convection can essentially sap a system of
better moisture before it makes it to the Carolinas, the presence
of this jet will provide a continuous source of Gulf moisture,
allowing convection to continue well east of the Mississippi
Valley instead of faltering on approach.  By Saturday evening,
winds will pick up in response to the leading edge of the jet,
becoming gusty especially over the GA and NC mountains.  Well in
advance of the severe weather, a low-end damaging wind threat
isn`t out of the question, particularly over the high terrain,
where less of the enhanced warm advection winds will need to mix
down to the surface to produce issues.

Then the actual convection will arrive.  Global and regional
guidance suggest the frontal boundary will become oriented NNE-SSW
as it crosses Georgia Saturday evening, while deep-layer shear
vectors across the Upstate and northeast Georgia will be almost
due westerly ahead of the system.  Though upstream convection
may be QLCS-like, the boundary-relative shear orientation over
our region is ideal for discrete cells to develop out ahead of
the system.  Should this occur, conditions in the warm sector
will feature some 300+ J/kg MLCAPE favorably aligned with robust
deep-layer synoptic forcing for ascent, more than enough to fuel
strong convection through much of the night and possibly into
Sunday morning.  The presence of the LLJ as well as the leading
edge of a 500mb speed max arriving around this time will drive
deep-layer shear well into the 50-60kt range, and 0-1km shear as
high as 45-55kts over the SC Upstate. And, broad hodographs will
permit 0-1km SRH on the order of 200 m2/s2. The thinking, then,
is that a mixed discrete/QLCS storm mode remains the most likely,
and that both damaging winds along organized lines and tornadoes
in both supercellular and quasi-linear structure are real risks.
The threat appears most pronounced during the overnight hours,
but may continue after daybreak Sunday as the system pushes out
over the I-77 corridor and continues its march east.

Finally...we continue to monitor the potential for hydro issues
with this system as well.  Given the amount of moisture pumped
into the region ahead of the front, guidance depicts PWs surging
to as high as 1.5-1.75" with (clearly) strong cloud-level flow,
excellent synoptic forcing, and an 8-10kft warm cloud depth.
It`s not a classic hydro setup, but with multiple rounds of
convection possible and QPF already forecast as high as 1-2" in the
non-mountain zones, and as high as 3" in the high terrain, these
ingredients should be more than enough for convectively-enhanced
rates and at least localized hydro issues where storms train or
where multiple rounds of heavy rainfall come into play.  At this
point, for mainstem rivers at least, HEFS ensemble hydrographs
depict a low (<25%) chance of action stage / nuisance flooding,
and a negligible chance of true minor flooding, even for forecast
sites in the southwest mountains, where forecast QPF is maximized.
This is consistent with the idea that issues will be mainly
localized, rather than widespread.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 217 PM EDT Thursday: Far quieter conditions are anticipated
in the extended.  With the departure of the front to the east,
drier high pressure will build in late Sunday, prompting a
return to clear skies and allowing high temperatures to dip back
toward normal.  Quiescent weather will continue through mid-week,
with clear skies permitting a few chilly mornings Tuesday and
Wednesday, before clouds return Wednesday in advance of the
next upper trough.  The most likely solution among LREF members
is currently for this system to pass by with little fanfare,
producing some scattered showers along a sluggish cold frontal
boundary sometime Wednesday night or Thursday.  However, a second,
less-likely solution supported by around 30% of ensemble members
depicts a narrow ribbon of surface- based instability that could
prompt another round of thunder.  Even members which depict this
solution, however, don`t have particularly impressive kinematics,
so for now, not much concern...will let the forecast evolve over
the coming days and go from there.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions are expected at all terminals
through the period, with the one possible exception being late
this afternoon at KAVL, should a shower develop right on top of
them. Extensive high clouds should move off to the east northeast
this afternoon, early enough that some high-based stratocu may
work in from the SW. Wind should be light SW. The passage of an
upper wave may allow the high clouds to thin out overnight, before
the warm advection starts to kick in from the south on Friday. At
this time, there appears little chance of a restriction developing
before 18Z Friday. Wind should become SE Friday after the morning
inversion is mixed away.

Outlook: Moisture returns Friday night, allowing for a low
cloud ceiling restriction to develop overnight and into Saturday
morning. A substantial cold front is expected to bring showers
and thunderstorms, and associated restrictions, Saturday night
and Sunday morning.

&&

.FIRE WEATHER...
RH values across Western NC have the potential to reach critical
levels again this afternoon. Given the minimum RH forecast and ripe
fuels, a Fire Danger Statement has been issued again following land
manager and neighboring WFOs coordination.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Increased Fire Danger until 8 PM EDT this evening for NCZ033-
     035>037-048>053-056>059-062>065-068>072-082-501>510.
SC...None.

&&

$$

SYNOPSIS...MPR
NEAR TERM...CAC/PM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...PM
FIRE WEATHER...CAC