Cornelius, North Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

589
FXUS62 KGSP 160302
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1102 PM EDT Thu May 15 2025

.SYNOPSIS...
Warm high pressure settles over our area through Friday. A cold
front will approach from the northwest and may bring a line of
showers and storms into the North Carolina mountains late Friday
night into early Saturday. The front will become stationary over our
region into early next week as the next storm system organizes over
the plains states.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 10:25 PM EDT Thursday: Over the past hour or so, one lone
thunderstorm has developed over far western NC and is currently
making its way SE over the far western Upstate. Otherwise, we
remain shower free across our area. An upper ridge will continue
to build over the region into the overnight with a notable capping
inversion lingering well into Fri morning. This should help keep
convection at bay with the exception of maybe a few more stray
showers and/or thunderstorms. With increasing high clouds, temps
overnight should remain roughly 8 to 12 degrees above climatology.
The fcst becomes more complex on Friday, as the upper ridge axis
shifts offshore and subtle height falls return as a potent shortwave
slowly moves across the Mississippi Valley. This will allow for a
period of quasi-zonal mid-level flow to become established over the
Southern Appalachians downstream of the base of the mean trof. A
pronounced Elevated Mixed Layer (EML) will get advected into the
region, which should largely keep most of the area capped. The latest
near-term CAM guidance continues to depict a wide range of solutions
ranging from too capped with no convection to the potential for
vigorous deep convection across northern portions of our CWA during
the afternoon. Overall, it`s still looking like more likely that the
stronger storms will remain just north of our CWA where the cap will
be somewhat weaker. Nonetheless, should any storms develop over our
CWA, they could become severe quickly. Model profiles continue to
depict sfc-based CAPE on the order of 3000 to 4000 J/kg along with
steep mid-level lapse rates of 7 to 8 C/km tomorrow afternoon. Deep-
layer wind shear of 40 to 60 kts with straight hodographs will support
clusters of splitting supercells within the robust thermodynamic
environment. Thus, any storms that are able to develop, will likely
become severe with the potential for large hail and very strong down-
drafts. Again, this is a conditional severe threat and it`s certainly
possible that no storms impact our area because of the strong cap.
Nonetheless, close attention will need to be paid if any storms do
develop on Friday.

&&

.SHORT TERM /SATURDAY/...
As of 100 PM Thursday, key messages:

1. Confidence has increased for organized convection to move from
KY/TN into the southern Appalachians late Friday night into early
Saturday morning, translating to a nonzero threat of severe weather
at that time.

2. Per the above, confidence is slightly higher for a cold pool to
overspread the area and suppress convection Saturday. The cold pool
also would bring lower humidity to much of the area Saturday,
although temperatures will remain above normal.

As a mature low pressure system crosses the upper Mississippi Valley
Friday night and Saturday morning, a shortwave will cross the lower
Ohio Valley. A convergence axis, arguably a dryline, will move into a
strongly unstable and sheared environment invof western KY/TN Friday
evening. It looks likely at least one linear MCS--maybe two depending
on how well the forcing mechanisms overlap--will take shape and
progress to the western slopes of the Appalachians overnight or early
Saturday morning. That suggests a widespread threat of damaging wind
across the lower OH and TN valleys with potential for large hail as
well. The track of the first MCS shown on some runs has generally
been such that it misses us to the north. However, the dryline
activity continues to be depicted as pushing across the TN/NC border
between 06-12z Sat, with the earlier timing more likely given the
potential for the cold pool to be driving development. We will be
coming off a remarkably unstable afternoon, but MUCAPE still is
likely to be greater than 1000 J/kg over our mountain zones. Thus it
is plausible the line will at least make it partway into the CWA
before weakening enough for the severe weather threat to diminish.
SPC has included our mountains in the Day 2 Marginal Risk area.

Many aspects of the forecast for Saturday remain contingent on how the
convection plays out during the early morning, but with that looking
more likely than it had been, confidence is not as low as before. PoPs
will be retained over a good portion of the area Saturday morning as
the convection decays along the edge of the cold pool and stratiform
rain fizzles. Most models show little to no QPF response east of the
mountains Saturday, The NAM shows some scattered response seemingly
progressing with the cold pool thru the Piedmont late morning to
afternoon, but that would be somewhat atypical; usually we experience
a complete lull for a time with diurnally forced redevelopment late in
the day, if the cold pool doesn`t completely work us over. PoPs are
being shown to taper from NW to SE during early to mid aftn. The cold
pool is associated with an appreciable drop in dewpoints following the
same trend; temperatures should be a few degrees cooler than Friday
although potentially will be offset by downsloping. Maxes remain at
least a few degrees above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
As of 215 PM Thu: The actual cold front associated with the Great
Lakes system should push into the CWA Saturday night. Still cooler
conditions and lower dewpoints are forecast Sunday in the wake of the
front. Ridge will be building in the lower MS Valley by that time,
however, and the cold front stalls and gets reactivated to our west.
Stable post-frontal airmass is most likely to persist over the NE
half of the CWA.  Seasonable CAPE of at least a few hundred joules
will redevelop in the other half of the area, nearest the front; T/Td
may actually be a little warmer in the Savannah Valley compared to
Saturday.  Furthermore, NW flow into the Appalachians will also
provide weak forcing along the TN border so small PoPs extend along
there.

The ridge to our west and NW-SE oriented warm front may put us in the
path of another MCS if one develops Sunday night or Monday. The
deterministic global models, plus a number of members of the NAEFS
and ECMWF ensembles, show precip developing variously in AR, MO, KY,
TN Sunday and/or Monday and carry it into our area as an apparent MCV
rounds the ridge. Per the pattern, that would appear possible Monday
night or Tuesday as well, although there appears less support for
that idea from the models. The MCS possibility notwithstanding,
spotty diurnal convection may develop over the mountains Sunday, with
climatological 20-40% chances Monday as dry air aloft should be less
of a limiting factor that day. 0-6km shear will be supportive of at
least an isolated severe threat if storms do develop either day.

Early in the week, cyclogenesis is probable in the central CONUS as
upper low moves across the Rockies.  By late Tuesday we may enter the
warm sector of that system if the front is able to shift far enough
north. Shortwave/cold fropa potentially will occur Wednesday. Precip
chances are highest those days but confidence on the extent of any
severe threats is limited by spread in timing and the position of the
front.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Expect VFR conditions to prevail thru the
00z taf period at all terminals. Light sct showers are currently
making their may into the NC mtns from the west and could poten-
tially reach KAVL over the next few hrs, however my confidence
that any showers will reach KAVL is too low to mention in the taf
at this time. On the other hand, there is a decent chance that a
fast-moving MCS could approach from the west, remain organized
moving thru our northern zones and impact KAVL and KHKY during
the late morning into the afternoon. As such, I have a PROB30 for
TSRA for those 2 terminals from roughly 14 to 20z on Friday to
account for this possibility. Chances are currently too low to
mention convection at the other taf sites. Otherwise, sct to bkn
high clouds will persist over the fcst area thru the taf period
with few to sct cumulus expected again Friday afternoon. Winds
will continue to favor a S to SWLY direction thru the taf period
with speeds becoming light again by the overnight. The Upstate
terminals will also likely see another round of low-end gusts
Friday aftn/evening. Winds at KAVL are expected to remain light
and VRB thru much of the overnight and morning and will eventually
pick up from the SW again tomorrow afternoon.

Outlook: A decaying line of robust storms is expected to move thru
our fcst area early Saturday morning and could produce brief restric-
tions as it move thru the area. Diurnal convection will be possible
on Sunday and early next week as the synoptic pattern remains active.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...JPT
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...JPT