Blackburn, North Carolina Weather Forecast Discussion

241
FXUS62 KGSP 051759
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
159 PM EDT Sun Oct 5 2025
.SYNOPSIS...
High pressure continues to dominate the pattern through Tuesday,
with low rain chances and a slow warming trend.  Moisture steadily
increases ahead of a cold front, which arrives on Wednesday.
High pressure and cooler temperatures return behind the front on
Thursday, then persists into next weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 140 pm EDT Sunday...
Key Messages:
1) Spotty showers across the upper Savannah River Valley and
Lakelands
2) Max temps near-normal; min temps above normal
3) Mountain valley fog/low stratus returns early Monday.
Inverted surface ridge will continue to gradually weaken as
anticyclone continues to meander away from the Mid-Atlantic
coast. A zone of enhanced E/SE onshore on the southern/western
periphery of the ridge will support a couple of surges of deeper
moisture across the upper Savannah River Valley and the Lakelands
through the period. The first of these is resulting in spotty,
mostly light showers across this area this afternoon...warranting 20-
40 PoPs. Guidance generally agrees that these showers will diminish
by this evening, with shower chances ramping up again (to 20-40%)
late Mon morning into the afternoon in association with the next
moisture surge. The potential for morning valley fog/low stratus
development will increase toward daybreak Monday, but lingering
stratocu responding to upslope and weak upglide flow will limit its
extent and/or residence time. Elevated moisture and clouds will
result in a regime characterized by above-normal min temps and near-
normal maxes.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 1117 AM EDT Sunday: Somewhat of a transitional period
appears likely on Tuesday, as surface high pressure shifts farther
offshore, dislodging its influence on the Carolinas and cutting
off residual cold-air damming from its synoptic source.  A h85
trough should slide across the Eastern Seaboard in the wake of
retreating high pressure, and although this alone likely won`t
be enough to fully scour out the CAD layer...it should certainly
do a number on it, and combined with what operational guidance
still depicts as aggressive daytime mixing, may spell the end
for our resident wedge.  Despite this, temperatures should run
at least a category above normal on Tuesday, owing largely to
weak low-level WAA developing as winds turn more S/SE (SW, even,
by Tuesday afternoon) in response to the advancing h85 trough axis.
The real action will be brewing well upstream of our region
for most of Tuesday and Tuesday night: a potent trough axis
extending from Ontario all the way to the Ozark Plateau will
spend much of Tuesday deepening, and confluent upper flow ahead
of it will amplify the upper pattern across the Carolinas.
Operational guidance depicts a few subtle shortwaves making
tracks across the NC and VA Appalachians as early as Tuesday
afternoon and evening...and some ensembles even support low-end
ridgetop showers on Tuesday...convincingly enough to warrant a
slight-chance PoP across parts of the NC mountains. But, the
system won`t actually arrive until Wednesday, when operational
models are in good agreement that a cold front will dig out of
the Ohio Valley, crossing the Carolinas during the daylight
hours.
For the most part, global ensembles suggest that the front will
arrive early enough in the day to beat much daytime destabilization,
and that the core of stronger upper flow will remain displaced
to our north, more toward the VA Piedmont and Chesapeake regions
than in our area...and this scenario would essentially preclude
any chance of significant convective response, keeping us limited
to just some showers along the front.  However, a cluster of
about one quarter of LREF members - mostly comprised of GEFS and
Canadian ensemble members - depicts a slightly less-progressive
upper pattern, and accordingly, a slower FROPA.  This scenario
would give the Carolinas, especially the southeastern half of the
forecast area, longer to destabilize; it`d also bring amplified
upper flow farther south, resulting in at least some opportunity
for thunder, and perhaps weak organization.  None of the CAMs
extend out this far yet, but both the RDPS and regional NAM do,
and both favor the latter scenario.  Watching the hi-res guidance
come in for Wednesday over the next day or so will be interesting.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 1226 PM EDT Sunday: In the wake of the front, a slug of
low-level CAA will stir up N/NW winds for Thursday.  The h85
trough will be deamplifying by this point, so breezier conditions
won`t last much longer than Thursday afternoon.  The supporting
high will wind up parked over New England beneath low-amplitude
shortwave ridging on Friday, but will remain progressive and
is likely, based on the bulk of LREF members, to shift offshore
over the weekend.  As a result, hybrid CAD will redevelop east of
the Appalachians on Friday and Saturday on the north side of the
remnant frontal boundary...which by this point should be somewhere
near the Atlantic coast.  Some guidance depicts a weak open wave
developing along this boundary on Friday or Saturday in response to
shortwave energy originating on the Gulf coast...but this feature
isn`t yet handled very consistently by the long-range ensembles,
and even if such a wave does develop, it`s unclear whether any
associated rain would make it this far inland.  At any rate, it
doesn`t appear to be a particularly significant event apart from
being our next chance for a wetting rain.  It still looks like
temperatures will run quite a bit below normal through the period,
with highs in the 60s on Thursday and Friday, and slowly climbing
back into the 70s over the weekend.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: E/SE flow just above the surface will
continue to support abundant low level moisture...especially
across the western third or so of the Terminal Forecast Area
through much of the period. This moisture is resulting in spotty,
mostly light showers this afternoon. Showers will mostly be
confined to areas near KAND, but cannot be ruled out at the
other upstate SC terminals and possibly KAVL. Nevertheless, a
mention of tempo -SHRA (accompanied by MVFR cigs) can only be
justified at KAND. Periods of MVFR visby are also possible in
RA, but should be very brief. Otherwise, tempo MVFR cigs remain
possible at KGSP/KGMU until late afternoon or so, while SCT/BKN
clouds in the 035-050 are expected at the NC TAF sites through
the afternoon. Low clouds are forecast to thin out a bit this
evening, paving the way for potential fog/low stratus development
late tonight/early Monday...mainly in the mountains valleys,
and perhaps near KHKY. Having said that, areas near KAVL will
likely be the last to see any stratocu dissipate...so confidence
in the extent and persistence of early morning restrictions is not
high. For now, will advertise MVFR conditions along with SCT003
at KAVL between 10-14Z. A brief period of MVFR visby and FEW001
SCT004 will also be forecast at KHKY around sunrise. Winds will
mostly remain E/NE at 5-10 kts through the period, although the
NC terminals are expected to see light E/SE winds this afternoon.
Outlook: Other than the continued likelihood of early morning
mountain valley fog/low stratus, generally VFR conditions are
expected through early week. Chances for showers and possibly
restrictions increase toward mid-week ahead of an approaching cold
front, with cooler and much drier air returning at week`s end.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...MPR
NEAR TERM...JDL
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...JDL

NWS GSP Office Area Forecast Discussion