Rosman, North Carolina Weather Forecast Discussion

799
FXUS62 KGSP 270022
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
822 PM EDT Fri Sep 26 2025
.SYNOPSIS...
A cold front will slowly track across the western Carolinas tonight
before stalling along the Carolina Coast this weekend, keeping
unsettled weather around. A tropical system may impact the area
early next week but confidence remains low at this time. Highs will
remain near normal through the weekend before dropping below normal
next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 820 PM EDT Friday: Seeing mostly showers with isolated
embedded thunder at times lift northeast across portions of the
forecast area this evening along and ahead of a cold front. Coverage
should gradually increase later this evening into the overnight
hours. With PWAT values between 1.50"-2.00" in place outside of the
mountains, any shower or thunderstorm that develops will be capable
of producing heavy rainfall through tonight. 300-850mb mean wind
show ~30 kts from the southwest indicating that storm motions should
be very progressive, but some training is possible along the cold
front. Thus, localized nuisance to minor flooding remains possible
through tonight. 12Z HREF 3-hour PMMs highlight the Charlotte area
and northwest Piedmont as the best candidates for heavy rainfall
overnight.Lows will run 10-13 degrees above-normal thanks to cloud
cover and rain. The axis of heavy rainfall should gradually shift
east of the I-77 corridor after mid-morning Saturday, with some
lingering light precip possible through the rest of the morning.
Otherwise, positively-tilted trough situated from the Lower MS
Valley to the OH Valley will only slowly propagate eastward, while
the attendant frontal boundary remains quasi-stationary across the
area, mainly east of the mountains throughout the forecast period.
Deep layer south-southwesterly flow will help to transport a deep
conveyor belt of moisture across the Southeast as a result. Model
guidance tries to cutoff the trough and have it stall over the
southeastern CONUS through the period, but has a hard time fully
completing this transition.
CAMs have consistently developed diurnal convection in the mountains
along the southwest facing slopes and ridgetops Saturday afternoon,
while a lull in precipitation is in store east of the mountains. The
trough axis begins to move across the area during this time frame
as drier air tries to punch into the mid-levels, while enough
available moisture, orographic enhancement, and instability
(500-1000 J/kg of SBCAPE) will help to develop convection. CAMs
try to have this activity break containment east of the mountains,
but will likely need to be outflow driven for this to occur,
which some of the guidance indicates. Any severe weather threat is
low, but nonzero as downbursts are possible in the strongest storms
that form. Low-end hydro concerns can`t be ruled out either,
especially for locations that received heavy rainfall overnight.
Afternoon highs on Saturday will remain near-normal with extensive
cloud cover and continued precip chances.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 130 PM Friday...Models are in reasonable agreement on an upper
trough axis over the Southern Appalachians to start the short term
at 00z Sunday. But they quickly diverge on how strong of a closed
low forms from this, as a piece of energy breaks off from the
trough Sunday into Monday. This weak upper low will likely linger
thru at least 00z Tuesday. Meanwhile, high pressure will build
over the Great Lakes. The biggest source of uncertainty in the
forecast is the evolution of a tropical disturbance (Invest 94L)
that is currently east of Cuba, but is expected to drift NW into
the Bahamas. The latest guidance is still coming in at the time
of this writing, but the 12z GFS is once again strengthening the
low fairly quickly and having it merge with the aforementioned
upper low. This would sling the tropical system NW into the
Carolinas. The GFS has consistently been the most bullish of the
deterministic models on this, but does have the support of some
of the hurricane models. But other guidance, including the 12z
Canadian and numerous ensemble members either stall the system
or push it east before making landfall. Even if the GFS were to
verify, any impacts to our forecast area wouldn`t start before
the end of the short term. If anything, conditions should be
relatively quiet thru Monday, as drier NELY flow increases around
the building high to our north and whatever tropical system forms
to our south. There may be enough diurnal instability for scattered
showers both Sunday and Monday. Highs will be near normal Sunday,
but a few degrees below normal Monday, as clouds increase ahead
of the tropical system. Lows will be a few degrees above normal.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 1:45 PM EDT Friday...There is still a lot of uncertainty on
what Invest 94L (which will likely become Imelda at some point)
will do. As mentioned in the Short Term section, the GFS is close to
a worse case scenario for our area, with a strong system (possibly
a hurricane) making landfall along the SC coast, but then drifting
west and stalling somewhere invof the Central Savannah River Valley.
This low would then be blocked by a strong ridge over the Great
Lakes to the northern Mid-Atlantic, which could keep our area in an
easterly atmospheric river setup well into the week. Storm total
precip could really pile up in this situation. With that said,
most of the guidance keeps the bulk of the heaviest precip with
this system to our south and east, with varying time periods of when
that heaviest rain would occur. This is due to the possibility that
the low gets blocked by the upper ridge before making landfall,
then meanders around Carolinas like the 00z ECMWF depicts. This
scenario could still result in areas of heavy rainfall during
the middle of next week, but not as bad the the GFS. Then, the
12z Canadian has continued its trend of keeping the low off the
Carolina Coast, with the sfc high pres axis further south. This
would bring just a brush of moisture along the northwest side of
the low`s circulation, then keep our area mostly dry with just
breezy NE winds for the rest of the week. All of this to say, the
fcst confidence is very low right now. Going with the latest NBM
results in high-end chc to low-end likely PoPs late Monday into
Tuesday, but then trending toward slight chc to dry condition
Wednesday and beyond. Temps should trend toward below normal,
as guidance at least agrees on a fairly strong sfc high to our
north that may cause cold-air damming thru the medium range.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Another messy forecast is expected through
the 00Z TAF period as a cold front slowly tracks across the foreast
area tonight into early Saturday before pushing east Saturday
evening. Seeing scattered SHRA, with some isolated TSRA at times,
lifting northeast across the western Carolinas as of 00Z. Activity
will gradually increase in coverage this evening into late tonight,
possibly linger through mid-morning Saturday. Thinking TSRA chances
will be fairly low across the terminals so went with prevailing SHRA
for most terminals this evening into Saturday morning. However, KAVL
should see drier conditions possible return by ~06Z or 07Z. Cigs
will once again lower to IFR to MVFR levels, with LIFR possible
again, mainly at KAVL and KHKY. Dense fog should develop again at
KAVL and KHKY overnight into daybreak Saturday so went with TEMPOs
for LIFR vsbys. Cigs should be slow to improve throughout Saturday,
with cigs lifting to MVFR by late morning or early afternoon and VFR
by early to late afternoon. Another round of TSRA should develop
Saturday afternoon and evening so went with PROB30s across the
terminals towards the end of the TAF period. Winds will be calm to
light and VRB across the terminals through early Saturday morning.
Winds will generally be E/ESE late Saturday morning into Saturday
afternoon before toggling NE late Saturday afternoon into Saturday
evening. Wind speeds on Saturday will generally be light with no
gusts expected, outside of SHRA/TSRA.
Outlook: Shower and thunderstorm chances, as well as associated
restrictions, linger into the weekend thanks to a stalled cold front
along the Carolina coast. Fog and low stratus are possible each
morning, mainly in the mountain valleys and any locations that
received heavy rainfall the night prior. A tropical system could
bring widespread restrictions and rain to at least a part of the
area early next week, but confidence remains very low at this time.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...AR/ARK
NEAR TERM...AR/CAC
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...AR

NWS GSP Office Area Forecast Discussion