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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 270538
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1238 AM EST Sat Feb 27 2021

.SYNOPSIS...
A front will remain stalled south of the region into Saturday as
high pressure remains to the north. Gulf moisture will continue
flowing north over the front through tonight. The boundary will
retreat northward as a warm front through Sunday, with warmer
temperatures gradually returning. Another cold front will cross the
area from the northwest Sunday night through Monday with abundant
moisture. Brief drying is expected Monday night into Tuesday before
unsettled weather likely returns to the region through the middle of
the week.

&&

.NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
1230 AM Update...No sigfnt changes made to the fcst as the atmos
remains fairly steady state with low clouds and weak winds. Periods
of IP are persisting across the NC piedmont and foothills with
little to no accum over the next few hrs as temps remain in the mid
to upper 30s.

As of 1000 PM Friday: Rain is still ongoing across much of the cwa,
with parts of the southern tier gradually drying out. In
coordination with WFO RNK, decided it was best to expire the
Advisory due to above freezing temperatures. Expect isentropic lift
to allow ongoing precip along the wedge boundary into the overnight
period. With the sfc high hovering off the New England coastline,
the wedge is still holding strong across the cwa with winds steadily
coming out of the N and NE. 850 mb winds are steadily coming out of
the S to SW at around 40 kts, but will gradually help erode the
wedge as a warm front lifts across the area from south to north
overnight into early Saturday. Winds will likely veer to the S and
SW tomorrow once the warm fropa occurs. This will set the area under
the warm sector and thus, temperatures will rise 10+ degrees
compared to today for Max T`s on Saturday as the WAA filters in. The
southern stream energy aloft will lift to the north with the sfc low
riding underneath as it moves across the lower MS and TN Valleys
through the northeastern CONUS tonight into Saturday, which will
lead to a much drier conditions compared to today. Cloud cover
should remain strong, but a few peaks of sunshine can`t be ruled out
during the day Saturday. Some lingering upslope showers should
persist across the northern Blue Ridge and southern mountains, as
well as the adjacent foothills on Saturday, but should remain mostly
dry outside of those locations. Temperatures will remain above-
normal for tonight as we stay socked in under cloudy skies, but
should slowly rise during the overnight period due to the
approaching warm front and eventual fropa. Tomorrow will remain
above normal as most locations will end up in the 60s and 70s across
much of the cwa for Max T`s tomorrow.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
As of 200 pm Friday: The upper air pattern will remain more or less
steady-state through the first half of the short term, with ridging
persisting off the East Coast and a trough over the interior West,
before a complex split flow pattern evolves late in the period. For
our forecast area, this means deep SW flow will persist though much
of the period, with a warm sector regime yielding well-above normal
temps (maxes 10-15 degrees above climo, mins 15-20 degrees above),
nocturnal low clouds, and low end shower chances. By Monday, a
potent northern stream short wave trough will progress across
southeast Canada and the northeast Conus, allowing frontal boundary
to sag into the CWA, bringing likely to categorical probabilities of
rain from late Sunday night into Monday morning. The latest guidance
is in general agreement in depicting a well-forced frontal zones
into the TN Valley and southern Appalachians which becomes less so
as it sags southeast into the Piedmont. Meanwhile, short term
guidance depicts barely >0 values of CAPE in the warm sector. As
such, current indications are that any heavy rainfall potential will
likely be confined to the NC mountains, while the severe wx threat
appears minimal in light of decreasing forcing/unfavorable frontal
orientation, very low instability and less than ideal shear
parameters given the meager buoyancy. The front will likely sag
south of the area by the end of Monday, yielding generally dry and
cooler conditions heading into the extended.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 210 pm Friday: Forecast confidence is relatively high for
roughly the first 24 hours of the extended range. After that,
everything goes to pot in the anticipated complex split flow
regime. There are essentially two model camps for the latter half of
next week: the GFS camp and the ECMWF/Canadian camp. The latter camp
is more potent with a mid-week southern stream disturbance, while
the GFS is more sheared/out and suppressed. As such, the GFS is
almost completely dry for our area during the Tue night/Wed time
frame, while the other model camp develops the next round of
widespread precip during this time frame. There`s enough of a signal
there to advertise solid chance pops, but would like to see more of
a consensus before going any higher than that. If precip does
develop early enough Wed, there may be, as usual enough cold air in
place to support a brief/low impact winter weather event across the
mountains Wed morning. By Day 7, the GFS is more progressive and
much stronger with a southern stream upper low originating from the
Four Corners region...also maintaining a distinct split flow pattern
while the ECMWF/Canadian camp begins to phase the flow be the end of
the forecast period. As such, the GFS has a blockbuster storm system
impacting the forecast area by next Friday, while the other camp is
essentially dry. Again, there`s enough in the guidance to support a
small pop, but 20-30% is as far as we`re willing to reach at this
point. Temps are forecast to return to more sane levels during the
medium range, generally within a category or so of climo through the
period.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
At KCLT and elsewhere: Low-end flight cats will continue or develop
this morning across all TAF sites as a shallow sfc wedge begins to
weaken and moisture levels remain high. Expect KCLT to remain
IFR/LIFR thru late morning and introduced a TEMPO VLIFR aft 08z with
light rain affecting the area and likely lowering CIGs. Conds
improve slowly by the afternoon, with most sites going VFR, as
hipres works across the OH Valley and mixes in llvl dry air.
Northeasterly winds will switch to a sw/ly direction by mid morning
as the sfc wedge continues to breakdown and the synoptic pattern
favors an Atl ridge axis.

Outlook: Scattered to numerous showers with associated flight
restrictions are expected to return Sunday and linger into early
next week. Drier hipres will build back into the area by Tuesday.

Confidence Table...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       High 100%     High  82%     High 100%     Med   75%
KGSP       High 100%     High 100%     High  94%     High  85%
KAVL       High 100%     High 100%     Med   78%     High  95%
KHKY       High 100%     High 100%     High 100%     High  90%
KGMU       High 100%     High 100%     Med   78%     High  90%
KAND       High 100%     High 100%     Med   72%     High  90%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...CAC/SBK
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...SBK