Areal Flood Advisory 310, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
221 PM EST Sat Dec 15 2018

.SYNOPSIS...
Low pressure will gradually lift north and then east of the area
tonight and tomorrow. As it does, drier air associated with broad
high pressure will spread over the region and linger through
midweek. Another low pressure system is expected to impact the
Southeast towards the end of next week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 100 PM: Main update for the 18Z TAF issuance along with minor
tweaks to sky cover, PoPs, and temperatures to coincide with latest
trends as the rest of the near term forecast remains on track.

Otherwise, as sfc low continues to move northeasterly up through
TN/KY, latest satellite imagery illustrates expansive cloud cover
across the southeast, with pockets of drier air creating some breaks
in the low cig shield as rain continues to taper off. 925-850mb flow
will veer somewhat as the day continues, gradually shutting off the
upglide over the wedge and introducing slight cold advection.
However the CAA is slow to set up and does not appear strong enough
to erode the wedge before the end of the day. Thus, I hit the cloud
cover pretty hard in the forecast, favoring the guidance that
depicted overcast lingering longer. Similarly, temps have been kept
on the cool end of the guidance envelope, but returning to about
normal.

With the upper low center moving along the spine of the
Appalachians, both the NAM/GFS depict some shallow sfc-based
instability developing beneath it, but equilibrium levels are not
very high or cold. Thus thunder looks unlikely even if convection
does develop. This does warrant a secondary uptick in PoPs in our
western zones this aftn/evening. Furthermore, as the system moves
north of the area tonight, flow continues to veer to upslope along
the Tenn border, and eventually does introduce downsloping over the
wedge beginning around midnight. This will induce clearing, albeit
slowly. The NW NC Piedmont likely will see abundant cloud cover
until after sunrise Sunday. Min temps will fall back a few degrees
under CAA, with occasional wind gusts, though still remaining a
couple categories above normal.

Some of the aviation guidance depicts areas of dense fog developing
for a time tonight over the northern zones along and east of the
Escarpment, where the wedge airmass becomes extremely shallow as
erosion occurs, and where soils remain saturated from snowpack and
today's rain. This development cannot be ruled out but presently
confidence in widespread dense fog is not great enough to warrant
any headlines.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 115 PM EST Saturday: Lingering showers will persist across the
nrn NC mtns to begin the period which will likely transition to a
ra/sn mix before daybreak with no snow accum. The overall
synoptic pattern will begin to change Mon with a developing h5
ridge to the west and a broad hipres beginning to build into the
fcst area. This will make for mostly clear skies Mon and max
temps shud have no problem reaching the lower to mid 60s outside
the mtns as llvl thicknesses remain relatively high. There will
be a transiting upper trof with some measure of a cP airmass
mix during the afternoon...however the degree of insol and
downsloping will keep temps quite mild. On Tue...the sfc high
will establish itself across the Carolinas and mid/Atl which
will advect lower theta/e air within n/ly flow. So...maxes will
drop a bit...yet likely remaining right arnd normal or just
above over most locales. Lows each night will drop below normal
by a few degrees as good rad cooling conds set up in a dry
column.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 215 PM EST Saturday: Upper-level flat ridging will persist into
Wed as sfc hipres weakens and moves off the Al coast. This will make
for a dry day Wed with seasonal temps. The atmos remains progressive
Thu thru the period as phasing btw nrn and srn stream ulvl jet cores
develop a deep latitude trof and swing it across the FA thru Fri
night. There is better confidence in the overall pattern as the GFS
has come in line with the other op model solns...however the GFS
upper low center still remains north of the other guidance. This
difference wont make much difference in the sensible wx fcst
however.

With the development of a broad Miller-B type sfc low Thu...the flow
over the FA will remain quite warm which is evident in the
evolution partial thicknesses. There could be some mixed ra/sn early
Thu associated with a weak insitu wedge across the nrn zones...but
it wont be cold long enuf to expect sigfnt accum. A rainy day is
on tap thru Thu as the sfc low occludes and takes it/s time pulling
north into Fri. Total precip amts don/t look too threatening for
now...but there may some low-end hydro events depending on the
actual longevity and degree of moisture transport to the system.
As the upper trof swings over the area Fri night...the mtns will
likely change over to all snow with low-end accums likely. Max temps
will remain seasonal. Min temps will be held a little abv normal as
the atmos remains moist through a deep layer.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Despite short-lived improvement to VFR/MVFR
in some locations as pockets of drier air continue to mix into the
expansive low cig cloud shield across the Southeast, primarily
IFR/LIFR continues at the TAF sites this afternoon, as isolated
showers continue to push NNE across the area and patchy areas of fog
persist. Would not entirely rule out isolated showers returning
tonight (mostly mountain areas) as upper low pressure system
supports additional forcing, but given lower confidence on
timing/location, have kept with VCSH into tonight. Latest guidance
continues to suggest the gradual retreating/weakening of insitu
wedge in place as CAD infiltrates in behind the exiting system.
Thus, anticipate overall MVFR/IFR cigs persisting through the
overnight hours, with periods of MVFR fog. Light winds will continue
through the rest of today and into tonight, gradually shifting from
NE to SW as the wedge weakens.

On Sunday, expect conditions to return to VFR as drier air
infiltrates in from the west. SW winds AOB 5 are expected, NW at
KAVL.

Outlook: VFR conditions will persist through the middle of next
week. The main exception will be lingering areas of upslope-driven
lower clouds near Tennessee border west of KAVL on Sunday.

Confidence Table...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       Med   68%     High  87%     High  93%     High  96%
KGSP       Med   75%     High  92%     High 100%     High 100%
KAVL       Low   56%     High  91%     High  80%     High  95%
KHKY       Med   69%     High  83%     High  83%     High 100%
KGMU       Med   72%     High  92%     High  85%     High 100%
KAND       Med   77%     High  94%     High  98%     High 100%

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

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Flood Watch until 6 PM EST this evening for NCZ033-035>037-053-
     056-057-063>065-068>072-082-501>510.
SC...None.

&&

SYNOPSIS...JPT
NEAR TERM...SGL
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...SGL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
528 AM EST Sat Dec 15 2018

GAZ010-017-018-026-028-029-NCZ048>052-058-059-062-SCZ001>014-019-
161030-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Madison-Yancey-
Mitchell-Swain-Haywood-Graham-Northern Jackson-Macon-
Oconee Mountains-Pickens Mountains-Greenville Mountains-
Greater Oconee-Greater Pickens-Greater Greenville-Spartanburg-
Cherokee-York-Anderson-Abbeville-Laurens-Union-Chester-Greenwood-
528 AM EST Sat Dec 15 2018

This Hazardous Weather Outlook is for northeast Georgia, western
North Carolina and upstate South Carolina.

.DAY ONE...Today and tonight.

Heavy rain will end today, however, high water levels may linger
along both main stem rivers and smaller rivers and streams through
the weekend.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.

NCZ033-035>037-053-056-057-063>065-068>072-082-501>510-161030-
Avery-Alexander-Iredell-Davie-Buncombe-Catawba-Rowan-
Southern Jackson-Transylvania-Henderson-Cleveland-Lincoln-Gaston-
Mecklenburg-Cabarrus-Union-Caldwell Mountains-Greater Caldwell-
Burke Mountains-Greater Burke-McDowell Mountains-Eastern McDowell-
Rutherford Mountains-Greater Rutherford-Polk Mountains-Eastern Polk-
528 AM EST Sat Dec 15 2018

...FLOOD WATCH IN EFFECT THROUGH THIS AFTERNOON...

This Hazardous Weather Outlook is for piedmont North Carolina and
western North Carolina.

.DAY ONE...Today and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flood Watch.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.