FXUS62 KGSP 232346

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
746 PM EDT Tue Oct 23 2018

Dry high pressure will give way to an increase in moisture by
Thursday night as low pressure along the gulf coast moves east.
A rainy Friday will give way to just token shower chances Saturday
and Sunday.


As of 725 PM: Another quiet evening across the western Carolinas
and northeast Georgia. No changes.

High pressure will build into the area over the next 24 hours, while
a sharp upper ridge moves east into the Mississippi Valley. The
upper level moisture and cirrus streaming across the Deep South will
be shunted further south, and skies will clear gradually through
evening. Virtually clear skies will persist into Wednesday, expect
perhaps for some upslope driven cloud cover along the Tennessee
border. Though the arriving airmass will effectively drive a dry
cold front thru the area, and winds will veer to the NE and become
a bit more gusty. These winds should offset radiative cooling and
thus min temps will be slightly warmer than they were this morning,
but still a little below normal. Cirrus may increase again tomorrow
afternoon, ejecting from upper disturbances on the other side of
the ridge. Max temps will also be a couple degrees below normal.


As of 200 PM EDT Tuesday: The fairly pleasant weather for the near
term comes to a screeching halt as we move into the short term. Deep
upper trough off the East Coast will continue to move offshore, with
ridging building up the MS Valley ahead of a shortwave over the
western Plains. This latter feature will have merged with the
remnants of Willa, spreading copious moisture into TX. The remnants
of Willa will reinvigorate as a surface cyclone off the TX Gulf
Coast overnight Wednesday night, spreading moisture across the Gulf
states and into the SE.

Meanwhile, a cold surface high coming down the NW flow behind the
departing upper trough will be locked in place by the confluent flow
aloft and begin damming down the east slopes of the Appalachians in
a dry-onset Classical CAD scenario. These are usually pretty strong
events, especially once diabatic processes come into play, as will
be the case as moisture lifts into the Southeast from the coastal
low and is isentropically lifted over the cold dome in place. Cloud
cover will increase on Thursday and with the low-level CAA,
temperatures will take a nosedive, at least 10 degrees colder across
the Piedmont than what we'll see Wednesday. The damming will be
strong enough to delay onset of precip a little later than earlier
forecast, with precip not really spreading into the area until later
on Thursday and especially Thursday night. Despite the increasing
moisture, the CAA will be strong enough to keep overnight lows below
seasonal normals.

Friday will just be a, to use a technical term, yucky day. Cold and
miserable with precip overspreading the area and the very strong CAD
in place that might keep afternoon highs closer to seasonal normal
lows for this time of year. The coastal low will lift across the SE
and deepen off the NC coast late Friday (in a very winter-looking
Miller A-type pattern...but of course kind of a waste of a great
winter setup this early in the season) as the precip starts exiting
the area.

New QPF coming in is a little higher especially across upslope areas
of the SW mountains early Friday, and spreading across the NW NC
Piedmont Friday afternoon. Nothing of huge concern, but enough to
point to the potential for brief heavy rain. Other item of note is
the continued chance for some light snow across the very highest
elevations of the northern mountains (specifically Beech,
Grandfather, Mitchell...the typical locations). Just a dusting of


As of 300 PM EDT Tuesday: Average model agreement and therefore
confidence exists for the extended period. Wrap around moisture from
the coastal low will gradually diminish from south to north
throughout the day Saturday except for possibly lingering showers
near the TN border of the NC mtns. Temperatures will be on the
rebound, especially for the Upstate of SC and NE GA where temps will
approach 60 Saturday afternoon.

Broad northwest flow will continue through early next week with a
few disturbances likely passing over the region during this time
acting to enhance cloud cover and precip chances focused across the
mtns near the TN border. Each one looks to be progressively cooler
aloft with enough cold air filtering in for rain mixing with or
changing over to snow at times mainly across higher elevations,
especially late Monday into Monday night when 850 mph temps fall to
near 0 C and 500-1000 mb thicknesses fall to near 5400 m. Light snow
accumulations will be possible during this time, mainly for higher
mtn elevations. Outside of the mtns, partly cloudy skies will
prevail with near to slightly below average temperatures prevailing
Sunday through early next week.


At KCLT and elsewhere: VFR through the period. Thin cirrus overhead
will thin out and be shunted to the south overnight. Wind should
go calm or light NW as a weak front drifts east this evening. Some
valley fog or stratus may develop late tonight in the Little TN
Valley, but dewpt mixed out a bit more this past afternoon so it
appears less likely than last few mornings, and even less likely at
KAVL. After sunrise, could see a few gusts across the NC Piedmont
with some mixing, but wind should settle down to northeast by
midday. Sky should be clear for the balance of the day.

Outlook: Patchy fog and/or low clouds will be possible across the
mountain river valleys around daybreak Thursday. Otherwise, expect
VFR through Thursday. Precipitation and associated restrictions
will likely redevelop Thursday night into Friday or Saturday as a
low pressure system moves east along the Gulf Coast and transitions
to a coastal Atlantic low.

Confidence Table...

23-05Z 05-11Z 11-17Z 17-18Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% 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:





NEAR TERM...PM/Wimberley
LONG TERM...Munroe
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