National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 210307
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1007 PM EST Mon Jan 20 2020

.SYNOPSIS...
Cold Canadian high pressure will bring below normal temperatures
through the middle of the week. Temperatures gradually return to
near normal late in the week. The next cold front approaches from
the west on Friday bringing the potential for a wet start of
the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
At 1002 PM...Still seeing light returns on the KMRX radar and
satellite imagery shows plenty of low clouds banked up against
the higher terrain on the NC/TN border, so expect there is still
some light snow or flurries falling on the TN border. The fcst was
updated to account for this. Backwards trajectories aloft show a
moisture source around Lake Huron, so there is some Great Lakes
connection helping out. The low level flow being from the N to NNE
is actually more favorable for the Smokies up to Madison County,
and less so for the nrn mountains. As we get past midnight, though,
the moisture source is cut off, so the activity should move more
southwest down the chain as the flow goes more NNE. Not seeing
any radar activity underneath the clouds that formed in the upper
French Broad valley, and the new guidance has backed off, so we
will cut back on the small area of low precip chances on the srn
slopes. Temps were running ok, but the dewpt trend was a bit drier
than fcst.

Meanwhile...we continue to watch a small, dynamic, yet
moisture-starved upper low swirling toward us on satellite imagery
with much interest. Problem might be...just how moisture-starved
with it really be? It is not hard to imagine a slightly better
blob of moisture coming down across the southwest mountains, north
GA, and western Upstate during the early morning hours to around
daybreak, such that we are able to squeeze out some snow flurry
activity. In fact, radar shows a small area of light returns that
was moving down over the southeast corner of TN. Have amended the
fcst to put that in during the early morning hours, but think it
will be gone by daybreak.

Otherwise...a cold evening is in store as high pressure works in
from the NW...however winds will weaken somewhat and offset any
significant wind chill issues overnight. Expect min temps in the
teens across the mtn valleys and lower 20s outside the mtns.

Another cold day is in store Tuesday yet with less wind as the
pressure gradient loosens. The dense morning airmass will be hard
to thermally modify with continued northerly flow...so expect max
temps remaining about 10-15 degrees below normal.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 130 PM MLK Day: A sharp upper ridge will replace the departing
shortwave trough early Wednesday. Surface high pressure will shift
east, both features progressing as a deep trough is carved out across
the Plains. Deep dry air will persist over the FA under an initially
northeast flow, which veers to a more easterly direction by the end
of the period Thursday evening. Moisture with the developing frontal
system most likely will remain too far west of our area to warrant a
mentionable PoP until later Thursday night. Temps will be 7 to 10
degrees below normal Wednesday morning, moderating a bit thereafter,
but still a few degrees below normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 200 PM MLK Day: A cutoff upper low is progged to develop within
a deep trough over the central US around the beginning of the medium
range; the low appears likely to track through the lower Ohio Valley
Friday and early Saturday. The GFS, which had depicted a slower
progression of this system as it entered our area, has trended toward
the Euro/Canadian camp, but remains the farthest north with its low
track. Confidence in timing the return of precip to the FA has
increased, as occluded front crosses the area Friday. With the
arrival of warm air aloft, and the expectation that cold/dry air will
be in place at the sfc from the midweek high pressure, there`s still
potential for a wintry mix that morning, in the middle to higher
elevations of the mtns along with the I-40 corridor of the northwest
NC Piedmont. The main difference in the prog soundings between models
is how much wet-bulbing occurs. For now the fcst reflects a warm nose
cooling as the precip picks up, but still enough sfc warming by late
morning to turn most areas back over to rain. Can`t rule out a brief
in-situ wedge-like event for a portion of the area; model
blend-derived temps are several degrees below climo on Friday as it
is, but could go lower.

Northwest flow on the back side of the system will induce upslope
precip Saturday, which changes to almost all snow Saturday night.
Depending on how long the moisture remains available--or how well the
Great Lakes connection is--these showers could continue through
Sunday. Mins are expected to remain a bit above normal next weekend,
with maxes around normal.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: VFR through the period at all TAF sites. Wind
will remain N to NE overnight and into Tuesday morning. The
passage of an upper low will bring a mostly mid-level cloud deck
across the region during the early morning hours on Tuesday, but
the cloudiness should move off to the east during the mid to late
morning hours. In its wake, only scattered high clouds with a few
northerly wind gusts, from roughly 16Z onward.

Outlook: VFR conditions persist through at least Thursday under deep
and dry high pressure. The next chance for restrictions will not be
until Friday when moisture returns ahead of the next weather system.

Confidence Table...

            03-09Z        09-15Z        15-21Z        21-00Z
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:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...PM/SBK
SHORT TERM...08
LONG TERM...08
AVIATION...PM