Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 181759

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1259 PM EST Thu Jan 18 2018

High pressure will overspread the region and drift offshore by early
Saturday, with temperatures increasing to above average through the
weekend. Another cold front will bring precipitation to the
Carolinas early next week.


As of 1245 PM EST: Water vapor imagery shows the closed low off the
east coast rapidly departing over the offshore waters. Meanwhile, a
closed low pressure system is moving east across Texas this
afternoon, with shallow ridging developing in between across the
southeast. The resulting full sunshine is permitting temperatures to
gradually rise above freezing, with melting of the snow/ice
underway. Decisions will be made soon on upcoming advisories or
statements for black ice potential tonight.

The closed southern tier system will move across the lower MS River
Valley tonight through Friday. The pressure gradient across our
region will steadily relax through the near-term with a warming
westerly, downslope flow developing, and a weak lee trough
persisting at the surface. Good radiating conditions tonight will
produce more teens and 20s min temps, and maxes will rebound above
normal in most locations by tomorrow afternoon to complete the
melting of any lingering snow.


As of 230 AM EST Thursday: The short term forecast looks quiet, as
an upper ridge builds over the eastern states in an amplifying
pattern. There is an interesting southern stream compact low that
lifts thru the building ridge, but has little moisture to work with.
The models are still in disagreement on exactly how the low will
track and eventually get sheared out. The GFS is the fastest and
keeps a closed low the longest. It brings some mid and high clouds
thru the area on Saturday, but otherwise, no sensible wx impacts.
The NAM and ECMWF are slower lifting the low out and keep it south
of the area near the Gulf Coast. So other than perhaps a little
increasing clouds on Saturday, it should be mostly clear thru the
period. Temps will be on a warming trends, as the ridge builds.
Highs near normal Friday, and a couple categories warmer on
Saturday. Lows slightly below normal Friday night, but a couple
categories warmer Saturday night.


As of 200 AM EST: The area will be under the influence of surface
high pressure and an upper ridge to start the medium range Sunday
morning, with relatively warm and dry conditions persisting through
Sunday and into early Monday morning. The next system will approach
the area Monday afternoon and evening, with a strong upper and
surface low propagating across the Great Lakes. Pre-frontal moisture
ahead of a cold front trailing the surface low will increase on
Monday, with the QG-induced lift from the upper low inducing QPF
response in our forecast area Monday some time around 18Z. The
system looks quite dynamic in global models and produces shear
profiles that would be quite conducive to organized severe weather
if the instability were not severely limited by the "wet noodle"
soundings at all sites in our CWA. The bulk of the precip and the
best forcing associated with the front will likely arrive overnight
Monday through early Tuesday morning, a timeframe that should also
prevent any diurnally-enhanced instability. Model agreement on the
lack of instability above 100 J/kg is striking, though this could
change if the timing of the front changes. The remains slight
disagreement in the 00Z model suite over when the precip will come to
an end Tuesday, though all global models have clearing with drier
air arriving by Tuesday afternoon. As some cold air arrives behind
the front in the NC mountains Tuesday morning, expect a transition
to rain/snow mix of briefly all snow in the higher terrain of NC.
All other locations will receive liquid precip for the duration of
the event.

The balance of the medium range remains quiet, with a dry
continental airmass moving into the area as a surface high over the
OH River Valley expands towards the northeast. Unusually warm
temperatures ahead of the front will moderate back towards average
by the end of the next work week.


At KCLT and Elsewhere: VFR conditions will continue through the
period. Winds will be light from the WSW to SW across the foothill
and piedmont sites, as a lee trough persists through the period,
with continued NW to N flow at KAVL and occasional early afternoon
gusts. Expect clear skies through tonight, with just a few cirrus
returning late in the period.

Outlook: Dry/VFR condition are expected to continue through the
weekend, with moisture returning ahead of a strong cold front
early next week.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
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:


GA...Winter Weather Advisory until 2 PM EST this afternoon for
NC...Winter Weather Advisory until 2 PM EST this afternoon for
     Winter Weather Advisory until 1 PM EST this afternoon for
SC...Winter Weather Advisory until 1 PM EST this afternoon for


LONG TERM...Carroll/Wimberley
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