Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 220558

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
158 AM EDT Wed Mar 22 2017

A cold front will move through the area later tonight, increasing
the chances for widespread showers and thunderstorms. A few of the
thunderstorms could be severe. Cooler air will return behind the
front to end the work week before another frontal system approaches
the area next weekend.


As of 150 AM EDT Wednesday...The remnant stratiform precip shield
associated with a decaying MCS continues to cross the area over the
next couple hours. From there, it looks like PoPs really taper off,
as low level flow picks up out of the north and advect cold, dry
air. Temps are still running warmer than the forecast trends,
despite the overturned air mass from previous convection. I have
updated the temps/dewpts with CONSshort thru daybreak. PoPs were
adjusted with CAMPoP.

With any broad frontal boundary progged to push through in the
early morning hours, I am somewhat cautious about advertising a
total "scouring" of low-level moisture. However, essentially all
guidance sources, including MOS, depict the low clouds pushing out
by daybreak, and cooler and drier conditions lasting thru Wednesday.
GFS still tries to develop a little instability over NE GA, but
currently this looks to be an outlier. All precip mention has been
dropped. Sunshine and gradual downsloping should permit high temps
near normal.


As of 2pm EDT Tuesday:  GFS and EC models in good agreement on
synoptic pattern transitioning Wednesday evening to Friday from
northwesterly flow with dry, cool low-level advection to a ridge
centered over the CWA by Friday afternoon.  Dewpoints begin to
improve Friday afternoon as surface high pressure center moves
eastward off the coast and low-level flow veers from easterly to
southeasterly, beginning the southeasterly advection of
moisture into the area.

With a dry boundary layer and ridging aloft, there will be little
chance for precipitation Wednesday night through Friday, with only
an outside chance for some orographic-related showers in far western
parts of the CWA.  Main issue will be chances for frost/freeze
Thursday and Friday mornings.  Current lows show freeze possible
with frost likely for western parts of North Carolina, with less
potential for Piedmont areas.  Drier air and few clouds northeast of GSP
leads to lower forecast lows to the northeast with CLT possibly
reaching low to mid 30s Thursday morning and mid to upper 30s Friday


As of 205 PM EDT Tuesday: the medium range fcst picks up at 00z on
Saturday with upper ridging centered over the SE CONUS and a
southern stream closed upper low moving across the southern plains.
Over the next 24 to 48 hrs, the low will approach the fcst area and
as it does, it will lift northward and up over the ridge. As it
does, it`s also expected to deamplify and open up as it rides up the
ridge. As we move into early next week, another H5 shortwave will
approach the CWFA from the west. It also appears to deamplify as it
approaches the CWFA.

At the sfc, broad high pressure will be centered well offshore with
moist SLY flow over the region. By early Sunday, a vigorous low will
lift NE towards the Great Lakes and push a moist warm front over the
CWFA. The cold front associated with the low, looks like it will
largely washout as it lays across our northern fringe early Monday.
As we move into Tuesday, another sfc low follows a similar track
towards the Great Lakes and brings another cold front to our
doorstep by the end of the period. As for the sensible wx, POPs
steadily ramp up from the west on Sat with likely POPs over half of
the CWFA by Sunday morning. Some drying is expected on Monday,
however POPs increase again on Tuesday with the approach of the next
frontal system. Temps start out above normal and remain above normal
thru the period.


At KCLT and elsewhere: Dissipating remnants of last evening`s
convection continues to shift east, with rain ending at all TAF
sites by 07z or 08z. N to NE winds will increase as a cold front
sags south of the area. This flow should advect some drier air into
the area and with mixing and lingering mid and high clouds, should
limit fog development. However, given the wet ground at all sites,
periods of light winds with clearing skies may result in patchy
ground fog, that could impact any of the airports thru daybreak.
However, confidence is too low to mention at this time, and whatever
does develop is not expected to be persistent. The increased mixing
may actually produce IFR or MVFR stratus cigs occasionally. The site
that the models hit hardest with that is at KAND, where I will put a
tempo for MVFR cigs. After daybreak, skies should clear and NE winds
will become marginally gusty, especially at the NC sites, with gusts
continuing thru the afternoon.

Outlook: Low level moisture begins to return from the south Thursday
thru Friday, resulting in a gradual increase in shower chances and
low cigs into the weekend.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High  99%     High 100%     High 100%     High 100%
KGSP       High  89%     High  94%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High  91%     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:




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