Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 270601

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
201 AM EDT FRI MAY 27 2016

Moist southerly flow will lead to continued warm temperatures and
mainly afternoon chances of showers and thunderstorms today. After a
dry day on Saturday, a period of cooler and wetter weather may
develop late in the weekend through early next week as Atlantic low
pressure moves toward the South Carolina coast.


As of 150 AM EDT, A 500 mb ridge will remain over the southeast
through the near term period, but with weak low development off the
FL coast north of the Bahamas through tonight. Under the high
pressure over our area, mainly mountain convection is expected today
with showers triggering in the southern mountains in upslope flow
this morning and then better ridge top showers and thunderstorms
this afternoon with heating and low level wind convergence. Mountain
SBCAPE values should again rise into the 1000 to 1500 J/kg range
this afternoon. The severe potential will be relatively low but weak
steering flow will likely produce some heavy rainers. Will feature
fairly solid precipitation chances over the mountains and taper
these off quickly farther east. Maxes will be about a category above
climo again today under partly cloudy skies.

A band of dry mid level air should work inland from the coast
tonight. Any lingering evening PoPs over the mountains should taper
off fairly quickly. Mins will remain above climo, but with better
radiating conditions developing over the low piedmont late in the


At 230 PM Thursday, on Friday evening an upper ridge will be over
much of the east coast, while an upper trough will be upstream over
central and wester USA, and an upper low associated with a potential
tropical system will be northeast of the Bahamas. The models move
the coastal upper low to the SC coast by Saturday evening, while the
upper ridge weakens over the western Carolinas and northeast
Georgia. The upper low is shown to move very little over coast SC
through Sunday.

At the surface, moisture is expected to remain over the western
Carolinas and northeast Georgia on Friday evening, while areas to
the east remain dry ahead of the approaching coastal surface low.
the drier air appears to spread west over our area by Saturday
morning, persisting through the day. By Saturday evening the models
bring moisture associated with the surface low inland toward our the
southeastern portion of our area, spreading it toward the mountains
by Sunday morning, and then over the mountains during the day.
Instability will be waning Friday evening, and and modest at best
until Sunday afternoon, when instability increases over the
Piedmont. Precipitation will be rather reserved due to limited
vertical lift, and maximized mainly over the mountains.

Temperatures will initially run slightly above normal under the upper
ridge, then will exhibit a slightly reduced diurnal range as the
moisture arrives.


As of 145 PM Thursday...Forecast confidence remains below avg for
the ext range. The op models continue to diverge wrt the track of
the eventual subtrop or trop low beginning Sun night. The GFS has
had varying ideas with this system and now brings the low onshore
north of Charleston. The track thereafter is odd looking with a jog
to the SW then up the SRV as it gets caught up in a broad ulvl trof.
The EC on the other hand has been consistent with keeping the low
track aligned along the Atl shoreline as a more acute s/w pulls it
NE of South Carolina through the period.

The GFS soln would be quite moist and more unstable than the EC the BR area would see prolonged moist upslope flow likely
leading to hydro issues. Scattered afternoon and overnight general
thunder is probable in a deeply moist theta/e column with the
passage of any mlvl pockets of dpva. With the GEFS mslp spread
reaching high levels by Sun eve...the GFS op soln will be given less
weight than the EC. Thus...will continue with chance pops non/mtns
and low likely pops across the BR escarpment through the period. Max
temps could be tricky as well with varying direc/intensity flow and
airmass mixes possible. For now...will keep most the FA a little
below normal with the ne/rn zones a couple degrees below that. Mins
shud avg a few degrees above in high column rh and nocturnal


At KCLT, a scattered VFR cloud layer will linger overnight around 6
to 7 kft. Scattered bases will lower with heating and convective
cloud development through the day. Brief cigs will be possible at
times, but SCT conditions are expected on average. The cumulus will
thin with the loss of heating through evening. Precipitation chances
appear small given some capping aloft and the lack of a significant
trigger. Light south to southeast flow will briefly pick up from the
SSW with mixing today, but with speeds generally less than 10 kt.

Elsewhere, SCT to BKN VFR clouds at 6 to 7 kft will be predominant
through the period, with some lowering today with heating and
convective cloud development. Brief MVFR fog will be possible at
KAVL and KHKY with enough breaks in the clouds early this morning.
The best chance of thunderstorms this afternoon will be near KAVL
with southeast upslope and wind convergence. KHKY will also see a
small afternoon chance. Will keep the Upstate TAFs dry for now given
just a bit more capping and less of a trigger, but isolated nearby
convection will be possible from mid to late afternoon. Clouds will
thin and scatter through evening as deeper drying pushes in from the
east. Expect mainly southerly flow through the period at less than
10 kt.

Outlook: Mainly VFR conditions will prevail through the period, but
patchy morning fog chances continue at KAVL. Scattered afternoon
SHRA/TSRA coverage will return on Sunday, with increasing chances
into early next week.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  97%     High  94%     High 100%     High 100%
KHKY       Med   73%     High  89%     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 schedule 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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