Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 211449

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1049 AM EDT THU JUL 21 2016

A Bermuda high pressure pattern will persist across the region through
the end of the week, resulting in typical midsummer conditions. Hot
high pressure will strengthen this weekend, then a weak cold front
will approach from the northwest early next week.


As of 1030 AM EDT: Weak lobes of upper vorticity will continue to
cross the region from the north today between the prominent ridge
over the plains and the trough over the coastal waters. Slightly
deeper moisture continues over the southwest half, where showers
show greater coverage and temps are off to a slow start. Drier NE
sections have temperatures running above the previous forecast
trends and less precip - but more building SBCAPE along and near
I-77. Temperatures have been updated to boost NE sections, but SW
sections look fine on temperatures as a few breaks in the clouds are
developing. Will also boost PoPs slightly along and east of CLT
where mesoscale models show a bit more afternoon convection.
Anticipate a continued marginal severe storms risk - with thresholds
today of 55 dBZ to 26 kft and 60 dBZ to 23 kft, a bit less in higher
DCAPE areas over the eastern piedmont. Max temps should be just
above climatological normals in most areas.

Convection will decay late this evening with some lingering debris
clouds and then patchy morning fog overnight. Persistence is a good
forecast for overnight lows in the 60s mountains to lower 70s east.


As of 300 AM Thursday...The large, massive upper ridge will begin to
retrograde slightly, as a series of progressively stronger
shortwaves ride over the top of the ridge and into the Great Lakes
during the short term. It seems the models continue to trend a
little deeper with a developing longwave trough over the Northeast
states for this upcoming weekend. So as a consequence, they are not
advertising quite as strong of heat wave for our area, as previous
days. Still, expect above normal temps and lots of humidity. Staying
on the warm side of guidance, I still get heat indices in the 100 to
105 range Saturday and Sunday, but fewer pixels of greater than 105.
In any case, will continue to mention excessive heat possible in the
HWO. As for convective chances, the upper ridge will build slightly
eastward over the area Friday and Saturday. So shear will be weak
and convection should be isolated to scattered in nature, basically
normal for late July. However, forecast soundings show moderate to
high DCAPE. So pulse severe microbursts will be a threat each day.
Also, the latest GFS/CMC/NAM all show an MCV rounding the ridge and
dropping south from Ohio to the southern Appalachians Friday night
thru Saturday. If we do get an MCS from upstream that may be the


As of 315 AM Thursday...Another shortwave trough will cross the
Great Lakes on Monday, then another on Wednesday. These waves should
weaken the subtropical ridge over the Southeast states somewhat.
Although the medium range guidance diverges on to what extent, the
00z ECMWF showing a deeper eastern CONUS trough than the GFS by Day
7. At the surface, a cold front will gradually slide southeast
across the Ohio Valley and the central Appalachians Monday and
perhaps settle across the CWFA on Tuesday and lingering thru
Wednesday. So temps will trend back down toward normal and PoPs will
trend up with the front in the area. Instability looks decent every
day, but shear remains weak. So expect solid coverage each
afternoon/evening with only a marginal severe threat.


At KCLT: VFR conditions are expected through the period. Morning
cumulus is developing some bases in the 3 to 4 kft layer, but these
should lift with heating to 5 to 6 kft this afternoon. Light winds
will steadily shift SE. Winds will veer to the SW through the
period, generally 5 kt or less. Convection chances still look too
low to mention at this point, but the convection allowing models are
showing a slight uptick in early to mid afternoon coverage.

Elsewhere: VFR will continue through most of the period. Any shower
coverage has been quite sparse so far and will continue the featured
VCTS mention ramping up 17Z to 19Z across the mountains/foothills.
LGT/VRB winds late this morning are trending more NE, but should
veer around to SE this afternoon and eventually SW this evening, but
still light. Expect at least some MVFR fog to develop in the
mountain valleys and have introduced 5SM for KAVL.

Outlook: Expect fairly typical midsummer weather with scattered
afternoon and evening showers and thunderstorms through the weekend.
Morning fog and low stratus will be possible each day in the
mountain valleys and also in locations that received heavy rainfall
the preceding afternoon/evening.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High  95%
KAVL       High 100%     High 100%     High 100%     High  93%
KHKY       High  98%     High 100%     High 100%     High  95%
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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      95 1983     69 1974     71 2015     50 1966
                1952        1938        1999
                1934                    1983
   KCLT     101 1987     73 1880     78 1991     56 2007
   KGSP     102 1952     74 1974     79 1934     59 1966


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      96 1983     68 1985     71 1934     52 1966
   KCLT     100 1983     73 1938     78 2010     59 1947
                1952                    1883
   KGSP     101 1952     70 1985     79 2010     59 1904


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      92 2010     68 2000     70 2012     51 1895
                2005                    2011
                1987                    2010
   KCLT     101 2010     69 2000     79 2010     62 1947
   KGSP     100 1995     72 2000     77 2010     57 1911




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