Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 212332

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
732 PM EDT THU JUL 21 2016

Bermuda high pressure and upper level ridging will remain in control
of the weather over the next few days. This will result in well
above normal temperatures...before a weak cold front pushes in from
the north early next week.


As of 730 PM: Overall convection continues to diminish across the
CWFA. However, colliding outflow boundaries are keeping strong
convection near GSP and AVL. Expect the overall downward trend to
continue, but with isolated better coverage where mesoscale
interactions dominate. Have updated PoPs to reflect these trends.
Still cannot rule out an additional severe storm or flash flood
warning before dissipation.

Otherwise...a broad upper ridge will remain centered over the
southern plains through Friday while a trough axis lingers just off
the Atlantic coast. Patchy fog development is possible wherever rain
falls and also the lower mountain river valleys - particularly from
the French Broad Valley and valleys farther southwest.

A little less in the way of upper energy moving southward east of
the ridge into the Carolinas is expected on Friday. Convection will
develop later in the day and primarily over the higher ridges mid
afternoon - with some survival into the adjacent foothills or
perhaps piedmont toward evening. Better insolation, weak downsloping
flow, and less moisture in profiles should lead to higher temps
Friday afternoon than Thursday. More dewpoint mixout is possible as
well, so heat index values should be capped around 100 in the
hottest areas.


At 130 PM Thursday: On Friday night and upper ridge will build east
front the plains across the southern Appalachians, completely
covering our area by late Sunday. Before this ridge overspreads the
area, weak lobes of vorticity may move southeast over the mountains
on the west side of a coastal trough. The models show modest
instability and weak shear each day, supportive of convection, but
not organized storms. Weak steering flow may support locally heavy
rainfall however, especially if cell can train over the same areas.
Temperatures will warm from around 3 degrees above normal to around
6 degrees above normal. Lingering moisture will allow apparent
temperatures to approach 102 degrees in the upper Savannah River
Valley on Friday, and 100 to 105 degrees from the foothills to the
Piedmont on Saturday.


As of 115 PM Thursday...Not much change needed to the going fcst.
Strong ulvl ridging will continue into Mon then slowly break down as
a couple H5 s/w trofs swing across the Glakes region. This will
bring a sfc front into the fcst area late Mon or early Tue. With
little flow aloft this front will become stationary and reinforced
somewhat on Thu as another weak bndry settles in from the north. As
far as the sensible wx goes...sct to num afternoon showers and
thunderstorms will be the norm...esp across the higher
enhanced llvl lift provides broad focusing in a moderately unstable
yet low sheared environment. Max temps were brought down a degree or
two most locale Mon with increasing cloud cover possible...however
heat index values shud still reach adv levels across the srn half of
the CWFA. With weakening in the upper heights and lessening deep
layered subs...max temps will return closer to normal levels Tue
through the period.


At KCLT: Convection has moved out of the area and low clouds are
dissipating. VFR conditions will continue overnight through Friday
with light S to SW surface winds. Profiles will be a bit drier on
Friday and no convection will be mentioned through the period.

Elsewhere: Convection is dissipating overall, but colliding outflow
boundaries are keeping ongoing near KGSP and KAVL. Expect activity
to end this evening, but held onto a brief mention in the TAF. Light
S to SW winds become calm or light and variable overnight. KAVL will
be the exception with light NNW wind. Fog will be possible overnight
at any location where rain fell, but with chances best in the
mountain river valleys. The MOS is hitting KAVL especially hard, but
it has not performed well of late. Will still feature IFR fog after
09Z but not hit dense fog hard yet. KAVL has the best chance of
seeing convection Friday, so only mention PROB30 there. Surface
winds will become more SW but remain less than 10 kt throughout,
with morning NNW flow at KAVL turning SSW for the afternoon.

Outlook: Expect 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 receive heavy rainfall the
preceding afternoon/evening.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High  83%     High 100%
KAVL       High 100%     High  83%     High  95%     High 100%
KHKY       High 100%     High 100%     Low   43%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High  83%     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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