Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 230600

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
200 AM EDT SAT JUL 23 2016

Broad deep layered high pressure will remain across the region
through early next week...with a general weakness developing over
the east coast on Monday. Moisture levels will gradually increase
across the western Carolinas and northeast Georgia by the middle of
next week as a weak cold front settles south into the area.


As of 150 AM, a couple of isolated weak convective cells are ongoing
across the southern Appalachians early this morning, so will
maintain a slight chance pop for a couple of more hours across the
mtns of northeast GA, SC, and southwest NC. Min temps should be
about a category or so above climo in most locations. Patchy fog
and/or low stratus will develop/continue within mtn valleys, and in
areas that saw heavy rainfall Friday.

Expect a repeat of the diurnal pattern on Saturday with mountain
convection slipping southward along the eastern periphery of the
upper ridge. The weak lee trough will persist over the foothills.
Dewpoints may be less conducive to mixing out on Saturday but there
will likely be less upper vorticity forcing. All in all, PoPs should
be similar to today or slightly less - with slowly moving scattered
mountain convection sliding S or SE. 850 mb temps will be a touch
warmer on Sat, with highs correspondingly warmer. The lower piedmont
areas could see heat index values of 100 to 103 but no advisory
appears to be needed.


At 145 PM Friday: On Saturday night and upper ridge will extend
across the southern tier of the USA. This ridge will persist over
our area into Monday. A surface ridge will be located east of the
Appalachians during the same period. Meanwhile, a cold front will
cross the upper MS River Valley, reaching the OH River Valley.
Although moisture will remain over our area, a relatively weak warm
nose aloft will limit instability. Although the models show slightly
better shear than in previous runs, it should still be too limited
to support organization convection. Steering flow now appears to be
slightly better, which should keep cells moving enough to limit
heavy precipitation coverage. The possibility of light downslope flow
east of the mountains may keep precipitation maximized over the
mountains. Although maximum temperatures will only run around 6 to 7
degrees above normal, moisture will support apparent temperatures
of 100 to 106 degrees east of the mountains both Sunday and Monday,
with the highest values in the Piedmont.


As of 130 PM Friday...A weakness in the ulvl subtrop ridge will be
maintained through the period as the Hudson Bay low is reinforced
with polar energy. This will allow a couple s/w trofs to swing east
and advance weak frontal bndrys toward the SE region. The models
disagree with the se/wrd extent of these bndrys...however a
persistent lee side trof and mtn top convg will provide the main
focusing for afternoon convection. The best llvl moist flux will
remain west of the fcst area...however pwats will hover arnd 1.7 in
each day as mid and high level moisture advects northeast.
Instability will be on the lower end...but enuf to produce efficient
rain rates and a few stg/svr tstms each afternoon. Pops favor the
higher elevations...where numerous activity will be possible. Less
coverage is anticipated non/mtns. Max temps will remain around
normal...but with high td/s apparent temps will feel about 4-5
degrees F warmer. Low temps will remain a couple degrees above


At KCLT and the Upstate SC terminals, expecting some MVFR visby this
morning at KGSP, which did experience some rainfall Friday
afternoon. Otherwise, VFR conditions are expected through the
period. Generally expect light S/SW winds to persist through the
period. Isolated to scattered convection is expected to develop once
again Sat afternoon, esp near the Upstate SC terminals, and PROB30s
are carried there from late afternoon into the evening. Cannot at
all rule out convection near KCLT either, but coverage should be a
bit more sparse in the Piedmont.

At KAVL/KHKY, another tricky forecast at KAVL, with the prospect of
a light surface wind once again preventing fog/low stratus formation
later this morning (as was the case yesterday). The preponderance of
the evidence suggests that a light wind will keep conditions from
crashing too harshly, but there`s still enough of a potential to
continue a tempo for 2SM/SCT003 from 10-12Z. The forecast for KHKY
is also a bit tricky, as heavy rain did fall there Fri afternoon,
and the temp/dewpoint spread was only two degrees at TAF issuance
time. Opted to include a tempo for 3SM/FEW004, but wouldn`t be
surprised if worse (or better) conditions are experienced there.
Otherwise, PROB30s for convection will be carried during the
afternoon/evening, as cells should fire once again along lee trough
and across the high terrain.

Outlook: Scattered/isolated afternoon and evening showers and
thunderstorms will continue across the mountains/piedmont through
early next week. 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...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High  97%     High  94%     High 100%     High 100%
KAVL       Med   73%     High  84%     High 100%     High  94%
KHKY       High 100%     High  94%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High  97%     High  94%     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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