Area Forecast Discussion
Issued by NWS Greer, SC

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665
FXUS62 KGSP 231504
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1104 AM EDT SAT JUL 23 2016

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1045 AM EDT, isolated shower development is already starting
in the SW mountains, and the latest HRRR runs have a good handle on
this and also depict slightly better SHRA/TSRA coverage east of CLT
this afternoon. Thus, the main two adjustments are slightly better
chance PoPs in both of those areas for the afternoon hours and minor
associated QPF adjustments. Temperatures look on track with the
latest obs and sounding thicknesses so no adjustments will be needed
with heat index capping out around 103 in the farther southern
piedmont. Thermal profiles suggest 55 dbz core thresholds to 26+ kft
for isolated severe convection today, with slightly lower values in
any DCAPE regions that spike to 1100 to 1300 J/kg.

Otherwise, Little change in the overall pattern is expected during
the near term, as the forecast area will remain parked between the
subtropical high centered over the Four Corners, and a weakness in
the S.T. ridge off the southeast coast. While this pattern is not
obviously supportive of substantial precip chances, it`s not
entirely hostile to development of deep convection. The mid-level
flow is expected to be more NE today, so it would stand to reason
that any convection developing within lee trough and across the
higher terrain would tend to drop south as opposed to SE, sparing
much of the Piedmont of the solid scattered coverage that was
observed yesterday. Convection should wind down this evening, with
another warm overnight expected.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As 250 AM Saturday: On Sunday, the axis of the H5 ridge will build
over the forecast area, increasing to 594 dm by the afternoon. At
the sfc, little to no pressure gradient will exist across the
western Carolinas and NE GA during the day. In fact, model guidance
indicates that wind speeds are forecast to remain below 5 kts from
the sfc up to H7. High thicknesses and good insolation should
support high temperatures from around 90 degrees within the mtn
valleys to upper 90s to around 100 across the I-85 corridor.
Forecast soundings show the mixed layer deepening slightly above H8
during the heat of the afternoon. The mixing may lower sfc dewpoints
from around 70 in the morning to the upper 60s during the afternoon.
Heat Index values may peak between 101 to 106. In addition, forecast
soundings indicate that llvl CIN will linger east of the mtns
through most, if not all, of Sunday afternoon. Thermal profiles
appear supportive of mtn ridge convection as early as mid day.
Storms may propagate by developing along outflow boundaries. This
process should support sct coverage across the mtns and isolated
coverage east. Convection should ash out shortly after sunset, with
debris gradually clearing into the late night hours. Low
temperatures Sunday night are forecast to range for the 60s across
the mtns to the low to mid 70s east.

On Monday, a sfc front is forecast to slowly slide across the Ohio
River Valley, with a lee trof across the foothills and Piedmont.
light south winds should result in a one to two degree rise in
afternoon dewpoint temperatures. As a result, llvl CIN appears
weaker than Sunday across the foothills and Piedmont. NAM forecast
soundings for KGSP indicates CAPE above 2500 J/kg and PW rising to
1.8 inches. Winds are forecast to remain less than 10 kts from the
sfc to H4. I will time chc PoPs across the CWA by mid day, rising
very quickly across the mtns around lunch, then spreading east across
all of the Piedmont. A few areas may see high Heat Index values
between 100 to 106 degrees during the mid to late afternoon.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 3 AM Saturday: Tuesday through Thursday, the center of the H5
ridge will shift over the Deep South. Models indicate that a series
of weak mid level S/W will ripple across the forecast area. Each
day, moderate instability and weak CIN will exist across the region
during the afternoon and early evening. I will continue to indicate
diurnal chc to ridge top likely PoPs each day, schc east. I would
expect that PW values will remain above normal as a front becomes
stationary to our north. Temperatures should range within a couple
of degrees of normal, cooler than Sunday and Monday.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere (except KAVL), VFR conditions are expected
through the period at most terminals. Generally expect light S/SW
winds to persist through the period. Isolated to scattered
convection is expected to develop once again this afternoon, esp
near the Upstate SC terminals and KHKY, and VCTS and/or PROB30s are
advertised at these sites from late afternoon into the evening.
Cannot at all rule out convection near KCLT, but coverage should be
a bit more sparse in the Piedmont so will only feature VCSH at KCLT
for now.

At KAVL, scattered convection is expected to develop once again this
afternoon, and VCTS is advertised beginning at 17Z, with PROB30s
carried from late afternoon into the early evening. Another round of
fog and/or low stratus is possible late tonight, but timing and
magnitude of this is completely uncertain attm, and restrictions are
limited to MVFR fog around daybreak.

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...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High  94%
KAVL       High 100%     High 100%     High 100%     High  82%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High  94%

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:

www.weather.gov/gsp/aviation

&&

.CLIMATE...
RECORDS FOR 07-24

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      96 1983     68 1985     71 1934     52 1966
                                                    1895
   KCLT     100 1983     73 1938     78 2010     59 1947
                1952                    1883
   KGSP     101 1952     70 1985     79 2010     59 1904



RECORDS FOR 07-25

               MAX TEMPERATURE         MIN TEMPERATURE
  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
                            1890

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...NED
NEAR TERM...HG
SHORT TERM...NED
LONG TERM...NED
AVIATION...HG
CLIMATE...GSP



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