Area Forecast Discussion
Issued by NWS Greer, SC

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819
FXUS62 KGSP 210835
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
335 AM EST Wed Feb 21 2018

.SYNOPSIS...
High pressure off the East Coast will provide a warm and
moist southerly flow of air throughout the week as a cold front
stalls and lingers west of the mountains. This front is not expected
to pass through the region until Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM: Little change in the pattern thru the near term, with
the CWFA remaining between a large upper high to the east and deep
trough to the west. Moist LLVL SWLY flow will persist thru the
period, keeping skies cloudy to mostly cloudy. So far, low clouds
have filled in and are keeping temps elevated and the BL mixed. This
is limiting fog development, and fog wording has been scaled back
with the morning forecast package. There will still be some patchy
fog around, especially in the NW NC piedmont, where temps are in the
upper 50s. The rest of the area is in the 60s with a light southerly
wind.

Cloud cover should scatter out somewhat like it did yesterday,
leaving a low-based cu deck thru the aftn. Temps will be a category
or two warmer than yesterday, and this combined with dewpts in the
60s will result in some sfc-based instability. CAPE is forecast to
range from 500 to 1000 J/kg. But forecast soundings show a mid-level
inversion that should cap convection to under 700 mb (where temps
are still above 0 C). So I think thunder chances will remain low.
Cannot rule out an isolated rumble of thunder in the NC mountains,
where upslope might help break the mid-lvl cap, but will not mention
thunder for now. In any case, scattered showers will be possible,
with greatest coverage in the SWLY upslope areas of the NC/GA
mountains. Temps will approach or break record highs at KCLT and
KGSP (See climate section below).

Tonight looks like it will be a lot like the current night, with
plenty of low clouds, patchy fog, isolated to scattered light
showers, and min temps way above normal. Lows look to be in the
upper 50s to lower 60s, which would tie or break high minimums for
Thursday, the 22nd.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 325 AM EST Wednesday: A persistent pattern remains in place
Thursday through Friday night with strong high pressure lingering
off the southeast coast, and a deep moisture fetch continuing west
of the MS Valley. Over our area, light south to southwest upslope
flow and continued sub-800 mb moisture will produce scattered
showers Diurnal instability will affect mainly the NC mountains on
Thursday afternoon, with thunder chances best in the extreme
southern Appalachians.

Marginal 850 mb drying is expected late Thursday night through
Friday; however, boundary layer moisture will persist. A back door
cold front will flirt with the northwest NC piedmont Friday, but
model consensus keeps the wedge front just north of the region
through Friday. In fact, the GFS which was bullish on southward
frontal movement has backed off significantly leaving the NAM the
sole model moving the front this far south. That said, even the NAM
keeps the front and the bulk of the colder air north of the area
just brushing Davie County. Precip chances will be limited to the NW
Piedmont Friday morning and the Northern Mountains during the
afternoon. Isolated showers increase across the Mountains into the
NC Foothills and Piedmont Friday night as deeper moisture returns.
Highs will be near records both days. Lows will be above normal
highs and near record high mins as well.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 1205 AM EST Wednesday: Circulating around the periphery of
deep layered hipres offshore, the very mild airmass will linger atop
the SE CONUS into the upcoming weekend. Saturday maxes are close to
persistence, 15 deg f or more above climo.  Deeper layer moisture
should continue it`s eastward creep with the associated upward
ramping of pops into solid chance range by later in the day. The
recently posted 21/00 utc op GFS supports the current thinking of a
questionably forced, decently sheared cold fropa Sunday within a
weak instability regime.  Sensible wx will continue to feature
shower coverage becoming numerous west to east acrs the cwfa
beginning Sunday morning. Based on the timing of shower chances,
piedmont max temps are slated to be equally as warm as Saturday,
solidly middle 70s. With the orientation of the llvl boundary
expected to become parallel to the upper flow, and additional energy
progged to ripple up the boundary on Monday, it is probable that an
additional round of numerous showers will redevelop across the
region. Tuesday continues to look dry with encroaching upper ridging
and sfc hi pressure. Max temps should be less mild but still two to
three categories above climo.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Low VFR to MVFR-level clouds continue to
expand across the area, and that seems to be helping limit fog
development so far. The eastern areas, like around KCLT, are still
expected to see fog develop by daybreak, as the cloud cover is
patchier. Confidence on vsby and cigs at the other sites is lower,
but guidance is still in good agreement on IFR cigs with variable
vsby during the pre-dawn hours to late morning. Like yesterday,
clouds/fog should mix out by early aftn, leaving low-VFR cumulus
around. With very warm conditions expected this aftn, there will be
some instability for a few showers to develop out of the cu deck,
with greatest coverage across the mountains. The air mass changes
little for tonight, so expect low cigs and patchy fog once again.

Outlook: Unseasonably warm and humid conditions are expected to
persist through the end of the week. Shower chances will be highest
across the mtns, while periodic CIG and VSBY restrictions will be
likely through the week, esp during the late night and morning hours.

Confidence Table...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       Med   68%     High  83%     High  82%     High  93%
KGSP       High  89%     High  87%     High  87%     High  84%
KAVL       Med   74%     High  90%     High  82%     High  89%
KHKY       High  83%     Med   79%     High  89%     Med   63%
KGMU       High  83%     High  89%     High  89%     High  88%
KAND       High  95%     High  90%     High  84%     High  82%

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 02-21

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      77 1986     12 1896     54 1997      8 1896
   KCLT      75 2011     32 1896     56 1997      6 1896
                1986
   KGSP      75 1917     35 1978     55 1997      9 1896
                            1902



RECORDS FOR 02-22

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      72 1897     27 1939     54 1897      2 1963
   KCLT      74 1990     33 1963     62 1897     12 1963
                1897
   KGSP      76 2011     35 1969     55 1980     10 1963
                            1963



RECORDS FOR 02-23

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      76 1982     29 1989     54 1922     10 1939
   KCLT      76 2012     29 1901     56 1944     19 2009
                1980                                1978
                1962                                1963
   KGSP      76 2012     36 1966     57 1922     15 1963
                1996        1939
                1980



RECORDS FOR 02-24

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      77 1930     26 1947     50 1985      6 1967
                                        1979
   KCLT      80 1982     26 1889     56 1992     16 1967
                1930
   KGSP      79 1982     33 1901     57 1909     15 1967
                                                    1901



RECORDS FOR 02-25

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      78 1930     17 1967     51 1985     -2 1967
   KCLT      82 1930     27 1967     58 1890      7 1967
                            1914
   KGSP      79 1930     30 1967     57 1985      8 1967

&&

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

&&

$$
SYNOPSIS...CSH
NEAR TERM...ARK
SHORT TERM...RWH
LONG TERM...CSH
AVIATION...ARK
CLIMATE...



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