Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 240541
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1241 AM EST Sat Feb 24 2018

.SYNOPSIS...
Very warm conditions will continue into the weekend. A cold front
will slowly cross the area Sunday into Monday, bringing greater
chances of showers and a few thunderstorms with it. Drier and cooler
high pressure will settle over the region Tuesday.

&&

.NEAR TERM /THROUGH TODAY/...
1230 AM Update...No sigfnt changes made to the fcst. Lowered PoPs
based on latest 88D trends and pushed back onset time over the
wrn zones. Hourly temps are running a little lower than the fcst
curve and have been adj in localized areas mainly across the
Upstate.

As of 940 PM: Overall the pattern hasn`t changed all that much
with a large upper anticyclone centered over the western Atlantic
keeping a stalled frontal axis to the west.  With that, another
round of above-normal temperatures is on tap for tonight. Updated
overnight temp trends reflect the adjustments made to sky cover,
that is, more radiative cooling. Another round of early-morning
Piedmont stratus and some fog is expected again, mostly on account
of persistence within this stagnant pattern. Some scattering is
expected later in the day, though a healthy if not shallow cu
field and patchy cirrus will make for mostly cloudy conditions
overall. PoPs are looking less and less likely through the wee hours
of the morning, so new values with this update were trimmed down
below mentionable criteria, away from the upslope areas of the SW
mtns and immediate vicinity. A little before dawn, guidance does
suggest a weak shortwave moving along the stalled front may allow
expansion of any precip to the remainder of the mtns and foothills.
Beyond that, heating into the afternoon hours on Saturday could
yield enough free SBCAPE along the TN line, given that area`s
distance from the aforementioned Atlantic ridge, thus iso/sct TSRA
cannot be ruled out. While much above normal temps will return
for Saturday afternoon, broken max temp records are less likely
simply because the records are a few degrees warmer.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
As of 100 PM EST Friday: At the start of the short term period
Saturday evening, the strong upper ridge will still be in place over
the western Atlantic, with a deep upper trough building over the
Rockies. The initial shortwave embedded within the trough will be
approaching the MS Valley at the start of the period, with a
secondary shortwave diving into the northern Rockies. Surface highs
in eastern Canada and over the western Atlantic will be separated by
the quasistationary warm front, while a cold front will drag across
the Lower MS Valley as the surface low over the Mid MS Valley
continues to occlude. Showery activity can be expected Saturday
night especially across typical upslope areas as low level WAA
continues. The cold front will push east on Sunday, losing some of
its oomph, as the upper ridge is forced south and will begin to
retrograde into the Gulf and western Caribbean. With the area
remaining in the warm sector, the synoptic lift (though weakening)
added by the front will likely be enough for at least a few
thunderstorms to develop across the Piedmont and maybe foothills,
with better chances across the Upstate and NE GA. SBCAPE is not
particularly impressive, remaining below 500 J/kg, with deep-layer
shear increasing (50-60kt) as the front approaches. Certainly some
minimal concern for HSLC convection Sunday afternoon, so will
continue to watch forecast evolution. Expect one more day of
afternoon highs 15+ degrees above seasonal normals.

Still seeing some differences in how the ECMWF and GFS are handling
the secondary surge of moisture on Monday, but the 12z ECMWF has
come in slightly farther SE with the QPF axis, closer to what the
GFS has been indicating. Basically that secondary shortwave will
push into the Plains and pull another slug of moisture out of the
Gulf as the upper wave begins to damp. The cold front will stall
across the area and may briefly lift back north with the surge of
moisture, but it`s starting to look like the more significant
rainfall is less likely (and even if so, it would be farther S) with
the surface low working it`s way more across the fall line rather
than I-85. Should see highs on Monday a good 5-8 degrees cooler (but
still 10 or so degrees above normal) than on Sunday, but this will
be highly dependent on how quickly the front moves through. All pops
should be pretty much out of the area by 00z Tuesday.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 1210 AM EST Saturday: Dry wx is still anticipated on Tuesday
as low amplitude upper ridging builds atop the SE CONUS and sfc
ridge axis translates from the mountains to the coast by evening.
Maximum temperatures remain progged to be about 2 categories above
climo.  Medium model solutions are in decent enough agreement with
respect to the sensible wx for Wednesday, with the consensus
developing waa pcpn eastward into the cwfa.  Based on this, will
plan on creeping chances upward to categorical in favored locales,
and with the clouds and pcpn, a smaller diurnal temperature range
should result, maxes topping out near the late February normal.
There is still plenty of time for model timing differences to work
themselves out with respect to the passage of a moderately forced
cold front Thursday and/or Thursday night.  Even at this point, it
is hard to believe there won`t be categorical shower coverage at
some point during this period followed by a dry punch on Friday
within a gusty post-frontal airmass.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Another overnight period of developing stcu
and lowering VSBY. Expect a mix of MVFR/IFR conds to develop close
to daybreak as good rad cooling continues and moisture remains
trapped within weak sfc/based inversions. Hires models favor the
lower elevation piedmont area including KCLT for the higher
h95-h85 layered moisture adv...thus have lowering CIGS/VSBY to IFR
at KCLT and the Upstate sites. KAVL and KHKY have a better chance
remaining MVFR/VFR. All sites will see a breakup of cloud cover this
afternoon within good isol.

Outlook: Moist conditions will keep chances for restrictions
elevated through the period, with the best chances for low cigs/vsby
to occur each morning.  Precipitation chances are also slightly
elevated, mainly across the high terrain.

Confidence Table...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       High 100%     Low   56%     High 100%     High 100%
KGSP       High 100%     High  81%     High 100%     High 100%
KAVL       High 100%     Low   56%     High 100%     High 100%
KHKY       High 100%     Med   75%     High 100%     High 100%
KGMU       High 100%     High  81%     High  85%     High 100%
KAND       High 100%     High  81%     Med   78%     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:

www.weather.gov/gsp/aviation

&&

.CLIMATE...
ERATURE         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



RECORDS FOR 02-26

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      78 1951     24 1920     55 1957      5 1967
   KCLT      81 1977     35 1993     57 1890      7 1967
                            1920
   KGSP      80 1996     28 1914     56 1985     12 1974



RECORDS FOR 02-27

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      78 1996     22 1935     58 1962      6 1934
   KCLT      82 2011     29 1934     59 1917      7 1963
   KGSP      81 1996     37 1987     58 1944     12 1963
                            1982



RECORDS FOR 02-28

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      77 1918     26 1941     58 1948     13 1935
                                        1896        1934
                                                    1906
   KCLT      78 2011     29 1934     61 1890     14 2002
                1962
                1948
   KGSP      77 1961     35 1934     59 1997     16 2002



RECORDS FOR 03-01

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      76 2006     31 1920     55 1997     10 1914
   KCLT      82 1918     36 1980     59 1997     15 1980
                            1969        1910
                            1927
   KGSP      80 1918     30 1934     60 2012     19 1906



RECORDS FOR 03-02

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      79 1976     21 1980     54 1997      8 1914
   KCLT      80 1887     24 1980     62 1997     14 1980
   KGSP      81 1976     27 1980     60 1997     16 1914



RECORDS FOR 03-03

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      80 1976     30 1947     55 1887      9 1980
                            1930
   KCLT      84 1976     36 2009     56 1945      4 1980
                            1978
                            1953
   KGSP      85 1976     36 1978     54 1945     11 1980

&&

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

&&

$$
SYNOPSIS...HG
NEAR TERM...SBK/Wimberley
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...SBK
CLIMATE...GSP


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