Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 241131
AFDGSP

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

.SYNOPSIS...
Very warm conditions will continue before a cold front slowly
crosses the area Sunday into Monday increasing the chances of
showers and thunderstorms. Dry and relatively cool high pressure
will settle over the region Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
630 AM Update...current fcst trends look pretty good. Increasingly
widespread  low clouds and some fg will continue to develop over the
the area thru the morning. The precip across the SW NC mtns has
remained light and transient...so the lower PoPs look good there.

Current Sat and obs indicate a very moist llvl atmos in place across
the region. Some stcu is developing over the wrn zones and a good fg
potential exists east as sfc tdd/s are running btw 0-4 degrees. This
area will be monitored for dense fg near daybreak and a possible
SPS/NPW issuance.

The persistent synoptic pattern finally begins to break down thru
the near-term as a strong wrn trof is reinforced with energy diving
south out of wrn Canada. This trof will propagate east and begin to
weaken and displace the ST high which has been the dominant factor
in the weather over the area the past several days. Model soundings
show PWAT values increasing arnd 70 percent over the next 24-36 hrs
as moisture increases thru a deepening layer this afternoon. The 00z
3-km NAM holds on to a dry stable layer aloft more than the other op
models and therefore has less of a chance of precip and thunder. Even
the moister and less capped GFS only produces arnd 300 J/kg of sbCAPE
this afternoon mainly over the higher terrain. So...PoPs will remain
low-end except across the SW facing srn mtns where mech lift is
aided by an increase in mlvl destabilization and difl aloft ahead of
a cold front. An isol tstm or two is possible across the NC mtns but
these will be short-lived and non/organized.

Max temps will once again reach abt 20 degrees abv normal in good
sw/ly flow with weak WAA noted in the h92-h85 layer. With high
moisture in the low-levels and sw/ly flow maintaining a mixed sfc
layer...mins will also be held abt 20 degrees abv normal.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
As of 310 AM EST Saturday: The model guidance suggests that we
can tighten up the time of arrival of the main precip associated
with the approach and passage of a cold front on Sunday. Still
plenty of support for bringing high precip probability across the
fcst area with excellent forcing and deep moisture, but all the
guidance has the front to the west of the mtns at 12Z Sunday. That
means the eastern zones will have a very low chance at daybreak,
although it will still ramp up into the likely range by the early
afternoon. The main concern is still the possibility of severe
thunderstorms with the front on Sunday, given what should be an
active boundary well to our west through Saturday evening. The
model guidance shows excellent low level convergence with the
front approaching from the west Sunday morning, supporting the
idea that some sort of weakening QLCS might be just to the west
at daybreak, suggesting that the western mountains might have
a wind damage threat early in the day as the front arrives. The
weakening trend continues into Sunday as the front crosses the
mtns though, with sfc-based CAPE perhaps only as high as 300 J/kg,
and shear perhaps only on the order of 20-30 kt. As such, not even
the Marginal risk translates eastward into the western Carolinas
for Day 2, and at this point this seems reasonable unless/until
we see either better instability or better shear. Have included
some thunder, but the severe possibilities are too low to mention
in the HWO right now. High temps will be at least 15 degrees or
so above normal. The guidance also agrees that the frontal precip
band will push off to the east late in the day, perhaps resulting
in brief lull Sunday evening before another shot of mid/upper
forcing moves in overnight to redevelop the precip along and west
of the front. Precip prob ramps right back up to at least likely
early Monday morning in response to the excellent agreement seen
in the model guidance. The jet streak lifts out to the northeast
during the day, along with most of the vorticity, taking the
surface boundary off to the east, so a steady tapering off of
precip is still expected Monday afternoon. Those developments
should help to keep temps merely ten degrees above normal. The
upper trof axis should pass Monday evening, followed by a flat
upper ridge supporting sfc high pressure moving in from the west
to dry us out on Tuesday. Temps will be another category cooler,
but still above normal.

&&

.LONG TERM /TUESDAY 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 /12Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Expect a mix of MVFR/IFR conds to develop
early on 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. A cold front advances toward the area overnight
which will keep llvl moisture high and the chances for flight
restrictions all sites.

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...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High  87%     High  83%     High 100%     High 100%
KGSP       High 100%     High  94%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High 100%     High  94%     High  94%     High  93%
KGMU       High 100%     High  94%     High 100%     High 100%
KAND       High 100%     High 100%     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:

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...SBK
NEAR TERM...SBK
SHORT TERM...PM
LONG TERM...CSH
AVIATION...SBK
CLIMATE...



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