Area Forecast Discussion
Issued by NWS Greer, SC

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433
FXUS62 KGSP 200539
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1239 AM EST Mon Feb 20 2017

.SYNOPSIS...
Warm high pressure will move over the area through the early part of
the week, bringing temperatures close to record highs. Modest
rainfall will move over the area by mid week, followed by brief
drying, before a frontal system arrives next weekend with rain and
thunder chances.

&&

.NEAR TERM /THROUGH TODAY/...
1230 AM EST Update...Made localized upward adjs to hr/ly temps where
subtle BL mixing continues. Min temps still look on track. Tweaked
sky cover to keep few/sct Ci across the mtns before main shield
moves in later today.

As of 1010 PM EST Sunday:  Sharp upper ridging to the west
continues to promote height rises this evening across the southern
Appalachians.  As a result, broad anticyclonic flow prevails at the
surface thereby yielding light/calm northerly winds.  Skies remain
mostly clear, with further clearing expected overnight as ridging
builds in.  As such, ample radiational cooling is favored with a
few Piedmont locale min temps possibly cooling enough to promote
saturation based upon the xover method.  Thus, although not likely,
woudln`t be suprised to see some patchy 4-5sm visb restrictions
around daybreak by way of radiation fog.  Otherwise, tweaked t/td
and sky through the overnight to align with recent trends/guid,
and left the remainder of the fcst unchanged.

As of 1230 PM EST: Satellite imagery continues to show clouds banked
up on the W side of the mtns. Seeing some stratocu development
downwind of the mtns...more than expected...but not enough to
mess up the high temp fcst. Temp trend was adjusted for obs,
but otherwise no changes.

Rather benign springtime weather is expected over the next 24 hours
as a progressive upper pattern brings a full-latitude upper ridge
eastward and supports high pressure moving past to the north. The
only problem is that it isn`t spring, it`s still winter, and now
the trees are blooming and the birds seem confused. Sky should
clear and wind should diminish with sunset. In spite of clear
sky and light wind, low temps will still be on the order of ten
degrees above normal. Sky should be sunny on Monday with more
light wind. High temps will continue well above normal and might
flirt with records, particularly at GSP.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
As of 2pm EST Sunday: Upper ridge will be in place over the area
Monday night with light and variable surface flow. Ridge and surface
high move east on Tuesday with light southwesterly flow picking-up
Tuesday afternoon that will gradually increase dewpoints. Airmass
remains convectively stable Tuesday evening with only an outside
chance of a light shower, primarily over the higher terrain. Chances
for precip. improves on Wednesday as boundary layer moisture
continues to improve and with upper flow becoming northwesterly with
some embedded shortwave impulses.  Models develop some marginal
instability with CAPE to 100 j/kg Wednesday afternoon and not a lot
of cap.  Deep layer shear is also marginal. Thus, some widely
scattered marginal convective showers will be possible late on
Wednesday, with any activity rapidly dying after sunset.
Temperatures remain well above normal Tuesday and Wednesday with
clouds increasing with the change in upper flow pattern Tuesday
evening.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 220 PM Sunday: A quasi-zonal/fairly progressive flow pattern
will be in place across much of the eastern 2/3 of the conus through
the period. SW low level flow will support plenty of warmth early in
the period, as temps are expected to remain around 20 degrees above
climo through the end of the work week. The southerly flow will also
bring about increasing low level moisture, which combined with very
strong insolation could yield positive surface-based buoyancy by Thu
afternoon. Also by this time, global model guidance hints at warm
frontal activation across the central/southern Appalachians and
vicinity, as cyclogenesis commences across the southern Great
Plains. Therefore, isolated-to-widely scattered convection,
including thunderstorms is not out of the question Thu afternoon and
evening.

Although the warm front will be long gone by Friday, additional
convection is possible Fri afternoon, particularly in response to
terrain effects, and chance pops will be carried in most locations
by the end of the day. Model guidance is gradually coming into
better agreement regarding the advance into our area of a frontal
boundary associated with aforementioned deepening cyclone early in
the weekend, with late Fri night/early Saturday appearing to be the
most likely time for fropa in our forecast area. Likely pops will be
carried across much of the area during this time. The convective
potential remains the most interesting aspect of this event, and
while it does not appear that the time of day will be conducive to
robust buoyancy, it appears fairly likely that some degree of sbCAPE
will be in place. Meanwhile, shear will likely be adequate for
organized convection, although the latest guidance depicts fairly
unidirectional profiles with a strong-but-not-scary low level jet.
This would certainly makes sense with the better deep layer forcing
passing west and north of the area, but it all honesty it`s still a
bit early to get too far in the weeds with severe wx parameters.

Cooler and much drier air will push into the area for the last
couple of days of the period, although temps are expected to remain
a good 10 degrees above normal through the weekend.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR conds thru the period at all TAF
sites...except at KAND where daybreak MVFR BR may form due to rad
cooling combined with wafting local lake moisture. Expect periods of
thin Ci crossing the terminals as a strong ridge axis slowly
transits east across the area. Winds will remain light and veer
se/ly as a sfc high builds in from the northeast. No good gust
potential either with column winds weakening beneath an h9 subs
invers.

Outlook: Expect VFR conditions to continue through early in the
week before another low pressure system gradually brings moisture
back to the area from Tuesday through late week. Precipitation and
associated restrictions remain highly uncertain from mid week on.

Confidence Table...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     Med   78%     High  87%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       Med   69%     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      75 1939     26 1908     50 1951      4 2015
                                        1939
   KCLT      77 2014     31 2015     59 1939      7 2015
                                        1890
   KGSP      75 2014     33 2015     57 1939      9 2015
                1986



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



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

&&

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

&&

$$
SYNOPSIS...JAT
NEAR TERM...CDG/PM/SBK
SHORT TERM...WJM
LONG TERM...JDL
AVIATION...SBK
CLIMATE...GSP



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