Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 271845
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
245 PM EDT FRI MAY 27 2016

.SYNOPSIS...
After a dry day on Saturday, a period of cooler and wetter weather
may develop late in the weekend through early next week as Atlantic
low pressure moves toward the South Carolina coast.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 2:15pm EDT Friday.  Some convective showers are currently
active over the mountains of western North Carolina, especially near
the TN border, and in northeast Georgia.  BUFKIT soundings for the
area show very low instability and a low implied storm top of up to
25kft.  Maximum buoyancy is around 12kft at a relatively warm 0 deg.
C.  Consequently, these showers have seen very little lightning and
should remain well below severe levels.  These showers are forming
from southerly upslope flow, combined with afternoon heating with
highs in the foothills reaching 80 degs.  Flow is weak southerly to
southeasterly throughout the sounding giving northerly storm
motion.

southerly low-level flow is weak and does not maintain boundary
layer moisture on saturday, with dewpoints actually dropping a
couple degrees.  consequently the weak convection seen today is less
likely tomorrow, with convective instability nearly non-existent.

Synoptically, area is on the west side of a broad upper and lower
ridge over the Atlantic as a stronger trough over the central CONUS
makes gradual eastward progress. Tropical low continues to organize
northeast of Florida and will begin to affect coastal areas on
Saturday.  With slow progression of synoptic pattern, main change
for Saturday will be a little warmer temperatures and dryer boundary
layer with few, if any showers over the mountains.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
At 230 PM Friday, on Saturday evening an upper ridge will extend
from the atlantic ocean to the mid atlantic states, while an upper
trough will be over the eastern plains, and an upper low will be
near the southern SC coast. The models move this upper low slowly
inland over SC on Sunday, while the upper trough progresses to the
wester Great Lakes, and the upper ridge progresses over New England.
By Monday the low weakens near the SC and NC border, while the
upper trough deamplifies over the easter Great Lakes, and the ridge
downstream reaches the eastern Canada.

At the surface, on Saturday evening the models show a surface low
ostensibly associated with tropical development approaching the SC
coast approaching, with associated moisture moving inland over the
Carolinas. The models differ on the movement of the low into Sunday,
and therefore the amount of moisture reaching the western Carolinas
and northeast Georgia. At this point the bulk of precipitation is
expected to be near the SC coast, but uncertainty remains on inland
amounts. Model soundings vary on the amount of instability over our
area on Sunday and Monday, depending on how moist the atmosphere
becomes. Temperatures should exhibit a reduced diurnal range if
moisture can indeed spread inland over our area.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
At 230 PM Friday, on Monday evening, an upper low will be weakening
near the SC and NC border. The models have disagreed on the precise
location of a an associated surface low over either SC or NC, but
now appear to move this system off the southern NC coast on Tuesday,
where it dissipated on Thursday.

By Friday an upper ridge progressing to the east coast deamplifies,
while a cold front approaches from the northwest, preceded by
sufficient moisture to support widespread precipitation.
Precipitation amounts are currently forecast to be rather limited
west of the coastal Carolinas, however if the surface low can reach
far enough inland, and linger there, rainfall totals could be
higher.

Temperatures may exhibit a reduced diurnal range if moisture lingers
over the area, otherwise they would run near normal under nearly
zonal upper level flow.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
At kclt...high-res model guidance is fairly consistent and
reasonable in its depiction of convective showers forming well
northwest of the aerodrome over higher terrain and moving northward
on prevailing winds...thus have left mention of showers out of the
TAF.  General flow pattern has the area on the west side of upper
and lower anticyclonic flow with weak flow at all levels, a pattern
that will persist through the next 24 hours as central CONUS trough
makes gradual eastward progress.   surface winds will be VRB to
8kts, southeasterly when not VRB.

Elsewhere... General flow has the area on the west side of a broad
lower and upper trough, with light generally southeasterly surface
winds.  Afternoon heating and upslope flow is creating areas of
convective showers over higher terrain.  These showers are moving
northward in prevailing flow and should not affect locations outside
of the mountains.  Only an occasional lightning strike is expected
with these showers due to their shallow nature.  Low-level flow is
weak enough that BL moisture weakens on saturday, with a reduction
in shower potential.  In mountain areas receiving rainfall today,
fog will again be possible in the morning.

Outlook: Mainly VFR conditions will prevail through the period, but
patchy morning fog chances continue at KAVL. Scattered afternoon
SHRA/TSRA coverage will return on Sunday, with increasing chances
into early next week.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     Med   76%     High  94%
KHKY       High 100%     High 100%     High  97%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the schedule 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

&&

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

&&

$$
SYNOPSIS...HG/SBK
NEAR TERM...WJM
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...WJM



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