Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 220251
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1051 PM EDT SUN AUG 21 2016
A cold front will push through the area from the northwest later
this evening. High pressure will then build in behind the front
on Monday, bringing cooler and drier air to the area for most of
the week. Another weak cold front will approach the Western Carolinas
by the end of the work week.
.NEAR TERM /THROUGH MONDAY/...
As of 1050 PM: I will update the forecast to lower PoPs and reduce
sky. In addition, I will update the HWO to remove hazards.
As of 8 PM: TCLT and KGSP radars indicated the sfc cold front was
located near the NC/SC state line between KCLT to Saluda, NC. A band
of SHRA/TSRA developed along and south of the boundary, drifting to
the east and weakening. The front will gradually slide south through
the late night hours. Winds in the wake of the front will veer from
the NNE, remaining through Monday morning. NAM12 sfc condensation
pressure deficits fall below 5 mbs with high values of h925 RH after
6z. I expect that low clouds will be widespread across the TN border
counties and within the French Broad Valley. I will update the
forecast to adjust to latest thinking.
As of 445 PM: Lines of storms will continue to move east across the
forecast area through this evening. Overall, the forecast appears on
track. I will issue an update to refine PoPs, sky, and temps.
As of 235 PM EDT Sunday: Convection firing along a pre-frontal
trough is moving across the area at this time. Expect another round
of convection later this afternoon and early evening as the actual
cold front moves across the area. Analyzed DCAPE is much high than
forecast, with current values 800 J/kg or greater along and south of
I-85. The best effective bulk shear is currently over the NC
mountains and should remain across NC through the event. This could
lead to an overlap of both parameters across the I-77 corridor late
this afternoon or early evening. Even though that would be the most
likely location for any severe storms, NE GA and the Upstate could
also see a damaging downburst given the increasing DCAPE. Heavy rain
remains a concern as well with the deep moisture and 2 inch PW
values. However, the threat is limited with fast storm motion from
the increase steering flow. That said, training of cells from
different rounds of convection could lead to some excessive rainfall.
The cold front sweeps across the area this evening taking convection
and clouds with it. The gusty SW winds will turn NW and diminish
through the night. The clearing skies and moist ground could lead
patchy fog formation, but the downsloping NW winds should keep any
widespread problems at bay. The mountian valleys have the best
chance of seeing any fog, but it could be more in the form of low
clouds. Lows will be near or a little below normal.
Dry and cooler high pressure begins to build into the area Monday.
There could be some lingering moisture leading to afternoon clouds
across the Upper Savannah River Valley and the mountains of NE GA
and the Upstate. However, no precipitation is expected. Temps should
end up a couple of degrees below normal with low humidity levels.
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM EDT Sunday: The short term fcst period kicks off
on Monday evening looking relatively quiet. An H5 trof axis will
continue ejecting to the northeast across Nova Scotia, while heights
rise over the OH/TN valleys as well as the mid Atlantic states.
At the surface, an old cold front will linger across portions of
the deep south while sprawling cool/dry high pressure settles
over New England on Tuesday, eventually sliding offshore into
Wednesday. As such, the only chances for precipitation look to
be on the periphery of the high, across the upper Savannah River
valley into the sw NC mtns each day. Meanwhile another H5 trof
and associated surface cold front will slide south out of Canada,
eventually approaching the OH valley by periods end. All in all,
the fcst will feature slight/chance pops across the a fore mentioned
zones, while remaining dry elsewhere. Dewpoints in the lower/mid
60s combined with below normal temperatures should yield fairly
comfortable conditions through the period.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 2 PM EDT Sunday: the medium range fcst picks up at 00Z on
Thursday with upper ridging in place over the eastern CONUS and
a closed upper low moving eastward across the US/Canada border.
Over the next couple of days the ridge flattens a bit, after which
the latest model guidance restrengthens it as we move into the
weekend. At the sfc, high pressure will be sliding off the East Coast
and a relatively dry cold front will approach the fcst area from the NW.
The front is still expected to approach the fcst area by late Thursday
and move thru the CWFA on Friday. The deeper moisture associated with
the front remains relegated mostly to the north. Behind the front,
another round of high pressure will settle over the region for the
weekend. No major changes were needed for the sensible fcst with
slight to solid chance POPs over parts of the high terrain Fri, Sat,
and Sun. Temps will steadily warm thru the period with highs starting
out around climatology and ending up at least a category above climo
over the weekend.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: At 8 PM, TCLT and KGSP radars indicated the
sfc cold front was located near the NC/SC state line between KCLT to
Saluda, NC. A band of SHRA/TSRA developed along and south of the
boundary, drifting to the east and weakening. The front will
gradually slide south through the late night hours. Winds in the
wake of the front will veer from the NNE, remaining through Monday
morning. NAM12 sfc condensation pressure deficits fall below 5 mbs
with high values of h925 RH after 6z. I expect that low clouds will be
widespread across the TN border counties and within the French Broad
Valley, with IFR to LIFR ceilings over KAVL. Low clouds should
dissipate by the mid morning hours. On Monday, conditions will
remain drier with light NNE winds decreasing during the afternoon.
Outlook: The dry air will remain in place across the area resulting
in fair weather through at least mid-week.
03-09Z 09-15Z 15-21Z 21-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL Med 61% Low 43% High 85% High 100%
KHKY High 100% High 83% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 83% 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: