Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 281746

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
146 PM EDT Fri Apr 28 2017

A Bermuda high will bring almost summer like weather to the western
Carolinas and northeast Georgia for most of the weekend, until a
strong cold front approaches from the west Sunday night. The cold
front will move across our region on Monday. After the front passes,
weak high pressure will move across the southeast for Tuesday and
Wednesday. However, the atmosphere will reload with another slow
moving system that may bring wet weather for late next week.


As of 1025 AM EDT: the Dense Fog Advisory was allowed to expire at
10 AM with an SPS issued for the same area valid until noon. Sfc obs
have been showing a gradual improvement in visby over the past few
hours, however most non-mtn zones continue to see IFR cigs. These
should lift and scatter out as we move into the early afternoon.

Otherwise, deep layer southwesterly flow is in place aloft over the
southeast, with a weak surface boundary stalled over the western
Carolinas. Any thermal/moisture contrast across this boundary should
continue to dissipate through the day. Upper level heights will
gradually rise over the area as an offshore ridge axis becomes
resurgent. Little to no upper level triggering should be available
through the period. Very warm profiles in the 5 to 10 kft layer
should effectively cap off deep convection, which is fortunate since
elevated CAPE above the capping looks very robust this afternoon.
Will keep any isolated shower mention confined to the immediate
southerly upslope areas this afternoon. Temperatures should rebound
solidly into the 80s today, with some lower mountain valleys just
about as warm as piedmont sections this afternoon in the southwest
flow. Another mild night with areas of fog is expected again


As of 200 AM Friday: A stacked Bermuda High pattern will dominates
the  FA thru the short range. By Sat afternoon...a 593 DM high will
be positioned off the Atl coast and an associated llvl high will
ridge across wrn GA. Return flow around the sfc high will bring just
enuf moisture to the area for mainly upslope -shra/tstms. The NAM is
still dry during this pops are held low. The models show
mod/stg sbCAPE within low expect some pulse stg/svr
storms into the late afternoon. Max temps will be in the mid to
upper 80s non mtns. On Sun, the sfc ridging eases off slightly...but
enuf to allow better GOM moisture flux across the entire FA. Max
temps will be a bit lower due to increased multi layerded
moisture...but sfc td/s will remain high. Soundings show much less
instability...yet shear will be slowly increasing thru the overnight
period. Think there will be enuf destabilization for another round
of deep shra and pulse-type tstms with a bit better overall coverage
than Sat.


As of 225 PM EDT Friday: Not much change to the previous fcst. The
models are in decent agreement with the timing of the fropa Mon. The
GFS is deeper with the ulvl low than the ECMWF/CMC solns yet
not enuf to expect major differences in the sensible weather fcst.
Will count on a weakly forced front to work into the mtns early in
the day...then swing east of the FA btw 00z-03z. There shud be
decent coverage of -shra/tstms with a few stg/svr storms possible in
a high shear / low cape environ. The main concern will be possibly
damaging winds as 50 kt h85 jet develops along the sfc convg zone
while weak accelerations are noted within the HGZ. Noticeably lower
sfc td/s will work in from the west during the day making for
pleasant yet breezy conds on the back side of the front. A small
scale srn stream high crosses the region Tue into Wed and temps will
slowly heat up...but generally remain arnd or a bit above normal.
The next good chance for precip and tstms will be late Wed into Thu
as a developing sfc low works toward the region. There are sigfnt
model differences wrt to the track and timing of this feature so
pops have been reduced into the mid chance range Thu.


At KCLT and elsewhere: expect predominately VFR conditions for the
18z taf period with some brief MVFR visby and IFR cigs at KCLT from
roughly 9 to 12z and similar restrictions at the other sites. Confidence
is not very high wrt the IFR cigs as cloud cover may remain sct during
that period and a ceiling does not actually develop. Otherwise, the
synoptic pattern will change little over the next 24 hrs with warm,
sly low-lvl flow persisting over the region and wind speeds picking
up this afternoon and tomorrow afternoon as we mix out. TSRA development
remains unlikely today/tonight as we should remain capped, however
increased daytime heating tomorrow could erode the cap and allow sct
convection to develop. This scenario will be most likely over the
higher terrain tomorrow afternoon.

Outlook: Areas of fog will be possible each morning as the near
surface layer remains moist through the weekend. Diurnally-based
showers and thunderstorms will be possible on Sunday, with more
organized thunderstorms possible on Monday.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High  85%     High 100%     High 100%     Low   57%
KGSP       High 100%     High 100%     Med   75%     Med   71%
KAVL       High 100%     High 100%     High 100%     Med   64%
KHKY       High  85%     Low   55%     Med   75%     Med   71%
KGMU       High 100%     High 100%     Med   75%     Med   71%
KAND       High 100%     High 100%     Med   75%     Med   71%

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:




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