Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 291035
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
635 AM EDT FRI JUL 29 2016
Broad surface high pressure will linger over the Southeast, while a
surface low tracks along a stationary front across the Mid-Atlantic.
This front will sag south into our area this weekend and linger
through the next week.
.NEAR TERM /THROUGH TONIGHT/...
As of 630 AM EDT Friday: Light shra continues to advect east across
western NC this morning, with little precipiation accumulation
being reported. Expecting said shra to continue on the current
trajectory, likely sliding north of CLT metro. Did tweak pops to
account for current radar trends as well as cam guid, otherwise
no other sig changes needed/made with this update.
As of 300 AM EDT Friday: Western Atlantic subtropical ridging
finally starts to flatten out today thanks to falling H5
heights consequent of an approaching longwave trof. At the
surface, weakening high pressure looks to prevail across much
of the southeast while a lee trof sets east of the Appalachians.
Guidance RH fields indicate modest moisture in the low/mid levels
of the atm, backed up by latest nam fcst soundings which exhibit
rather deep/moist profiles amidst poor mid level lapse rates.
These conditions will be favorable for isolated/scattered showers
and thunderstorms across the fthills/piedmont, with slightly better
chances over the mtns. Given the a fore mentioned lapse rates,
think most thunderstorms will struggle to become strong to severe,
however a few cannot be ruled out, thus will mentioned such in
the HWO with the primary threats being gusty/damaging winds and
frequent lightning. Pwats are somewhat elevated, however modest
unidirectional low/mid level flow should allow for enough storm
motion to prohibit any widespread flooding concerns.
Given the flattening ridge and falling heights aloft, as well as
partly to mostly cloudy skies at times this afternoon, guidance
favors max temps around a degree or two lower than that of yesterday
on average. The only exception to that will perhaps be over the
central/western Upstate into northeast GA where maxes will be
around a degree or two warmer. HI`s will once again approach the
100 degree mark south of I85, with the highest levels likely over
the lakelands as well as the lower NC piedmont region, however
all remaining below heat advisory criteria. Convective coverage
will once again decrease into the late evening hours as heating
is lost, thus pops are allowed to taper from east/west, keeping
slight chances over the mtns through the overnight.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 215 AM Friday...subtropical ridge over the SE US breaks down
over the short range. A weak upper low moving into the Great Lakes
pushing a weak trough over the area. A short wave moving through the
trough on Sunday deepens the trough over the area. At the surface,
lee trough remains over the area both days providing low level
forcing for convection. The mountains have the best chance of
convection on Saturday. Chance increases all areas Sunday with
increasing moisture leading to more instability and the
strengthening trough leading to better forcing. Although instability
increases into the moderate range by Sunday, DCAPE is forecast to be
significantly lower than earlier this week. Cannot rule out an
isolated severe storm however. Temps will remain above normal each
day, but heat index values should remain below heat advisory level.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 320 AM Friday...an upper level trough remains over the eastern
CONUS through much of the period, but the axis of the trough slides
eastward by the end of the period as ridging builds over the MS
valley. At the surface, a weak quasi-stationary boundary will remain
draped over our area through most of the period, but dissipates on
Thursday. This surface boundary provide a focus for showers and
thunderstorms over the area. This combined with the upper trough
will lead to convection that is slightly enhanced over the normal
diurnal summertime trend. Despite the boundary washing out and the
weakening upper trough, lee trough at the surface and some upslope
flow will prevent keep diurnal convection over the area on Thursday.
Above normal temps at the beginning of the period drop to near
normal by the end.
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
At KCLT: VFR through the period aside for any restrictions
associated with aftn/evng tsra on Friday. Initialized taf with
modest sw flow under few low stratus beneath sct mid/high cirrus.
Otherwise, expecting diurnal convection to initiate to the west
early this afternoon, advecting east into the NC piedmont late
in the afternoon. Thus, carried over the previous tsra prob30
amidst low vfr cu into early evening before any convection wains
and/or advects east. Winds on Friday will remain out of the wsw,
generally around 6-10kts.
Elsewhere: VFR through the period at all sites aside for any
restrictions associated with tsra on Friday as well as possible
mtn valley fog at KAVL on Saturday morning. Few low/mid stratus
beneath sct high cirrus to prevail through morning before heating
builds yielding increased tsra coverage amidst low vfr cu, thus
prob30s were continued at all sites. WSW Winds look to remain in
the 8-12kts range, with some low end gusting possible at the SC
sites, especially at KAND.
Outlook: Broad troffing to move across the east/central CONUS
through the weekend into next week. Moisture in the low/mid
levels combined with a series of impulses working through the mean
flow aloft will yield continued/increased chances for shra/tsra
into/through the start of the new work week. As such, restrictions
associated with shra/tsra are possible, as well as early morning
10-16Z 16-22Z 22-04Z 04-06Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 81% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% 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 scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link: