Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 290535
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
135 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 early next
week. Another front will approach by the end of next week, keeping
afternoon thunderstorm chances elevated.
.NEAR TERM /THROUGH TODAY/...
As of 115 AM EDT Friday: Light shra continues to work across
the TN/NC line with only marginal accumulations being reported,
generally less than 1-2 tenths at best. Guidance trends favor
depletion of said shra towards daybreak, thus did allow for pops
to taper down, however holding at slight chances along the spine
of the apps. Otherwise, modest mixing on Thursday afternoon has
setup xover temps in the 65-68 degree range, thus think widespread
fog issues are not likely given min temps bottoming out in the
mid 70s across the piedmont. If any patchy fog did occur, think
the best chances will be in the mtn valleys where xover temps are
the highest, and min temps are the lowest. All in all, the fcst
looks good with no sig changes needed/made through sunrise.
Previous Discussion: Models have midlevel shortwave west of the
Appalachians becoming more diffuse tonight and Friday, with another
piece of mid-level energy replacing it from the West by late Friday.
Relatively strong surface trough along and in the lee of the
Appalachians weakens on Friday in concert with the upper wave.
Result will be fewer diurnal wind gusts as 850mb winds of 20kts
today weaken to below 10kts on Friday. Temperatures on Friday
will also be generally a few degrees cooler as due to reduction in
strength of upper ridge over the area east of the diffusing trough.
Heat indices in the warmest areas today will approach 105, areas
which are currently covered by a HEAT ADVISORY. Warmest heat
indices should be at or just below 100 degrees on Friday with the
lower max temps.
Afternoon CAPE is analyzed at about 1000 j/kg, with a little
CIN and not much forcing. CAMs have some scattered TRW over the
mountains this afternoon (where CAP should be broken more easily)
and isolated convective activity in Piedmont areas. Slightly better
low-level shear with the 850mb flow may support some storm outflows
approaching severe limits, though upper winds are extremely weak.
Some similar convective activity is possible Friday afternoon,
but with reduced CAPE and shear factors.
.SHORT TERM /TONIGHT THROUGH SUNDAY/...
As of 230 PM Thursday...it looks like we will see a gradual shift of
the upper pattern through the weekend, as the broad weakness in the
subtropical ridge drifts east on Saturday and Sunday. This subtle
change should promote a bit greater coverage of deep convection east
of the mountains both days, although it might still take awhile for
convection to really get going. Thus, precip chances are slow to
ramp up and then expand east of the Blue Ridge on Saturday, meaning
that most places outside the mtns have a better chance in the early
evening. On Sunday, with a small increase in moisture, convection
may ramp up a bit earlier and coverage should be a bit better still,
so a chance will be included across the whole fcst area. Cannot rule
out a few strong/severe storms, but lapse rates look poor because of
some mid-level warm air, so that will be a limiting factor. Temps
will remain warm...on the order of a category or so above normal...
through the period. The combination of high temps and dewpoints
should not be enough to require any heat advisories.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 PM Thursday...the medium range begins 00Z Monday with a
modest upper level trough over the eastern CONUS. At the surface, a
weak quasi-stationary boundary will move over the southern
Appalachians and remain draped over our area through the early part
of next week. This surface boundary plus the moistening influence of
the subtropical "Bermuda" high will provide a focus for showers and
thunderstorms over the Carolinas and Georgia, so it appears
convection will be slightly enhanced over the normal diurnal
summertime trend. The boundary washes out by Wednesday as the upper
trough tilts and shifts over the east coast of the U.S. Upper
heights will rise briefly on Thursday, but lee troughing at the
surface and some upslope flow will prevent any lull in our enhanced
convective chances later next week. Another surface front and upper
trough will approach by the end of next week.
Though temperatures will decrease from current levels, maximum and
minimum temperatures will remain about a category above average
through the extended period.
.AVIATION /06Z 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 high cirrus, however wouldn`t be suprised
if a few mid clouds advected downstream of the mtns near daybreak,
thus did favor such. Otherwise, expecting diurnal heating to
gradually improved instability over the NC piedmont, possibly
overcoming deep layer subsidence late in the afternoon, therefore
opted for a 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 possible
mvfr fog/cigs at KAVL around daybreak, as well as any restrictions
associated with tsra on Friday. Few mid/high clouds to prevail
through morning before heating builds on Friday yielding increased
tsra coverage amidst low vfr cu, thus prob30s where included at
all sites. Winds looks to remain in the 6-10kts 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
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 75% 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: