Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 310600
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
200 AM EDT SUN JUL 31 2016
A subtropical high off the Atlantic coast will maintain shower and
thunderstorm chances and high temperatures above normal through the
rest of the weekend and early next week. A stationary boundary will
sag into the area next week, keeping afternoon rain chances in the
.NEAR TERM /THROUGH TODAY/...
As of 200 AM EDT Sunday: Current fcst looks on track for the most
part as weak convection remains westward over east TN. However,
did allow for lowering of pops over the central/eastern tier of
the fcst area, while also tweaking t/td to align with recent obs.
Still expecting fog/stratus to develop in the mtn valleys, with
patchy fog certainly possible across portions of the Upstate where
moderate/heavy rainfall fell last evening.
Previous Discussion: We should see another impulse moving through
the flow aloft tomorrow, much more evident in the 700mb flow as a
weak shortwave trough that will bring with it a slug of low-level
moisture, and a weak 500mb vort max (maybe "max" is a misnomer
but it`s all relative). These should help to enhance convective
potential for tomorrow, but not necessarily intensity as WAA at
mid-levels will further decrease lapse rates. The best are for
convective development will be across the mountains as usual as
well as the northern tier of the foothills and Piedmont closer
to the upper system, where sbCAPEs tomorrow are progged to be at
least 500 J/kg higher tomorrow than today.
Temperatures will continue to run a degree or so above seasonal
normals for both highs and lows. With continued afternoon mixing,
despite the plentiful low-level moisture, we should continue to
remain below below heat advisory criteria, though heat indices
will likely creep into the lower 100s across our southern zones
and into the Upper Savannah Valley.
.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
As of 225 PM Saturday...the models continue to suggest we should
have a decent chance of developing mainly duirnal showers and
thunderstorms early in the week. The axis of a broad upper trof
should move across the region slowly on Monday with one or two weak
waves embedded in it. This should push a weak sfc boundary down
across the fcst area that will help to pool moisture and provide a
focus for deep convection once we heat the boundary layer. Think it
best to keep precip probability in the chance range for the time
being, but storms should be more numerous than the past several
days, so the probability might need to be bumped up with later
forecasts. Temps will remain seasonally warm, about a category above
normal, with the heat index reaching the upper 90s along and S of
I-85, but this is not unusual. The storms should move off the mtns
in the evening and then dissipate during the late evening. Tuesday
is a bit more interesting in that the new guidance, especially the
NAM, develops more in the way of precip coverage in the afternoon.
Perhaps this is because the sfc boundary remains strung out across
the region instead of being driven south of the region. Will bump
the precip chances up across the region a bit to put more of the
fcst area in the chance range. Precip chances will diminish again
with a loss of heating. Temps will be similar to Monday, so again no
heat advisory is anticipated.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 230 PM Saturday...medium range begins 12Z Wednesday with a
longwave trough moving off the East Coast and an upper ridge
building over the eastern third of the CONUS. This will temporarily
bring our CWA under the influence of northwesterly flow on Wednesday
and Thursday, allowing a train of shortwaves to make their way over
the area. The upper support coupled with the weak surface boundary
that will likely still be in place over the Carolinas will slightly
enhance our normal summertime diurnally driven convection. The
surface boundary appears to wash out on Thursday, though warm and
moist southwesterly flow (including an upslope component for the
higher terrain) will keep afternoon shower and thunderstorm chances
a bit above normal. Guidance then diverges somewhat through the end
of the period. The general trend depicted by most major models is
the development of an upper longwave trough over the eastern CONUS
next weekend, with a frontal boundary approaching the area. Timing
and strength of these features is still quite uncertain, so precip
chances were kept near to a little above climo for next weekend.
Still...it is reassuring to see that extended guidance may be
hinting at the possibility of some increased rain chances and high
temperatures closer to normal at the very end of the period. Until
next weekend though, max and min temps will stay about a category
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
At KCLT: VFR through the period aside for any possible mvfr/ifr
restrictions associated with late afternoon/evening tsra.
Initialized taf amidst light wsw flow beneath mid/high cirrus.
These conditions are expected to prevail through mid/late morning
before heating builds allowing for low vfr cu development.
Guidance favors increasing shra/tsra potential across the fthills
by mid afternoon, possibly propagating east into the NC piedmont to
affect KCLT later in the afternoon. Thus a fm group was featured
at 19z with vcsh and prob30 for tsra from 21z-02z amidst low vfr
bkn/ovc stratus. Conditions will improve towards midnight as
convection wains and or exits the region to the east, thus the
taf complies. Winds throughout the day will back sw and increase
with light gusting possible during the middle part of the day.
Elsewhere: Trends similar to that of KCLT above with VFR prevailing
for the most part aside for possible morning mvfr/ifr fog/cigs
at KAVL/KHKY, with mvfr fog possible at KGSP as well given heavy
rainfall last evening. Otherwise, mid/high cirrus will prevail
ahead of low vfr cu development with heating by the late morning
hours. Carried vcsh fm groups at all sites with tsra prob30s, aside
for at KHKY where guidance favors likely pops thus shra/vcts was
prevailed. Conditions will improve as convection advects east late
in the afternoon/evening, thus the taf indicates such improvement.
Outlook: Current upper level troffing will give way to rising
heights and thus building high pressure into midweek, while at
the surface a weak cold front moves through Tuesday and stalls on
Wednesday. Restrictions can be expected with any afternoon/evening
convection as well as each morning in the mtns valleys where
fog/cigs are possible.
06-12Z 12-18Z 18-24Z 00-06Z
KCLT High 100% High 100% High 100% High 98%
KGSP High 97% High 97% High 100% High 100%
KAVL Low 50% High 87% High 100% High 100%
KHKY High 100% High 100% High 100% High 92%
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: