Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
716 PM EDT Friday Jul 31 2015
dry high pressure will build into the region tonight and will remain
in place through the weekend. Low level moisture will gradually
return through next week as another cold front approaches from the
Near term /through Saturday/...
as of 715 PM EDT Friday...rather nice evening in store for the vast
majority of the forecast area as drier air continues to advect in.
Latest cam guidance continues to favor weak and short lived showers
across the upper Savannah River valley this evening...thus opted to
introduce isolated probability of precipitation for such through midnight.
Otherwise...tweaked probability of precipitation/temperatures and sky to better align with recent
obs/Sat...and left the remainder of the forecast unchanged as it was on
As of 200 PM EDT Friday...a very quiet near-term period in store in
the wake of the front that passed through last night. Upper low over
the Hudson Bay with troughing down the Appalachians will remain in
place through the period with very little change. Base of the trough
should reach to the northern portion of the forecast area but with
the bulk of the County Warning Area in a col area with little to no upper flow
between upper ridging in the Atlantic and Desert Southwest and south
of the upper low. Weak shortwave looks to push through the base of
the trough overnight tonight and early Saturday but no real sensible
weather impacts expected from it.
Some of the hi-res reflectivity guidance does want to develop
isolated convection especially across southern and western zones
this afternoon and evening...and at afd time there is one shower
that has developed across Rabun County. Have not included enough
probability of precipitation in grids to warrant shower or thunder mention but did keep probability of precipitation
around 10 percent in those areas. Storm Prediction Center day1 outlook continues to keep
general thunder across the southern portion of the forecast area.
Temperatures through the near-term should be very close to seasonal
averages...with very weak cold air advection behind the front competing with very
week downsloping...and the two probably just about canceling each
other out. The noticeable difference will be due to the drier
dewpoints...allowing it to feel almost pleasant outside. Enjoy the
Short term /Saturday night through Monday/...
as of 205 PM Friday...the weather still looks exceedingly quiet for
middle Summer. The upper pattern will remain essentially unchanged from
Saturday night through Monday...which keeps the East Coast at the
bottom of an upper trough and the western Carolinas with a dry northwest flow
aloft. The model guidance shows high pressure settling down over the
southern applachians from Saturday night into Sunday...then falling apart
on Monday. Shower activity seems highly unlikely outside the mountains
through the period...especially with surface dewpoints expected to mix out
into the middle/upper 50s. However...even with the warm air aloft...we
cannot rule out a few showers developing in the middle/late afternoon
over the higher terrain. Temperatures should be a few degrees above
normal...but that should not pose any heat threat given the
relatively dry air mass.
Long term /Monday night through Friday/...
as of 230 PM Friday...the medium range begins with the trough over
the East Coast beginning to lift. This will place the County warning forecast area in the
track of multiple shortwave crossing the Ohio River valley...though
a lack of deep moisture will preclude much instability. Probability of precipitation early
the week will therefore be kept mainly to low-end chance in the
higher terrain...with only slight chance or less in lower
elevations. Some moistening will occur gradually through the week as
the Bermuda high exerts its influence...so probability of precipitation increase slightly
each day through the end of next week. A frontal boundary will
propagate out of the Ohio River valley by mid-week...though it
appears to stall and become semi-stationary before it is allowed to
influence the County Warning Area. Guidance has come into better agreement on the
next frontal passage by the end of next week...with a surface low
ejecting out of the Great Lakes region and accompanying cold front
trailing through the southern Appalachians. The front will provide
some level of forcing...and with sufficient moisture having built
back into the area...probability of precipitation were increased back to just above climatology
for Thursday and Friday.
General height rises will allow maximum temperatures to warm to a couple of
categories above average early in the period...falling back to just
a degree or two above climatology by the end of next week.
Aviation /23z Friday through Wednesday/...
at kclt and elsewhere...VFR through the period as high pressure
prevails overhead with a cold front stalled to the south.
Light/moderate northerly flow will weaken into the evening leading
to light/calm winds by midnight at all sites. Skies will remain sky clear
across much of western NC...however soundings/mosguide do favor a
window of few low VFR stratus at kavl...generally around 6-8kft.
The same low VFR stratus is prognosticated across much of northeast Georgia and
the SC upstate...however confidence is low in persistence thus as
with kavl...kept only mention of few 060-070 in the SC tafs. Beyond
that expecting a fairly nice taf day on Saturday with light/moderate
northerly winds under few high level clouds for the SC sites with
sky clear possible over western NC.
Outlook...flight conditions will remain restriction free through
much of the weekend ahead of gradually increasing
precipitation/restriction chances through middle week as moist
southerly flow returns.
23-05z 05-11z 11-17z 17-18z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 100%
kavl high 100% 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: (must be lower case)