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fxus62 kgsp 211903 

Area forecast discussion
National Weather Service Greenville-Spartanburg SC
303 PM EDT Wed Aug 21 2019

typical summertime heat and storms will continue into Friday ahead
of a southward moving cold front. This front will push into the
region by Saturday, and then gradually settle just to our south on
Sunday. An area of high pressure will build in from the north
resulting in cooler than normal temperatures and lingering moisture
into Monday.


Near term /through Thursday/...
as of 255 PM EDT wednesday: as hot and humid conditions prevail this
afternoon (temperatures in the upper 80s to lower 90s and dewpoints
in the lower 70s), latest radar imagery depicts showers and
thunderstorms continuing to Blossom across the western portions of
the forecast area attm, stretching from the Blue Ridge Escarpment and French
Broad River Valley, Down into northeast Georgia. With west-southwest-ly flow in
place, storm motion will be generally west to east through the rest
of today and tonight. Per latest mesoanalysis, instability is
slightly better than yesterday, with SBCAPE 2000-3000 j/kg and dcape
800-1000 j/kg with somewhat drier mid-levels. Thus, a few strong to
severe thunderstorms will be possible, as these storms continue to
be driven by a weak vort moving overhead within weak upper
troughing, and a developing weak Lee trough.

With the persistence of ridging aloft to the west and east, guidance
continues to prog the weak upper trough over the Carolinas to
retreat off to the northeast overnight, as another upper trough digs
through the upper Midwest, which will continue to drive a cold front
into the Ohio Valley and towards the area, though not pushing through
the area until beyond the near term forecast period. Thus, for
tonight, with the loss of daytime heating, expect convection to wane
across the upstate, northwest Piedmont, and northeast Georgia, giving way
to dry conditions. Meanwhile, along the Tennessee border, with upslope
flow, some available moisture, and limited instability, could not
rule out lingering light showers through the overnight hours. Min
temperatures will remain just above normal.

On Thursday, the unsettled weather pattern will continue as the
upper trough across the upper Midwest continues to drive the cold
front southeastward towards the southeast. Max temperatures once again
will climb a few degrees above normal.


Short term /Thursday night through Saturday/...
as of 255 PM EDT wednesday: heights will fall sharply across New
England and the mid-Atlantic on Friday. Moisture will deepen ahead
of an associated frontal boundary as it slowly settles southward
toward the forecast area. The front may move south into NC by late
in the late in the day. This keeps an unstable warm sector to stay
in place most of the day. With SBCAPE values running 2500 j/kg and
precipitable water values closing in on two inches, expect numerous
to possibly widespread showers and thunderstorms. Heavy rain will be
more likely than severe storms. The front continues to slowly sag
southward on Saturday even as the best height falls remain to our
north. The highest precipitable water values sag south as well. However, they will
remain near 2 inches. The instability gradient sags south as well,
but will remain high enough for thunderstorms over much of the
mountains and I-85 corridor. The upper jet will be favorable for
divergence, so expect numerous showers and storms again. Heavy rain
potential continues to be higher than the severe storm potential.
The string of hot weather looks to finally break as highs near 90
outside of the mountains Friday fall Saturday to around 80 along the
I-40 corridor to mid 80s along the upper Savannah River valley.


Long term /Saturday night through Wednesday/...
as of 200 PM EDT wednesday: the medium range model consensus
maintains sfc ridging nosing swwd into the cwfa on Sunday. Sensible
wx will feature continued unsettled conditions and below climo
temperatures. Will plan on maintaining likely probabilities for
showers, especially throughout the southern cwfa, closer to the
deeper moisture. Falling pressures within linger llvl damming
region are on tap to start off the workweek with energy encroaching
from the west, and the mean SW flow picking up. We are still not
expecting much of an upward jump in temperatures thanks to lingering
cloudiness and scattered showers. A warming trend is slated for the
latter half of the period with a return to near climo temperatures
by the new day 7. Within the broad but weak cyclonic flow aloft,
there looks to be little to inhibit daily convective chances, so
diurnally enhanced scattered thunderstorms are expected daily.


Aviation /19z Wednesday through Monday/...
at kclt and elsewhere: VFR prevails this afternoon with latest radar
imagery depicting isolated showers and thunderstorms developing
along the Escarpment, moving eastward. Through the afternoon/evening
hours, expect thunderstorms in the vicinity/vcsh, though confidence is low on timing of any
storm moving overhead a taf site. Thus, have carried tempo groups
for this afternoon. Into tonight, expect convection to wane with mid
to high level clouds, few/sct, allowing for VFR to prevail, with SW
winds 5 to 7 kts. However, towards daybreak, anticipate
MVFR/marginal IFR fog development at kavl (and possible stratus),
with marginal MVFR fog possible at khky as well. On Thursday,
afternoon showers and thunderstorms are anticipated once again, as a
cold front slowly moves towards the area from the northwest.

Outlook: rain showers/thunderstorms and rain chances will increase with a cold front Thursday
and Friday, remaining elevated thru the weekend as the front stalls
over the area. Some morning fog and low stratus will be possible
each day, especially in the mountain valleys.

Confidence table...

19-01z 01-07z 07-13z 13-18z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 100%
kavl high 100% high 100% Med 66% high 96%
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:



Gsp watches/warnings/advisories...



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