817
FXUS62 KGSP 300748
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
348 AM EDT Sun Jun 30 2024

.SYNOPSIS...
Hot and humid conditions will arrive today, as well as showers
and thunderstorms, ahead of a robust cold front.  Drier and cooler
conditions will set in behind the front Monday and Tuesday, before
the summer heat returns Wednesday and beyond.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 320 AM Sunday...Still seeing a few patches of shower activity
on the KGSP radar at this early hour in the continued light
southerly moist upslope flow across the region. Like last night,
this should continue on toward daybreak with scattered coverage
mainly close to the higher terrain. The better convection was along
the TN border, where a few lightning flashes have been detected,
so an additional embedded thunderstorm will not be ruled out. Cloud
cover will help to keep temps above normal and dewpoints relatively
high even for this time of year.

The next 24 hours should be a little more active across the region
as the nearly zonal flow we`ve been under for the past several days
finally buckles as a short wave digs down over the Appalachians
today and helps to amplify a broad mid-level trof along the East
Coast. The upper wave will help to drive a cold front from the OH
Valley southeastward toward the region today. Before it arrives, we
have the matter of the Heat Advisory to contend with. We should get
out to a warm start this morning, but cloud cover will act to limit
or delay the heating over parts of the fcst area. And then there
is the possibility of better convective coverage this afternoon,
as forcing should be sufficient to bring the best chances that
we`ve had in the past few weeks for some needed rainfall across the
western Carolinas. The CAMs are in general agreement that a lee trof
will be the focus of storm development east of the mtns early this
afternoon. The extra cloud cover and storm coverage could limit
the high temps and keep us from reaching Heat Advisory criteria
in some places. The trend in the guidance was slightly down on the
Heat Index. Suffice to say, no indication the Advisory needs to be
expanded. However, we won`t shrink it either at this point, even
though confidence in reaching criteria is trending downward. The
front should bring another round of showers and storms into the
mtns this evening, and then east of the mtns overnight. Weak shear
could help to organize this activity. As to the severity, the lapse
rates remain relatively weak and we lack mid-level dry air. A
Marginal Risk on the Day 1 from SPC looks okay just on general
principles with a boundary moving across the area, but it might
be a stretch to get more than a few strong storms. For tonight,
the front will move to the east after midnight and help to keep a
chance over the eastern zones through daybreak Monday. Low temps
will continue to run above normal.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 215 AM EDT Sunday: The short term is shaping up to be a dry
few days as ill-defined surface high pressure migrates out of the
Great Lakes and across the Upper Mid-Atlantic.  The resulting
subsidence aloft will hold any prospects of convection at bay,
while ushering in cooler temperatures and drier dewpoints after
the oppressive weekend heat.  A CAD-like regime will set up on
Tuesday, further cooling and drying the forecast area.  On Monday,
afternoon temps will only reach the mid- to upper-80s with RHs in
the upper 40s; on Tuesday, they`ll stay in the lower 80s with RHs in
the lower 40s.  It`s worth noting that forecast soundings from both
the GFS and the NAM depict a steep dropoff in dewpoints around 750mb
each afternoon...which hints at the possibility of a dewpoint crash.
For now, accounted for this by giving added weight to the raw model
output for the dewpoint forecast...as this tends to perform better
in these scenarios.  An afternoon breeze is likely on Monday as what
remains of constrained postfrontal flow aloft mixes to the surface;
by Tuesday even fleeting wind gusts will be difficult to come by.
By all accounts, both days should be beautiful!

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 224 AM EDT Sunday: An increasingly summer-like pattern will
set in for the medium range.  Deep upper ridging will set up over
the southern Great Plains and into the Southeast, while Atlantic
high pressure allows a southerly moisture flux to develop with
a weak Gulf fetch.  In the latest round of operational guidance,
the more potent moisture transport is depicted remaining displaced
to our west.  So forecast profiles remain basically dry through
Wednesday, and only begin to exhibit modest moistening on Thursday.
With minimal synoptic forcing and a questionable amount of available
moisture, it therefore seems like any diurnally forced showers and
thunder will be focused over the mountains, and limited in coverage,
through Thursday afternoon.

By Friday, better moisture should be working into the forecast
area...with even the driest members of the latest LREF cycle at
least as moist as the consensus on Thursday in the 850-700mb layer.
So, somewhat better coverage of mountain showers and thunderstorms
is expected, and convection is more likely to break containment
and start developing over the Piedmont and Upstate by the end of
the week.  At this point, temperatures will also be on the rebound
beneath the ever-intensifying heat dome.  On Friday and Saturday,
temperatures may surge into the upper 90s, paired with downright
soupy dewpoints.  So, heat index may once again become an issue
toward the end of the 7-day period.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: For the third night in a row we are seeing
widely scattered showers developing in a light moist southerly
flow across the region. Will be handling the restrictions
with amendments, as confidence in showers impacting any of the
terminals is sketchy through daybreak. Wind will be light S or
calm. On Sunday, expect with minimal heating we should develop
a low cloud deck, followed by the development of deep convection
in the early afternoon. The CAMs show some decent agreement, so
confidence is high enough to present a TEMPO for the mid/late
afternoon hours at most terminals. Convection should persist
well into the evening ahead of an approaching cold front, so a
PROB30 will be employed. Restrictions should be contained to the
TEMPO/PROB30 groups. Wind should be light S to SW. The cold front
should move southeast across the region in the late night hours
with wind coming around to NW after the front moves through.

Outlook: The cold front will push thru and stall just south of
the area, resulting in quieter weather for Monday thru mid-week.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from noon today to 8 PM EDT this evening for
     GAZ018-026-028-029.
NC...Heat Advisory from noon today to 8 PM EDT this evening for
     NCZ070>072-082.
SC...Heat Advisory from noon today to 8 PM EDT this evening for
     SCZ008>014-019-104>109.

&&

$$

SYNOPSIS...MPR
NEAR TERM...PM
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...PM