937
FXUS62 KGSP 301051
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
651 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 640 AM Sunday...Apart from some lingering debris clouds and
light rain over the nrn foothills, the bulk of the precip over
the next hour or two looks like it will move past just to the
north. Meanwhile, we look upstream at more numerous showers and
thunderstorms over the Cumberland Plateau ahead of an approaching
cold front.

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. This could also be aided by an outflow
boundary from the ongoing convection to the WNW. 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 /12Z 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