419
FXUS62 KGSP 181829
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
229 PM EDT Tue Jun 18 2024

.SYNOPSIS...
High pressure atop the region will suppress any storms from
developing this week until moisture returns on Saturday. A heat
wave gets underway on Friday and remains hot through the weekend.
A weak cold front approaches from the north early next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 150 pm EDT Tuesday: Upper anticyclone and attendant strong
ridge will continue to gradually pivot west-through-north of the
forecast area through the period. This will result in establishment
of deep easterly flow across the CWA, which will act to support a
relatively low theta-E air mass beneath warm mid-level temps.
Diurnal instability will therefore be very limited through the
period, with positive sbCAPE generally expected to be limited to
locations near the TN border this afternoon...and west of the
forecast area on Wednesday. There`s currently a respectable amount
of enhanced cu-stratocu across western areas, so can`t rule out a
shower or two developing across the ridgetops...and perhaps even
along the eastern Blue Ridge escarpment. However, even that will be
difficult to come by on Wed. Drier air will finally allow min temps
to settle to near-normal tonight, while maxes Wed should be within a
degree or so of climo.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 230 PM EDT Tuesday: The forecast remains on track for the
short-term period with very little change to the previous package.
The period begins with the persistence of an impressive 597dm
ridge centered over the Mid-Atlantic, placing our region on the
southern periphery of the broad, deep-layer anticyclonic flow.
The resultant easterly flow to the south of the attendant
subtropical high over the Atlantic will allow Thursday to be the
"coolest" day for the foreseeable future, with temperatures maxing
out near normal for mid-June.  Thursday into Friday, the upper-level
anticyclone drifts south and west over the forecast area.  As the
easterly flow weakens with the ridge axis overhead, broad-scale
subsidence will dominate and temperatures will begin to climb.
High temperatures on Friday will peak in the lower 90s east
of the mountains or about 2-4 degrees above normal, with highs
in the upper 80s to near 90 for the mainstem mountain valleys.
The subsidence will result in a weak inversion and poor lapse
rates above the deep mixed layer so it will remain dry.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 230 PM EDT Tuesday: Saturday into Sunday, the center of
the upper-level ridge will gradually continue to migrate west
towards the Desert Southwest in response to height falls across
the Midwest and Ohio Valley.  The proximity of shortwave activity
and lowering heights aloft should gradually improve forcing
and lapse-rates, respectively, especially over the mountains.
Therefore, the forecast maintains a slight chance PoP over the
favored ridgetops on Saturday and a more widespread chance PoP
over the mountains and foothills for Sunday, as a weak front
enters the Ohio Valley.  The synoptic-scale guidance begins to
diverge on the propagation of shortwaves embedded in the westerly
flow to our north, but the general expectation is that by Monday,
a weakness in the heights aloft will set up over the Southeast
as the weak cold front approaches or enters the forecast area.
The front will result in likely PoPs in the mountains and chance
PoPs elsewhere for Monday, but the subtropical ridge axis will
effectively shutdown moisture advection from the Gulf of Mexico.
Therefore, we are not expecting appreciable rainfall from this
system; most areas will receive less than a tenth of an inch.
On Tuesday, the front is expected to stall near or to the south
of the forecast area, so uncertainty regarding PoPs is high.
Nevertheless, at this time we are expecting a more climatological
diurnal pattern Tuesday afternoon.

While the synoptic setup may suggest a cooling trend, unfortunately,
our low-level flow will veer west-southwesterly as the ridge axis
sets up south of the area.  Therefore, the airmass will remain
hot and if anything, the presence of weak moisture will work to
increase dewpoints and uncomfortable humidities into early next
week.  The best combination of low-level warm-air advection and
upper-level subsidence will occur on Sunday, but generally speaking,
highs will reach the mid-90s Saturday through Tuesday east of
the mountains and the lower 90s in the mainstem mountain valleys.
Lows will be 5-7 degrees above normal or in the lower 70s east of
the mountains and in the mid- to upper 60s in the valleys.

While the forecast temperatures may be a broken record, at this
point we do not expect any records to be broken through the
extended period.  The site most likely to tie or slightly break a
record will be at Asheville, where record highs are at or near 94.
Records for GSP and Charlotte are closer to 100.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: SCT/BKN stratocu in the 035-050 range will
continue across the Terminal Forecast Area through the afternoon
before thinning out this evening. Otherwise, VFR conditions are
forecast through the period, as relatively dry/stable air filtering
into the area on easterly low level flow will significantly limit
the potential for diurnal convection as well as morning fog/low
stratus. Winds will therefore be the primary concern, with
directions expected to range between E/NE and E/SE at 5-10 kts at
most sites through much of the period (except for light winds
tonight).

Outlook: An expansive upper ridge will keep things mostly dry with
VFR conditions thru Friday. Mtn valley fog and/or low stratus will
be possible most mornings, while diurnal convection could return over
the weekend.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...DEO
NEAR TERM...JDL
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...JDL