-- Discussion containing changed information from previous version are highlighted. --
061
FXUS62 KGSP 031440
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1040 AM EDT Mon Jun 3 2024

.SYNOPSIS...
Scattered afternoon showers and thunderstorms are expected today and
Tuesday with temperatures warming back into the mid to upper 80s.
Showers and thunderstorms will increase in coverage Wednesday into
Thursday morning as a cold front crosses our area. Drier weather is
expected to return by the end of the week and persist into the
weekend, although a few isolated mountain showers will remain
possible.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 1025 am: A steadily weakening batch of showers continues to
skirt the southern border of the CWA late this morning...and should
finally scoot east of the area by noon. Weak upper ridging will
build in from the west through the day, warming the mid levels and
weakly suppressing the atmosphere...especially for areas outside the
mountains. However, cloud cover will continue to thin into the
afternoon, allowing back to return to near-normal levels, combining
with sfc dewpts in the m60s, to allow for moderate destabilization,
with sbCAPE of around around 1500 J/kg expected at peak heating. The
latest guidance has featured in uptick in coverage of diurnal
mountain convection, warranting an increase to 50-60 PoPs across
much of that area this afternoon. However, with little shear and
modest instability expected, afternoon thunderstorms will likely
remain sub-severe, with perhaps a handful of strong storms possible.
Otherwise, expect a humid/warm day with modest sw/ly winds.
Overnight lows will be held abv normal by a few degrees, with fog
formation likely over many areas as the sfc layer becomes saturated.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 234 AM Monday: The short term forecast kicks off on Tuesday
with an intense Pacific jet nosing into the Pacific Northwest and a
downstream trough ejecting out of the Northern Rockies, both of
which will ultimately influence the forecast across our area. Closer
to home, the 12z suite of global guidance is in good agreement that
a weak southern stream shortwave trough will be located over the
Lower Mississippi Valley within a broad zone of weak westerlies
extending out of the Southern Plains. This feature is forecast to
lift across the Tennessee Valley late Tuesday. At the same time, low-
level mass response to a rapidly strengthening surface low over the
southern Canadian Prairies will in turn strengthen low-level flow
across the Gulf states and into the Southern Appalachians. Resulting
increased moisture flux will allow for the advection of a ThetaE
ridge into the forecast area with PWATs surging to near 2". This
moisture surge in concert with temperatures in the low to upper 80s
will foster moderate instability (2000-2500 J/kg of surface-based
CAPE). Now that we`ve entered the CAM window guidance has trended
wetter for Tuesday with a greater coverage of diurnal showers and
thunderstorms. The consensus form the 00z suite of CAMs is for
thunderstorms to develop within the nose of the surging ThetaE plume
across north Georgia into the Upstate and western North Carolina. 15-
25kts of 850mb flow will also likely be sufficient for loose
organization of storm clusters/line segments along composite cold
pools. Any deeper convection and organized clusters will be capable
of producing wet microbursts with a few isolated severe
thunderstorms not out of the question.

By Wednesday, the previously mentioned trough over the Northern
Plains will take on a negative tilt as the Pacific jet further helps
to dig the trough over the Midwest with a large upper low eventually
closing off. A series of two attendant surface cold fronts will
encroach on the area with the lead front progged to be draped from
west Tennessee across northern Kentucky by Wednesday night. Ahead
of the front, several shortwave ripples aloft will pass over the
Southern Appalachians with southwesterly 850mb flow continuing to
strengthen in response to the deepening low. Showers may already be
ongoing Wednesday morning within the moist airmass. Coverage will
only further increase through the day with showers and thunderstorms
likely across much of the area. A severe weather threat may also be
realized, but will be conditional as to how much destabilization can
be achieved within the very moist environment. Too many morning
showers/clouds could dampen recovery for the afternoon, especially
if convection gets an early start in the uncapped atmosphere.
However, several severe thunderstorms will be possible should
moderate instability nearing 3000 J/kg of SBCAPE depicted in more
aggressive solutions be observed. The approaching cold front will
likely keep showers and a few thunderstorms going well past the
traditional diurnal cutoff with activity expected to fester through
the overnight as additional convection moves east out of Tennessee,
although a lack of instability overnight should preclude any severe
threat.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 302 AM Monday: The first cold frontal boundary will be
knocking on our doorstep by daybreak Thursday morning. Showers and
perhaps a few isolated thunderstorms will likely be ongoing ahead of
the front. With time, as the front pushes through the area, any
showers and thunderstorms will become shunted farther southeast with
rain chances gradually coming to an end from west to east through
the day. Dry air will quickly filter into the area in the wake of
the frontal passage, but temperatures will actually be quite warm.
Clearing clouds, downsloping flow, and very deep mixing will foster
high temperatures in the mid to upper 80s with several readings
around the 90 degree mark possible. Deep mixing in the dry post-
frontal airmass will be key with some forecast soundings indicating
the potential to mix as deep as 650mb, which is quite remarkable for
this part of the country, especially in early June. High
temperatures may actually be underdone should this degree of mixing
actually occur. A second reinforcing front will cross the area
Thursday night into early Friday morning. This front is expected to
be moisture starved, but a narrow band of moisture pooling may prove
sufficient to squeeze out a couple showers along the Tennessee
border. Cooler air will finally advect into the region behind this
reinforcing front along with very low PWATs for early June. Forecast
PWATs of 0.4-0.7" Saturday morning would rival the daily record low
based on sounding climatology at Greensboro. The sprawling closed
upper low will become stagnant over the weekend and centered over
the Mid-Atlantic. This will allow for pleasant and dry weather
within large scale northwest flow on the southwest flank of the
upper low. A few isolated northwest flow rain showers will be
possible along the Tennessee border through the weekend, but
profiles elsewhere will be too dry to support precipitation chances.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Flight conds will lower thru the overnight
across all terminals with IFR/LIFR more likely at KAVL and KHKY arnd
daybreak. Other terminals shud see mainly MVFR conds, with TEMPO IFR
due to CIGS. Active weather continues this afternoon with showers
and thunderstorms returning to the area. The extend of tstm coverage
will be rather low and confidence is below avg for storms at any
given airport. However, the best chance thunder will be at KAVL,
KHKY where prob30s have been included due to more distinct upper
energy traversing the flow over these locales. Overall shra/tstm
coverage arnd the other sites only warrant a VCTS at KAND and VCSH
elsewhere, including KCLT. Winds will remain low to moderate and
aligned s/ly to sw/ly across the area today.

Outlook: Diurnal shower and thunderstorm chances with associated
restrictions will linger thru the middle of the week.

&&

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

&&

$$

SYNOPSIS...TW
NEAR TERM...JDL/SBK
SHORT TERM...TW
LONG TERM...TW
AVIATION...SBK