-- Discussion containing changed information from previous version are highlighted. --
807
FXUS62 KGSP 041832
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
232 PM EDT Sat May 4 2024

.SYNOPSIS...
A front will remain stalled over the region through the weekend
resulting in periodic showers and thunderstorms. A general
summertime pattern sets up early next week, which will keep
scattered thunderstorm chances around each afternoon. Highs will
trend well above normal by Tuesday, remaining well above normal
through at least Thursday.

&&

.NEAR TERM /THROUGH SUNDAY/...
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As of 210 PM EDT Saturday: Good coverage of showers and isolated
thunderstorms continues across the are this afternoon. The strength
of the storms and intensity of the rainfall have dropped for now.
However, areas of heavy rainfall and isolated flooding will be
possible through the afternoon as the rainfall intensity may pick
back up or storms train over the same areas. Coverage is expected to
increase ahead of a short wave crossing the area. An isolated strong
or even severe storm will also be possible, especially where
instability is higher from the weak heating taking place in
locations without widespread showers.

Coverage should diminish overnight as the short wave moves out of
the area, but isolated showers may linger off and on all night. The
chance of strong storms and heavy rainfall also tapers off. Lows
will be around 10 degrees above normal.

Scattered convection, numerous across the mountains, returns Sunday
afternoon as instability redevelops. An isolated severe storm will
be possible as mid level dry air returns and DCAPE values increase
with heating. The mid level dry air will decrease PW values limiting
the flood threat. That said, isolated heavy rainfall will be
possible. Highs should end up a few degrees above normal.
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&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
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As of 145 PM EDT Saturday: Short term period will be generally
dominated by building mid-level ridge, but with a shortwave embedded
in the pattern lifting up from the MS Valley and traversing the area
through the period. Meanwhile a strong system will be gearing up
over the northern Rockies and push off into the northern Plains to
impact us into the extended. We`ll see a warming trend Monday into
Tuesday afternoon as the ridge builds aloft and surface high off the
New England coast slides south toward Bermuda, with moist southerly
flow rounding the base into the Southeast. A summerlike pattern will
set up as moisture and instability increase Monday, but very little
deep-layer shear to work with. Categorical pops pretty much area-
wide but highest in the mountains.

Shortwave pushes east on Tuesday and ridging builds in with stronger
SW flow aloft. NAM is a little faster with bringing some deep-layer
shear in ahead of the next system. Pops are a little lower on
Wednesday as moisture is not quite so widespread, but with warmer
temperatures (mid 80s in the Piedmont as opposed to lower 80s on
Tuesday) instability is a little higher as well, 1500-2000 J/kg so
could be looking at isolated strong to potentially severe with some
wet microburst potential.
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&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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As of 215 PM EDT Saturday: Active period for the extended as the
upper system moving across the northern plains drags a front through
the country Wednesday into Thursday. Should see continued low-level
WAA Wednesday with temperatures across the Piedmont climbing again
into the upper 80s, even flirting with 90 in the Charlotte Metro
area. Best pops will be in the mountains closer to the deep-layer
shear and moisture, but cannot rule out isolated activity elsewhere.
With the increased heating and better upper dynamics approaching the
area, SBCAPEs will climb again from Tuesday, now reaching 2000-2500
J/kg with over 30kt of deep-layer shear across the area, so where we
can get a storm going certainly can`t rule out isolated severe
activity with a very summer-like microburst feel, though there will
at least be movement in the storms so expect some organization.

Things get a little more interesting Thursday as the cold front will
begin to push into the area. Although the front will be stretched
out somewhat rather than just blasting through, strong DPVA combined
with the upper jet provide plenty of synoptic lift. It`s a little
far out for details but at least the GFS is trying to show a decent
850mb jet as well midday Thursday. Timing of the instability surge
and juxtaposition with strongest deep-layer shear might be critical,
but somewhere in our forecast area we are currently progged to have
2000-2500 J/kg lined up with >50kt deep layer shear, which is
impressive. Forecast trends will need to be monitored. SPC`s Day 6
outlook is vague on the area but mentions the possibility of needing
to introduce an one or more 15% areas for Thursday when guidance
comes into better agreement.

Upper shortwave actually begins to approach later on Friday so pops
remain in the forecast until then. However, depending on the actual
timing of the front itself, cannot rule out an insitu increase in
instability right along the front where there would be a local
enhancement in deep layer shear, but uncertainty is quite high on
when the front would push through. Pops remain high as in line with
the blends but timing will likely change in subsequent forecasts.
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&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: The very messy aviation forecast continues
with convection over the area and everything from VFR to LIFR.
Expect convection to continue through the afternoon becoming
isolated to scattered SHRA this evening. VFR TEMPO MVFR or IFR in
SHRA and TSRA this afternoon. Conditions deteriorate overnight even
as precip becomes isolated. Expect MVFR to IFR vsby and IFR to LIFR
cigs. Will see a slow improvement after daybreak with vsby becoming
VFR but cigs only slowly rising through MVFR to eventually VFR.
Scattered convection expected to begin developing before the end of
the period, but best chance holds off until after 18Z except KAVL.
Light and variable to S to SE wind this afternoon becomes light and
variable overnight into the morning Sunday.

Outlook: Enhanced moisture will combine with a weak/stalled front
through the middle of next week, resulting in a period of
active/mainly diurnal convective weather each day. There will also
be the potential for restrictions associated with widespread fog
and/or low clouds each morning.

&&

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

&&

$$

SYNOPSIS...TDP
NEAR TERM...RWH
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...RWH