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000
FXUS62 KGSP 171735
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
135 PM EDT Wed Apr 17 2024

.SYNOPSIS...
Warm and humid weather continues with showers and thunderstorms
possible through Friday, as a weak front could reaches the area.
Much cooler weather returns over the weekend, with a chance of rain
returning by Sunday and into the beginning of the next work week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 135 PM Wednesday: Showers ahead of a weak short wave will move
into the area by late afternoon and out of the area by late evening.
A thunderstorm or two is possible, but chance of any severe storms
or heavy rainfall is low. Gusty S to SW winds will continue ahead of
the showers with wind becoming light as the showers depart. Dry high
pressure and upper ridge return on Thursday with lighter winds. Lows
tonight around 10 degrees above normal and highs Thursday around 15
degrees above normal. Right now, it appears that only GSP will
threaten a record high with AVL and CLT having much higher records,
both set in 1896.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 415 AM Wed: Thursday still looks like another exceptionally
warm day for the area, with mid to upper level ridging developing
overhead. Weak cold front will have passed and led to low-level
drying, while midlevels warm via subsidence under the ridge and/or
downslope flow aloft. Diurnal convection looks unlikely in the
Piedmont due to resultant capping, although models generate some
SBCAPE in the afternoon. The NAM and NAMNest show the cap mixing
out on prog soundings from KAVL, but given the other factors and
CAPE still being limited to a few hundred joules, this does not
appear worthy of a mentionable PoP. Still anticipate near-record
highs in the Piedmont.

The ridge will be transient, already shifting east of the CWA
Thursday evening as a developing cold front and associated frontal
wave advance out of the western Ozarks and across the lower OH
and TN valleys. North of the Ohio River, the front will orient
meridionally, with frontal wave being bolstered by the trough over
the northern Plains. The portion of the front that approaches
the southern Appalachians Thursday night will have less initial
dynamic support, but height falls may occur upstream and result
in a weak shortwave reaching the area with the front. Associated
convection likely will wane nocturnally before it reaches the CWA
Friday morning, and the fropa itself is not all that dramatic; in
fact the true surface front probably will not pass the mountains
until Saturday. Nevertheless PoPs do ramp up overnight and to
categorical near the TN border Friday morning with activity along
the front aloft. Weak low-level capping is likely to persist and
make thunderstorms unlikely, but if an updraft does manage to
go up, storms could pose a risk of strong to severe microbursts
or marginally severe hail. Not sure this conditional probability
warrants the SPC Marginal Risk. Temps generally will drop back a
few degrees owing to cloud cover; the mountains will drop a bit
more with their higher elevation and exposure to the first push
of coler air.

Models are a little more supportive of QPF in the Piedmont Friday,
but the subsident air still will have to be overcome in that area.
With WAA continuing into the SC Midlands and central NC and some
runs even suggesting a weak frontal wave or MCV will persist, we
will advertise at least a chance PoP for the whole CWA, lasting
into evening for our lower Piedmont.  Upslope PoPs linger behind
the front along the TN border into Friday night also. Mins will
trend cooler in the mountains as noted above, but still well above
normal across the board.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 230 AM Wed: A weakly forced quasi-zonal flow regime is
expected for the Southeast this weekend. Low-level convergence
will persist across the Piedmont Saturday near the elevated cold
front. Airmass change still looks unlikely to occur for our area
until late in the day or Saturday night, with most models showing
the surface front still just pushing across the Appalachians
at 00z Sun. The model spread which had once limited confidence
in Sunday`s highs now is greater on Saturday, depending on the
advance of the front. It does look likely temps will fall back to
more seasonably warm weather, with highs only 3-6 degrees above
normal. Drier air is likely to have arrived aloft, although the
low levels may still be moist.  Midlevel subsidence is expected
to limit convection although some prog soundings still show small
diurnal CAPE. Thus we will advertise a mostly dry forecast Saturday.

As the front pushes further through the area Saturday night, a
weak shortwave may develop near the western Gulf Coast, turning
the zonal flow slightly cyclonic across the Southeast. The wave
will stall and/or reactivate the front to our south, possibly
Saturday night but more likely Sunday into Monday. The exact timing
remains uncertain, as well as the position of the incipient frontal
wave. The consensus solution puts most of our area on the cool
side of the front under dry northerly flow, which implies low-end
QPF. Thunderstorms now look unlikely with instability more likely
shunted south by the front.  Sunday and Monday do look likely to
be cool days with below-normal temps.  Within the cyclonic flow,
a compact shortwave may move out of the mid-MS Valley, possibly
enhancing lift and QPF for Sunday night or Monday.  Weak high
pressure may give us a break Tuesday along with milder/sunnier
weather, but another shortwave may approach by Tuesday night.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: Thickening and lowering clouds expected into
the evening, but not expecting anything lower than low VFR at the
TAF sites. Low VFR in SHRA, and possibly a TSRA, late this afternoon
and early evening. Gusty S to SW winds also in place into early
evening. Can`t rule out a brief MVFR vsby or cig in any heavier
shower. VFR expected overnight with light winds behind the departing
showers. That said, mountain valley fog possible, but unlikely at
KAVL. Light W to NW wind and SKC for Thursday.

Outlook: An unsettled pattern with precip chances and periodic
restrictions may develop from Thu night into Monday, but confidence
remains low.

&&

.CLIMATE...
RECORDS FOR 04-18

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      90 1896     44 1921     60 1927     28 1905
                                        1891
   KCLT      93 1896     45 1983     66 1896     32 2001
   KGSP      89 2002     51 1983     66 1927     28 1905
                1967

&&

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

&&

$$

SYNOPSIS...CP
NEAR TERM...RWH
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...RWH
CLIMATE...