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094
FXUS62 KGSP 250733
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
333 AM EDT Tue Jun 25 2024

.SYNOPSIS...
Dry and less humid conditions continue today before the heat and
humidity returns Wednesday ahead of an approaching cold front. This
front will bring showers and thunderstorm chances back to the area
late Wednesday into Thursday. Hot and humid conditions will persist
into the weekend with a chance of showers and thunderstorms each
afternoon. Another cold front approaches the area late this weekend
keeping unsettled weather around.

&&

.NEAR TERM /THROUGH TONIGHT/...
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Key Messages:

1) Dry Weather and Lower Humidity Stick Around Today

2) Well Above Normal Temperatures Continue through the Period

As of 230 AM EDT Tuesday...Sfc high pressure will continue to build
into the region from the north through daybreak and will remain over
the western Carolinas and northeast Georgia through tonight leading
to continued dry weather. Temps this morning will be noticeably
cooler compared to yesterday morning but will remain a few degrees
above climo. Lows will dip into the mid 50s and low 60s in the North
Carolina mountains, with lows elsewhere ranging from the mid 60s to
low 70s. Wind speeds will increase slightly as the pressure gradient
tightens briefly around daybreak but should gradually die down
throughout the rest of the morning. Although humidity will remain
low again today, with minimum RH values dropping down to 30%-35%
across much of the area this afternoon, hot temperatures will return
once again. Highs will climb into the low 90s in the mountain
valleys and the low to mid 90s east of the mountains. Lows tonight
will be warmer (and ~5-8 degrees above climo) thanks to 850 mb winds
turning S/SW`ly. This will also allow humidity to increase again
tonight east of the mountains.
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&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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As of 130 AM Tue: Shortwave crossing the Great Lakes Tue night will
promote height falls Wed afternoon and evening over our region;
sfc front should reach the Ohio River before sunset. With midlevel
ridge to the west, we will mix up into dry air again for part of the
day, although 850-700mb flow will become southerly in advance of the
trough during the afternoon. Thus, despite diurnal instability model
QPF response is low during the day, and PoPs appear warranted only
over the mountains. Convection will develop ahead of the front in
KY/TN but with the front itself not reaching the mountains until
overnight, the convection is expected to ash out before it gets
to our border. Under exceptionally high thicknesses, temps Wed
may be the hottest of the year so far, with upper 90s across the
Piedmont and low 90s for the mountain valleys. As noted however
dewpoints will mix out enough that heat index should peak "only"
around 100 in the lower Piedmont.

Models differ as to how quickly the front settles through our area,
and it becomes rather diffuse as it is. It looks mainly to serve
as a source of weak convergence and promote moisture pooling,
thus a focus for diurnal convection. Confidence remains best for
mountain and northwest NC Piedmont PoPs during the day Thursday,
50 to 60% in those areas. The front should reach the southern half
of the CWA by the end of the day and our southern zones still get
at least 40% PoP. Shear will remain seasonably weak but lapse rates
not strong enough through a deep layer to produce especially high
CAPE, although a damaging microburst or two can`t be ruled out.
Dewpoints don`t look to mix out as much but temps will be slightly
cooler and heat index again peaks around 100 at worst.  Thursday
night into Friday morning, the major models depict a weak low
partially or completely shearing off from the base of the trough
near the Gulf Coast, and that will have the effect of stalling the
front and perhaps reactivating it.  Accordingly some PoP will linger
in the Piedmont Thursday night after diurnal convection diminishes.
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&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
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As of 305 AM Tue: Sfc high on the cool side of the front will
migrate across the Northeast Friday into early Saturday. The
influence of this high will keep temps relatively mild Friday but
still actually a degree or two above normal. Low-level flow will
turn easterly and then southeasterly; remnant of the front or
weak low mentioned in the late short-term period should exit to
the east as heights rise. The onshore flow will bring dewpoints
a bit higher and suggests diurnal PoPs around climo, with some
chances lingering overnight into early Saturday. This general
evolution continues through Saturday, with temps and dewpoints
ticking upward via airmass modification. PoPs also rise slightly.

The real feature of interest for the period will be another
trough passing the Midwest and carrying another front south and
east. Global models/ensembles really agree fairly well on this
occurrence, just varying in the timing thereof. The GFS is fastest,
followed by the GDPS and then ECMWF, sometime between midday Sunday
and late Monday morning. GFS is also the most bullish with precip
coverage. Peak temperatures and PoPs are depicted Sunday, with
slightly cooler and lower values Monday, but still above climo in
both regards. Although dewpoint mixing will not be as effective
within this pattern, a slight afternoon dip is likely. Values may
edge above 100 each afternoon in the Piedmont, but Sunday would
be the day of most concern with most areas outside the mountains
rising to 100-104, with a few isolated spots perhaps exceeding 105.

Any thunderstorms in the period, even near the fropa, likely will
remain of the pulse or loosely clustered variety. PWAT values
upwards of 150% of normal can be expected and a localized heavy
rain threat is a reasonable bet, although dry soils may initially
mitigate flood concerns.
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&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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Key Messages:

1) Dry and VFR through Wednesday Morning

2) Shower and Thunderstorm Chances Return Ahead of a Cold Front
Wednesday afternoon and evening

3) Shower and Thunderstorm Chances Linger Wednesday Night into
Thursday as the Cold Front Tracks Over the Western Carolinas

At KCLT and elsewhere: VFR and dry through the 06Z TAF period
thanks to sfc high pressure. Wind speeds will range from 3-7 kts
through daybreak, potentially increasing to 5-9 kts east of the
mountains for a short period after daybreak. With wind speeds
remaining elevated, fog formation is not expected at this time.
Brief low-end wind gusts cannot be entirely ruled out east of the
mountains from 11Z-13Z as the pressure gradient tightens slightly.
However, confidence remains too low add any mention of gusts for
now. Wind direction will remain N`ly through daybreak before
gradually turning more NE east of the mtns through the morning
hours. Winds become more light and VRB this afternoon into tonight
across the terminals. A few cumulus should develop this afternoon
before dissipating around sunset.

Outlook: Widely scattered SHRA/TSRA returns Wednesday afternoon and
evening as a cold front approaches out of the west. The cold front
will track over the terminals Wednesday night into Thursday before
stalling south of the area on Friday, keeping SHRA/TSRA chances
around.
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&&

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

&&

$$

SYNOPSIS...AR
NEAR TERM...AR
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...AR