097
FXUS62 KGSP 210549
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
149 AM EDT Tue May 21 2024

.SYNOPSIS...
Warm high pressure will persist across the region through the
middle of the week. A cold front approaches from the northwest on
Thursday, bringing a chance of showers and storms mainly to the
mountains. The front will stall over the area Friday, keeping rain
chances through weekend and into early next week.

&&

.NEAR TERM /THROUGH TODAY/...
As of 145 AM EDT Tuesday: Given cloud cover across the mountains
and foothills is being more stubborn than the models suggest, sky
cover was bumped up thru daybreak and fog largely removed. Still
some patchy fog may form in any valleys that can manage to stay
clear for a while before sunrise. The I-77 corridor is mostly clear,
but drier BL should limit any fog potential there.

Otherwise, persistence looks like a really good forecast over the
next 24 hours as the salient features don`t change much. We continue
to enjoy a positively-tilted mid/upper ridge that supports weak
high pressure to our northeast. As a result, expect another round
of mountain valley low stratus/fog late tonight, with some locally
dense. Once that mixes out in the middle-part of the morning, the
day should be quiet again east of the mtns, but ridgetop showers
can be expected in the mid/late afternoon. High temps will nudge
upward a bit, maybe a category above normal Tuesday afternoon.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
As of 130 AM Tue: Upper ridge will persist over the Southeast
coast Wednesday. Cold front will push slowly past the Ohio River,
having limited dynamic support with parent low occluding north of
Lake Superior. The front looks to remain west of the Appalachians
thru Wed night. Max temps will trend warmer, both at the sfc and
at around 700 mb. Any uptick in low level instability looks to be
stifled despite good lapse rates developing above 700 mb; we also
lack much of a trigger, so deep convection looks questionable even
over the mountains.

Vort lobe encircling the Canadian low will rotate past the
Great Lakes Wednesday night, and RR quad of associated jet
streak will promote development of a weak, possibly convectively
enhanced shortwave. This may result in some convection in East
TN and remnants thereof could reach the mountains in the very
early morning. The shortwave itself is likely to push across the
Appalachians near peak heating Thursday, flattening the ridge a bit.
700mb temps cool slightly and although this may not totally erode
the inversion it makes convection more likely than Wednesday. Storm
motion will be a bit faster and steering flow westerly, so small
PoPs are warranted in the upper Piedmont in addition to the high
chance to likely values over the mountains. The better flow will
also translate to a bit better deep layer shear, perhaps above 30
kt. However the column may be too moist for the level of severe
threat than we would typically see with convection this time
of year, or for strong cold pool generation, thus not especially
concerned for severe. Locally heavy rain may be of greater concern.
Although increased cloud cover may knock temps back a little in the
higher terrain, the Piedmont will trend a little warmer Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 215 PM EDT Monday: An active pattern returns for this period
as a series of short waves move east across the area. These will
push a series of low pressure/frontal systems across the area as
well. Expect good to numerous, mainly diurnal, convective coverage
each day, with the highest PoP favoring the mountains. Still to
early to be certain on the severe storm chances given the potential
for limited instability, even though forcing and shear will be
decent. Heavy rain potential may eventually creep up as well,
especially if the better coverage hits the same areas day after day.
Highs will drop a few degrees on Friday then remain nearly steady
through the period. Lows rise a few degrees then remain nearly
steady.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: High-based stratocu continues to expand
across the NC mountains and south into the Foothills and much of the
Upstate. Guidance seems to be too quick to dissipate the clouds,
and so will keep more clouds in the TAFs thru daybreak. This
results in much less fog potential than previously thought. Have
opted to remove fog mention with the 06z TAFs, as a result. AT
KCLT, despite clear skies, fog is not expected there, as air mass
looks too dry. Otherwise, today looks similar to yesterday. Another
round of VFR cumulus should develop by midday and persist thru the
afternoon and evening. Isolated to widely scattered convection is
expected across the mountains again today. With decent confidence
of SHRA never KAVL, will add a PROB30 for mid to late aftn. The
rest of the TAF sites are expected to be dry. Wind will be light
thru the period, favoring a S/SE direction, and not expected to
be above 5 kt this aftn.

Outlook: High pressure remains over the terminals through Wednesday
but isolated mountaintop convection is expected in the aftn.
More numerous showers and thunderstorms, along with restrictions,
may return with a cold front late Thursday into Friday. A more
active pattern may persist into the weekend.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...ARK/PM
SHORT TERM...Wimberley
LONG TERM...RWH
AVIATION...ARK