000
FXUS62 KGSP 140730
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
330 AM EDT Sun Apr 14 2024

.SYNOPSIS...
Dry high pressure will linger to our south into early next
week, allowing temperatures to warm well- above normal for
mid April. Another frontal system will approach our area by the
middle of next week, and could bring showers and thunderstorms to
the region.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM: Clear skies across the CWA under sfc/upper ridge
centered over the lower MS Valley and Gulf of Mexico. A pocket
of upper level moisture is seen on water vapor imagery upstream,
in conjunction with a minor jet streak. This still appears capable
of mountain wave cirrus, but any such clouds would come too late
to preclude radiational cooling. Made minor adjustments to morning
T/Td based on recent obs.

The sfc/upper ridge will migrate gradually eastward today; some
patchy cirrus associated with weak upstream shortwave may replace
the mtn-wave cirrus by afternoon, but still not likely enough to
impact max temps. The day will be warmer owing to higher partial
thicknesses and a warmer start than yesterday. While the Piedmont
won`t really experience downsloping as flow will be southwesterly
due to the position of the ridge, abundant sunshine and initially
light winds should result in rapid warming, and maxes look to end
up around 10 above normal. Dewpoints may rebound a bit owing to
the SW flow, but the warming should maintain deep mixing and RH
still is expected to drop into the upper 20s percent across much
of the area. The mixing appears better than many of the models
would suggest, and furthermore the gradient will amplify a bit
between the migrating ridge and weak shortwave and sfc low moving
thru the Midwest. Thus, have leaned in favor of wind gusts toward
the higher end of the guidance range. Despite these adjustments,
it looks like we will fall short of the respective criteria for
an Increased Fire Danger Statement in any of our states.

Tonight, winds will taper off nocturnally but a light SW breeze
is expected to persist, and a slow increase in dewpoints should
continue. Although radiational cooling is expected to be fairly
strong, owing to higher thicknesses, mins look to remain a few
degrees above normal.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 246 AM Sunday: The new work week kicks off Monday morning with
a potent closed upper low over the Four Corners region and a belt of
northern stream westerly flow draped along the Canadian border. Two
well defined shortwave troughs will be embedded within the northern
stream with the lead wave progged to be centered over the Great
Lakes region/southeast Canada. Farther south, upper ridging
extending from the Gulf of Mexico into the Lower Mississippi Valley
will amplify ahead of the upstream Four Corners low. At the surface,
a cold front is forecast to extend from southern Illinois into
central Pennsylvania. This front will slowly ooze south into the
Ohio Valley through the day on Monday, but southward progress will
be limited as the front will be oriented parallel to the upper flow
and become increasingly displaced from stronger forcing as the
parent wave slides into New England.

There`s good agreement amongst guidance that deep convection will
initiate just south of the cold front where richer boundary layer
moisture is able to pool along the front. Modest deep-layer vertical
wind shear will help this activity organize into loose clusters from
central Kentucky, across southern West Virginia, and into
central/southern Virginia. Broad northwest flow will drive this
activity towards east Tennessee and northern North Carolina by mid
to late afternoon Monday. Uncertainty increases thereafter with
regards to how far south any storms are able to make it. Previously
mentioned ridging extending from the Gulf of Mexico will result in a
gradual increase in heights across the area with a lack of forcing
to support convection, especially as it propagates farther from the
initiation zone near the cold front. Forecast soundings are also
mixed as to whether a mid-level subsidence capping inversion can be
overcome across western North Carolina. The NAM solution keeps the
cap in place whereas most of the CAMs weaken the cap just enough to
allow for at least isolated to scattered convection to spill into
the northern half of the area. Should robust convection make it into
the area, the environment will be supportive of a conditional severe
threat. 25-35kts of deep-layer shear will be sufficient for loosely
organized clusters. 1000-1500 J/kg of surface-based instability will
also be present along with very steep lapse rates. Forecast
soundings also depict a very deep and well mixed boundary layer with
classic inverted-V profiles extending up to 800mb. Thus, any deeper
convection/robust updrafts that make it into the area could pose a
threat for damaging winds. A marginal risk for severe thunderstorms
has been added by the Storm Prediction Center just to our north and
may need to be extended south should future guidance come into
better agreement on convection impacting the area. Otherwise, high
temperatures on Monday will be quite warm in the low to mid 80s.

By Tuesday, amplified upper ridging will slide into the Appalachians
as the Four Corners low ejects into the Great Plains. Strong warm
advection across the Plains into the Ohio Valley will send the
stalled cold front across the Ohio Valley north as a warm front.
Another round of northwest flow convection may develop along the
frontal boundary, but a farther north position of the front would
place most of this activity from Ohio, across West Virginia and
into northeast North Carolina. A few showers and storms may graze
the foothills/Piedmont mainly north of I-40, but confidence is low
as heights continue to rise across the area as ridging builds in.
Temperatures will continue to be warm in the low to mid 80s,
although increasing cloud cover may shave a degree or two off
compared to Monday.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 319 AM Sunday: Forecast confidence quickly wanes by mid to
late week as guidance continues to struggle with the evolution of
the synoptic pattern. The Plains trough will become absorbed into a
deep longwave trough dropping out of the Canadian Prairies. This will
result in a marked weakening of the wave with little forcing left
across the Appalachians. Upstream convection across Tennessee on
Wednesday will make a run at the area, but coverage east of the
mountains will be spotty. Timing differences also become apparent,
especially with regards to a diffuse frontal boundary that will also
push into the region. By Thursday into late week and the weekend,
the northern stream longwave trough will eventually slide towards
the Great Lakes, with very broad zonal flow across much of the
country. Another cold front will approach the area late week into
the weekend, but very large timing differences are once again
plaguing the forecast. Ensemble clusters also depict a wide range of
solutions as the slow progress of the front combined with boundary
parallel flow may ultimately result in slower timing and a prolonged
period of at least low end rain chances until the boundary is able
to fully clear the area.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR, initially SKC. Some mountain wave cirrus
still may develop closer to daybreak with jet streak crossing the
southern Appalachians, and a very weak shortwave approaching later
in the day likely will generate patchy high altitude clouds as
well. Winds will be calm in many areas until daybreak but otherwise
varying between NW and SW. By mid-morning they should pick up from
the SW. Deep mixing is likely to produce low end gusts around the
region this afternoon. KAVL could experience some variability due
to deep SW flow, but should trend back to NW late tonight. Winds
probably won`t go calm as quickly tonight with gradient tightening
again.

Outlook: Some brief low VFR to MVFR clouds may develop Monday
and Tuesday as a result of a weak frontal zone developing to our
north. Otherwise VFR generally will persist through midweek under
high pressure regime.

&&

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

&&

$$

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