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000
FXUS62 KGSP 141616
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1216 PM EDT Sun Apr 14 2024

.SYNOPSIS...
Dry high pressure will linger to our south into the first half
of the week giving our region above normal temperatures.
A backdoor front will drop south from Virginia late Monday and
Monday night bringing a few showers and thunderstorms, but the front
quickly retreats back north on Tuesday.  Another frontal system will
approach our area from the west through the middle of the week, and
could bring more showers and thunderstorms by Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1206 PM: No significant changes. Forecast is generally on
track, altho a few places are warming faster than expected.

Otherwise...the sfc/upper ridge will migrate gradually eastward
today; some patchy cirrus associated with weak upstream shortwave
may replace the mtn-wave cirrus this 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, we
fall short of the respective criteria for an Increased Fire Danger
Statement in most areas. See Fire Wx section below for details.

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 /16Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR. Mountain wave cirrus will be seen in
some fashion at all sites through the morning, particularly at
KHKY, where they will form a cig. A very weak shortwave approaching
later in the day likely will generate patchy clouds in the 150-200
layer as well. By 13-14z winds should pick up from the SW and at
all sites except KAVL the direction will remain similar thru the
period. Deep mixing is likely to produce low end gusts around the
region this afternoon. In the SW flow regime, KAVL could experience
some variability, but should trend back to NW late tonight. Winds
probably won`t go calm as easily tonight with gradient tightening
again. LLWS conditions may be met at KAVL after midnight.

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.

&&

.FIRE WEATHER...
Dry and breezy conditions will develop again today, although
relative humidity and wind gusts won`t be quite as impactful on
fire weather as they were Saturday. Fuel moisture is expected to
be low. Some locations in NC mountain valleys and the foothills
probably will meet criteria for an Increased Fire Danger Statement,
but areas in the NC Piedmont most likely will fall just short
of both wind and RH criteria. Further coordination with land
managers will be done early in the day to determine the extent of
any statements. In SC and GA, state criteria are not expected to
be met and no statements are planned for today.

&&

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

&&

$$

SYNOPSIS...Wimberley
NEAR TERM...PM/Wimberley
SHORT TERM...TW
LONG TERM...TW
AVIATION...Wimberley
FIRE WEATHER...