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000
FXUS62 KGSP 151039
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
639 AM EDT Mon Apr 15 2024

.SYNOPSIS...
Dry high pressure will linger to our south into the first half
of the week giving our region above normal temperatures and more
humidity than we`ve felt lately. Small chances of showers and storms
do return to some areas of the mountains today and Tuesday as a
result. A front will approach our area from the west through the
middle of the week, and could bring more showers and thunderstorms
by Friday into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 625 AM: Skies are clear across the CWA aside from a few
low clouds banked against the mountains of NE TN and far NW NC
where weak westerly flow regime is upslope. Over the course of the
day today, the upper trough over the NE CONUS will move offshore
and the ridge to our west will become the dominant feature for
our weather. Westerly flow will continue in the midlevels, but
low-level flow will back to SW over the Piedmont which will aid
in marginal moisture return.  As partial thicknesses continue to
rebound temperatures will also trend warmer, well into the 80s,
within a few degrees of record highs. Owing to the very warm temps
and associated mixing, RH will drop into the lower 30s percent
but not quite to the critical level for fire wx; winds will be
too light for Fire Danger statements as it is.

With the influence of the ridge diminishing, the warm conditions
appear to mix out the subsidence inversion, such that a respectable
amount of SBCAPE is generated by many of the models. We are for
want of a trigger mechanism. Embedded shortwave will pass thru
the middle OH Valley into Virginia today, but heights remain on an
upward trend owing to the migration of the ridge. Nonetheless, the
GFS/ECMWF/GDPS develop spotty QPF response over our mountains. Based
on CAM output, this looks to be especially isolated and worthy
only of a brief isolated shower/t-stm mention near the Blue Ridge
Escarpment. Soundings are very dry aloft and updrafts may not
amount to much especially given minimal trigger. Any such storms
should diminish diurnally; some CAM runs hint at semi-organized
convection moving off the frontal zone in the OH Valley and
propagating southward into our northern CWA. The chance of that
appears no greater than before; we had previously carried a small
PoP in our north as a nod to that possibility. In light of recent
model runs have moved the overnight PoP to late evening in our
northern mountains. Partial convective debris clouds do stand
a good chance of reaching the CWA, so a partly to mostly cloudy
night is expected in the I-40 corridor. Mins tonight again 10 or
more degrees above normal with light winds.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 331 AM Monday: The short term forecast period kicks off
Tuesday morning with a northern stream trough over New England and a
potent closed upper low over the central Great Plains. Upper ridging
ahead of the encroaching Plains low will slide into the Appalachians
Tuesday. At the same time, a lead shortwave perturbation trapped
south of the ridge is forecast to swing across the Southern
Appalachians and may provide just enough forcing to instigate
isolated to scattered showers and thunderstorms mainly along and
north of the I-40 corridor. Should any deep convection materialize,
a conditional threat for a few strong to marginally severe storms
will be possible. Modest surface-based instability and around 30kts
of deep-layer vertical wind shear would support locally damaging
winds, especially with inverted-v profiles apparent in near-storm
forecast soundings. By Wednesday, the Great Plains upper low is
progged to quickly lift into the Midwest and gradually become
absorbed into a large sprawling northern stream longwave trough
dropping out of the Canadian Prairies. As such, available forcing for
ascent wanes through the day with only weak height falls and
weakening wind fields. A weak band of convection will likely
encroach on the mountains late Wednesday afternoon into the evening
ahead of a surface cold front pushes across Tennessee. The lack of
upper forcing, however, should greatly limit coverage with only
isolated to scattered showers and storms expected.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 342 AM Monday: A low confidence pattern takes shape late week
into the weekend as the previously mentioned sprawling longwave
trough slowly makes its way along the Canadian border and off the
New England coast by Sunday. This is expected to be a very broad and
flat trough which results in a prolonged period of quasi-zonal flow
across much of the country east of the Rockies. Thursday will be dry
and very warm with downsloping flow and rising heights and warming
low-level temperatures. Thereafter, a much stronger cold front is
anticipated to drop through the Ohio Valley heading into the weekend
and eventually into the Appalachians. Multiple embedded shortwave
perturbations in the quasi-zonal flow ahead of the front will allow
rain chances to gradually return on Friday with the front pushing
into the area over the weekend. Guidance also depicts a more well
defined shortwave trough sliding across the Gulf states and into the
southeast late weekend, which would result in a more focused period
of increased rain chances.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR, with SW winds thru the period at
all sites except KAVL, where initially NW winds are likely to go
light/VRB once flow backs slightly to SW, before winds increase
diurnally to support actual SW sfc wind. Some low-end gusts likely
less than 20 kt are possible at all sites during the afternoon. A
diurnal cu field should develop in the afternoon over the mountains
and foothills, with bases comfortably VFR. A stray SHRA or TSRA
is possible near KAVL and KHKY but chance too low to mention. Some
convection developing along backdoor front north of the NC/VA border
may propagate south into the northern NC mountains this evening
to very early Tue morning, but resultant chance of SHRA/TSRA is
even lower at the terminals. Midlevel clouds and/or cirrus debris
likely will spill over the NC sites overnight however. The front
will shift south into NC early Tue morning and is likely to result
in a period of N winds at KCLT, but with mixing late Tue morning
southerly winds should prevail again.

Outlook: Isolated SHRA/TSRA are not out of the question Tue and
Wed afternoons near the NC sites. Otherwise VFR generally will
persist through midweek. An unsettled pattern with precip chances
and periodic restrictions may develop Thu-Fri but confidence
remains low.

&&

.CLIMATE...

RECORDS FOR 04-15

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      89 1972     42 1943     64 1887     23 1907
   KCLT      89 1936     46 1889     66 2006     28 1907
   KGSP      91 2006     45 1913     69 1922     22 1907



RECORDS FOR 04-16

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      87 2006     42 1905     62 1945     26 1943
   KCLT      89 2006     49 1890     64 1998     29 2008
                1896                    1991        1962
                                        1945
   KGSP      88 1888     54 1903     64 1945     24 1907

&&

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

&&

$$

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