Area Forecast Discussion
Issued by NWS Greer, SC

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531
FXUS62 KGSP 241801
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
201 PM EDT Fri Mar 24 2017

.SYNOPSIS...
High pressure will move off the east coast today. A low pressure
system emerging from the Great Plains over the weekend will bring
moisture to the southeast Saturday through Sunday. Unsettled weather
will continue through Tuesday as another low pressure system moves
from the plains to the Ohio Valley, allowing Gulf of Mexico moisture
to persist over the southeast.

&&

.NEAR TERM /THROUGH TONIGHT/...
1020 AM EDT Update...low to mid lvl clouds continue to stream across
the CWFA from the SW late this morning. Overall cloud cover is not
expected to change significantly over the next few hours with cigs
more likely to scatter over the S and SE zones during the afternoon.
Things should remain dry today, with POPs increasing tomorrow.

Previous Discussion: A strong ulvl ridge axis will cross the fcst
area over the period. This will keep mid lvl air relatively dry as a
subs inversion develops down to h85. An associated sfc high will be
shifted eastward during this time and good llvl GOM moist flow will
encompass the wrn half of the FA. Good waa is noted at h925 and this
will limit any potential for convection this afternoon while holding
mixing to arnd 15-18 Kft. Thus...no good gust potential will be had.
There will be increasing mechanical lift associated with the llvl jet
across the srn escarpment overnight and this will help spawn shallow
-shra with limited precip amounts thru daybreak. Clouds shud scatter
out most locales this afternoon and allow max temps to reach right
arnd normal levels. Re-developing stratocu overnight will hold mins a
couple cats above normal.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 230 AM EDT Friday: The numerical models feature relatively
good agreement through the short range with a 500 mb low pressure
center lifting from the southern plains Saturday morning to the
southern shores of the Great Lakes by late Sunday. At low levels of
the atmosphere, upslope/upglide flow and increasing moisture should
allow scattered showers to gradually break out in and near the
mountains through the day on Saturday. Meanwhile, strong pre-frontal
convection moving east across the lower MS valley will slow down as
it approaches the base of the southern Appalachians through Saturday
night - getting increasingly hung up in the veering southwesterly
flow aloft east of the lifting wave. Peak PoPs for our area should
develop late Saturday night into Sunday morning as the upper trough
acquires a negative tilt, the associated upper level forcing lifts
northeast through the western Carolinas, and deeper moisture
arrives. 850 mb flow will back slightly and strengthen through
Saturday night, with surface to 3 km bulk shear values reaching
around 35 to 40 kt in western sections. Instability should be a bit
limited, however, given the general early morning timing, but a
thunder mention for most southern tier sections seems warranted for
AM Sunday.

An open Gulf and persistent southwest flow at low levels will then
keep shower chances going through Sunday despite the departure of
the better upper support. Sunday afternoon SBCAPE values could well
reach 1000 J/kg across the lower piedmont and scattered to numerous
thunderstorms will be featured across the area with max temps in the
70s east of the mountains. Sunday night should again be quite mild
with 50s min temps all but the higher ridges.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 240 AM EDT Friday: Deep layer southwesterly flow will persist
between systems on Monday as another plains trough moves east to the
mid MS River Valley. Expect mainly scattered diurnal convection
during day Monday with maximum temperatures in the 70s all but the
northern mountains. The approaching trough should then cross the
Appalachians Monday night/Tuesday morning and pull east through the
day on Tuesday. The timing of the overnight passage of the deeper
pre-frontal convection may serve to limit instability somewhat, but
shear will need to be closely monitored for an isolated strong to
severe thunderstorm threat.

Some drying is then indicated from late Tuesday through Wednesday.
Broad upper ridging should be in place Wednesday through Thursday as
the next upstream low pressure system carves out across northern TX.
A passing cold front may settle just south of the region and stall
on Wednesday, but with limited attendant moisture. Atlantic/Gulf
moisture may then start working back north over the boundary on
Thursday.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: VFR conditions expected thru tonight and
the overnight with cigs lowering after about 09z. Both KCLT and
KAVL carry MVFR cigs from 10z onward with KAVL improving to VFR
by about 15z.Cigs at KGSP, GMU, and AND lower to IFR by roughly
11z with a 2-hr TEMPO for LIFR cigs at those sites. They will
likely improve to VFR again by the end of the taf period. Otherwise,
winds will weaken tonight and remain predominately SLY with some
sites seeing light and vrb winds during the overnight and early
morning. KAVL and KHKY have been getting some decent gusts in the
18 to 22kt range over the past few hours, but these should subside
by the early evening.

Outlook: Increased precip chances return late Saturday thru Sunday
which will likely create flight restrictions across the area. An
unsettled and moist pattern will persist next week and maintain the
chances for low CIGS and VSBY.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High  94%     High  84%
KGSP       High 100%     High 100%     High  91%     High  93%
KAVL       High 100%     High 100%     High  84%     High  92%
KHKY       High 100%     High 100%     High  81%     High  89%
KGMU       High 100%     High 100%     High  90%     High  89%
KAND       High 100%     High 100%     Med   79%     High  85%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...HG
NEAR TERM...JPT
SHORT TERM...HG
LONG TERM...HG
AVIATION...JPT



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