Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 271113

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
713 AM EDT Mon Mar 27 2017

Moist southerly flow will linger over the southeast through Tuesday,
with several rounds of showers and thunderstorms possible. Drier air
will briefly return by the middle of the week as a cold front
settles south of the area. Another low pressure system will bring
moisture back to the southeast Thursday, increasing rain chances
through late Friday.


As of 650 AM EDT: PoPs have been trimmed back further for the
morning hours given the meager appearance of lingering isolated
showers on radar.

Otherwise, water vapor imagery reveals a cyclonic mid/upper level
circulation moving over Missouri early this morning. Low level flow
east of this system is generally south to southwest and this
persistent fetch of Gulf moisture across the southeastern states
will yield continued morning clouds and lingering isolated to
scattered showers for our region. This flow regime will continue
across the southeast through the day. The combination of
temperatures warming quickly through the 70s, despite the mostly
cloudy conditions, and dewpoints solidly in the 50s will likely
produce SBCAPE values in the 1000 to 2000 J/kg range this afternoon.
Narrow lobes of vorticity lifting east ahead of the main trough this
afternoon will provide a triggering mechanism for deep convection.
Although thunderstorm coverage will be in the solid scattered range,
several of the storms could be strong to severe as CAPE improves in
the minus 10 to minus 30 C hail growth zone. Relatively modest
Spring freezing levels should permit 55 dBZ cores reaching the lower
20kft range this afternoon and early evening to yield some
marginally large hail and briefly gusty winds. Fortunately, 850 mb
flow and associated deep layer shear will be less than observed on
Sunday, so cells should not persist as long and a bit less storm
organization is indicated. Will mention the severe potential in the

The deeper forcing will occur with the trough as it crosses the
southern Appalachians overnight with better upper jet divergence and
deep layer Q vector convergence indicated. However, instability
should be waning a bit overnight and low level flow will start
veering, so this may limit the strong to severe potential somewhat
for the early morning hours. The real question mark will be how well
the more robust convection from the upstream Slight to Enhanced
severe thunderstorm risk areas is able to survive as it approaches
the mountains. All in all, expect a mild and increasingly wet night.


As of 225 AM EDT Monday: An ulvl s/w will continue to cross the area
Tue and drag a broad cold front east throughout the day. The atmos
will remain unsettled during this time and isol/sct tstms are
probable early on thru the afternoon. The main focusing area for
stronger storms will be east of the mtns as pre-frontal lift
coincides with destabilizing warm sector by 21z. The op models have
varying ideas with the placement of convec and the degree of
instability...but the ern zones with better sfc td pooling
associated with increased sfc convg shud be the favored area for
deep convection...possibly producing a few svr storms. This activity
will wane rather quickly aft fropa arnd 00z with little if any
showery activity lingering thru the overnight period.

Heights actually begin to rise quickly during the afternoon Tue and
by 12z Wed a deep layered ridge axis will be situated just west of
the FA. A strong subs inversion will engulf the area and prevent
deep convec activity from developing thru the day. There may be some
-shra late and overnight across the nrn zones as a moist wedge
begins to build in. Max temps will reach 10-12 degrees above normal
in good downslope flow...however td/s will be about 10 degrees
cooler than Tue`s values. good chance will be had to break
the h7 cap in a non/triggered environ. Min temps will remain 8-10
degrees above normal both Tue and Wed nights.


As of 305 AM EDT Monday: A strong ulvl ridge will cross the ern
CONUS early Thu thru Fri morning. This will force a cP sfc high off
the mid-Atl coast which will ridge south across the FA. This ridge
will bring some Glakes moisture which will combine with advecting
llvl Atl moisture. Isent lift and increasing precip coverage will
thereby strengthen and hold a wedge in during this time. This will
make for a tricky temp forecast Thu and also the amount of thunder
activity possibly developing across the wedge bndry to the south and
west. For now...have tstms developing across the far sw/rn zones and
max temps ranging from the u50s nrn piedmont to m70s over the far
srn zones. This could change over the next few fcst packages.

Meanwhile...a strong low pressure system will develop across the
srn Plains early Thu and advance toward the OH Valley by Fri
morning. This feature will bring yet another frontal system to the
area Fri. The models agree well with breaking down the sfc wedge
arnd 12z Fri leaving plenty of time for the atmos to destabilize in
a highly dynamic environ....possibly producing stg/svr storms along
a retreating TMB. This scenario has a good amount of uncertainty
however as the speed of the cold front or upper s/w could change and
the inherent complexities and uncertainty involved with
frontal/wedge interactions. The front looks to cross east of the
area late Fri and a dry airmass shud build in over the weekend. Max
temps Fri could be tricky as well...but for now have highs reaching
near normal levels. Over the weekend...highs will likely increase to
about 5 degrees above normal in good insol within a drying column.


At KCLT: Only very spotty shower activity is expected nearby this
morning, but MVFR cigs should settle in and lower through late
morning. Slow improvement to lower VFR is expected during the early
afternoon. Thunderstorm chances will improve once again after 20Z
and continue into the early evening hours. Expect SW winds around 10
kt or less throughout, with a few low end gusts possible this
afternoon. Decreasing nocturnal instability should lead to mainly
showers overnight. MOS is suggesting some IFR early morning ceilings
early Tuesday, but confidence is low at this point.

Elsewhere: Isolated shower chances will continue through the morning
hours in persistent, moist southwest flow. Anticipate MVFR level
clouds developing and persisting across the mountains and foothills
before slowly lifting and scattering late morning into early
afternoon. The thunderstorm potential will increase again after 18Z
across the mountains and 20Z across the foothills. Expect south to
southwest winds throughout at 10 kt or less, with a few low end
afternoon gusts possible. Showers should continue tonight with the
main trough. IFR cigs will be possible, but confidence is low so
will keep cigs MVFR overnight for now.

Outlook: Another round of thunderstorms will be possible on Tuesday,
especially near KCLT. Continued low level moisture will provide a
good chances of restrictions throughout. Drier conditions should
briefly return during mid-week before another storm system begins
affecting the region Thursday and Friday.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High  87%     High  83%     High 100%     High 100%
KGSP       High  87%     High  83%     High 100%     High  83%
KAVL       High  87%     High 100%     High 100%     Low   56%
KHKY       High  87%     Med   72%     High 100%     High  87%
KGMU       High  81%     High  83%     High 100%     High  83%
KAND       High  94%     High  94%     High 100%     High 100%

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:




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