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Area forecast discussion 
National Weather Service Greenville-Spartanburg SC
1120 am EDT Thursday may 28 2015

Synopsis...
a Bermuda high pattern will remain across the region into the
weekend before a cold front pushes in from the north early next
week. This front will then weaken and stall over the area through
the middle of next week.

&&

Near term /through tonight/...
as of 11 am...showers linger across southeast tenn in association
with remnant/slow moving mesoscale convective vortex. The precipitable water from the 12z kffc radiosonde observation
exceeded 1.58 inches within deep moist plume ahead of this
feature...certainly above climatology but not substantially so. Although
much of the area was clear as of late morning...clouds were
increasing across the NC mountains...and this will limit instability
during the afternoon. However...combination of diff heating/high
precipitable waters and mesoscale upward vertical velocity in the vicinity of the mesoscale convective vortex should support
numerous coverage of showers and thunderstorms across the mountains this
afternoon. Wind profiles are verifying a bit stronger than what was
suggested by yesterday/S numerical guidance...and indeed this
afternoon/S forecast soundings support storm motions of around 10
kts. Therefore...locally excessive rainfall issues should be
confined to any areas that see training cells...which is certainly
not out of the question. Probability of precipitation taper off southeast of the mountains...with
40-50 percent favored over the foothills and the upper Savannah
River valley (nearer the moisture plume)...tapering to 30 percent
along the I-77 corridor. With cape already exceeding 1000 j/kg this
morning outside the mountains...a few strong to severe storms will be
possible...especially across the eastern half of the area...where drier air
aloft and warmer temperatures/lower b.L. Relative humidity should result in reasonably
high dcape.

As of 650 am...patchy dense fog across the area should burn off early
this morning. Special Weather Statement issued to address this. Rain showers just west of the County warning forecast area
may move into the western counties this morning...but only very light
rain expected. There is a swirl seen in this activity which will
move into the mountains today. Higher pop already in place there.
Otherwise...going forecast on track with only updates mainly for current
conditions.

As of 310 am...convection over central Georgia diminishing as it slowly
moves NE toward the Savannah River. However...a few cells continue
to regenerate along the leading edge of the weakening cold pool. If
the cells can maintain themselves...this activity would move into
our NE Georgia...and possibly...western upstate counties. If this does
happen...the cells should be short lived and dissipate before
daybreak. Otherwise...expect patchy fog and/or low clouds this
morning. Should be more diurnal convection today as precipitable water values rise
above normal and a weak short wave and upper divergence move into
the area. Moderate instability develops but shear is weak. Dcape
values between 500 j/kg and 750 j/kg develop along with decent surface
Delta Theta-E values. However...there will be quite a bit of
convective debris clouds across the area today which could limit
heating. All that said...isolated severe storms are possible with
damaging winds the main threat. The convection should be diurnal in
nature...but could linger well into the evening...and possibly early
overnight...before dissipating. Highs will be near to 5 degrees
above normal with lows around 5 to 10 degrees above normal.

&&

Short term /Friday through Saturday night/...
as of 230 am Thursday...an upper ridge will persist along the East
Coast...while a weak trough will slowly cross the central-northern
plains Friday through Saturday. A surface ridge axis will linger across the
area...extending westward from the North Atlantic to the Florida
Panhandle. The models agree that this ridge will help keep things
more capped...especially on Saturday. However...there will still be
scattered mountain convection both days...with isolated convection possible
across the Piedmont. Saturday will probably have the least coverage
per model consensus. Temperatures will be a couple categories above normal
for daytime highs...and a few categories above normal for overnight
lows...as air mass remains humid. Forecast soundings show modest instability on
Friday...with weak shear. So expect slow-moving storms producing
heavy rainfall as the main threat...while a severe wind threat will
be low. Saturday has even less instability...so overall heavy rain and
severe threats will be very isolated.

&&

Long term /Sunday through Wednesday/...
as of 245 am Thursday...the latest medium range guidance has been
trending toward breaking off the southern end of the approaching
shortwave over the middle MS valley on Sunday...closing off a weak
closed upper low in vicinity of the middle south Monday through Wednesday. This
allows the East Coast ridge to persist through early next week. This
slows down the approaching cold front. The 00z GFS and European model (ecmwf) now
keep the front north of the area through the weekend...then slowly back
door the front early next week...as high pressure settles in across the
northeast states. In any case...there be a return to above climatology
probability of precipitation each day next week. Temperatures will be about 5-8 degree above normal on
Sunday...then back to just a category above normal for Monday and
Tuesday...with increased coverage of afternoon/evening convection. Overnight
lows are nearly the same each night within the humid air mass. The
atmosphere will continue to be weakly sheared atop the County warning forecast area...so
expect locally heavy rain to be the main threat again next
week...with a marginal/isolated severe wind/hail threat each day.

&&

Aviation /15z Thursday through Monday/...
at kclt...despite surrounding sites developing restrictions...the
airfield remains VFR. If nothing develops soon...then VFR can be
expected through the morning. Will adjust as latest observation are issued.
Otherwise...expect developing cumulus with diurnal convection. Prob30
remains in place. Restrictions seem unlikely overnight unless rain
falls at the airfield which will increase chance. Southerly wind through the
period.

Elsewhere...everything from VFR to vlifr at the rest of the taf
sites. Will take the latest ob and improve to VFR by noon...unless
already there. Otherwise...expect developing cumulus with diurnal
convection. Prob30 remains in place. Restrictions likely again at
kavl/khky overnight. Less certain other areas...so forecast VFR there. S
to SW winds through the period...except kavl where light northerly wind this
morning becomes southerly for the afternoon.

Outlook...moist SW flow will continue to affect the terminal
forecast area through the upcoming weekend...as a cold front lays
over to the north of the area. Expect pockets of morning fog and/or
stratus most days...with continued chances of afternoon/evening rain showers/thunderstorms and rain
each day.

Confidence table...

15-21z 21-03z 03-09z 09-12z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 92%
kavl high 100% high 100% high 100% high 84%
khky high 100% high 100% high 94% high 91%
kgmu high 100% high 100% high 100% high 94%
kand high 100% high 100% high 100% high 94%

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: (must be lower case)

Www.Weather.Gov/gsp/aviation_tables

&&

Gsp watches/warnings/advisories...
Georgia...none.
NC...none.
SC...none.

&&

$$
Synopsis...Arkansas
near term...jdl/rwh
short term...Arkansas
long term...Arkansas
aviation...rwh

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