Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Greenville-Spartanburg SC
1023 PM EDT Tuesday Jul 26 2016

broad surface high pressure will linger over the southeast, before
sliding offshore as a surface low develops and moves northeast
across the Midwest and Great Lakes regions. A surface front will
remain off to our north and linger within a region between the Ohio
Valley, lower Great Lakes, and mid-Atlantic regions. This front may
finally move into our area early next week.


Near term /through Wednesday/...
as of 1020 PM EDT tuesday: with nearly all convection either
exiting the region, or weakening below any mentionable levels,
and latest hrrr favoring further reductions in coverage, opted
to go ahead and clear out the severe weather potential statement for the evening. Latest Storm Prediction Center
mesoanalysis still indicates modest MUCAPE, upwards of 1.5-2.0k
j/kg, however given the lack of any triggering mechanisms, think
new development will be limited to non existent. For the overnight,
expecting a few low/mid clouds to linger beneath patchy high cirrus,
while temperatures slowly fall into the into the mid 70s across the
Piedmont and mid/upper 60s over the high terrain. Patchy fog is in
the fcst once again with the highest probs of occurrence residing
in the mtns valleys, and elsewhere that experienced appreciable
rainfall this afternoon. Tweaked T/TD and pops to account for
recent ob/radar trends and left the remainder of the fcst as it was.

Wednesday: moisture will actually lift back north slightly,
resulting in convection being more confined to the mountains and
I-40 corridor. The Georgia/SC Piedmont may not see much of any deep
convection, as weaker mid-level lapse rates pivot around the the
ridge from the south. So will feature a tighter pop gradient from
less than slight chc pop in the lower Piedmont to likely along
the NC mountain peaks.


Short term /Wednesday night through Friday/...
as of 230 PM EDT tuesday: not much change to the overall synoptic
pattern from what we've been advertising the past few days. The
subtropical ridge will continue to dominate, with moisture
associated with a tropical weakness moving onshore today moving up
the lower Mississippi Valley at the start of the period. Meanwhile a
broad shortwave will push across the northern tier of the country,
pulling the moisture associated with the lower Mississippi weakness
to the north toward the Ohio Valley. Surface high pressure will
continue to pump a warm and moist air into the region with in
general a fairly typical summertime pattern continuing, but with the
additional moisture creeping into northwest zones from the
approaching wave/front. Additionally, a Lee trough progged to
strengthen tomorrow will continue into the short term, which will
provide additional focus for convective development. Deep layer
shear will marginally increase with the approach of the shortwave,
and combined with healthy SBCAPE values between 2000-3000 j/kg, the
continued marginal threat outlined on the swody3 for northern zones
looks good. As has been the case, low-level lapse rates will
continue to support isolated wet microburst threat, but mid-level
lapse rates not high enough for much in the way of hail concerns.

As we push into Friday, vort Max should ride up the southwest flow
aloft ahead of the wave, with the GFS farther south with an area of
enhanced qpf, more over the northern mountains, but the European model (ecmwf)
farther north up in WV. Either way this doesn't help the upstate and
other areas in continued drought, but with the additional synoptic
lift, could certainly see more widespread coverage across NC. Have
not reflected the GFS solution in pops for Friday and will have to
reevaluate as operational guidance comes into better consensus.

Temperatures will remain a category or so above seasonal normals,
but could be adjusted further one way or another depending on model
evolution of precipitation/cloud shields. Humidity will remain high
with areas in extreme southeast zones continuing to flirt with heat
advisory levels, though should see some minimal improvement on


Long term /Friday night through Tuesday/...
as of 200 PM Tuesday...the broad scale pattern will not change much
over the ext range. An h5 trof axis remains west of the fcst area
and will likely get pulled slowly NE late in the period. This will
advance a weak sfc front toward the County warning forecast area...perhaps pushing
into/across the mtns by Mon. The flow remains weak and generally
W/ly within the h9/h7 mech lift along with enhanced llvl
moisture from the nearby front will support above normal pops across
the higher terrain. Downsloping in the Lee will help suppress convec
activity...thus near normal pops will be maintained over the
non/mtns. Warm temps continue in a relatively stagnant pattern with
Max temps will reaching around or a couple degrees above normal each
day. Mins will also be held a Cat or so above climo.


Aviation /03z Wednesday through Sunday/...
at kclt and elsewhere: VFR through the period aside for possible
mtn valley MVFR/IFR fog to affect kavl, with some patchy MVFR
also a possibility at khky. Otherwise, guidance favored a
restriction free night with low/mid stratus slowly giving way
to high clouds by dawn, aside for the mtns where low VFR stratus
remains in the taf. Expecting another round of diurnally favored
convection on Wednesday as deep layer ridging prevails while a
cold front slowly approaches from the north. All tafs feature
prob30s for said tsra with cigs likely remaining in the low VFR
range, while visbs lower to MVFR/IFR amidst any heavier downpours.
Winds through the taf cycle will predominately be out of the SW,
light/calm overnight, increasing to around 8-12kts on Wednesday,
the strongest of which residing over the Piedmont sites.

Outlook: a plume of deep moisture will gradually build across the
western Carolinas and NE Georgia through the late week. Scattered rain showers and
thunderstorms and rain will be possible each afternoon and evening, coverage the
greatest across the mtns. Pre dawn fog and low clouds will be
possible over areas of recent rainfall.

Confidence table...

02-08z 08-14z 14-20z 20-00z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 100%
kavl high 100% low 58% high 100% high 100%
khky high 100% high 87% high 100% high 100%
kgmu high 100% high 100% high 100% high 100%
kand high 100% high 100% 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:



records for 07-27

Maximum temperature min temperature
station high low high low
------- ---------- ---------- ---------- ----------
kavl 97 1952 70 1946 72 1936 48 1911
kclt 103 1940 74 1926 76 1944 57 1920
kgsp 103 1940 70 1946 75 2012 54 1911


Gsp watches/warnings/advisories...


near term...Ark/cdg
short term...tdp
long term...sbk

National Weather Service Glossary of Abbreviations