Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 270602
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
202 AM EDT WED JUL 27 2016

.SYNOPSIS...
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 TODAY/...
As of 155 AM: Short range guidance indicates that a sfc front will
remain stationary across the Virginias and mid Appalachians today.
The forecast area should remain of the western edge of a H5 ridge
centered off the GA coast. By this afternoon, a weak mid level
shortwave is expected to ripple east of the mtns, resulting in a
frontal wave to develop across eastern VA and a lee trof across
Carolina Piedmont. Convection should develop very similar to
Tuesday. I expect that storms will initially develop over the ridges
around 18z, then development occurring east of the mtns by 20z. I
will highlight the period of favor TSRA with a PROB30, KAND is
expected to remain dry. Deep convection is expected to ash out one
to two hours after sunset. Wind are forecast to remain out of the
SW, speeds between 5 to 9 kts.

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 HWO for the evening.  Latest SPC
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 GA/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 /TONIGHT 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 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
Friday.

&&

.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 CWFA...perhaps pushing
into/across the mtns by Mon. The flow remains weak and generally
w/ly within the h9/h7 layer...so 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 /06Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and Elsewhere: Early morning MVFR fog is possible at KAVL
and KHKY, highlighted with a TEMPO. Short range guidance indicates
that a sfc front will remain stationary across the Virginias and mid
Appalachians today. The forecast area should remain of the western
edge of a H5 ridge centered off the GA coast. By this afternoon, a
weak mid level shortwave is expected to ripple east of the mtns,
resulting in a frontal wave to develop across eastern VA and a lee
trof across Carolina Piedmont. Convection should develop very
similar to Tuesday. I expect that storms will initially develop
over the ridges around 18z, then development occurring east of the
mtns by 20z. I will highlight the period of favor TSRA with a
PROB30, KAND is expected to remain dry. Deep convection is expected
to ash out one to two hours after sunset. Wind are forecast to
remain out of the SW, speeds between 5 to 9 kts.

Outlook: A plume of deep moisture will gradually build across the
western Carolinas and NE GA through the late week. SCT SHRA and
TSRA 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...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High  94%     High  94%     High 100%     High 100%
KAVL       High  86%     High  91%     High 100%     High 100%
KHKY       High  91%     High  94%     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:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...SBK
NEAR TERM...NED
SHORT TERM...TDP
LONG TERM...SBK
AVIATION...NED



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.