Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 272042

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
442 PM EDT SAT AUG 27 2016

Surface high pressure will build over the region through the
weekend, keeping temperatures above average through next week. A
frontal boundary will push through by the end of the next work week,
though a lack of moisture will keep rain chances near or below
normal for most of the week. The tropics remain active as we near
the peak of the season...though no systems appear to be a threat to
our area at the current time.


As of 430 PM EDT Saturday:  Convection continues to slides
westward across the NC Piedmont this afternoon associated with
weak sfc convergence and abundant sbcape on the order of 2-3k j/kg.
Updraft nature has been rather pulsy over the last two hours with
tops in the 40-50kft range at times, before collapsing sharply.
With that, cores have been able to become rather icy and thus
reflective.  However, due to the abundant warmth in the low/mid
levels, still think that large hail will be the outlier as far
as any strong/severe threats are concerned.  Speaking of those
threats, the latest spc meso continues to indicate upwards of 1200
j/kg dcape across the Piedmont therefore damaging downburst winds
are still the primary threat this afternoon/evening, as well as
brief heavy rainfall and frequent ltg.  As for the fcst itself,
adjusted pops up across the NC/SC piedmont region, west/southwest
toward the foothills and along the I85 corridor as residual outflow
boundaries are expected to initate additional convection as the
evening progresses.  Otherwise, tweaked t/td and sky and left the
remainder of the fcst as it was.

At 200 PM Saturday: An upper ridge will drift northeast from VA to
the NJ coast by Sunday, while a weak upper low drifts from the Gulf
Stream toward the SC coast. Modest upper level divergence west of
the upper low is expected to move inland toward the southern Blue
Ridge on Sunday

At the surface, a band of low level moisture is expected to drift
west from the Piedmont to the Blue Ridge this afternoon and evening.
Instability will be sufficient for convection, with enough downdraft
cape present for a few damaging wind gusts. Convection may be slow
to taper off this evening as instability lingers. Another round of
convection is expected again on Sunday, perhaps supplemented by the
modest aforementioned upper divergence. This activity could end as
early as late afternoon however if a dry slot moves inland to the
east of a band of coastal moisture. Temperatures will generally
run slightly above normal.


As of 140 PM Saturday: A weak offshore Atlantic circulation may
migrate west toward the SC/GA coast on Monday as a weakness develops
in the mid level ridge and the nose of surface high pressure draped
across the region. Low and mid level drying will continue to work
into the area from the NE and this will translate into very limited
surface based instability and below climo PoPs - shunted mainly
toward far southern/southwestern parts of the CWA during the
diurnally favored period. Monday morning mins will continue well
above climo, with maxes at or just above climo in the NE flow.

Most of the vorticity and upper divergence with the approaching
offshore system will likely stall along the coast through Tuesday.
Generally easterly to northeasterly flow is expected to continue,
but without much of a corresponding increase in Atlantic moisture.
Expect scattered ridgetop convection to redevelop Tuesday afternoon
in weak mountain wind convergence. Temps may rise a notch over
Monday values.


As of 200 PM EDT Saturday...the medium range picks up on 00Z
Wednesday with the area under the influence of general height falls.
An open wave that is currently being monitored by the National
Hurricane Center for tropical development (Invest 91L) will begin to
near the coastal Carolinas Wednesday morning, though recent model
runs suggest that only a modest increase in moisture could occur in
our area before a frontal boundary associated with an upper trough
sweeps the weak system out into the northern Atlantic. As far as
Invest 99L is concerned, the majority of global models do not
develop it to any noticeable extent, and keep it on a track that
would have almost no influence over our area. Both systems will
continue to be watched, but the likelihood of tropical impacts
through the extended period still looks quite low at the current

As far as sensible weather is concerned, northeasterly flow at the
surface will keep the CWA relatively warm and dry Wednesday through
Friday. Guidance now disagrees on the timing of a frontal boundary
that approaches the area on Friday, though the front is generally
weak in most models. Without much moisture to work with, it does not
generate much QPF response, so pops were kept just below climo
through the end of next work week. Heights rise on Friday briefly
before a couple of shortwaves cross over the southern Appalachians
next weekend, and with the surface flow taking on a more
southeasterly component, the upper support coupled with better
moisture suggests that pops should be raised to near climo by the
end of the period. Max temps are above average for most of the
medium range, though modest height falls and an increase in sky
cover/pops led to max temps being decreased to normal levels by next


At KCLT and elsewhere: Convective chances this afternoon and
evening appear better than in recent days. Although model time
heights generally favor low clouds this afternoon, and again late
tonight and Sunday morning, cloud cover and heights only favor
restrictions at KAVL around dawn, with LIFR is expected. an IFR vsby
restriction at KAVL is expected at the same time, with MVFR at all
other sites. Of course afternoon and evening rainfall at foothill
sites could change things. Winds will generally favor the east this
afternoon outside the mountains, and the southeast at KAVL. Winds
back to the northeast east of the mountains tonight.

Outlook: A deep ridge of high pressure will persist across the
region through early next week. The environment should support mid
to late afternoon thunderstorms each day, primarily over the mtns
and adjacent foothills. Weak steering flow should favor iso to sct
coverage, with storms dissipating within two hours following sunset.
Patchy fog will be possible any morning following a late afternoon
to early evening shower or thunderstorm.

Confidence Table...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       High 100%     High 100%     High  82%     High  95%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Low   55%     High 100%     Med   72%     High  87%
KHKY       High 100%     High 100%     Med   66%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High  95%     High  93%

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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