Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 211443

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1043 AM EDT Thu Sep 21 2017

A weak trough will settle over the southeast coastline today. Moist
easterly flow will develop through Friday. Drier and stronger high
pressure will settle across the region over the weekend and likely
persist through early next week, as Tropical Systems Jose and Maria
remain off the east coast.


As of 1030 AM: Sharp upper ridging will dominate the pattern today,
though a shortwave with multiple embedded vortices remains over
the region. The best DPVA is expected to be either northwest or
southeast of the CWFA, however.  At the surface, northeasterly
flow amidst high pressure will dominate amidst mostly sunny skies.
Profiles once again exhibit modest lapse rates, with mucape values
likely pushing into the 1500 J/kg range with little shear and weak
nly steering flow. Given said steering flow but lack of
significant upper forcing, think convection is most likely to
occur over the high terrain where any inhibition will be
weakest, which continues to correlate well with the CAMs.
Outside of the mtns, the aforementioned profiles could support
convection if any forcing mechanisms are in place, which doesn`t
look to be the case. Revised PoPs incorporate a bit more CAM
output and are accordingly a tad higher in the mtns and lower in
the Piedmont. As for thunderstorm intensity, said mtn profiles
would support deep convection, therefore wouldn`t be shocked if
a few cells became strong with gusty winds and lightning being
the primary threats. DCAPE from morning RAOBs suggests a nonzero
damaging microburst threat, but the threat appears less than
yesterday overall. Temperatures today will once again top out
nearly a category or two above normal levels, generally 70s to
lower 80s in the mtns, mid/upper 80s elsewhere.


As of 250 AM EDT Thursday: A dominant 590 dm mid-level ridge axis
will stretch from the Great Lakes to the southern plains on Friday,
with a trough axis lingering over the southeast coastline.
Meanwhile, low-level easterly flow will provide some upslope
triggering along the high terrain on Friday, with peak shower
coverage during the diurnally favored afternoon period. CAPE values
in model profiles appears a bit less on Friday compared to Thursday
across the northern tier, but with some fairly decent 1000 to 1500
J/kg values in the southern tier where thunder will be more

Maria will continue a slow but steady march northward well east of
the southeast coastline through the weekend. Drier air should wrap
southward along the Appalachian mountain chain from high pressure
building over to the north, with associated lower precipitation
chances Saturday given the diminished moisture and instability.
Temperatures will remain about 5 to 10 degrees above climatology for
min temps through the period, with maxes 3 to 7 degrees above climo.


As of 255 AM EDT Thursday: Still anticipate a complicated
interaction of Jose and Maria over the coastal/offshore waters of
the western Atlantic Sunday through Wednesday, but with subsidence
and ridging persisting over the southern Appalachians and
surrounding areas through the period. Temperatures will remain at
least a couple of categories above climo. A full latitude central
CONUS trough will then likely begin sweeping east of the plains on
Wednesday. Southwesterly flow will increase ahead of this feature
and possibly push maxes to around 10 degrees above climo by
Wednesday afternoon, with some lower piedmont highs around 90 not
out of the question.


At KCLT and Elsewhere: VFR conditions expected at all sites through
the taf cycle aside for possible tsra induced MVFR at KAVL this
afternoon.  Winds will gradually increase out of the n/ne through
the mid/late morning hours at all sites with flow expected in the
4-6kts range.  Any residual fog about the region should erode
quickly if not already cleared up leading into mid/high clouds
by late morning, with llv cu gradually forming toward midday.
Aside for a prob30 at KAVL and vcts at KHKY accounting for mtn
convection, all remaining sites are wx free through the period.

Outlook: Chances for diurnally favored showers and thunderstorms
remain in the fcst thru Friday. Restrictions from early morning
fog across the northern NC Piedmont and foothills, as well as in
the mtn valleys will also be a concern. Drier weather is expected
to return for the weekend.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High  88%
KHKY       High 100%     High 100%     High 100%     High  95%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High  95%

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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