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Area Forecast Discussion

FXUS62 KGSP 300544

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
144 AM EDT SAT JUL 30 2016

A pretty typical mid-summer weekend is on tap for the region as
a broad and weak pressure pattern lingers atop the Southeast.
Little change in the weather pattern is expected through the start
of next week.


As of 140 AM EDT Saturday:  Current fcst remains on track this
morning thus opted for no sig changes.  However, did tweak t/td to
align with recent ob trends.  Also removed all hazard wording from
the HWO through the rest of the first period.  Given light/calm sfc
flow, am still expecting patchy fog to develop across the mtns,
possibly southward into portions of Northeast GA and the western
SC Upstate where xover temps are most elevated.

Previous Discussion:  Conditions will remain generally the same as
recent weeks, with seasonally warm morning lows, high humidity and
temperatures above normal with chances for afternoon thunderstorms,
and mostly light winds.

Upper trough west of the area has become somewhat broad this
afternoon and is expected to change little over the next 24
hours, except for some eastward movement of the main axis.
Meanwhile, lee surface trough has a closed low east of NJ and
has moved eastward some this afternoon with more northwesterly
flow in areas east of I26.  Lower dewpoints associated with the
northwesterly flow has reduced CAPE over eastern parts of the CWA
to 500 j/kg versus over 1000 elsewhere.  Edge of better moisture
to the south functions as a weak boundary east-west across the CWA.
This boundary may help focus afternoon convection in piedmont areas
this afternoon as some light convection already exists along it
from Laurens to Anderson.  The other focus for convection will be
the higher terrain areas of western North Carolina.  Wind shear
this afternoon is weak, with low CAPE and forcing, thus little
strong convection is expected.  Any shower activity should decline
diurnally after dark.  With mesoscale boundary across the area,
blended in CAM POPs into the forecast, which made for higher POPs
over western areas on the warm side of the boundary.


As of 230 PM Friday...looks like we are still on track for a
breakdown of the subtropical ridge over the southeastern US for the
early part of next week. The models have the pattern slowly evolving
on Sunday with the axis of a broad upper trof approaching and then
moving across the region in the afternoon and evening. The extra bit
of mid/upper forcing should provide for a slightly more healthy
environment for deep convection for Sunday afternoon and then again
on Monday, so the forecast will feature slightly higher precip
chances than the last few days. The activity will be mainly diurnal
in nature and typical for the time of year, initiating over the mtns
during midday and then moving out over the Piedmont in the evening.
Cannot rule out a few strong/severe storms both days, but poor lapse
rates and weaker dCAPE suggest little chance of that happening.
Temps will remain above normal by a few degrees, but a few degrees
less than this past week. Still warm, but not anywhere close to an
advisory. In short...not much more than typical summer weather.


As of 215 PM Friday...not much to get worked up about through next
week, as it looks like typical summertime weather. The upper pattern
gradually evolves from a weak upper trof on the East Coast early
in the week to a weak upper ridge expanding eastward from the Plains
late in the week. The trof axis should be to the east on Tuesday,
resulting in an unfavorable NW downslope flow E of the Blue Ridge,
and a surface boundary perhaps to our east.  Thus, at first glance
Tuesday might have the least chance of precip. That changes for
mid-week as we get enough moisture return to allow for scattered
mainly diurnal showers and storms each day through Friday. Temps
should warm back to the mid-90s for mid- to late-week, altho this
should not threaten any records or suggest any heat advisories.


At KCLT: VFR through the period.  Mid/high clouds to persist
through the overnight into midday before few/sct low vfr cu builds
with heating.  Profiles on Saturday remain relatively unstable
in the low/mid levels, however exhibit poor lapse rates in the
mid/upper levels which would limit overall depth/intensity of tsra.
Thus, think convection will initiate about the region, however
confidence in placement/timing is low at this point, therefore
opted for broad 6hr tsra prob30.  Winds will remain light wnw/wsw
this morning before backing sw by late morning in the 6-8kts range.

Elsewhere: Trends very similar to that of KCLT above, however with
restrictions due to fog/cigs possible by daybreak at a few sites.
Xover temps are most elevated at KAND as well as at KAVL/KHKY,
therefore given light/calm flow and only few/sct mid clouds, opted
to include mvfr restrictions, possibly ifr at KAVL.  Otherwise, said
mid/high clouds will prevail through late morning before llv lapse
rates increase with heating allowing for low vfr cu development
at all sites.  Kept tsra mention in at all sites by way of prob30s
as chances are rather uniform across the region thanks to synoptic
scale troffing.  Winds will remain generally out of the wsw around
6-10kts aside for at KAVL where wnw flow will prevail.

Outlook: Broad troffing continues to build across the east/central
CONUS lasting into mid week.  Moisture in the low/mid levels
combined with a series of impulses working through the mean flow
aloft will yield continued/increased chances for shra/tsra through
mid/late week.  As such, restrictions associated with shra/tsra
are possible, as well as early morning fog/cigs.

Confidence Table...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     Low   55%     High 100%     High 100%
KHKY       High 100%     Med   66%     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:






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