Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 121752
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1252 PM EST Thu Jan 12 2017

.SYNOPSIS...
Expect southerly flow and rising temperatures through Friday.
Cool high pressure is forecast to be centered near New England on
Saturday cooling our region closer to seasonal normals.  Low
pressure will move from Texas Sunday reaching the Great
Lakes in mid week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 915am Thurs.:  Region is under weak WSW flow aloft with a
large high over FL.  Main continental cold front remains well to the
northwest through this evening.  High will keep any significant
weather well to the north, though some embedded energy aloft could
support some cloudiness and possible light rain over the higher
terrain, especially with upslope effects along the TN/NC border.  Light
southerly to southwesterly surface flow will slowly increase
dewpoints increasing the potential for fog Thursday night.

Currently, some patchy fog persists in parts of western NC, though
this should dissipate in the next couple of hours as fairly strong
warming commences.  With mostly clear skies and surface and upper
high pressure, temperatures will warm considerably today with highs
today and lows Friday morning 10 or more degrees above normal,
reaching the upper 60s in Piedmont areas and low 60s in the
mountains.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 215 AM EST Thursday: the short term fcst picks up at 12z on
Friday with a fairly robust upper ridge centered over Florida and
a broad upper trof moving across the northern Great Lakes. Over the
next 24 hrs or so, the ridge will persist while a southern stream
trof cuts off an H5 low over Northern Baja. Over the remainder of
the period, the ridge flattens out while the H5 low lifts NE and
into southern New Mexico.

At the sfc, a weak cold front will approach the CWFA from the NW by
late Thursday and stall over our northern fringe by Fri morning with
a reinforcing Canadian high sliding over the Great Lakes behind the
frontal bndy. Sly low-lvl flow will weaken over the fcst area on Fri
and early Sat in response to the pattern change. On Sat, a Cold air
damming pattern develops as the above mentioned high slides eastward
and over New England. The model guidance suggests that the CAD won`t
persist for very long as the parent high moves off the New England
Coast by early Sunday. This will likely allow southerly flow to
increase again over the CWFA while a broad area of deeper moisture
lingers across our northern fringe thru Sunday. As for the sensible
fcst, precip chances gradually increase on Fri but remain largely
confined to the northern third of the CWFA. Chances increase for Sat
as the wedge sets up and isentropic upglide increases. As the wedge
breaks down later in the day and into Sunday, POPs diminish again
with a slight to solid chance confined to the northern zones. Total
QPF is expected to be light with no more than about a quarter inch
likely. Temps will be well above climatology on Fri with cooler values
on Sat as the wedge sets in.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 140 AM Thursday.  On Sunday we will be increasingly into the
first half of the week under the influence of the warm sector of low
pressure moving NE out of Texas and its cold front.  The warm front
should be moving north of our area Sunday morning as the low
organizes near far western Texas.  925MB flow is SSE beginning
Monday in upsloping fashion continuing into early Tuesday. This
should enhance shower development across the southern mountains from
Rabun County GA to near Tryon NC. The low level wind flow then
shifts to South into mid week and eventually SW just ahead of the
approaching cold front on Thursday. For Wednesday night the 925mb
flow is shown to be howling at 30 to 40 kts. At this point it
appears that we are fortunate that the max wind shear is well ahead
of the instability which maxes late Thursday. The GFS and ECMWF
roughly agree on late Thursday CAPEs 200 or better but the EC also
has 200 to 300 CAPE along and south of I-85 for Wed afternoon. If
the low CAPE and shear were to match up then we could have some
storm issues. We have a week to look at that possibility. The speed
of this system has slowed over the past few days. Last weekend we
saw models showing frontal passage on Tuesday and now it appears
Thursday will be the day.

We will have max temps around 12 degrees above normal through the
medium range. Min temps are forecast to be about 20 degrees above
normal with the extensive cloud cover. These Min Temps would be
about where the normal Max Temps are for this time of year.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere:  Patchy fog has dissipated this morning and
rest of today will be IFR with SCT to OVC mid to upper clouds with
some SCT stratocu over the Piedmont and upper OVC over the
mountains. southwesterly winds at 10 to 15 kts with some gusts to
25kt.  Region is under the influence of high pressure with a cold
front well to the northeast across central TN/KY that will gradually
move towards the region.  Surface high will maintain the light
southwesterly surface flow today with 850mb flow of 30kts
contributing wind gusts with diurnal boundary layer mixing this
afternoon.  Increase in dewpoints on southwesterly flow will give
some increase in fog Friday morning over what was seen this morning.

Outlook: Springlike conditions will develop over the area to end
the work week. Cool high pressure ridges down the East Coast over
the weekend, bringing chances for precipitation and restrictions.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High  97%
KGSP       High 100%     High 100%     High  81%     High  94%
KAVL       High 100%     Med   60%     Med   74%     Med   77%
KHKY       High 100%     High 100%     High  85%     High  88%
KGMU       High 100%     High 100%     High  97%     High  94%
KAND       High 100%     High 100%     Med   66%     Med   76%

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...DEO
NEAR TERM...WJM
SHORT TERM...JPT
LONG TERM...DEO
AVIATION...WJM



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