Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 211713

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
113 PM EDT Sat Sep 21 2019

Dry high pressure will persist over the region through the weekend,
with temperatures gradually warming. A weak cold front will cross
the area from the northwest early next week, but with limited
moisture. Dry and warm high pressure will return for the rest of
next week.


As of 1pm EDT Saturday: Weather pattern changes marginally over the
next 36 hours, with upper ridge slightly further east as upstream
trough approaches, and surface high also edging slightly eastward
with no gain in pressure gradient over the area.  Winds will remain
weak with a southerly to southwesterly bias, and skies will remain
mostly clear, with cumulus over the mountains, as dynamical features
remain away from the area for the near term, and moisture remains
subdued. There is a slight chance some of the mountain cumulus could
develop into a light shower this afternoon. Valley fog in the
mountains that has been occurring in the morning seems likely to
repeat in the same places again today/Sunday morning. High and low
temperatures will also be similar to recent history, with perhaps a
degree or two of warming on Sunday.


As of 215 AM EDT Saturday: A prominent upper ridge will be firmly in
place over the southeast on Sunday. With dry conditions, afternoon
maximum temperatures will continue to warm, reaching some 4 to 8
degrees above climatology. The ridge will flatten slightly Sunday
night through Monday as prominent height falls develop over the
Great Lakes under the influence of a progressive trough. However,
continued warming of low-level thicknesses, along with a developing
downslope flow, will push Monday maximum temperatures another 1 to 3
degrees above the expected Sunday temperatures.

A cold front associated with the advancing northern tier trough will
lay over into the region from the northwest late Monday into Monday
night. Moisture along the front will likely peak over the southern
Appalachians during a narrow window Monday evening, when shower
chances will be best, but still modest, over the mountains.
Locations east of the mountains should remain dry given the WNW flow
at 850 mb with the fropa. Meanwhile, the upper trough axis will move
quickly to the eastern seaboard Monday night, with associated
dynamics passing north of the region.


As of 230 AM EDT Saturday: Flat upper ridging will return to the
southeast on Tuesday behind the weak cold frontal passage, with deep-
layer northwest flow and very dry profiles setting up. Relatively
zonal upper flow will then continue into Wednesday, with heights
gradually rising. Temperatures will continue to run some 5 to 10
degrees above climo.

Upper ridging will become resurgent Thursday through Friday, with
500 mb heights approaching 595 dm by the end of the week. The
forecast area will bake with hot and dry conditions as any backdoor
boundary over the mid-Atlantic will stay well north of the region.
Any diurnal convective coverage each afternoon looks quite limited
given 700 mb temperatures likely near +10 deg C along with a lack of
forcing under the ridge. Will feature below climo PoPs in the
isolated range for the mountains and keep non-mountain areas dry.
Recent trends suggest that temperatures could get within a couple of
degrees of record values Thursday and Friday. See the climate
section of the discussion for the records.


At KCLT and elsewhere: Clear skies this afternoon, except for
moderately dense areas of cumulus over the mountains with bases down
to 4kft.  Some isolated showers are possible from these cumuli over
the mountains for a few hours this afternoon. Surface anticyclone
remains parked over the region, giving a southerly to southwesterly
bias to light winds today through tomorrow.  Little change expected
to the mostly VFR forecast for the next 36 hours, with the only
restrictions expected to be with valley fog in the mornings in
places that are fog prone.

Outlook: Patchy mountain valley fog will be possible each morning
for the next week. Otherwise expect VFR conditions.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High  83%     Low   48%
KHKY       High 100%     High 100%     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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      86 1945     51 1956     67 2018     38 1943
   KCLT      94 1961     54 1956     72 1881     42 2001
   KGSP      95 1933     56 1956     69 1972     41 1907


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      88 1998     54 1956     67 2018     35 1879
   KCLT      93 1900     55 1956     72 1881     43 1940
   KGSP      93 1986     59 1956     69 1999     38 1899




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