Area forecast discussion
National Weather Service Greenville-Spartanburg SC
722 am EDT Thursday Jun 20 2013
Synopsis...
high pressure centered over New England will continue to drift to
the southeast...eventually setting up over Bermuda by Saturday.
Continued east to southeast winds will push some Atlantic moisture
into the region...with enough clouds to keep temperatures at or
slightly below normal through the weekend. Temperatures will warm to
around or just above normal early next week as high pressure lingers
along the southeast coast.
&&
Near term /through tonight/...
as of 500 am EDT Thursday...latest guidance continues to keep any
shower or thunderstorm activity this afternoon associated with
upslope flow along the higher terrain as previously forecast.
Broken layer of low clouds continues to infiltrate the NC
foothills/Piedmont...and portions of the upstate. Forecast remains
on track therefore no changes were made.
Previous discussion...
As of 300 am EDT Thursday...broad upper trough finally beginning to
migrate off the northeast coast allowing surface high pressure to
continue to build. Cold front that affected the region on Tuesday
night and into Wednesday morning remains stalled across the Gulf
coastline stretching east into the low country of SC. The above
mentioned surface ridge will slowly migrate to the southeast over
the next few day eventually setting up over Bermuda.
In the near term...expecting fairly nice weather for the most part
across northeast Georgia and the Carolinas. There will however be
some chances for scattered afternoon thunderstorm development on
Thursday as modest easterly winds provide upslope flow in the higher
terrains. Thus...kept slight to chance probability of precipitation across the higher
terrain to include the foothills of NC and SC. Most convection
should remain sub severe with a few strong storms possible during
the peak daytime heating hours. Otherwise...low/mid cloud cover
this morning should give way to predominant scattered middle/high
clouds by early afternoon...except for areas adjacent to above
mentioned convection. Slight chance probability of precipitation will remain in the
forecast after 00z Friday across the higher terrain...while probability of precipitation
elsewhere remain low. Temperatures on Thursday will be slightly
below normal.
&&
Short term /Friday through Saturday night/...
as of 245 am EDT Thursday...a broad upper trough will generally cover the
southeast U.S. Friday into the weekend...but with a weakness in the height
field stretched along the Appalachians. At low levels...a persistent
easterly flow is expected Friday through Sat. In this Atlantic
fetch...some moisture from the coastal trough could work inland on
Saturday. The GFS is the most aggressive in this regard...but the
other models keep the moisture confined more to the coastal plain of
the Carolinas. A consensus would indicate more clouds than average
but with limited Piedmont and foothill probability of precipitation. Will thus feature the
best scattered late day convection over mainly the western mountains Friday and
Sat afternoon/evening where instability and low level convergence will be
greatest. Maximum temperatures will remain a couple of degrees below normal.
&&
Long term /Sunday through Wednesday/...
as of 300 am EDT Thursday...low level flow around the Bermuda high
pressure will become more southerly late in the weekend...and then
SW through the early part of next week. Building instability along
with triggering S to SW upslope flow should allow isolated to scatter
mainly diurnal coverage to set up. Temperatures may continue to warm
slightly Sunday...but will still remain a bit below normal.
Increased westerly flow Monday through Wednesday will permit more of a Lee
trough to develop. Heights will begin to fall slightly across the
east through middle week...with a cold front approaching from the north
late Wednesday. High temperatures Monday through Wednesday will be right around
normal.
&&
Aviation /12z Thursday through Monday/...
at kclt...VFR conditions will prevail through the period. Middle/high
level ceilings early on will give way to high level scattered clouds by around
18z. Expecting any thunderstorms and rain that forms during the afternoon hours
Thursday to remain well to the west associated with upslope flow
along the higher terrain. Winds will be north of east and in the
8-10kt range most of the day...before calming around nightfall.
Elsewhere...remaining low clouds at all SC sites should scatter out
later this morning...and remain that way through the period. Model
guidance continues to indicate upslope flow across the higher
terrain late Thursday morning into the afternoon hours...thus
prevailed thunderstorms in the vicinity at both kavl and khky beginning at 15z.
Furthermore...added tempo groups for thunderstorms and rain from 18-22z to account for
maximum daytime heating fed updrafts. Beyond that...carried thunderstorms in the vicinity
for a few more hours before dropping to scattered clouds and no weather by 03z
Friday. Some MVFR restrictions due to fog will also be possible at
kavl and perhaps khky during the early morning hours Friday as
todays rainfall will moisten the boundary layer further.
Outlook...afternoon and evening convection is expected...with the
best coverage over the mountains. Early morning stratus is possible
each day...accompanied by valley fog in the mountains.
Confidence table...
11-17z 17-23z 23-05z 05-11z
kclt high 96% high 100% high 100% high 100%
kgsp high 90% high 100% high 100% high 100%
kavl medium 78% high 100% high 100% high 91%
khky high 81% high 100% high 100% high 100%
kgmu high 88% high 100% high 100% high 100%
kand high 94% 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: (must be lower case)
Www.Weather.Gov/gsp/aviation_tables
&&
Gsp watches/warnings/advisories...
Georgia...none.
NC...none.
SC...none.
&&
$$
Synopsis...hg
near term...cdg
short term...hg
long term...hg
aviation...cdg
