Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
255 PM EDT Thursday Oct 23 2014
dry high pressure will remain in control of the weather through
early next week.
Near term /through Friday/...
as of 230 PM EDT Thursday...ejecting upper trough and associated
surface cyclone will allow for pressure gradient forces to relax
across the region this evening. Until then...expecting occasional
15-20mph gusts across portions of the NC Piedmont with 20-25mph
gusts possible through the French Broad valley as channeling
enhances flow. Otherwise...predominate downslope flow across the low
terrain will continue to yield sunny skies with temperatures
approaching normal levels. As short wave upper ridging slides
overhead this evening...expecting clear skies to allow for abundant
radiational cooling resulting in below normal lows. As a
consequence of this combined with relaxing pgf/winds...frost
conditions are still favorable for the central/northern mountains of
western NC. It is possible that a few locations across the NC
Piedmont could experience patchy frost...however expecting this to
be rather sparse in coverage. Thus...no changes planned to the
frost advisory that is currently in effect.
Guidance indicates a weak upper short wave disrupting the pattern
Friday with a few high clouds being the only weather of consequence.
Otherwise...surface high pressure will dominate the pattern leading
to mostly sunny skies and near normal temperatures by the afternoon
Short term /Friday night through Sunday/...
as of 145 PM Thursday...northwest flow develops across the area Sat as an upper
trough slowly moves east of the area. The flow begins to flatten out
on sun as low amplitude ridging begins to move toward the area from
the west. High pressure ridges into the area Sat then weakens Sat
night as a weak cold front drops across the area. A weak short wave
moves across the area in the northwest flow during this time as well. There
will be quite a bit of low level moisture associated with this
system...but the main forcing will be from northwesterly upslope flow.
Guidance blend now favors a slight chance of rain showers across the Tennessee border
counties Sat night...so have added this to the forecast. There certainly
will be quite a bit of clouds across that area during this time...
along with gusty northwest winds. Generally mostly clear skies and lighter
winds will prevail across the rest of the area. High pressure
returns Sunday with clouds and winds diminishing. Near to slightly
above normal temperatures Sat rise above normal sun.
Long term /Sunday night through Thursday/...
as of 250 PM Thursday...guidance remains in decent agreement through the
medium range. An upper ridge moves over the area Monday then the ridge
axis moves off shore Tuesday. At the surface...high pressure slowly slides
across the area Monday and off shore Tuesday...but remains weakly ridged
across the area. This leads to clear skies Monday and slowly increasing
clouds Tuesday. Highs remain nearly steady above normal while lows start
out a little above normal and rise even higher Monday night. An upper
trough crosses the area Wednesday...with the European model (ecmwf) showing a stronger and
deeper trough than the GFS. A couple of weak short waves move over the
area Thursday in the lingering weak long wave trough or southwesterly flow. A cold
front moves into the area Wednesday...with the European model (ecmwf) showing a stronger
and more moist system. The European model (ecmwf) then pushes the front south of the
area Thursday with dry high pressure moving in from the north while the
GFS stalls the front over the area with moisture returning north
along the front. Have gone with a blend and have pop increasing to
chance west and slight chance east Wednesday/Wednesday night then dropping back to
slight chance Thursday. Temperatures remain above normal but show a slow cooling
trend from Wednesday to Thursday.
Aviation /19z Thursday through Tuesday/...
at kclt and elsewhere...VFR conditions will prevail at all sites
with the exception of possible MVFR level fog restrictions at kavl
and kand by morning. Light/moderate northwest gusting will persist through
the day across the high terrain into portions of the NC Piedmont due
to pgf and mixing...therefore gusts are featured at kclt and kavl.
All sites will remain sky clear through the majority of the period with
the exception of possible upslope enhanced low stratus in the
mountain valleys tonight. As mentioned above...guidance hints at
MVFR fog restrictions at kavl and kand as winds calm and the
boundary layer cools therefore added tempos for such at each site.
Model time heights indicate increasing upper level moisture during
the day on Friday ahead of an approaching upper shortwave
trough...thus included scattered middle/high clouds at all taf locations.
Outlook...quiet weather will continue across the region...as deep
layer ridging settles in through this weekend.
NC...frost advisory from 2 am to 9 am EDT Friday for ncz033-049-050-