Area forecast discussion
National Weather Service Greenville-Spartanburg SC
351 am EDT Friday may 24 2013
Synopsis...
an upper level trough will swing through the region today...bringing
cooler and drier conditions for the weekend. Temperatures will
moderate by the beginning of next week...with a chance of afternoon
showers and thunderstorms each day concentrated over the mountains.
&&
Near term /through tonight/...
as of 300 am...conditions are gradually drying out behind the
passage of a cold front early this morning. There is enough low level
moisture in the northwesterly flow for scattered showers to develop and affect
the upslope areas along the Tennessee line. This activity should wane by middle
morning...as upper shortwave trough passes by and drier air works in.
Today...dry high pressure will begin to continue build into the area
from the northwest. Most of the guidance...the NAM in particular...indicate
breezy to windy conditions across the County warning forecast area. In fact...the high terrain
and some of the valleys where a gap wind will set up may approach
wind advection criteria...mainly during the morning hours. Confidence not
high enough to go with a wind advection in the mountains elsewhere...breezy
conditions warrants caution on area lakes. Temperatures will be below
normal under sunny to mostly sunny skies.
Tonight...the surface high will still be centered to our northwest...so mixing
is expected to continue through the night. Clear skies and cold air advection will
allow temperatures to drop into the 30s in the mountains and 40s across most of
the Piedmont. Patchy frost is possible in the sheltered
valleys...but widespread frost is not expected due to the mixing
across the high terrain.
&&
Short term /Saturday through Sunday night/...
as of 300 am Friday...generally fair weather Saturday through Sunday
night. Cloud cover will increase Saturday night...with variably
cloudy conditions expected into Sunday night. This will be the
result of warm advection on the back side of a strong long wave
trough. Overall the forcing looks weak and most of what we should
see during this period will be ac/SC and perhaps a few areas of
high-based sprinkles or light showers...particularly Saturday night.
Maximum temperatures Saturday will be a couple categories below
normal...rebounding a few degrees on Sunday.
&&
Long term /Monday through Thursday/...
as of 240 am Friday...the extended forecast looks good and no major
changes have been made to the grids. The 00 UTC GFS and ydays 12 UTC
European model (ecmwf) are in good agreement in gradually building a long wave ridge
across the lower MS River Valley and deep south states through the
period. We will start out the period under northwest flow on the back side
of a large long wave ridge centered over the western Atlantic. The
models have quite a bit of middle and upper level moisture on the back
side of the trough...the result of low and middle level isentropic
upglide. Still...the surface dewpoints are low and precipitation chances Monday
should mainly be confined to sprinkles or light high-based showers
over the mountains Tuesday through Thursday boundary layer moisture increases as the
surface ridge axis moves off the coast. The GFS has the best instability
by far over the mountains Tuesday and Wednesday...with a little more drying on
Friday. At this point low chance probability of precipitation over the mountains and slight chance
probability of precipitation elsewhere all three days still looks good. I did nudge temperatures up
a little Tuesday. I think Wednesday and Thursday are probably a little too
cool...but I/ll leave that for the day shift to decide.
&&
Aviation /08z Friday through Tuesday/...
at kclt...VFR with some lingering middle clouds for the first few hours
of the 06z taf. A north-northwest wind expected through the period...increasing
into the 10-15 knots range by middle morning...with gusts in the 20-25 knots
range expected through the afternoon. Winds diminish around sunset this
evening.
At kavl...strong gap winds expected to pick up before daybreak...and
continue through the day. Generally sustained 15-20 kts and gusts
possibly in the 30-35 knots range. Some moisture will continue to work
up the valley through about middle morning...with any ceilings expected to be
VFR. However...a brief period of MVFR ceiling cannot be ruled out...most
likely right before or during daybreak. Winds will begin to diminish
after sunset this evening.
Elsewhere...VFR conditions are expected at all other taf sites
through the period...with middle clouds eventually clearing out by
daybreak. Winds will be the main concern today. Expecting all sites
to have winds in the 10-12kt range with gust approaching 25kts from
late morning through the afternoon.
Outlook...VFR through the period.
Confidence table...
08-14z 14-20z 20-02z 02-08z
kclt high 100% high 100% high 100% high 100%
kgsp high 100% high 100% high 100% high 100%
kavl high 82% high 100% high 100% high 100%
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: (must be lower case)
Www.Weather.Gov/gsp/aviation_tables
&&
Fire weather...
it will be windy over the mountains and breezy over much of the rest
of the forecast area today. Afternoon minimum relative humidity
values will fall to between 25 and 30 percent. With recent
widespread rainfall...fuel moisture values are generally still
high...and we do not anticipate needing any fire danger products
today. If any land management officials think that a Fire Danger
Statement is warranted please contact our office.
&&
Gsp watches/warnings/advisories...
Georgia...none.
NC...none.
SC...none.
&&
$$
Synopsis...level
near term...Arkansas
short term...McAvoy
long term...McAvoy
aviation...Arkansas
fire weather...McAvoy
