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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Tuesday
• 
• High: 84 °
• Low: 68 °
• T-Storms

• Wednesday
• 
• High: 82 °
• Low: 66 °
• Chance of T-Storms

• Thursday
• 
• High: 82 °
• Low: 61 °
• Chance of T-Storms

• Friday
• 
• High: 79 °
• Low: 48 °
• Partly Cloudy

• Saturday
• 
• High: 75 °
• Low: 52 °
• Clear

Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
622 am EDT Tuesday may 21 2013 


Synopsis... 
an approaching upper level trough will continue to influence the 
region for most of the week. Southerly flow will keep the area in a 
moist and generally unsettled airmass with storm chances each 
afternoon. Rain chances diminish after a cold front crosses through 
by the end of the week. 


&& 


Near term /through tonight/... 
1015 UTC update...visibility was updated from observations...placing 
patches of dense fog in some locations. As the dense fog areas are 
scattered about...no dense fog advisory is planned at this time. 


At 300 am EST Tuesday...a weak but persistent upper low will drift 
northeast and away from our area today and tonight...while an upper 
ridge axis crosses the southern Appalachians...and an upper trough 
moves from the plains to the MS River Valley. Model time heights 
show lingering moisture in the wake of the departing trough...but 
with diminished upper forcing...precipitation will be driven by 
diurnal heating. Instability in excess of 1000 j/kg will support 
thunderstorm formation this afternoon if a weak low level cap can be 
overcome. Dry air aloft and beneath cloud bases will support 
evaporative cooling and downdraft production. Shear will decrease 
through the day...limiting storm organization. A weakening steering 
flow will mean slow moving thunderstorms may produce locally heavy 
rainfall. Convection will linger into the evening before the low 
levels stabilize. Temperatures will run several categories above 
normal under the upper ridge. 


&& 


Short term /Wednesday through Thursday night/... 
as of 245 am Tuesday...short waves rotating around an upper trough 
move into the area Wednesday and Wednesday night. The upper trough then sharpens 
and moves into the area Thursday night. At the surface...a weak ridge 
extending from the Atlantic is over the area Wednesday morning. The ridge 
weakens as a cold front approaches from the west. This will allow 
southerly flow to develop bringing moisture back into the area. 
Instability develops...but remains weak. However...forcing will 
increase as the short waves move in. Best precipitation chance remains over 
the mountains and diminishes south of I-85. Given the forcing and weak 
but increasing shear...isolated severe storms cannot be ruled out. As 
the short waves move east and atmos stabilizes overnight...precipitation 
chance diminishes with chance pop mountains and slight chance elsewhere. Cold 
front jumps into the developing Lee trough on Thursday. This brings best 
forcing to the northern and eastern County warning forecast area...where highest pop will be forecast. 
Precipitation chance retreats to the mountains overnight with lingering moisture 
and northwesterly upslope flow. Highs will be a little above normal each day. 
Lows around 5 degrees above normal Wednesday night drop to near normal Thursday 
night in the cooler air mass moving in behind the front. 


&& 


Long term /Friday through Monday/... 
as of 345 am Tuesday...the County warning forecast area remains in northwesterly flow aloft as a trough 
slowly moves out over the Atlantic and an upper ridge moves east 
across the central Continental U.S.. short wave energy then moves across the 
area by early next week as the flow becomes more zonal. At the 
surface...dry high pressure settles in from the northwest for Friday and Sat. A 
weak warm front develops to our west on sun and moves toward the 
area through Monday. The GFS and European model (ecmwf) disagree on the amount of moisture 
and lift that develop as the front moves east. However...they do 
agree that precipitation may develop for Sun night and Monday. Have slight chance 
pop for now. However...the bigger story is that the air mass moving 
in with the high is quite cool. In fact...highs will be around 5 
degrees below normal Friday and Sat...rising to a couple of degrees 
below normal sun and Monday. Lows will be around 5 degrees below normal 
Friday and Sat nites...rising to near normal Sun night. 


&& 


Aviation /10z Tuesday through Saturday/... 
at kclt...a brief MVFR ceiling or visibility restriction will be possible 
early this morning in a moist air mass. Otherwise...low VFR clouds 
will persist for much of the day...with midday breaks possible. 
Instability will be supportive of convection today...mainly in the 
afternoon. Light south-southwest winds will persist. Blended guidance doe not 
support Wednesday morning restrictions...but if precipitation falls 
at the field today...fog and stratus would be more likely late 
tonight. 


Elsewhere...restrictions at kavl will linger into middle morning. 
Foothills sites may experience brief restrictions as well before 
heating takes place this morning. Convection will be supported by 
instability this after noon and evening...perhaps even by late 
morning in the mountains. Light winds will favor the south-southwest. Guidance 
supports MVFR fog at kavl early Wednesday morning...with low VFR at 
khky and kand. Any sites that receive rain this afternoon or evening 
would be vulnerable to lower restrictions. 


Outlook... ceiling and visibility restrictions in scattered showers 
and thunderstorms again Wednesday and Thursday aftn/eve. Generally 
VFR weather Friday and Saturday. 


Confidence table... 


10-16z 16-22z 22-04z 04-10z 
kclt high 86% high 98% high 100% high 100% 
kgsp high 88% high 100% high 100% high 100% 
kavl high 83% high 100% high 100% high 90% 
khky high 85% high 100% high 100% high 98% 
kgmu high 83% high 100% high 100% high 100% 
kand high 81% 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...rwh 
near term...jat 
short term...rwh 
long term...rwh 
aviation...jat