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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Saturday
• 
• High: 81 °
• Low: 64 °
• T-Storms

• Sunday
• 
• High: 79 °
• Low: 64 °
• T-Storms

• Monday
• 
• High: 81 °
• Low: 66 °
• Chance of T-Storms

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

• Wednesday
• 
• High: 86 °
• Low: 68 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
206 PM EDT Sat may 18 2013 


Synopsis... 
a weak upper level trough will linger over the region through 
Monday...then lift northeast. The forecast area will remain in a 
moist and rather unstable airmass...before a cold front crosses east 
late next week. 


&& 


Near term /through tonight/... 
as of 200 PM...area of showers has been gradually eroding over the 
past couple of hours across the eastern half of the area...but 
remains vigorous enough to support likely probability of precipitation for at least a couple 
more hours. Otherwise...widespread cloud cover and lingering effects 
of the shower band are resulting in only weak instability across the 
area at this time. Therefore...it/S somewhat unclear as to how convective 
trends are going to evolve for the duration of the afternoon/ 
evening. Nevertheless...some clearing is occurring across the 
western zones...and within this very moist air mass supported by 
remnant upper low upstream over the tenn valley...it/S not going to 
take much to see new convection initiate. Therefore...will trend 
back toward likely probability of precipitation late this afternoon into the evening...especially 
across the western mountains in light of the weak instability...severe 
storms appear to be of minimal concern...although rainfall rates 
will need to be monitored closely. 


The low and trough slide into the Piedmont tonight. The southerly flow 
slides eastward as well. This will take the focus of the convection 
east as well. Best precipitation chance will be over the Piedmont during the 
night and diminish elsewhere. Expect the best quantitative precipitation forecast to slide east through 
the night as well. Wpc quantitative precipitation forecast forecast is 1 inch or less total through the end 
of the night. Therefore...while isolated heavy rainfall is 
possible...widespread heavy rainfall is not. Especially as it looks 
like the mountains will see the highest rainfall during the day and the 
Piedmont during the night. Lows will be 5 to 10 degrees above normal. 


&& 


Short term /Sunday through Monday night/... 
at 300 am EST Saturday...on Sunday morning...the remains of an upper 
low will be somewhere over the central Appalachians. A weak trough 
associated with this system will cross the western Carolinas and NE 
Georgia Sunday and Sunday night. Upper level ridging moves slowly east 
over the southern and central Appalachians on Monday and Monday 
night in the wake of the upper trough. 


Moisture associated with the trough will support widespread 
precipitation on Sunday. Instability will be limited by cloud 
cover...but should still be sufficient for convection. Model 
soundings show a very moist profile...with little dry air aloft and 
limited dry air beneath the cloud layer for evaporative cooling or 
downdraft production. Steering flow will be enough to keep cells 
moving slowly to the NE. A light southerly surface flow will provide 
upslope flow enhancement of precipitation...mainly along the south 
facing Blue Ridge Escarpment. Some instability will persist through 
Sunday night as the upper trough passes...with steering flow 
gradually veering to the east. 


On Monday some dry is introduced at middle levels as the upper trough 
departs. Clouds heights rise...with more dry air at the surface. 
Instability increases...supporting more of a convective Mode to 
precipitation...though with decreasing coverage. Moisture will be 
slow to depart to the east on Monday night...but the best moisture 
will be near the coast. 


Maximum temperatures will be near normal...with minimum temperatures 
a couple of categories above normal. Precipitation totals could 
exceed one inch along the south facing Blue Ridge Escarpment of 
SW NC...with most of that falling on Sunday and Sunday night. 


&& 


Long term /Tuesday through Friday/... 
at 300 am EST Saturday...an upper ridge will move slowly across the 
Carolinas and Georgia on Tuesday and Wednesday...while an upper trough 
associated with another closed low in the plains moves to the MS 
River Valley. The trough deamplifies as it crosses the Ohio and Tennessee 
valleys on Thursday...and reaches the central and southern 
Appalachians on Friday. 


A warm and moist air mass remains over the southeast from Tuesday 
through Friday. Diurnally modulated convection is expected on 
Tuesday and Wednesday. On Wednesday night both the GFS and European model (ecmwf) 
show a convergence of Atlantic moisture with moisture left over from 
a dying cold front that arrives from the west...just about over the 
southern Appalachians. This moisture linger over our area into 
Thursday...before starting to move off to the east on Friday. If 
this scenario hold...precipitation would be more likely to persist 
overnight...with greater coverage and accumulation. On Saturday a 
cold crosses the area from the north. 


Temperatures will briefly warm above normal as the upper ridge axis 
arrives...falling to around normal as heights fall with the advance 
of the upper trough. 


&& 


Aviation /18z Saturday through Thursday/... 
at kclt/khky...the band of showers has become more ragged/less 
concentrated as it moves across the NC foothills and Piedmont. Will 
continue to include a tempo for rain showers/MVFR conditions at kclt for the 
first couple of hours of the period. It is somewhat unclear as to 
how convective trends will evolve this afternoon...as the showers 
have stabilized the atmosphere across much of the region. However...some 
clearing is occurring across northwest South Carolina and portions of the 
NC mountains convection will likely reignite in these areas during the 
afternoon...and possibly approach kclt by early evening. Tempos have 
therefore been included for thunderstorms and rain. Occasional showers and possible ts 
will continue off and on through the end of the period. With the 
very moist air mass in place...deteriorating flight conditions are 
expected overnight...with IFR ceilings eventually becmg likely. Gradual 
improvement is expected by the end of the period. 


Elsewhere...showers have cleared the terminals leaving MVFR/VFR 
conditions in their wake. (The small area of IFR ceilings at kgsp should 
lift no later than 19z). Convection is expected to redevelop over 
the tenn valley/southern Appalachians/upper Savannah River valley 
this afternoon...and thunderstorms in the vicinity/rain showers will be carried from late afternoon 
on. Occasional showers and possible ts will continue off and on 
through the end of the period. With the very moist air mass in 
place...deteriorating flight conditions are expected overnight...with 
IFR ceilings eventually becmg likely. Gradual improvement is expected by 
the end of the period. 


Outlook...showers and thunderstorms...and associated restrictions... 
will persist through Monday. Fair weather may return by Tuesday. 


Confidence table... 


18-24z 00-06z 06-12z 12-18z 
kclt high 98% high 98% high 97% high 93% 
kgsp high 100% high 95% high 98% high 88% 
kavl high 81% high 95% high 89% high 90% 
khky high 100% high 80% high 96% high 95% 
kgmu high 91% high 95% high 96% high 83% 
kand high 96% high 88% high 92% high 83% 


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...jat 
near term...jdl/rwh 
short term...jat 
long term...jat 
aviation...jdl