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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Tuesday
• 
• High: 84 °
• Low: 66 °
• T-Storms

• Wednesday
• 
• High: 82 °
• Low: 64 °
• T-Storms

• Thursday
• 
• High: 82 °
• Low: 64 °
• Chance of T-Storms

• Friday
• 
• High: 75 °
• Low: 50 °
• Partly Cloudy

• Saturday
• 
• High: 73 °
• Low: 50 °
• Clear

Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
802 PM EDT Tuesday may 21 2013 


Synopsis... 
an approaching upper level trough will continue to influence the 
region through midweek. Southerly flow will keep the area warm and 
generally unsettled with storm chances each afternoon. A cooler and 
drier airmass settles in for the weekend after a cold front moves 
through Thursday. 


&& 


Near term /through Wednesday/... 
as of 800 PM...a little bit of shortwave energy crossing the western 
third of the County warning forecast area is working to enhance convection. 
Fortunately...shear is still weak and the last of the unable-overnturned 
air mass is currently being worked over. So still expect things to 
wind down over the next 2-4 hours. The rest of the County warning forecast area should remain 
tranquil. Probability of precipitation were adjusted accordingly...with other changes being 
for 00z aviation grids. 


As of 530 PM...convection has been favoring the western site of the 
County warning forecast area in the last hour or so...as decent westward propagating outflow 
boundaries are working into 3500 j/kg cape air mass. The pulse 
convection has been fairly robust...with large hail and damaging 
wind threats. Have updated the probability of precipitation...blending in the 18z NAM and 
latest hrrr...which agree on convection working over the upper 
Savannah valley and SW NC mountains during the early evening hours. 
Meanwhile...convection is trying to organize over eastern Tennessee where the 
better upper forcing and deep layer shear exists. I/M expecting most 
of this to struggle to reach the southern Appalachians...due to the lack 
of shear and forcing over our area. 


At 230 PM EST Tuesday...still seeing an evolving convective 
situation across the County warning forecast area as weak forcing is maintained within a 
very broad 500 mb trough. Still expect pulse severe later this afternoon 
mainly across the eastern upstate aligned with a line of vorticity energy and 
across NC mountains where rather steep lapse rates are moving in from the 
west. These storms will be mainly diurnally driven...but some -shra 
will be maintained across the NC mountains in upslope flow through the 
middle morning. Debris clouds will persist overnight...but enough 
clearing should be had to enable morning fog...and patchy/areas of 
dense fog through 13z or so. Not much change is in store with the 
synoptic pattern Wednesday. The western upper trough impinges upon the area and 
the western zones will have a better chance for afternoon precipitation/conv 
than the eastern zones and have maintained high end chances across the 
mountains a good heating day in SW/ly flow with maxes a couple degrees 
above normal will set the stage for another high cape environment 
and pulse severe storms possible. 


&& 


Short term /Wednesday night through Friday/... 
as of 210 PM Tuesday...model guidance remains in fairly good 
agreement with regards to the weather across northeast Georgia and 
the Carolinas for the remainder of the work week. Deep upper level 
trough and an associated surface cold front will slowly migrate 
eastward over the next 24 hours. Surface ridging to the southeast 
will allow for southerly flow...thus setting up a modest warm sector 
across the region on Thursday leading to above normal temperatures. 
Expecting cold front to move into far western portions of the County Warning Area by 
around 12z Thursday morning. Precipitation chances will increase 
near and along this boundary as it moves across the North Carolina 
mountains...and then spreads eastward across the piedmonts. Highest 
probability of precipitation will be across the North Carolina foothills/Piedmont due to 
closer proximity to both upper and surface lows. Expecting any activity 
across the above mentioned regions during the middle to late morning 
hours on Thursday to remain subsevere as low level inversion remains 
in place. Later in the afternoon as surface temperatures increase into the 
80s near and along the i85 corridor...and shear profiles improve 
somewhat along the passing frontal boundary...a severe storm or two 
cannot be ruled out. Conditions will improve across the region late 
on Thursday as diurnal heating is lost...and drier air begins to 
advect in behind the front. 


Slight chance probability of precipitation remain in the forecast across the higher terrain 
during the early morning hours on Friday morning. By daybreak...all 
precipitation should have dissipated and skies will begin to clear 
as high pressure builds. Upper level ridging across the Midwest 
will advect to the east during the day on Friday allowing heights to 
build over northeast Georgia and the Carolinas...leading to pleasant 
weather conditions for the remainder of Friday evening. 
Temperatures on Friday will be on average about ten degrees cooler 
than previous days as northwest flow Ushers in a cooler/drier 
airmass. 


&& 


Long term /Friday night through Tuesday/... 
as of 220 PM Tuesday...the shortwave trough moves off the East Coast 
Friday night and drier cooler air filters in from the northwest. 
Driest air varies per model from Friday night through the day 
Saturday. As the upper ridge slowly builds from the west and warm 
front channels showers closer to the NC mountains to start the new 
week...probability of precipitation will increase at least into the slight range. Based on 
the blend of the models...looks like the best time for rain will be 
going into middle week. Seems best organized bands of convection would 
be late Tuesday. Considered going to low chance probability of precipitation at that 
time...but that is a week away and much could change. Convective available potential energy on the 
GFS for Tuesday PM are 1100 to 1400 and winds going up from surface not 
too bad for that time. Temperatures...highs near normal or slightly 
below and lows cooler than normal early in weekend and going above 
into new week. 


&& 


Aviation /00z Wednesday through Sunday/... 
at kclt...VFR with a light S/southeast wind under convective debris clouds 
overnight. Guidance is showing stratus and fog developing again across 
the region during the pre-dawn hours. Will go with an IFR ceiling right 
around daybreak...similar to last morning. The clouds should 
quickly lift and scatter after sunrise. Scattered convection 
expected again Wednesday afternoon. Will go with a prob30. 


Elsewhere...VFR expected this evening...as convection gradually 
wanes to the west. Expecting similar conditions overnight to what 
occurred the previous night. Fog and stratus expected to develop 
first int he mountains valleys...then across the Piedmont closer to daybreak. 
Fog and stratus should dissipate after sunrise Wednesday. Scattered to 
numerous rain showers/thunderstorms and rain expected Wednesday afternoon. Will go with prob30 for 
ts at all sites from 18z to 00z. 


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


Confidence table... 


00-06z 06-12z 12-18z 18-24z 
kclt high 100% high 91% high 90% high 100% 
kgsp high 100% high 91% high 85% high 100% 
kavl high 100% high 89% high 94% high 100% 
khky high 100% medium 62% high 91% high 100% 
kgmu high 100% high 89% high 87% high 100% 
kand high 100% high 89% high 86% 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...level 
near term...Ark/sbk 
short term...cdg 
long term...deo 
aviation...Arkansas