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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 77 °
• Low: 59 °
• Chance of T-Storms

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

• Friday
• 
• High: 88 °
• Low: 64 °
• Partly Cloudy

• Saturday
• 
• High: 90 °
• Low: 68 °
• Chance of T-Storms

• Sunday
• 
• High: 88 °
• Low: 68 °
• Clear

Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
804 PM EDT Tuesday may 22 2012 


Synopsis... 
an upper low pressure trough will slowly move through the region 
tonight into Wednesday. High pressure will build over the area for 
unseasonably warm temperatures and mostly dry weather Thursday 
through the weekend. 


&& 


Near term /through Wednesday/... 
as of 530 PM...only minor tweaks to probability of precipitation/weather per radar trends. 
Scattered to numerous showers and thunderstorms across the County warning forecast area at this time. Two main 
clusters...one over the northwest NC Piedmont and another across the western 
upstate. Strong upper vorticity can be seen on water vapor entering north Georgia. 
So expect coverage to remain high into early evening. Both the 
severe threat and Hydro threat seem to be not as bad as earlier 
thought. But still some potential for large hail...damaging wind 
gusts...and localized flooding with strongest storms and mergers. 


Overnight...the trough strength remains steady state with the best 
energy and DPVA displaced south of the County warning forecast area. However...there will be 
enough lift and some measure of elcape and mlvl lapse rates for the 
continuation of isolate/scattered -shra/tstms. Dont anticipate a flooding 
concern...but there is the potential for some storms to redevelop 
over the same areas and if they are over the low ffg zones...then 
minor flooding could be produced. Min temperatures will remain a few 
degrees f above normal with the debris cloud cover. Also...patchy 
dense fog will be favored across the mountain valleys. 


Wednesday...heights will begin to rise...however an overall broad 
trough will encompass the entire southeast region. Model soundings show 
enough SBCAPE developing...especially across the south and east for some 
stronger convection. Deep shear will be very low as the upper low 
becomes less defined. However...at the surface there will be weak low 
pressure centered across eastern Georgia and the western upstate...so a natural 
convergence zone will develop north and to the west of this feature. 
This will be the area advertised for higher chance probability of precipitation...especially across 
the northern NC mountain and fthills. Maximum temperatures will be a few degrees above 
normal south and a few degrees below normal north as higher cloud 
cover will limit insolation for a good part of the day across most 
of NC. 


&& 


Short term /Wednesday night through Friday/... 
as of 230 PM Tuesday...used a general GFS/NAM model blend for 
Thursday-Friday timeframe. Expect probability of precipitation to taper off to slight chance Wednesday evening 
with cooling. The 500 mb low will fill and lift NE as an open wave 
Wednesday night-Thursday with upper level difluent flow over the area Thursday. Also 
expect incrsng low level S-southeast flow to bring some moisture off the 
Atlantic up over the area. Look for a chance of mountain thunderstorms to spread out 
across much of the NC Piedmont Thursday afternoon...with isolated coverage 
upstate SC and NE Georgia. Temperatures should warm about a category above average. 
Upper wave moves NE of the area Thursday night with a ridge building in 
behind it. Upper ridge continues to build over the region Friday while 
a surface ridge pushes down over the area from the NE. Low level east flow 
could bring enough Atlantic moisture off the East Coast...combined with 
weak upslope flow and afternoon heating...for slight chance thunderstorms over the 
mountains temperatures will warm another Cat above Thursday readings. 


&& 


Long term /Friday night through Tuesday/... 
as of 230 PM Tuesday...the latest medium range models continue to 
indicate that the large 500 mb high will build over the Mississippi 
Valley on Friday and migrates east across the eastern Continental U.S. Through 
the weekend. Therefore...expect high temperatures warming into the 
upper 80s Friday and reaching the low 90s on Saturday over the 
Piedmont. Warming temperatures aloft in the ridge will provide a 
degree of capping for convection...but a combination of upslope flow 
due to predominant southeast to east flow and elevated diurnal instability may 
support the development of afternoon isolated/scattered 
thunderstorms along the Blue Ridge mountains Friday through Sat. So 
have kept slight chance probability of precipitation there with dry elsewhere. 


Sunday through Tuesday...confidence is low as the models show 
different solutions for handling the tropical feature over the 
southeast. The GFS indicates that a tropical low over the Atlantic 
Ocean approaches the southeast coast on Sunday and crosses northern Florida on 
Monday while the European model (ecmwf) has the low lingering off the southeast coast 
through the period. Given the uncertainty of the track/intensity of 
the low...will carry slight chance probability of precipitation over much of our County Warning Area through 
the period. Temperatures will remain well above normals. 


&& 


Aviation /00z Wednesday through Sunday/... 
at kclt...main concern in the next 4 hours or so is numerous rain showers 
and thunderstorms and rain around the airfield. High-res/near term models seem to have 
initialized well with the convection...and keep scattered to 
numerous storms in the clt area through at least 04z. Coverage should 
diminish overnight. With widespread rainfall and light southerly low level 
flow...some of the guidance is picking up on possible stratus and/or 
fog development. Conditions are not ideal with plenty of middle 
cloudiness lingering. So left out restrictions for the late 
overnight/Wednesday morning. However...if guidance trends more pessimistic 
and the airfield receives some heavy rain this 
evening...restrictions may be added with an amendment later this 
evening. For Wednesday...convection should be widely scattered. Have 
left out mention with the 00z taf for now. I may add a prob30 with 
an update later this evening. 


Elsewhere...most of the taller convection has shifted east of the 
area...with lingering showers remaining. Still could be a few 
embedded thunderstorms and rain within the waning convection...but have gone with rain showers 
or vcsh for the rest of the evening. Guidance mixed on possible 
restrictions in fog and/or stratus given moist bl from earlier 
rainfall. Have added some MVFR visibility and/or ceilings at sites which had 
some rainfall and already low dewpt depressions. Trends will be 
watched for possibly more pessimistic amendments. Convection should be 
less numerous Wednesday...so no mention of ts with the 00z tafs. 


Outlook...diurnal thunderstorms toward the end of the week are more 
likely to be confined to the mountains and foothills. Early morning 
restrictions due to fog are a good bet mainly in the mountain 
valleys. 


An experimental aviation forecast consistency table showing the 
percentage of guidance members agreeing with the scheduled issuance 
category is available at following link (use lower case)... 


Www.Weather.Gov/gsp/aviation/tables.Htm 


&& 


Gsp watches/warnings/advisories... 
Georgia...none. 
NC...Flash Flood Watch until midnight EDT tonight for ncz033-049- 
050-053-501-503-505. 
SC...none. 


&& 


$$ 
Synopsis...joh 
near term...Ark/sbk 
short term...rb 
long term...joh 
aviation...Arkansas