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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 79 °
• Low: 57 °
• Chance of T-Storms

• Thursday
• 
• High: 79 °
• Low: 66 °
• Chance of T-Storms

• Friday
• 
• High: 86 °
• Low: 61 °
• Partly Cloudy

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

• Sunday
• 
• High: 86 °
• Low: 66 °
• Clear

Area forecast discussion 
National Weather Service Greenville-Spartanburg SC 
948 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 930 PM...the latest upper air analyses and Sat imagery 
indicate the strongest upper forcing is across the southeast 
portions of the County warning forecast area this evening. A large cluster of convection 
resulting from that forcing is slowly working northeastward into the 
Charlotte metropolitan area. The main threat seems to be shifting back to 
heavy rainfall...as slow-moving storms working into the metropolitan area. 
The Piedmont convection is robbing the Blue Ridge of moisture 
transport within weak southeasterly low level flow. So the heavy rain threat has 
waned within the existing Flash Flood Watch...given the trends. So I 
will cancel the Flash Flood Watch with this update...but keep 
mention of heavy rain/flooding in the severe weather potential statement...highlighting the 
Charlotte area. Otherwise...slow-moving upper vorticity will keep 
lingering shower activity through the overnight...especially in the mountains 
both the NAM and GFS keep some elev instability. Plenty of middle-upper level 
moisture with convective debris...but may moist llvls may still 
manage to develop patchy fog and/or stratus. Min temperatures still seem on 
track in the 50s to lower 60s. 


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 foothills. 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 /02z 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...none. 
SC...none. 


&& 


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