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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 86 °
• Low: 64 °
• Chance of T-Storms

• Thursday
• 
• High: 84 °
• Low: 64 °
• Chance of T-Storms

• Friday
• 
• High: 81 °
• Low: 63 °
• Chance of T-Storms

• Saturday
• 
• High: 82 °
• Low: 63 °
• Chance of T-Storms

• Sunday
• 
• High: 79 °
• Low: 59 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service Charleston SC 
1039 am EDT Wednesday may 16 2012 


Synopsis... 
a weak area of low pressure will linger across the region through 
Thursday. High pressure will build in from the north and northwest 
late in the week and persist into early next week. 


&& 


Near term /until 6 PM this evening/... 
a deep layered southwesterly flow persists across the forecast 
area this morning but a weakening flow is expected through the day 
as the upper trough axis shifts slowly east. Substantial middle and 
upper level debris cloudiness have been streaming over the 
southeast United States this morning from overnight convection in 
the northern Gulf. Additionally...a nice coupled jet exists and 
will maintain strong upper level divergence across the area today. 
The extensive cloudiness has thus far limited the rise in 
temperatures and kept values in the lower 70s most areas. Some 
erosion in cloudiness is expected by this afternoon but we still 
should maintain substantial coverage which may limit high 
temperature potential. We may end up bumping down high temperatures a 
degree or two based on the next 1-2 hours of satellite trends. 


The slower rise in temperatures will result in a later start to the 
convection which is expected to initially pop on the seabreeze. By 
late afternoon there will likely be numerous convective outflow 
boundaries that allow more activity to fire. 


Isolated severe thunderstorms will again be possible due to modest 
instability parameters. Middle-levels are a bit cooler today due to 
the proximity of the upper low...while the atmosphere is quite 
moist with precipitable water at 1... hail could again be the more prevalent 
concern. 


&& 


Short term /6 PM this evening through Saturday/... 
upper troffiness continues to press into the southeast states tonight 
with a nice deep moisture gradient bisecting Georgia and the 
Carolinas. Evening convection should wane but will need to watch 
for coastal low level moisture convergence and some middle level weak 
short waves to keep some showers and storms going longer or just 
redeveloping after midnight north of the Savannah River. We kept some 
chance probability of precipitation going well into the night to trend north of Savannah. 


Thursday and Thursday night...the long awaited upper trough will 
finally be poised to move across the region through the overnight. 
As it does...a backdoor cold front cold front will sink southward 
into the region with a surface ridge firmly in place by late 
Thursday. With shortwave energy moving through and plentiful low 
level convergence along the backdoor front and diurnal heating 
should result in pretty good coverage of showers and storms. I have 
increased probability of precipitation a bit...favoring southeast Georgia for the best coverage in the 
afternoon where the best heating will take place. With moderate 
instability and 500 mb temperatures falling to around -14 c...a few 
strong/severe storms will be possible. Highs are expected to be in 
the low to middle 80s with lows in the middle 60s. 


Friday through Saturday...upper ridging will build into the north 
with the remnant upper trough becoming cut off over the southeast. 
This feature will move very little into the weekend with some model 
solutions depicting it as a closed low. At the surface the high will 
remain to the northeast with NE flow and ridging in place across the 
Carolinas and into Georgia. Model guidance is a bit mixed on precipitation 
potential...but favoring the coastal waters and along the coast 
within a possible coastal trough. Overall confidence in precipitation 
potential for any one time period is low...so I have kept probability of precipitation in 
the slight chance to chance range favoring just offshore. Expect 
highs in the low 80s and lows in the low 60s. 


&& 


Long term /Saturday night through Tuesday/... 
model solutions continue to evolve regarding the long term 
period...and especially the upper low expected to sit over the 
southeast for the first few days. General consensus is for the upper 
low to drift around the southeastern Continental U.S. Sunday into Monday. Then 
the ridge to the north moves offshore as another trough approaches 
from the west and begins to absorb the closed low. This will keep 
the region in an area of troffing into the middle of the week. The 
low level ridge associated with the surface high to the northeast 
will remain in place across the forecast area through Monday. The 
ridge and the high will then weaken on Tuesday...leaving behind a 
rather nebulous surface pattern into the middle of the week. It 
appears any Atlantic surface low that develops will remain well 
offshore and overall rain chances will favor the coastal waters and 
coastal regions. I have kept the slight chance to chance pop regime 
in the forecast with temperatures running close to climatology. 


&& 


Aviation /15z Wednesday through Sunday/... 
timing/coverage/intensity of mainly diurnal convection remains 
difficult to pin down today as numerous complex synoptic features 
at play. We have both ksav/kchs with thunderstorms in the vicinity this afternoon with cumulonimbus 
clouds as the sea breeze should be active later today. Tonight... 
thunderstorms should decrease during the early evening hours then a shield 
of middle/high clouds expected overnight. These clouds will likely diminish 
the risk for fog but a few lower clouds not out of the question. At 
kchs...there may be vcsh/thunderstorms in the vicinity late tonight but confidence in any 
occurrence is quite low at this point. Overall a VFR forecast. 


Extended aviation outlook...periodic MVFR or lower conditions 
will be possible Thursday due to diurnal shra/tsra. VFR conditions 
with gusty winds will occur Friday and Saturday. 


&& 


Marine... 
through tonight...a weak pressure gradient is forecast and winds 
should be mainly S to SW less than 15 knots and seas 2-4 feet...highest 
beyond 20 nm off the coast. There are slight chances for showers 
and thunderstorms but the strongest storms should be inland from the Atlantic 
waters. 


Thursday through Sunday...a cold front will sink southward across 
the local waters Thursday and Thursday night which will result in 
the low level flow becoming increasingly north/NE as high pressure 
builds in. The surface high will remain positioned to the north 
through the weekend and a pinched NE gradient will set up. Winds and 
seas will be on the increase within the strengthening NE flow Friday 
through Sunday...with Small Craft Advisory conditions becoming increasingly likely. 


Rip currents...an elevated risk of rip currents appears likely at 
the beaches Friday through Monday...with a persistent and at least a 
moderate NE and east wind to prevail. 


&& 


Chs watches/warnings/advisories... 
Georgia...none. 
SC...none. 
Marine...none. 


&& 


$$ 


Synopsis... 
near term...jrl 
short term...bsh 
long term...bsh 
aviation... 
marine...bsh