901 
fxus62 kchs 201427 
afdchs 


Area forecast discussion 
National Weather Service Charleston SC 
1027 am EDT sun Jul 20 2008 


Synopsis... 
Tropical Storm Cristobal will slowly move away from the upper South 
Carolina coast today as Atlantic high pressure builds in. A weak trough 
of low pressure will develop to the west on Monday and then persist through 
much of the week. 


&& 


Near term /through tonight/... 
ts Cristobal moving along the southeast coast of North Carolina 
this morning with a weak surface trough extending east-west through our 
forecast area from S of Charleston to north of Metter. Synoptic 
parameters suggest a continuation of prior forecast trends today 
with hot afternoon temperatures 95-100 degrees not far away from 
the immediate coast. Model soundings are inverted-v style this 
afternoon...especially over our inland zones. Given the decent 
morning downslope component and position of the tropical storm... 
we will continue to allow surface dew points to mix down into the 
60s during maximum heating which will also keep most locations from 
reaching heat advisory criteria. The corridor between Savannah and 
Charleston bears watching with the alignment of the sea breeze as 
the NAM does show some decent late day dewpoint pooling. Forecast 
high temperatures below record values which are all at or above 
100 degrees at chs/sav/chl. 


As for clouds...models show some middle level moisture lingering 
today and there may be scattered areas of middle clouds at times 
but most areas should see plenty of sunshine. 


Finally...convection potential seems limited overall...especially 
inland from the sea breeze. Plenty of subsidence capping today 
with 3c-5c middle level lapse rates. The only concern is the axis 
of the horizontal surface trough bisecting the Savannah River 
entrance region late afternoon. The NAM seem reasonable with a few 
thunderstorms late day from Jasper County down along I-95 in our Georgia 
region. Coverage should be slight with the very poor middle level 
environment. Slight chance probability of precipitation were continued along the pinned sea 
breeze region. 


&& 


Short term /Monday through Monday night/... 
after a warm and muggy night tonight...another sultry Summer day 
on tap Monday which may still necessitate a heat advisory 
issuance for portions of the area later on later packages. 
Temperatures may be near today/S values or even a little 
warmer in spots. Afternoon surface dew points will likely be a 
bit higher especially along and east of I-95. Diurnal convection 
mostly confined to the sea breeze and fairly sparse due to overall 
warm temperatures aloft and lack of regional low level moisture 
convergence. There is a upper level shear axis over the forecast 
area Monday and this feature may aid in a weaker cap late in the day. 


&& 


Long term /Tuesday through Saturday/... 
the pattern will ease into one that favors climatology. Deep 
layered moisture will increase with a weak low level trough 
in the Lee of the mountains. Scattered afternoon and evening 
thunderstorms should increase toward middle week with possibly some late 
night convection near the coast given instability forecasts and 
favored nocturnal land breeze/coastal convergence. Temperatures 
will moderate to near climatology values with the increased debris 
cloud coverage and lower convective temperatures. 


&& 


Aviation /15z Sunday through Thursday/... 
latest short term models continue to indicate very sparse chances 
of convection this afternoon. However...if isolated thunderstorms can 
manage to develop... they would likely be somewhere in the ksav to 
kchs taf corridor. Confidence is much too low to consider any cumulonimbus 
mentions this afternoon at this time. 


Extended aviation outlook...mostly VFR conditions should prevail 
outside of any diurnal convection...which looks to increase in 
coverage significantly by Wednesday and Thursday afternoons. 


&& 


Marine... 
Tropical Storm Cristobal will continue to move away from the region 
this morning. Other than some weak 1-2 feet backswell noted at 41004 
and 41008 no direct impacts are expected as the cyclone moves east 
of the Outer Banks. 


The synoptic pattern both at the surface and aloft will quickly 
morph into a summertime configuration with deep subtropical 
ridging anchored well offshore. This pattern will favor Standard 
sea breeze surges along the land/sea interface and late night 
nocturnal surges for the next several days. Seas will remain 4 feet 
or less through the period. 


&& 


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


&& 


$$ 


Jrl