920 
fxus62 kilm 181935 
afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
335 PM EDT Friday Jul 18 2008 


Synopsis... 
a low pressure system developing off the Georgia coast will lift 
slowly northeast through the weekend...before finally exiting to 
the northeast of the area Monday. A front will drop south over 
North Carolina on Tuesday...where it will linger through Thursday. 


&& 


Near term /through tonight/... 
as of 3 PM Friday...area of low pressure off the Georgia/SC coast this 
afternoon will continue its generally nwrd movement overnight. GFS 
keeps the low along on just inland of the SC coast overnight while 
the NAM keeps the low a little farther off the coast through the 
period. Both scenarios would provide abundant precipitation chances for the 
coast...but have implications for inland areas. The GFS solution 
results in precipitation being spread a little farther inland. The GFS has 
seemed to have a better handle on this system so went with a blend 
of the 2 solutions but with slightly more weighting given to the 
GFS. Forecast soundings from both the GFS and the NAM show deep 
moisture arriving overnight with precipitable waters  exceeding 2 inches around 
midnight. Dynamics remain limited with little to no thunder or 
severe weather expected. Clouds...low level moisture...and good 
boundary layer mixing will keep temperatures above climo(mid 70s) for most 
of the area. 


&& 


Short term /Saturday through Sunday night/... 
as of 3 PM Friday...short term hinges on development and movement of 
low pressure system presently off the coast of Georgia. TPC is 
looking closely at this system and there is a possibility that 
this may be designated as a tropical depression later today or 
tomorrow. Until a decision is made on that have leaned on the NAM 
for winds as its track up the coast looked more realistic than the 
GFS partial overland solution. Plus it is more in line with HPC 
forecasts. This will bring US another day of likely probability of precipitation...especially 
along the coast...for Saturday. As this will be primarily a tropical 
airmass do not expect much in the way of thunderstorm activity but 
could see some substantial quantitative precipitation forecast values...1 to 3 inches...in some 
locations. Probability of precipitation and quantitative precipitation forecast trend down Sunday as system moves NE and 
exits the area. All this could change depending upon what TPC 
decides to do. 


&& 


Long term /Monday through Thursday/... 
as of 3 PM Friday...northwest flow at the middle levels initially will 
translate to a more typical ridging pattern Tuesday and Wednesday as 
another shortwave pushes a front just north of the area Thursday and 
Friday. 


An interesting anomaly Monday as the flow actually advects in some 
very warm at the low and middle levels from the Central Plains. Latest 
mex guidance and HPC numbers are advertising middle to upper 90s across 
all areas Sans the usual cooler locations along the coast. More 
seasonal values return for the remainder of the period. 


Regarding probability of precipitation...made only a few adjustments especially later in the 
period increasing values slightly Wednesday and Thursday as the 
front slides closer. 


&& 


Aviation /19z Friday through Wednesday/... 
convection propagating a bit further inland than previously thought 
so flow and lbt could see some brief convection. Models trending 
toward a wetter scenario overnight as surface low tracks a bit more 
west than previous model runs. Best chance for rain will be after 
midnight...as a slug of moisture rotates onshore around the low. 
Look for MVFR ceilings...with brief IFR visibilities in showers. 
Showers will continue into Saturday...as the low tracks slowly 
northeast. Ceilings could stay below VFR most of the day. 


Outlook through Tuesday...scattered showers and thunderstorms 
expected through Saturday night across all terminals. Much improved 
conditions Sunday into Tuesday. 


&& 


Marine... 
near term /through tonight/... 
as of 3 PM Friday...southeast flow will slowly increase overnight as surface 
low off the Georgia/SC coast slowly lifts north. Movement of low has been 
somewhat erratic...though overall is has been north as expected. Center 
of circulation will not reach southern waters until beyond the scope of 
the near term period...so onshore flow will dominate the period. 
Speeds will increase overnight...but will remain below 20 knots. May 
see scec conditions met late tonight with seas 5 feet...but Small Craft Advisory 
headlines trumps mentions of scec so no flags. 


Short term /Saturday through Sunday/... 
as of 3 PM Friday...short term hinges on development and movement of 
low pressure system presently off the coast of Georgia. TPC is 
looking closely at this system and there is a possibility that 
this may be designated as a tropical depression later today or 
tomorrow. Until a decision is made on that have leaned on the NAM 
for winds as its track up the coast looked more realistic than the 
GFS partial overland solution. Plus it is more in line with HPC 
forecasts. Based on NAM winds have raised Small Craft Advisory for our 
northern 3 marine zones where seas look to be the highest. Based 
on NAM track of low it looks like our southernmost zone will 
escape Small Craft Advisory criteria winds and seas. 


Long term /Sunday night through Tuesday /... 
as of 3 PM Friday...westerly flow Monday will quickly back to 
south/southwest later Monday as a front passes well off to the 
north. The southern end of this front will slowly trudge toward the 
waters but wont be a factor until the middle or latter part of the 
week. Will see the Standard 10-15 knots of southwest flow 
throughout. Seas of 2-4 feet will prevail with the primary 
component being wind waves. 


&& 


Ilm watches/warnings/advisories... 
SC...none. 
NC...none. 
Marine...Small Craft Advisory from 8 am to 8 PM EDT Saturday for amz250- 
252-254. 


&& 


$$ 
Synopsis...rek 
near term...iii 
short term...rek 
long term...shk 
aviation...dl