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afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
130 am EDT Thursday Oct 16 2008 


Synopsis... 
high pressure over the southeastern U.S. Will weaken on Thursday. 
A cold front will cross the area early Friday before stalling 
offshore. A wave of low pressure will develop along this front 
offshore with a chance of rain Friday into early Saturday. This 
system will accelerate northeastward...leaving dry conditions for 
Sunday and Monday. 


&& 


Near term /through tonight/... 
as of 9 PM Wednesday...large area of high pressure centered over 
northern Georgia will show little movement in the near term although 
axis of attendant 500 mb ridge will shift offshore Thursday morning. 
Very dry air column with precipitable water values of under an inch through the 
period. Clear skies and calm winds will lead to another night of 
ideal radiational cooling. Temperatures will not be quite as cool as 
last night...but still well down in the 50s with a few 40s in 
traditional cool spots. Similar to last night expect patchy fog to 
redevelop after midnight. 


&& 


Short term /Thursday through Friday night/... 
as of 3 PM Wednesday...another day of unseasonably high temperatures on 
tap for Thursday as upper ridge tries to hang on a little 
longer...and with west-southwest flow at the surface. Prefer the NAM MOS over the 
warmer mav based on todays observations. Heights will fall through 
the day Thursday as the middle and upper ridge flattens and zonal 
flow sets up over the eastern Continental U.S.. this progressive pattern will 
push a cold front across the area Friday...with latest models 
suggesting a wind shift entering the western County Warning Area as early as 
Friday morning. Friday forecast may become a bit more problematic 
if a surface low develops inland similar to the NAM solution. If 
this happens...frontal passage over NE SC would be delayed until later 
Friday evening. For now am leaning more towards the GFS which 
pushes the front off the coast and develops the low offshore. This 
solution also favors better precipitation chances...or at least higher 
quantitative precipitation forecast...remaining off the coast. Will continue the going forecast of 
slight-low chance probability of precipitation increasing west to east on Friday with the 
highest probability of precipitation Friday night. 


Record highs for Thursday for 3 cities across the ilm County Warning Area... 
ilm flow cre 
Thursday 87(1975) 87(1975) 82(1953) 


&& 


Long term /Saturday through Wednesday/... 
as of 3 PM Wednesday...latest model runs still showing a bit of a 
discrepancy in terms of timing of the low pressure system clearing 
out of the area. GFS still the faster of the two with most weather 
now ending by early Saturday. European model (ecmwf) holds onto chance of pcp through 
Sat afternoon. Will probably keep low end probability of precipitation through Sat afternoon for now 
but show a clearing trend through the evening hours. As low moves 
off to the NE and high pressure begins to build in...tightened 
gradient will produce breezy conditions through Sat. Either way 
pattern remains very progressive with one high pressure system 
early in the week being replaced by another surface high building in 
through middle week. In between these two systems...winds may back 
around to the west-northwest briefly as one high pressure system moves off 
the coast early Tuesday. A dry looking back door front may push 
through Tuesday...but does not look like it will bring much aside 
from possible clouds and a reinforcing push of cold air. 


Overall looks like weather for sun through much of next week will be 
dominated by dry high pressure and seasonable temperatures. Maximum cold air advection and 
dry air will occur early Sunday...once 500 mb trough clears the East 
Coast on Sat night. Middle level heights build rapidly through Sunday 
night. Low level thicknesses and 850 temperatures increase through Sunday 
peaking late Monday and then get driven back down slightly as dry 
front pushes south through area on Tuesday. Therefore expect temperatures 
to moderate quickly Post frontal through the end of the weekend into 
Monday reaching a few degrees above climatology by Monday afternoon. Overall 
temperatures will be within a few degrees of climatology Sunday through Wednesday 
showing fairly decent diurnal swings with plenty of dry air in place. 


&& 


Aviation /06z Thursday through Monday/... 
high pressure is expected to continue to affect the terminals 
through the overnight. Excellent radiational cooling continues with 
moonlit skies and calm winds. Followed the trend of the past two 
mornings with MVFR-IFR visibilities possible at the coastal 
terminals due to fog. Both kcre and kmyr have already dropped to IFR 
visibilities but have rebounded over the past couple hours. Will 
likely see visibilities bounce around at those terminals through the early 
morning hours since cross-over temperatures will be met. Similar to 
the past two mornings visibilities should improve toward 10-11z and 
VFR conditions expected shortly thereafter. 


For the rest of today VFR weather is expected with some high clouds 
moving in late in the day...especially at the inland terminals. 
Winds will be light out of the southwest except at the coastal 
terminals where winds will shift into the south after 18z with the 
resultant sea breeze developing and pushing inland. 


Outlook through Monday...a slight chance for late night or early 
morning IFR visibilities...otherwise VFR expected. Showers are 
possible late Friday into early Saturday as a cold front moves 
across the area. Thunderstorms are not expected. High pressure 
will be building in behind the front Saturday. A slight chance of 
IFR visibilities Sunday morning. 


&& 


Marine... 
near term /through tonight/... 
as of 9 PM Wednesday...ridge axis will gradually shift offshore. 
Gradient will remain weak across the area. Land breeze will result 
in a predominately westerly direction. Seas will remain in the 2 to 
3 feet range...which is higher than the local wind speeds would 
indicate. This will be primarily be due to an 8/9 second east-southeast swell. 


Short term /Thursday through Friday night/... 
as of 3 PM Wednesday...high pressure will weaken and drop to the 
south on Thursday with the approach of a cold front. Light 
offshore flow will become SW as the front crosses the central 
Carolinas Thursday night. A wind shift to the north is expected 
Friday...early in the day across the northern zones and afternoon 
across the SC coastal waters. Speeds will increase Friday night as 
a low develops offshore. Small Craft Advisory conditions expected north of Little 
River Inlet by late Friday night. 


Long term /Saturday through Monday/... 
as of 3 PM Wednesday...low pressure system along frontal boundary 
intensifies as it moves off to the NE on Saturday. Aside from a 
slight difference in model solutions in terms of timing...should 
still expect a decent northerly surge Saturday. Magnitude of the 
surge will depend on the timing and intensity of developing 
coastal low...but latest GFS shows up to 25 kts of surface wind speeds 
in a tightened gradient from 12z Sat through Sunday afternoon. For now 
forecast seas will be just below Small Craft Advisory thresholds for most waters. 
The increasing northerly component to the flow on Sat should push 
seas into Small Craft Advisory criteria in the outer waters...remaining between 6 
to 7 feet most of Sat through Sunday afternoon. There will be a large 
range in seas with near shore seas remaining less than 3 feet. Seas 
will be diminishing Sunday into Monday in a decreasing northerly 
flow as storm system moves rapidly off to the northeast into the 
distant Atlantic while high pressure builds into local waters. 


&& 


Ilm watches/warnings/advisories... 
SC...none. 
NC...none. 
Marine...none. 


&& 


$$ 


Near term...rjd 
short term...crm 
long term...rgz 
aviation...heden/srp 

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