Weather

771 
fxus62 kilm 110749 cca 
afdilm 


Area forecast discussion...corrected 
National Weather Service Wilmington NC 
348 am EDT Sat Oct 11 2008 


Synopsis... 
an area of low pressure off the southeast coast will drift 
southwest today and dissipate by tonight. High pressure will 
build into the Carolinas from the north Sunday...before settling 
over North Carolina by Tuesday. The high will weaken as it moves 
offshore by middle-week as a weak trough develops across the 
Carolinas. 


&& 


Near term /through tonight/... 
as of 3 am Saturday...a well defined upper low sitting just east 
of Charleston is bringing a deep easterly flow across the coastal 
Carolinas. The troposphere is saturated and widespread light rain 
continues. Embedded heavier showers and even a few T-storms over 
the coastal waters will push westward through the morning hours. 
This suggests the heaviest precipitation amounts today...around an 
inch...will fall near the coast with progressively lighter totals 
expected as you head inland. East to northeast winds could gust to 
35 miles per hour at the coast today...with sustained speeds around 15 miles per hour 
even across inland areas. 


An inverted trough roughly follows the Gulf Stream from Florida to 
near Cape Fear. This trough is mainly a reflection of the upper low 
but is helping to provide some isentropic lift as tropical moisture 
over the Atlantic is lifted up and over slightly cooler air west of 
the trough axis. As a 500 mb ridge axis builds across the Ohio 
Valley and central Appalachians later today...the upper low will get 
shunted southward. The deep moisture axis will follow the low 
southward as well...allowing drying conditions to slowly build in 
from the north. Models suggest North Carolina and the Pee Dee region 
as far south as Florence should dry out this evening...but the 
Georgetown/Greeleyville area may remain under the clouds and 
occasional showers through the night. 


Diurnal temperature ranges will be constricted by the clouds and 
rain today. Highs should reach the middle 70s. With some clearing 
expected across the northern half of the forecast area tonight... 
lows should reach the upper 50s around Lumberton...with lower to middle 
60s elsewhere. This is near or slightly above MOS consensus given 
the healthy winds still expected to continue. 




&& 


Short term /Sunday through Monday/... 
as of 3 am Saturday...Sunday forecast hinges on exactly how much 
dry air is able to filter into the area from the NE as the surface and 
upper ridge build in. Have gone with a dry forecast across the 
northern tier...and trended probability of precipitation upward to 30-40 for the far 
southern zones. However it could be a much sharper transition than 
advertised...but hard to say where in the County Warning Area that will be. 


Ridging should start to win out by Sunday afternoon...so trended 
probability of precipitation down below slight chance...with no mention of precipitation Sun 
night or Monday. 


Made little change to previously advertised temperatures...which are a 
bit below the latest GFS/NAM guidance but a little above the 
cooler Eta model MOS. 


&& 


Long term /Monday night through Friday/... 
as of 3 am Saturday...expect dry weather through the period. Strong 
upper ridging over the southeast through Tuesday...with the 
pattern flattening out after that. Weak cold front Wednesday night will 
be starved for moisture...and dynamics will remain too far 
north...so look for a dry frontal passage. 


Temperatures will be above normal throughout the extended. Warmest days 
will be Tuesday/Wednesday under the upper high...with highs reaching the middle 
80s...not too far from records for mid-October. 


&& 


Aviation /07z Saturday through Wednesday/... 
an upper level low centered south of chs will impact weather for the 
terminals through the next 24 hours. IFR ceilings are likely at all 
terminals through middle morning. Waves of rain and drizzle have spread 
well inland from the coast...and the character of the precipitation 
has become more showery along the coast as warmer more unstable air 
advects westward. Ceilings are uniformly in the 700-1200 feet range 
and should settle in the 700-800 feet range through 14-15z. 


The upper low and associated surface wave offshore will slowly 
weaken and move back to the southwest this evening as high pressure 
builds in from the northwest...resulting in slowly decreasing 
precipitation chances and slowly improving ceilings. Despite the 
improvement all of the terminals are still expected to see MVFR 
ceilings through afternoon. 


Outlook through Wednesday...VFR conditions are expected...except for 
possibly some early morning MVFR/IFR visibilities around sunrise 
each morning. 


&& 


Marine... 
near term /through tonight/... 
as of 3 am Saturday...a tight pressure gradient has developed over 
the eastern Carolinas between an inverted trough off the southeast 
coast and high pressure pushing south out of the Middle-Atlantic 
States. Strong east to northeast winds should continue through today 
leading to steadily building seas. The offshore Lejeune buoy (41036) 
has reported wind gusts of 33 knots in heavy rain this morning. Similar 
conditions are expected near Cape Fear this morning...then spreading 
southward along the South Carolina coast this afternoon. 


The trough will retreat southward tonight as the high continues to 
build southward. Winds across the Cape Fear area waters will subside 
somewhat tonight...but rough conditions are expected to continue 
along the South Carolina coast through the night. Seas could reach 9 
feet even within 20 miles of shore. Showers and a few thunderstorms 
today will taper off from Myrtle Beach northward this evening as 
drier air bleeds in from the north. Rain may continue through the 
night in and around Georgetown and Winyah Bay. 


Short term /Sunday through Monday/... 
as of 3 am Saturday...frisky east-northeast winds will continue at a solid 20 
to occasionally 25 knots through Sunday...as the gradient remains tight 
on the southern periphery of a 1030+ mb surface high building down the 
coast. Enough of an easterly component to keep the seas well above 
Small Craft Advisory thresholds...with 5-7 feet looking like the norm across the 
coastal waters. Longest fetch and highest seas will actually 
affect the outer portions of our far southern waters...where we 
may see 8 footers at times. 


Expect a gradual diminishing trend in wind speeds Sun night into 
Monday as the high settles into the NC Piedmont. Still only looking 
for winds to drop off to around 15 knots...and with a continued 
onshore trajectory the seas will be slow to subside. Marginal Small Craft Advisory 
seas should continue at least through Sunday night...so the advisory 
has been extended accordingly. 


Long term /Monday night through Wednesday/... 
as of 3 am Saturday...look for high pressure inland to dominate 
through at least Tuesday night...maintaining light NE winds across the 
waters. Could go variable for a time on Wednesday as the weakening 
high is pinched overhead...and a weakening cold front approaches 
from the northwest. Seas will lay down early in the period...and maintain 
2-3 feet Tue-Wed. 


&& 


Ilm watches/warnings/advisories... 
SC...none. 
NC...none. 
Marine...Small Craft Advisory until 8 am EDT Monday for amz250-252-254- 
256. 


&& 


$$ 


Near term...tra 
short term...Ras 
long term...Ras 
aviation...tra/heden 

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