920 
fxus62 kilm 181904 
afdilm 


Area forecast discussion 
National Weather Service Wilmington NC 
304 PM EDT Thursday Mar 18 2010 


Synopsis... 
low pressure just off the Carolina coast will move out to sea 
tonight. High pressure will build overhead from the Gulf Coast 
Friday through Saturday...bringing warm daytime temperatures to 
the area. Low pressure over Arkansas Sunday will move through the 
central Appalachians early Monday...dragging a cold front through 
the Carolinas. Cool temperatures Monday and Tuesday will moderate 
later in the week. 


&& 


Near term /through tonight/... 
as of 3 PM Thursday...very light intermittent rain across forecast 
area as moisture wrapping around back end of low. Finally crossed 
the measurable mark of pcp with .01 around noon at ilm. This low 
pressure system located around 200 miles southeast of Cape Fear this 
afternoon will move slowly off to the east-NE through tonight. As low 
tracks farther away...winds at the low to middle levels will become 
more northerly and will advect drier air into area. There is very 
dry air in a shallow layer close to the surface advecting in from 
the north this afternoon with dew point temperatures in the 20s just to the 
north of County Warning Area. Will keep lower dew points this afternoon but will 
raise them back up a bit for this evening. Overall expect 
intermittent rain to continue to wrap around into forecast area 
through this evening with very little in terms of quantitative precipitation forecast. As winds back 
to a more northerly direction through this evening the moisture will 
be lined up closer to the coast and will not make it as far inland. 
Highest probability of precipitation and quantitative precipitation forecast will be focused along the NC coastal counties. 
Drier air will make its way in after midnight as low tracks farther 
away from the coast. Clouds should start clearing out after midnight 
from north-northwest to S-se. Temperatures overnight will be slow to drop until clouds 
clear out and therefore expect most places to drop into the middle 
40s..but may see a few spots over northwest NC counties to drop to 
near 40. 


&& 


Short term /Friday through Saturday night/... 
as of 3 PM Thursday...vertically stacked low pressure moving away 
from the area Friday morning will give way to a very dry airmass 
advecting in from the west. High pressure from the surface through 
the upper levels will settle overhead Friday night...and will push 
offshore Saturday. Low pressure will dive into the arklatex region 
Saturday night with some middle and upper level moisture increasing 
locally. 


With no precipitation and very few clouds through the period... 
attention was placed on temperatures...winds and dewpoints. Highs Friday 
should reach the lower 70s most areas...with middle 70s widespread on 
Saturday away from the ocean. There should be enough offshore flow 
remaining Saturday afternoon to prevent a seabreeze from developing 
along the NC coast...but weaker winds near the incoming high could 
allow one to sneak in late in the day along the grand strand into 
Georgetown. With the high offshore and a light synoptic onshore flow 
Saturday...the 15-degree land-to-Sea Air temperature contrast will 
generate a moderate seabreeze with winds near the beaches increasing 
to around 15 miles per hour during the afternoon. 


Friday night's lows will be surprisingly chilly given the warm day 
prior. Excellent radiational cooling with clear skies and dry air 
will allow temperatures to drop as much as 35 degrees below daytime 
highs...into the lower 40s most areas. A little more wind behind the 
departing high Saturday night will temper lows into the upper 40s to 
around 50. 


&& 


Long term /Sunday through Thursday/... 
as of 3 PM Thursday...main challenge is the timing of a cold front 
slated for Sunday night or perhaps even Monday. Last couple GFS 
runs and the 00z European model (ecmwf) are much more bullish with a cutoff upper low 
that will slow down the front. As such...still expecting above 
normal temperatures on Sunday but have delayed the increase in probability of precipitation enough 
that coastal locations will be hard pressed to see any precipitation Sunday 
afternoon. 


Highest probability of precipitation now Sunday night into Monday morning...and it looks 
like we will have a decent but not stellar moisture feed as 
precipitable water reaches about an inch and a quarter. Respectable 
forcing with the upper vorticity center and lifted indices going negative 
will provide at least a brief window for thunder. Probability of precipitation in the high 
chance category for now. However...since it is more a matter of 
when it will rain than if...later shifts should be able to narrow 
down the time window for a likely pop. 


As the front pushes through and the upper low heads offshore...flat 
ridging aloft will follow resulting in dry weather and temperatures near 
normal Tuesday through Thursday. 


&& 


Aviation /18z Thursday through Tuesday/... 
low pressure offshore will continue to advect patchy light 
rain...mainly over the northern half of the County Warning Area. Look for these 
conditions to persists through the afternoon. Ceilings will remain 
VFR for the most part...but could not rule out brief MVFR ceiling 
where the precipitation has persisted. Winds will continue mainly 
out of the north on the backside of the low. The winds could be 
briefly stronger than forecast...if the low deepens a bit. Look for 
VFR conditions overnight...with precipitation ending as the low 
tracks slowly away from the coast. VFR Friday with light winds and 
scattered skies. 


Extended outlook...VFR through Sunday morning. Moderate confidence 
tempo IFR visibilities/isolated thunderstorms Sunday evening through 
midday Monday. 


&& 


Marine... 
near term /through tonight/... 
as of 3 PM Thursday...winds basically north-northwest 15 kts south of Cape 
Fear and north around 15 kts to the north as low pressure located 
southeast of Cape Fear. Fairly tight gradient flow should produce 
northerly winds on back end of low through tonight peaking around 20 
knots. Small Craft Advisory will continue through tonight. Although seas seem 
borderline for a Small Craft Advisory expect seas should see 6 feet 
in portions of outer waters to the north of Cape Fear. 


Short term /Friday through Saturday night/... 
as of 3 PM Wednesday...low pressure will push rapidly offshore 
Friday morning with offshore winds diminishing in strength 
throughout the day. It is even possible with the lighter flow 
Friday afternoon that wind directions could veer onshore along the 
grand strand with a weak seabreeze. High pressure will move 
overhead Friday night with winds becoming light and variable. The 
high will push offshore late Saturday morning with light southerly 
winds developing. Large temperature contrasts between the 
relatively cold marine air (60 degrees) and warmer conditions 
inland (mid 70s) will create a moderate seabreeze Saturday with 
speeds increasing to 10-15 knots nearshore during the afternoon. 


Seas will rapidly decrease during the day Saturday behind the 
departing low. Seas north of Cape Fear could still be in the 3-5 feet 
range early...but will fall to 3 feet or less by evening. 1-2 feet seas 
are expected otherwise. 


Long term /Sunday through Monday/... 
as of 3 PM Thursday...southerly gradient will tighten up on Sunday 
ahead of the approaching cold front. Now looks like a better shot 
at realizing Small Craft Advisory conditions with the slower frontal passage...as the onshore 
fetch will be stronger and last longer into Sunday night. Wind 
speeds look marginal but 5-7 feet seas are a pretty good bet for at 
least a brief period near daybreak Monday. 


Gradual subsiding trend on Monday as winds come around to 
west-southwest and diminish. Due west trajectory will maintain a 
large enough variation in fetch length to warrant a wide range in 
seas...dropping off to 2-4 feet within 20nm on Monday night...while 5 
footers persist well into Tuesday out near Frying Pan buoy. 


&& 


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


&& 


$$ 


Synopsis...tra 
near term...rgz 
short term...tra 
long term...Ras 
aviation...dl 

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